Understanding the environmental fate of pesticides in South African planted forests: Part 1 – concentrations of pesticides in soil and risk posed to non-target soil organisms

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However, these chemicals have the potential to negatively affect the environment, including non-target soil organisms such as earthworms and microorganisms. It is therefore imperative that relevant pesticide environmental fate data is available to guide responsible pesticide use and/or the application of risk mitigation measures (where necessary). To this end, a 24-month field study, covering the period from pre-plant to canopy closure, was conducted to investigate the soil fate of commonly used pesticides in South African forest plantations and assess the risk they pose to non-target soil organisms. The trial was established in a Eucalyptus stand managed for pulpwood production in the KwaZulu-Natal Midlands, South Africa. Pesticides were applied at different stages of stand development according to standard operational practices. Pesticides (active ingredients) applied included glyphosate, triclopyr, metazachlor, cypermethrin, azoxystrobin, and tebuconazole. Following each application, soil samples were collected at pre-determined intervals (based on the DT₅₀ value of each pesticide) from two depths (0–10 cm and 10–50 cm) to evaluate persistence and leaching potential. The results were largely positive. Glyphosate, azoxystrobin, and foliar-applied cypermethrin degraded rapidly and posed a low risk to non-target soil organisms. While triclopyr, tebuconazole, metazachlor, and soil-applied cypermethrin persisted for more than 90 days, their concentrations either remained below risk thresholds or require further investigation to fully determine their ecological impact. forest plantations glyphosate pesticide risk pesticide-use soil South Africa Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 1. Introduction Forestry is an important contributor to the South African (SA) economy, with forest plantations covering approximately 1% of the total land area of the country. The sector contributes 1.07% to the national Gross Domestic Product (GDP) and supports an estimated 648 000 livelihoods ( Oberholzer 2021 ). Forest plantations occur predominantly within the summer rainfall region of the country, with only 3.6% found within the winter rainfall region (Godsmark 2017 ). A significant portion (57%) of forest plantations are established within the warm temperate (WT) climatic region, followed by cool temperate (CT) (33%) and subtropical (ST) (10%) (South African Site Classification Database 2021 ). The mean annual temperature (MAT) and mean annual precipitation (MAP) ranges for the different climatic zones are: <14 to 16 ⁰C and 925 mm for CT; 16 to 19 ⁰C and < 850 to 1 000 mm for WT; and 19 to 22 ⁰C and 1075 mm for ST regions. Pinus spp. (48.6%), Eucalyptus spp. (44.2%) and Acacia mearnsii De Wild. (6.8%) are the main species grown, mainly, for pulpwood (57.2%) and sawtimber (37.7%) ( Oberholzer 2021 ). The productivity and sustainability of forest plantations in SA is compromised by pests (including weeds) and pathogens/diseases (Greyling et al. 2016 , Little et al. 2018 , Roux et al. 2024 ). Biological, cultural and chemical (pesticides) control methods are often used to manage pests and pathogens to economically acceptable levels (Mead 2001 ). Although pesticides (herbicides, insecticides and fungicides) are used as a last resort, they remain necessary for the management of some economically important pests and pathogens (Ndlovu et al. 2022 ). For instance, the effective and efficient management of some difficult to kill weeds, like Setaria grass spp. (Letaoana 2018 ), Gonipterus spp. at high altitudes (Tribe 2005 ), white grubs and cutworms at establishment (Sivparsad et al. 2020 ) is still reliant on pesticide-use in SA forest plantations. The SA forestry industry is a minor pesticide user (Roberts et al. 2021 ), constituting 4% of the total pesticide use in the country (Gous 2014 ) . Pesticides are used infrequently, with up to seven applications over a rotation of 7 to 25 years (Roberts et al. 2016 , Rolando et al. 2017 ). The highest quantity of herbicides in forestry are applied between the pre-plant and canopy closure period (Roberts et al. 2021 ), due to the heightened vulnerability of young trees to competition (Wagner et al. 2006 ). Roberts et al. ( 2021 ), in a study estimating herbicide use in SA forestry, found that an average of 1.67 kg a.i. ha − 1 is applied during this period while 0.27 kg a.i. ha − 1 is applied post-canopy closure. The time to canopy closure is influenced by various factors such as the genus planted and climate (Little and Rolando 2008 , Rolando and Little 2009 ). For instance, canopy closure of Eucalyptus in ST regions occurs at 9 to 12 months, whereas it takes approximately 18 months in WT, and 24 months in CT regions (Little and Rolando 2008 ). All post-planting herbicide applications are directed sprays (spot sprays) which result in reduced pesticide quantities used and area treated than aerial or broadcast applications (Roberts et al. 2021 ). There are often fewer and more sporadic insecticide and fungicide applications in response to a pest or pathogen outbreak, at any stage of tree growth (Thompson 2011 ) . Silvicultural operations in SA forestry, including pesticide applications, are mostly carried out manually (Ramantswana et al. 2020 ). In the last decade of the 20th century, various industries including forestry have been under pressure to reduce reliance on pesticides (Little et al. 2006 , Joemat-Pettersson 2010 , World Health Organization (WHO) and Food and Agriculture Organization of the United Nations (FAO) 2019 ). This is due to the potential harm posed by their use to human health, and aquatic and terrestrial environments (Joemat-Pettersson 2010 , Mensah et al. 2013 , Dabrowski 2015 ). This pressure in forestry was further driven by national legislation (Joemat-Pettersson 2010 ) and the voluntary compliance with forest certification standards (Rolando et al. 2011 ); which facilitate access to global markets (Zubizarreta et al. 2023 ). More than 80% of forest plantations in SA are certified through the Forest Stewardship Council (FSC) scheme ( FSC 2017 ), with approximately 58% certified through the Programme for the Endorsement of Forest Certification (Sustainable African Forest Assurance Scheme 2024 ). Forest certification schemes have similar goals related to responsible pesticide-use which includes the need to avoid the use of highly hazardous pesticides, reduce and, where possible, eliminate the use of pesticides ( FSC 2017 , Sustainable African Forest Assurance Scheme 2024 ). The SA forestry industry has a mandate to ensure that all activities conducted within forest plantations preserve and protect environmental values—both aquatic and terrestrial—and safeguard the wellbeing of people working or living within plantations, as well as those affected by plantation practices, such as downstream water users (Forestry South Africa (FSA) 2019 ). Since pesticides are chemical compounds with a potential to cause harm, it is imperative that relevant data is available to guide responsible pesticide use and/or the application of risk mitigation (where necessary) (Ndlovu et al. 2022 ). Ndlovu et al. ( 2022 ), in a study evaluating environmental fate studies of pesticides relevant to the SA forestry industry, found that no studies have been implemented within SA forest plantations to understand the impact of the SA forestry pesticide use to the environment and human health. The study found that numerous pesticide environmental fate studies have been carried out in forest plantations abroad and in the SA agricultural industry (Ndlovu et al. 2022 ). Although these studies provide insights into the environmental fate and risk posed by pesticide use, the observations made and/or conclusions from these studies cannot be readily transferable to the SA forestry landscape due to differences in climatic and physiographic conditions, pesticides used and pesticide-use patterns (rates, methods and frequencies) (Ndlovu et al. 2022 ). The purpose of this field-based study was therefore to determine the environmental fate of pesticides within SA forest plantations, as used operationally, and the risk posed by their use to non-target environments and human health. This study covered two components: (1) the soil fate of pesticides and the risk posed by their use to non-target soil organisms; and (2) the aquatic fate of pesticides and the risk posed by their use to non-target aquatic organisms and human health. This paper presents the soil fate component which studies the persistence and potential leaching (vertical movement) of pesticides in soil. Pesticide in this study refers to the active ingredient, and not the pesticide product formulation. As no previous research had been conducted on the environmental fate (soil and water) and risk of pesticides used under typical operational practice within SA forest plantations (Ndlovu et al. 2022 ), a benchmark study which would represent a ‘worst-case scenario’ for environmental contamination by pesticides was preferred. 2. Materials and methods 2.1 Study location and site characteristics The field study was carried out at Natal Co-operative Timbers’ (NCT) Ingwe Farm in the KwaZulu-Natal (KZN) Midlands, South Africa (29˚24'S; 30˚06'E). A 16.6 hectare (ha) compartment was selected as the trial site, situated within a 386 ha drainage basin in the Lions River Water Management Unit of the Umngeni Catchment (Warburton et al. 2010 ). The site was located within a warm temperate summer rainfall region, with an altitude range between 1 165 meters and 1 210 meters above sea level (m a.s.l.), an MAT of 16˚C and MAP between 976 to 1 024 mm. Although rain can occur throughout the year, most of the precipitation occurs during spring/summer thunderstorm events (September to March). Dolerite (approximately > 90%) and shale were the dominant geologies (Heathman 1994 ), with humic ferralsol as the main soil form. The site was previously planted with Eucalyptus smithii R.T. Baker at a density of 1 667 stems per hectare, managed on a 10-year pulpwood rotation. The stand was clearfelled in August 2019 and subsequently replanted with seedlings of the same species and at the same density in January/February 2020. The study site was considered representative of typical SA forestry climatic and soil conditions, as well as the commonly planted genus and intended end-product. The site also represented a worst-case scenario for environmental contamination by pesticides since: (1) it was established on an ex-eucalypt stand meaning more herbicides would be required to kill the stumps of the previous rotation; (2) burning was the harvest residue management method employed; (3) the study was completed over a period of 24 months, covering the period from pre-plant to canopy closure. This is considered the period of the most intensive pesticide application in forest plantations; and (4) pesticides were intentionally the only intervention or method used to manage pests and pathogens. Prior to planting, harvest residues from the previous rotation were windrowed within every fifth row along contours and then burned on 20 November 2019. This is a common practice in SA forest plantations (Ross 2004 ). Following the prescribed burn a wild fire occurred on the site on 30 November 2020. The prescribed burn and wild fire resulted in minimal organic matter (OM) remaining on the site (0.73 tons ha − 1 of harvest residues post fire events), creating a worst-case scenario for environmental contamination as OM can mitigate or minimize the risk of pesticides leaching down the soil profile (Garrett et al. 2015 ) and pesticide runoff from the site (Cawson et al. 2012 ). The physical characteristics of the site (e.g. slope, aspect, soil type and depth) were evaluated prior to strategically establishing four sample plots (40x20 m plot − 1 ) that were representative of the study area (Fig. 1 ). These four sample plots formed the main sampling units for further site description (pH, soil texture, organic carbon (OC), and bulk density) and subsequent soil sampling for investigating or quantifying the persistence of any pesticide (active ingredients) following their application to the soil, and potential to leach down the soil profile. All pesticide applications were completed within a day or two (in the case of cypermethrin at planting) within the four sample plots whereas pesticide application over the whole site occurred over numerous days and sometimes over a couple of weeks due to the manual nature of the work and limited labour force. This paper will present pesticide applications and findings specific to the four sample plots (Tables 1 and 2 ). An iWeather® automatic weather station (AWS) (iWeather SA, 26 Brick Rd, George Industria, George, 6536, SA) was installed approximately 450 m from the trial site to record temperature, wind speed, wind direction, rainfall, vapour pressure deficit, humidity, solar radiation and evapotranspiration. Data was recorded at 10-minute intervals and summarised daily. The rain gauge of the AWS experienced periodic technical faults. Substitute rainfall data was obtained daily after rainfall events from a funnel rain gauge approximately 370 m from the trial site. Refer to Online Resource 1 for a summary of the weather data recorded throughout the study period. 2.2 Pesticide application Depending on the pesticide and rationale for application, pesticides were applied either as a broadcast spray and/or broadcast spray with planted trees protected with cones, or over the top of the planted trees, or within the planting pit (a manually prepared planting hole 25 cm wide and 25 cm deep made prior to planting the seedlings) (Tables 1 and 2 ). All pesticides were applied manually using a 16 L Matabi knapsack backsprayer, with the exception of the insecticide applied at planting which was directly poured into the planting hole (within the planting pit). All pesticides were applied according to label recommendations, and as per standard operational practice for SA forest plantations. For each pesticide application, the quantity of product used (and volumes of water used) within each sample plot and for trial site was recorded (Table 1 ). From this the quantity of a.i. applied could be determined on a sample plot and hectare -1 basis. Pre-plant broadcast herbicide application On 21 January 2020 the four soil plots received a broadcast pre-plant spray with the non-selective herbicide glyphosate (Roundup WeatherMAX®, glyphosate at 660 g a.i. L -1 , Bayer, 27 Wrench Road, Isando, 1600, SA ) and selective herbicide triclopyr (Triclon®, triclopyr at 480 g a.i. L -1 , Arysta LifeScience, 7 Sunbury Office Park, La Lucia Park, La Lucia Ridge, 4019, SA ) to ensure the site was free of competing vegetation prior to the planting of seedlings (Table 1 ). Glyphosate and triclopyr were applied at 7.9 and 1.32 kg ha -1 over the four plots (Table 1 ). The combined glyphosate/triclopyr treatment targeted the vigorous coppicing of the stumps remaining from harvest and the high glyphosate rate was necessary for the control of Rubus cuneifolius Pursh. (bramble). Insecticides for soil-borne pests at planting: Eucalyptus smithii seedlings were planted on 22 and 23 January 2020. Each seedling received 1 L of water which was poured into the planting pit immediately prior to the placement of the seedling thereafter covering the pit with soil (known in SA as puddle planting). To prevent damage to the seedlings from soil-borne pests, 1.25 ml of the insecticide Kemprin® 200 EC (cypermethrin at 200 g a.i. L − 1 , Arysta LifeScience, 7 Sunbury Office Park, La Lucia Park, La Lucia Ridge, 4019, SA), at a rate of 0.42 kg ha − 1 , was incorporated into each 1 L water (Table 1 ). Post-planting herbicide application For the short-term suppression of grasses and some broadleaf weed seeds, a pre-emergent herbicide metazachlor (Claw® 500 EC, metazachlor at 500 g a.i. L − 1 , Arysta LifeScience, 7 Sunbury Office Park, La Lucia Park, La Lucia Ridge, 4019, SA), at a rate of 1.0 kg a.i. ha − 1 , was applied as a banded 1 m line spray (0.5 m on either side of the tree) over the planted seedlings (24 January 2020) (Table 1 ). Although some of the herbicide was intercepted by the newly planted seedlings, most was evenly distributed over the soil within this 1 m swathe. To prevent interspecific competition, the weeds on the trial site were controlled on two more occasions (14 May 2020 and 13 November 2020) (Table 1 ). In May 2020, glyphosate (Roundup WeatherMAX®, glyphosate at 540 g a.i. L − 1 , Bayer, 27 Wrench Road, Isando, 1600, SA) was applied at 2.16 kg ha − 1 and triclopyr (Triclon®), was applied at 0.79 kg ha − 1 , in a broadcast spray operation (Table 1 ). The seedlings were protected by inverted cones during this operation, known as a coning vegetation management operation or broadcast coning spray operation in SA forest plantations. The operators did apply additional herbicide to woody weeds and coppice regrowth to ensure improved cover and hence control. As such, higher amounts of herbicide were applied in areas with more woody weeds and it is expected that herbicide runoff off from the foliage to the soil will be higher than the rest of the inter- and intra-row. In May 2020, the site had minimal vegetation, with Eucalyptus coppice constituting the main vegetation type controlled. In November 2020 the coppice regrowth was inadvertently removed (manually by labourers using machetes). As such only glyphosate (Roundup WeatherMAX®) was applied as a broadcast coning spray for the November 2020 weeding event at 2.81 kg a.i. ha -1 (Table 1 ). Post-planting insecticide and fungicide application Due to high seedling mortality (41.9% in February and 28.9% in October 2020) dead seedlings were replaced (blanking) in February to April and October 2020, with the total cypermethrin applied, over the 16.6 ha trial site, being 2.9 kg a.i. ha − 1 and 2 kg a.i. ha − 1 in February to April and October 2020, respectively (Table 1 ). The seedlings were replanted in a similar manner as they were planted in January 2020 – puddle planting with 1.25 ml Kemprin® added to the 1 L of water. Following blanking, nursey tags were placed around the seedlings that were replaced. This was to prevent the sampling of planting pits that had received more than one application of cypermethrin. Nevertheless, due to frequent rainfall events most of the tags got washed away. Although only limited numbers of Gonipterus spp. larvae and adults were observed on the site and no other pathogens observed, to fulfil the study objectives to assess the environmental fate of all pesticides that may be used during re-establishment, an insecticide and fungicide were applied to the foliage of the trees (Table 1 ). These were applied in early summer, the time of year when climatic conditions become conducive to an increase in insect pest and pathogen incidence. On the 12 November 2020, a tank-mix containing cypermethrin (Kemprin® 200 EC) at a rate of 0.02 kg a.i. ha − 1 as well as and the fungicides azoxystrobin and tebuconazole (Custodia® 320 SC, azoxystrobin and tebuconazole at 120 and 200 g a.i. L − 1 , ADAMA, 99 Jip de Jager Drive, Belville, 7530, SA) were manually applied as a banded 1 m line spray (0.5 m on either side of the tree) over the planted seedlings. Azoxystrobin and tebuconazole were applied at 0.1 and 0.2 kg ha − 1 , respectively (Table 1 ). Table 1 Details of pesticide application in a trial investigating the environmental fate of pesticides in South African forest plantations. Soil sample plot area = 800 m 2 Pesticide application operation Date of operation Active ingredient (a.i.) Pesticide (a.i.) applied plot − 1 . Values within bracket shows the amount of product Water volume (L ha − 1 ) Targeted rate of application for the trial site (kg a.i. ha − 1 ) Mean application rate ha − 1 for sample plots (kg a.i. ha − 1 ) (standard deviation) Actual rate of application for trial site (kg a.i. ha − 1 ) 2 Pre-plant: Weed management spray (broadcast application) 21/01/2020 glyphosate (660 g a.i. L − 1 ) Plot 1: 693.0 g (1.05 L) 404.9 3–5 7.9 (0.06) 5.85 Plot 2: 640.2 g (0.97 L) Plot 3: 646.8 g (0.98 L) Plot 4: 547.8 g (0.83 L) triclopyr (480 g a.i. L − 1 ) Plot 1: 120.0 g (0.250 L) – 1.32 (0.01) 0.97 Plot 2: 101.3 g (0.211 L) Plot 3: 107.5 g (0.224 L) Plot 4: 93.6 g (0.195 L) At planting: Soil-borne insect pests management (within planting pit) 22&23/01/2020 cypermethrin (200 g a.i. L − 1 ) Plot 1: 33.0 g (0.165 L) 1667 0.01–0.02 0.42 (0.001) 0.41 Plot 2: 32.0 g (0.160 L) Plot 3: 34.6 g (0.173 L) Plot 4: 34.8 g (0.174 L) At planting: Pre-emergent weed management spray (line spray) 24/01/2020 metazachlor (500 g a.i. L − 1 ) Plot 1: 102.5 g (0.205 L) 105.1 0.8 1.0 (0.02) 0.56 Plot 2: 77.5 g (0.155 L) Plot 3: 74.5 g (0.149 L) Plot 4: 67.0 g (0.134 L) Blanking (replacement of dead seedlings) 1 02/2020–04/2020 cypermethrin (200 g a.i. L − 1 ) - - - - 2.9 Post-plant: Weed management (broadcast coning operation) 14 May 2020 glyphosate (540 g a.i. L − 1 ) Plot 1: 137.3 g (0.208 L) 239 Varies dependent upon on vegetation type and abundance 2.16 (0.03) 1.62 Plot 2: 159.7 g (0.242 L) Plot 3: 185.5 g (0.281 L) Plot 4: 208.6 g (0.316 L) triclopyr (480 g a.i. L − 1 ) Plot 1: 49.9 g (0.104 L) Varies dependent upon on vegetation type and abundance 0.79 (0.01) 0.59 Plot 2: 58.1 g (0.121 L) Plot 3: 67.7 g (0.141 L) Plot 4: 75.8 g (0.158 L) Blanking (replacement of dead seedlings)1 10/2020 cypermethrin (200 g a.i. L − 1 ) - - - - 2.0 Post-plant: Foliar insect pests and disease management (line spray) 12 Nov 2020 cypermethrin (200 g a.i. L − 1 ) Plot 1: 1.2 g (0.006 L) 109.9 0.01–0.02 0.02 (0.0002) 0.02 Plot 2: 1.2 g (0.006 L) Plot 3: 1.6 g (0.008 L) Plot 4: 1.6 g (0.008 L) azoxystrobin (120 g a.i. L − 1 ) Plot 1: 7.4 g (0.062 L) 0.06–0.12 0.10 (0.001) 0.10 Plot 2: 6.8 g (0.057 L) Plot 3: 9.1 g (0.076 L) Plot 4: 9.0 g (0.075 L) tebuconazole (200 g a.i. L − 1 ) Plot 1: 12.4 g (0.062 L) 0.2 0.17 (0.002) 0.16 Plot 2: 11.4 g (0.057 L) Plot 3: 15.2 g (0.076 L) Plot 4: 15.0 g (0.075 L) Post-plant: Weed management (broadcast coning operation) 13 Nov 2020 glyphosate (540 g a.i. L − 1 ) Plot 1: 194.7 g (0.295 L) 221.7 Varies dependent upon on vegetation type and abundance 2.81 (0.05) 2.28 Plot 2: 235.0 g (0.356 L) Plot 3: 293.7 g (0.445 L) Plot 4: 175.6 g (0.266 L) 1 Blanking (replacement of dead seedlings) occurred over 16.6 ha. 2 This was calculated by dividing the total active ingredient quantities applied (derived from the total product applied) by the trial area (16.6 ha). Pesticide applications within the trial site were completed over several days and sometimes weeks, whereas in the four sample plots applications were completed within a day or two (as was for the cypermethrin application at planting) 2.3 Soil sampling for pesticide analysis Soil sampling commenced prior to the application of any pesticides for the new rotation (12 August 2019) and extended over 24 months (until 12 August 2021) with a total of 12 sampling events carried out over the study period. To understand pesticide-specific persistence sampling was planned to occur at the following periods: \(\:\frac{DT50\:\left(days\right)}{2}\) ; 𝐷𝑇50 (𝑑𝑎𝑦𝑠); and \(\:DT50+\:\left(\frac{DT50\:\left(days\right)}{2}\right)\) , following pesticide application. DT 50 indicates the time taken for 50% of the initial dose to degrade/dissipate (Navarro et al. 2007 ). The DT 50 values for each pesticide are listed in Table 2 . For each pesticide (active ingredient), three soil sampling events were initially planned following its application. However, since some pesticides were analyzed using the same procedures, additional analyses were possible beyond the originally planned three. Although the degradation of tebuconazole and azoxystrobin are different, due to budget constraints tebuconazole soil sampling and analysis was carried out based on the degradation period of azoxystrobin. While soil sampling for each pesticide at the proposed periods was not always feasible, sampling occurred as close to the proposed time as was possible (Table 2 ). An additional soil sample was taken from the pit at 568 DAT to determine whether cypermethrin was still detectable months following its last application. This was especially important since pesticide analysis results showed that cypermethrin levels in the pit did not reach undetectable levels at the third soil sampling event (that is, at 33 to 34 days after the first application of cypermethrin within the pit at planting) and there were additional cypermethrin applications during blanking events. Table 2 Soil sampling for pesticide analysis in a trial investigating the environmental fate of pesticides in South African forest plantations Operation Active ingredient DT 50 (days) 2 Application date Planned sampling 3 Actual soil sampling date Days after treatment Sampling point Pre-pesticide application - - - - 12/09/2019 Within interrow Pre-plant: Weed management spray glyphosate 23.8 21/01/2020 12 02/02/2020 12 Within interrow 24 14/02/2020 24 36 25/02/2020 35 triclopyr 30 21/01/2020 15 02/02/2020 12 Within interrow 30 14/02/2020 24 45 25/02/2020 35 At planting: Soil-borne insect pest management (at planting) cypermethrin 22.1 22&23/01/2020 11 02/02/2020 10–11 Within pit 22 14/02/2020 22–23 33 25/02/2020 33–34 - 12/08/2021* 567–568 Post-plant: Pre-emergent weed management spray metazachlor 6.8 24/01/2020 3 27/01/2020 3 Within pit 7 No samples taken No samples taken 10 02/02/2020 9 - 14/02/2020* 21 Within interrow - 25/02/2020* 32 - 26/11/2020* 307 - 08/12/2020* 319 - 17/12/2020* 328 Blanking (replacement of dead seedlings) 1 cypermethrin 22.1 02/2020 to 04/2020 - - - - Post-plant: Weed management (coning operation) glyphosate 23.8 14/05/2020 12 29/05/2020 15 Within interrow 24 12/06/2020 29 36 29/06/2020 46 triclopyr 30 14/05/2020 15 29/05/2020 15 Within interrow 30 12/06/2020 29 45 29/06/2020 46 - 26/11/2020* 196 - 08/12/2020* 208 - 17/12/2020* 217 Blanking (replacement of dead seedlings) 1 cypermethrin 22.1 10/2020 - - - - Post-plant: Foliar insect pests and disease management cypermethrin 22.1 12/11/2020 11 26/11/2020 13 Within interrow 22 08/12/2020 25 33 17/12/2020 35 azoxystrobin & tebuconazole 78 & 47.1 12/11/2020 39 17/12/2020 35 Within interrow 78 02/02/2021 81 117 09/03/2021 117 Post-plant: Weed management (coning operation) glyphosate 23.79 13/11/2020 12 26/11/2020 14 Within interrow 24 08/12/2020 24 36 17/12/2020 34 1 Blanking (replacement of dead seedlings) occurred over the 16.6 ha. 2 Lewis KA, Tzilivakis J, Warner D, Green A. 2016. An international database for pesticide risk assessments and management. Human and Ecological Risk Assessment: An International Journal 22: 1050–1064. 3 Days after treatment *Additional soil sampling events Samples were collected from within the pit, or interrow depending on how the pesticide was applied (Table 2 ). Each of the four sample plots were divided into four quadrants, with soil samples obtained from three quadrants at each sampling event, thus leaving one quadrant undisturbed. An area of 0.1 m 2 was first cleared of any slash and/or litter, with samples collected at two depths (0 to 10 cm and 10 to 50 cm) using graduated stainless-steel cores. When sampling soil within the planting pit three seedlings were randomly selected within a quadrant. Previously sampled pits were avoided on subsequent sampling events. During earlier sampling events (February 2020) it was easier to identify planting pits that were sampled in previous events as the soil sampling ‘hole’ was still evident. Also, during earlier sampling events the nursey tags showing blanked/replanted were still in place. As such, blanked trees were not sampled. The sampling depths were chosen to assess pesticide persistence in the topsoil (0 to 10 cm) and the potential for leaching into the subsoil (10 to 50 cm). At each soil sampling event a total of 48 individual soil samples were collected. Since soil properties can be more variable within topsoil soil layers compared to subsoil layers, a higher number of soil samples were collected within the topsoil compared to the subsoil. In each of the four sample plots, a total of nine topsoil (three from each quadrant) and three subsoil (one from each quadrant) samples were collected plot − 1 and combined to form two composite samples (one topsoil and one subsoil sample plot − 1 ). These were placed on ice in a cooler box before decanted into sealed 100 ml amber glass bottles and stored in a refrigerator at 4˚ C ( United States Environmental Protection Agency (US EPA) 2007 ). The samples were transported overnight (chilled) to Bureau Veritas M & L Laboratory Services (40 Modulus Rd, Ormonde, 2091, Johannesburg, SA) for pesticide analysis. 2.4 Pesticide extraction and analysis Pesticide extraction and analysis in soil samples was carried out using the QueCHERs method based on EN 15662 for pesticide extraction and clean-up (European Standards 2018 ). Following the use of QueCHERs glyphosate, triclopyr, tebuconazole and azoxystrobin were analyzed using Liquid Chromatography–Mass Spectrometry (LC-MS) whereas cypermethrin and metazachlor were analyzed using Gas Chromatography–Mass Spectrometry (GC-MS). Detection limits were 0.01 mg kg -1 for all pesticides analysed in soil and pesticide recoveries were between 70 to 120%. 2.5 Risk posed by pesticides to non-target soil organisms The potential risk posed by pesticide use to non-target soil organisms was assessed by comparing the measured pesticide concentrations in soil to toxicity values derived for standard soil ecotoxicity test species (like earthworms) and/or concentrations reported to impact soil microbial functioning. To approximate a worst-case scenario, the 97th percentile concentrations were used rather than mean pesticide concentrations. The 97th percentile concentrations were calculated using a formula by Rumsey ( 2011 ) . In this study, the 97th percentile concentration coincided with the maximum pesticide concentration observed across the four sample plots, at each sampling event. Although various species (such as Collembola spp.) can be used to evaluate the risk posed by pesticides to non-target soil organisms, this study predominantly used pesticide ecotoxicity data derived for earthworms. Earthworms are the most studied soil organisms in pesticide ecotoxicity (Gunstone et al. 2021 ) and are more sensitive to pesticides tested in this study compared to Collembola spp. (Lewis et al. 2016 ). Standard soil ecotoxicity values were obtained mainly from the Pesticide Properties Database (PPDB) (Lewis et al. 2016 . Online Resources 2–4 ) and any observations made in literature, especially in field studies. Although there is a large amount of pesticide toxicology data (of many tiers) available, the PPDB was consulted since it an extensive, open-access, database with consolidated pesticide risk data from a wide range of sources ( Online Resources 2–4 , Lewis et al. 2016 ). In addition, toxicity exposure ratios (TERs), which are widely used in pesticide ecotoxicology studies as indicators of the risk posed by pesticides to non-target soil organisms, were calculated to assess the potential ecotoxicity risk (European Commission 2002 , Mu et al. 2023 ). Toxicity exposure ratios were calculated for short-term or acute (using the LC 50 concentration of the most sensitive soil organism) and long-term or chronic (using the No Observed Effects Concentration (NOEC)) exposure risk. LC50 and NOEC values were sourced from the PPDB ( Online Resources 2–4 ). Pesticides are considered high risk if the TER is below the trigger value of 10 for acute and 5 for chronic exposure (European Commission 2002 ). Worst-case TERs were calculated by using 97th percentile pesticide concentrations measured in the topsoil (0 to 10 cm). The use of worst-case 97th percentile pesticide concentrations, especially for calculating TER (chronic), is precautionary since non-target soil organisms are unlikely to be exposed to the measured (topsoil) 97th percentile pesticide concentrations for extended periods because of pesticide dissipation over time. $$\:TER\:\left(acute\right)\frac{LC50\:of\:the\:most\:sensitive\:soil\:organism\:(mg/kg)}{Measured\:concentration\:of\:the\:pesticide\:in\:soil\:(mg/kg)\:}$$ $$\:TER\:\left(chronic\right)\frac{NOEC\:of\:the\:most\:sensitive\:soil\:organism\:(mg/kg)}{Measured\:concentration\:of\:the\:pesticide\:in\:soil\:(mg/kg)\:}$$ 3. Results and discussion 3.1 Soil characteristics The soils on the site were acidic (pH (KCl): 4 to 5.8) and clayey in texture (topsoil and subsoil), with bulk density ranging between 1.08 to 1.48 g cm − 3 (Table 3 ). Organic carbon (OC) was higher in the topsoil (0 to 10 cm) (average OC in 0 to 10 cm soil depth: 4.9%); compared with 3.5% for the 10 to 50 cm sub-soil depth) (Table 3 ). 3.2 Pesticide concentrations in soil and risk posed to non-target soil organisms Before the trial commenced in August 2019, residual pesticide concentrations in soil samples from the previous rotation were below the detection limit (BDL) (< 0.01 mg kg⁻¹). Therefore, only pesticide concentrations in soil following application events from January 2020 onward are discussed. 3.2.1 Herbicides (i) Glyphosate Glyphosate concentrations were BDL (< 0.01 mg kg − 1 ) in all soil samples collected at 0 to 10 cm and 10 to 50 cm soil depths, irrespective of repeated applications over a period of varying climatic conditions. This finding is significant for the SA forestry industry, as glyphosate is the most widely used herbicide, accounting for 97% of total herbicide applications (Roberts et al. 2021 ). The results observed in this study may in part be due to the application of glyphosate during the summer rainfall period where runoff from rainfall events occurring soon after pesticide application are considered an important mode of pesticide transport from the site (Screpanti et al. 2005 , Boithias et al. 2014 ). For example, following the January 2020 broadcast glyphosate application (Table 1 ), there was a cumulative rainfall total of 19.5 mm before the first soil sampling event (12 days after treatment (DAT), data not shown). Similarly, following the broadcast (coning) glyphosate application in November 2020 (Table 1 ), there was a cumulative total of 38.4 mm before the first soil sampling event (14 DAT, data not shown), possibly resulting in the movement of majority of glyphosate from the soil prior to sampling. It is also possible that some glyphosate leached down preferential flow paths in the soil profile due to the presence of root channels from previous rotations. Reviews by Vereecken ( 2005 ) and Borggard and Gimsing (2008) on glyphosate environmental fate and leaching in agricultural soils and soils under multiple land-use suggest that leaching risk is higher in well-structured, macroporous soils, particularly when rainfall occurs soon after application. However, in this study, glyphosate dissipation via leaching is likely minimal. This is because many pesticide-fate studies conducted within forest plantations have reported negligible leaching of glyphosate in forestry soils (Roy et al. 1989 , Feng and Thompson 1990 , Newton et al. 1994 , Thompson et al. 2000 ). Leaching and runoff are not the only plausible explanations for the rapid dissipation or undetectable levels of glyphosate observed in this study, as even with minimal rainfall following glyphosate application that occurred in May 2020 ( Online Resource 1 ), concentrations remained below the detection limit. No rainfall occurred between the May 2020 application of glyphosate (1.62 kg ha⁻¹) and the first two soil sampling events (15 and 29 DAT). A total of 7.5 mm was recorded at 35 DAT, with no further rainfall until the third sampling event at 46 DAT. Rapid dissipation of glyphosate following application has been reported in numerous publications (such as Roy et al. 1989 , Veiga et al. 2001 , Guijarro et al. 2018 ). Glyphosate environmental fate studies conducted in South America and Europe have reported DT 50 values in the range of 8.6 to 17.5 days (Screpanti et al. 2005 , Simonsen et al. 2008 , Guijarro et al. 2018 ). Glyphosate dissipation is mainly through microbial pathways (Sviridov et al. 2015 , Singh et al. 2020 ) with warm and moist conditions increasing the rate of microbial activity (Bento et al. 2016 , Silva et al. 2018 ). The low glyphosate concentration levels detected following the January 2020 and November 2020 applications may have also been due to warm summer temperatures (mean daily temperatures for January/February: 18˚C; November/December 2020: 17˚C), and high moisture contents (total rain for January/February 2020: 264.1 mm; November/December 2020: 236.2 mm) ( Online Resource 1 ) facilitating rapid breakdown. (ii) Triclopyr Following the broadcast pre-plant herbicide application in January 2020 (Table 1 ), triclopyr was detected in soil samples taken after application on three occasions in February 2020 ( Fig. 2 ) in both the 0 to 10 cm and 10 to 50 cm depth, with the concentrations at 10 to 50 cm sampling depth consistently lower (Fig. 2 ). Rapid triclopyr dissipation occurred during the January/February 2020 period (Fig. 2 ), with triclopyr concentrations below detectable levels at 35 DAT in all but one of the 10 to 50 cm depth soil samples (Plot 2 = 0.02 mg kg − 1 ). Concentrations in samples collected at 0 to 10 cm remained above the detection limit, albeit at a 97th percentile concentration of 0.122 mg kg − 1 (Fig. 2 ). Following the second triclopyr and glyphosate application in May 2020 (Table 1 ), triclopyr residues were again detected in all soil samples collected at the 0 to 10 and 10 to 50 cm soil depth (Fig. 2 ). Similar to the January 2020 pre-plant operation, triclopyr residues were consistently lower within the 10 to 50 cm soil sampling depth (Fig. 2 ). Overall, triclopyr concentrations in soil samples collected shortly after the May 2020 broadcast coning event were higher (9.433 mg kg − 1 ) than triclopyr concentrations recorded in February 2020 (1.495 mg kg − 1 ) after the January 2020 application, despite the lower application rate (1.32 kg a.i. ha − 1 vs 0.79 kg a.i. ha − 1 ). Triclopyr residues were below the detection limit in all soil samples collected at 0 to 10 cm and 10 to 50 cm at 196, 208 and 217 days after the last application of triclopyr on 14 May 2020. The only exception was a 0 to 10 cm soil sample in Plot 1 (at 196 days), which had a concentration of 0.035 mg kg − 1 . Triclopyr residues are often detected in soils following triclopyr application (Johnson et al. 1995 ). Thompson et al. ( 2000 ) reported triclopyr in soil following its application in an Acadian Forest (Canada). The peak concentrations reported by Thompson et al. ( 2000 ) were, however, higher than those found in this study (11.72 mg kg − 1 versus maximum 97th percentile concentration of 9.433 mg kg − 1 in this study). The differences were possibly due to the higher application rate applied in the study by Thompson et al. ( 2000 ) (3.98 kg ha − 1 versus the 1.32 and 0.79 kg a.i. ha − 1 used in this study). Microbial breakdown and photodegradation are the main degradation pathways for triclopyr in soil (Ganapathy 1997 , Tu et al. 2001 ). The rapid degradation of triclopyr following the broadcast pre-plant application (January 2020) could be a result of the warm, moist conditions that occurred during the summer months ( Online Resource 1 ), and the increased duration and intensity of sunlight facilitating rapid microbial degradation and photodegradation (Tu et al. 2001 , Sanchez-Bayo and Hyne 2011 ) . Total rainfall following the 21 January 2020 herbicide application to 25 February 2020 (last soil sampling event, 35 DAT) was 114.8 mm compared to 7.5 mm received between 14 May (day of herbicide application) and 29 June 2020 (day of soil sampling at 46 DAT). In a review comparing the fate of pesticides in tropical and non-tropical environments Sanchez-Bayo and Hyne ( 2011 ) indicated that rainfall events contribute to the dissipation of pesticides in soil (through runoff). Similarly, Berisford et al. ( 2006 ) reported higher triclopyr persistence during periods with reduced rainfall. They hypothesized that the lower degradation rates were associated with lower microbial activity due to reduced available soil moisture (Berisford et al. 2006 ). During the first spraying event (broadcast pre-plant treatment), herbicides were evenly sprayed over the entire area, whereas some localised (more intense) application of herbicide occurred during the treatment of woody weeds (including coppice regrowth) during the second spraying event (broadcast coning event). Although not measured, it is possible that soils during the May/June 2020 sampling were collected from these areas with potentially higher herbicide concentrations. Despite the lower triclopyr application rate in May 2020 (0.79 vs. 1.32 kg a.i. ha⁻¹ in January) (Table 1 ), soil triclopyr concentrations were higher than those detected after the January 2020 broadcast pre-plant spray. This could be attributed to a combination of factors, including: (1) the cumulative effect of both applications. It is possible that residues from the January application had not fully degraded by the time of the May treatment, resulting in elevated concentrations due to accumulation; (2) reduced rainfall; (3) lower temperatures; and (4) the manner in which the herbicides were applied. The movement of triclopyr down the soil profile was expected as triclopyr is considered moderately mobile (water solubility of 440 mg L − 1 ) ( Online Resource 2 , Lewis et al. 2016 ), with previous studies testing triclopyr on different textured soils and/or properties recording vertical mobility (Stephenson et al. 1990 , Newton et al. 1990 , Johnson et al. 1995 ). Similar to this study, most studies reported lower triclopyr concentrations in soil lower down the profile compared with the topsoil concentrations (Stephenson et al. 1990 , Newton et al. 1990 , Johnson et al. 1995 , Berisford et al. 2006 ). Berisford et al. ( 2006 ) compared the persistence and leaching of four herbicides (including triclopyr applied at 3.5 kg ha − 1 ) on four sites with variable soil properties. They concluded that, although mobile, triclopyr at the levels detected in their study (< 6 µg L − 1 ) was unlikely to leach to concentrations which would be considered detrimental to aquatic species ( Daphni a O.E Miller; bluegill sunfish ( Lepomis macrochirus Rafinesque, rainbow trout ( Oncorhynchus mykiss Walbaum)), or render water unsafe for drinking. Ecotoxicity of triclopyr within the soil environment Triclopyr concentrations in soil of the present study (Fig. 2 ) were > 100-fold lower than the acute LC 50 concentrations for earthworms ( Online Resource 2 , Lewis et al. 2016 ). Studies investigating the use of triclopyr in North American forest plantations with higher application rates and slower dissipation/degradation rates than in this SA study indicate that triclopyr as currently used (mostly aerial application of triclopyr at rates between 1.65 to 3.98 kg a.i. ha − 1 ) is unlikely to be of concern (such as Newton et al. 1990 , Stephenson et al. 1990 , Thompson et al. 2000 ). This is because the reported triclopyr residues in soil were consistently below concentrations considered detrimental to soil organisms (< 100 mg kg − 1 ) (Newton et al. 1990 , Stephenson et al. 1990 , Thompson et al. 2000 ). Busse et al. ( 2004 ) tested the influence of three herbicides, including triclopyr applied at 4.5 and 9 kg a.i. ha − 1 , on soils with differing clay and OM contents on ectomycorrhizae of conifer species. Observations made three to four months after herbicide application, indicated no impact to soil microbial biomass and activity. Souza-Alonso et al. ( 2013 ) investigated the impact of triclopyr as a spot application on the soil microbial community (enzymatic activity and soil respiration) and native species diversity in a Pinus pinaster Aiton forest in Spain. Over the initial six-month sampling period, no significant differences in soil microbial responses were detected between the control treatment and triclopyr treated plots (total quantity of a.i. ha − 1 not specified). However, there was evidence of changes in bacterial community structure at one year, but the bacterial richness, density, and diversity were not impacted (Souza-Alonso et al. 2015 ). They also detected no changes in the fungal community over the same sampling period. Nolte and Fulbright ( 1997 ) investigated plant, small mammal, and avian diversity following the use of a mixture of picloram and triclopyr (each applied at 1.9 kg a.i. ha − 1 ) for the control of honey mesquite ( Prosopis glandulosa Torr.) in humid, subtropical Texas. They observed no difference in plant and vertebrate species richness between herbicide treated plots and control plots over a two-year period. According to the calculated TERs, triclopyr concentrations at the trial site posed a low acute risk to non-target soil organisms (Table 4 ). However, a high chronic exposure risk was identified ( Table 4 ). A TER below the relevant trigger value signals a need for further testing such as conducting field tests to determine the ecological significance of the exposure to the pesticide identified as a high exposure risk pesticide (European Commission 2002 ). Nevertheless, since short- and long-term field studies have indicated that triclopyr effects to soil organisms are negligible (such as Potter et al. 1990 , Busse et al. 2004 , Souza-Alonso et al. 2013 ) the same result is expected within SA forest plantations and therefore further testing is not a priority. Table 4 Pesticide toxicity exposure ratios (TERs) for acute and chronic exposure risk of non-target soil organisms in a trial investigating the environmental fate of pesticides in South African forest plantations. Values in bold represent values below the trigger value of 10 for acute risk exposure and 5 for chronic risk exposure Pesticide Maximum 97th percentile pesticide concentrations (mg kg − 1 ) at 0–10 cm depth TER (acute) TER (chronic) glyphosate < 0.01 560 000 2 131 triclopyr 9.43 55.2 0.6 metazachlor 5.97 83.6 0.4 cypermethrin (soil applied) 4.37 22.9 1.2 cypermethrin (foliar applied) < 0.01 10 000 530 azoxystrobin 0.04 6 910.9 73.2 tebuconazole 0.09 15 293.5 110.7 (iii) Metazachlor Following the application of the pre-emergent herbicide metazachlor (at 1.0 kg ha − 1 ) as a 1 m line spray (centered on tree rows) in January 2020, the active ingredient was detected in all soil samples up to 32 DAT (Fig. 3 ). Concentrations of metazachlor were higher in the 0 to 10 cm soil depth than at 10 to 50 cm soil depth (Fig. 3 ). Despite a single application at planting, metazachlor was still detected at 307 DAT in the 0 to 10 cm soil samples, albeit at a low 97th percentile concentration of 0.087 mg kg − 1 (data not shown). At subsequent sampling events (319 and 328 DAT) concentrations in all samples were BDL (< 0.01 mg kg − 1 ). In a study investigating the differences in dissipation of metazachlor (0.5 kg a.i. ha − 1 ) and clomazone (0.096 kg a.i. ha − 1 ) under field and laboratory conditions in Greece, Szpyrka et al. ( 2020 ) also reported metazachlor residues in the topsoil following application. Although the study had a similar application rate and similar soil texture to this study, Szpyrka et al. ( 2020 ) reported lower metazachlor concentrations (range of average concentrations at 0 to 20 cm of 0.05 to 0.52 mg kg − 1 ) compared to the current study (range of concentrations at 0 to 10 cm of 1.597 and 5.974 mg kg − 1 ). This was possibly due to the dilution effect of increasing sample depth. Concentrations in Szpyrka et al. ( 2020 ) were less than 0.1 mg kg − 1 after 30 days of application. More rapid dissipation was expected in the present study compared to the Szpyrka et al. ( 2020 ) study due to a combination of the high rainfall following application, clay textured soils, and higher levels of OM (range = 3.63 to 5.25% compared to 0.87% for the Greece study), especially as high clay and OM content facilitate increased metazachlor degradation (Mamy et al. 2005 , Sadowski et al. 2012 ). It is also possible that the differences in metazachlor dissipation between the present study and that reported by Szpyrka et al. ( 2020 ), could in part be related to the prevailing temperatures over the sampling period. Temperatures ranged from 12 to 27˚C, which were higher than those recorded in this study in the first 34 days after metazachlor application (13 to 22˚C). Increased soil temperatures result in a more rapid breakdown of metazachlor (Mantzos et al. 2016a ), with Walker and Brown ( 1985 ) recording a reduction in metazachlor half-life from 77 to 29.2 to 11.6 days with an increase in soil temperature from 5 to 15 to 25°C (at a constant humidity of 12% w/w). However, microbial degradation is a main pathway of metazachlor degradation (Mamy et al. 2005 ), with slower degradation rates observed in cooler winter months (Rouchaud et al. 1992 ). Detectable levels of metazachlor in the months following application in this study were likely due to slower degradation rates over the winter period (April/May to August/September). Despite being relatively mobile (water solubility of 450 mg L − 1 ) ( Online Resource 2 , Lewis et al. 2016 ), in laboratory and field studies metazachlor was observed to exhibit limited vertical movement in soil (European Food Safety Authority 2017 , Jursík et al. 2019 ). The results in this study are consistent with observations reported by Mantzos et al. ( 2016a ) where metazachlor residues were lower in subsoil layers. Mamy et al. ( 2008 ) and Mantzos et al. ( 2016a ) reported increased vertical movement of metazachlor in the presence of preferential flow paths or during intense rainfall events, especially if these occurred shortly following metazachlor application (Włodarczyk 2014 ). In the present study, the vertical movement of metazachlor could have been facilitated by the presence of preferential flow paths through root channels still present from previous crops, together with diffusion that likely occurred following the rainfall event of 12 mm, two days following metazachlor application. Ecotoxicity of metazachlor within the soil environment Metazachlor concentrations in this study were below the threshold of 7.5 mg kg⁻¹, which is reported to have no significant impact on soil microorganisms (such as nitrogen and carbon mineralization) and below the LC 50 value (500 mg kg − 1 ) for earthworms (Lewis et al. 2016 , Online Resource 2 ). Beulke and Malkomes ( 2001 ) studied the effects of metazachlor in a laboratory on the soil microflora and degradation and adsorption of metazachlor under different temperature and soil conditions. They found that metazachlor applied at 1.5 kg ha − 1 inhibited dehydrogenase activity (indicator of microbial biomass) and substrate-induced short-term respiration (indicator of potentially active soil microbial biomass) but stimulated nitrogen mineralisation. The degree of inhibition was more pronounced in soils incubated at 20˚C than those incubated at 30˚C (although not statistically significant). Due to the lower application rates used in SA forestry, metazachlor impacts on soil microorganisms are likely to be lower or insignificant. A greenhouse pot trial by Gyamfi et al. ( 2002 ) reported minor impacts of metazachlor (application rate of 1 kg a.i.) on eubacterial and Pseudomonas rhizosphere community structures. Eubacterial and Pseudomonas communities play a key role in soil fertility and thus plant growth, and the breakdown of environmental pollutants in soil (such as pesticides) (Ahmad and Malloch 1995 , Mandelbaum et al. 1995 , Kriete and Broer 1996 ) . Their study showed that the impacts of metazachlor on eubacterial and Pseudomonas communities were short-lived, with negative impacts detected at 42 days after application, but not at 104 days (Gyamfi et al. 2002 ). Metazachlor accounts for less than 2% of herbicides used within SA forestry (Roberts et al. 2021 ), however, to ascertain protection and preservation of key soil microorganism communities in areas where the herbicide is used, field testing of the effects of metazachlor on non-target soil organisms under conditions relevant to SA forest plantations is recommended. This is important since metazachlor was persistent on the site, the maximum 97th percentile concentrations (5.974 mg kg − 1 ) were above the chronic NOEC of > 2.31 mg kg − 1 , and the calculated chronic TER in this study identified a possible high risk of exposure to non-target soil organisms (Table 4 ). 3.2.2 Insecticides (i) Cypermethrin Cypermethrin within the planting pits was detected at both the 0 to 10 and 10 to 50 cm sampling depths up to 568 DAT (Fig. 4 ) and was regarded as persistent as it was detected 10 months after the last application in October 2020 (that is, on soil samples taken on 12 August 2021 (568 DAT). Cypermethrin concentrations within the soil decreased marginally between 11 DAT and 34 DAT (Fig. 4 ) but increased at both soil depths 568 DAT (Fig. 4 ). Following the foliar application of cypermethrin in November 2020, for the management of foliar insect pests, cypermethrin concentrations in all soil samples collected at 13, 25 and 35 DAT were consistently BDL. The soil samples collected to determine cypermethrin concentrations following foliar application were taken along the tree lines where cypermethrin was sprayed (not within the planting pit as with samples collected after the application of cypermethrin into the planting pit for the management of soil-borne insect pests). The high cypermethrin concentration reported at 568 DAT in soil samples collected in the planting pit were most likely a function of sampling from planting pits that had been replanted. Early tree growth across the site was variable, with some degree of difficulty in terms of separating the replanted (blanked) versus the original seedlings, especially at the later sampling dates. As a relatively high number of plants were replanted, resulting in three times the quantity of cypermethrin in these pits, it is likely that soil samples (at 568 DAT) were also taken from these pits. It is unlikely that the foliar application of cypermethrin caused the increase in concentrations in planting pits at 568 DAT given that post-application samples were BDL. Across a range of application rates tested under varying soil and climatic conditions in field studies, foliar-applied cypermethrin has been shown to dissipate rapidly in soil following application (Battu et al. 2009 ; Mukherjee et al. 2012 ; Mantzos et al. 2016b ). For example, in a study carried out in chilli ( Capsicum annuum L.) fields in Ludhiana (India) where cypermethrin and chlorpyrifos were applied at 15-day intervals and at rates higher than those in the current study (0.05 and 0.1 kg a.i. ha − 1 versus 0.02 kg a.i. ha − 1 ), Jyot et al. ( 2013 ) found that fifteen days following the last of three applications, cypermethrin concentrations in 0 to 15 cm soil samples were BDL of 0.01 mg kg − 1 . Although selected soil properties were reported (sand = 78%; silt = 10.2%; clay = 11.8%; pH = 8; OC = 0.3%), no weather data was provided, nor were possible reasons given for this rapid dissipation (Jyot et al. 2013 ). In another study, Mohapatra ( 2014 ) investigated the fate of foliar applied cypermethrin (and chlorpyrifos) applied twice, at two-week intervals, at two rates (0.25 and 0.5 kg a.i. ha − 1) on a sandy loam (OC = 0.4%) pomegranate cultivated research field in Bangalore, India. Cypermethrin concentrations were BDL limit (< 0.05 mg kg − 1 ) in 0 to 15 cm soil samples after one month. The slower degradation of cypermethrin in the soil pits could be attributed to a combination of: 1) lack of sunlight exposure; 2) higher application rates (0.42 versus 0.02 kg a.i. ha − 1 for foliar application); 3) repeated applications of cypermethrin in planting pits; 4) reduced likelihood of surface runoff following rainfall events; and 5) the high clay (> 40%) and OC (2.18 to 5.25%) content. There is consensus within the literature that due to the high adsorption affinity of cypermethrin ( Online Resource 3 ), dissipation is slower in soils with high levels of OM and/or clay (Chapman and Harris 1981 , Cycoń and Piotrowska-Seget 2016 ). In addition to hydrolysis and microbial degradation, photolysis is also considered an important dissipation pathway for cypermethrin in soil (Takahashi et al. 1985 ; Class 1992 ; Raikwar and Nag 2006 ). Rafique and Tariq ( 2015 ) reported a photodegradation half-life of 0.64 hours for alpha-cypermethrin (a compound closely related to cypermethrin) under laboratory conditions. Chai and Zaidel ( 2011 ) concluded that differences in cypermethrin dissipation rates observed at three sites in Malaysia were due to differences in the amount and intensity of sunlight recorded. Therefore, any cypermethrin on, or near the soil surface, or on leaves, following foliar application in this study may have been exposed to and broken down by solar radiation and/or sunlight. Studies by Jin and Webster ( 1998 ) and Gu et al. ( 2008 ) reported faster soil dissipation at lower cypermethrin application rates compared to higher doses, possibly due to the inhibitory effects of higher concentrations on microbial communities (Eneyi et al. 2021 ). In addition to the higher application rate, the soil-applied treatment was concentrated over a smaller area (planting pits of 25×25 cm), whereas the foliar application was distributed over a 1 m swathe. Consequently, soil microorganisms in treated pits were exposed to higher concentrations, potentially inhibiting their ability to degrade the pesticide efficiently. Although cypermethrin adsorbs strongly to soil, some can be transported off-site during rainfall events (Jergentz et al. 2005 ). As a cumulative total of 33.5 mm of rain occurred within nine days of the foliar cypermethrin application, it is possible that runoff could have also contributed to the rapid dissipation following application. Cypermethrin has been found to exhibit limited vertical movement (leaching) in soils with variable properties (Sakata et al. 1986 , Chai and Zaidel 2011 , Rani et al. 2014 , Mantzos et al. 2016b ). This has been attributed to the hydrophobic nature and high adsorption affinity ( Koc of 307 558 ml g − 1 ) of cypermethrin ( Online Resource 3 , Lewis et al. 2016 ). In the present study, however, cypermethrin residues were detected at the 10 to 50 cm soil depth, in all soil samples collected from within the planting pit (Fig. 4 ). The detection of cypermethrin at the lower soil depth (10 to 50 cm) may not necessarily be as a result of leaching but could be attributed to the application method. Cypermethrin was applied into the planting pit, to a depth of approximately 25 cm. Therefore, soil collected for determining the fate of cypermethrin at 10 to 50 cm by default contained and/or incorporated soil initially contaminated by cypermethrin. It is therefore difficult to determine whether cypermethrin moved below the 25 cm depth at which it was applied. Ecotoxicity of cypermethrin within the soil environment No field-based studies on the influence of cypermethrin on soil functioning could be cited, as such use was made of laboratory studies to interpret the environmental risk likely to be posed by cypermethrin use within SA forest plantations. Most studies have found that cypermethrin enhances soil biota enzymatic activities (such as Xie et al. 2009 , Butt 2020 ). A laboratory-based study investigating the impact of insecticides (including cypermethrin) on soil enzymatic activity (dehydrogenase and protease) found a directly proportional positive relationship between cypermethrin-dose (2.5 kg a.i. ha − 1 up to 10 kg a.i. ha − 1 ) and enzymatic activity (Rangaswamy et al. 1994 ). The impact was, however, short-lived as no stimulation was observed beyond day 30. Application rates within the study by Rangaswamy et al. ( 1994 ) were higher than those applied within the present study. Under laboratory conditions, Gundi et al. ( 2005 ) testing three insecticides (including cypermethrin) applied alone or in combination, found that cypermethrin (applied on its own as an aqueous solution added to soil) in concentrations ranging from 5 to 25 mg kg − 1 of soil significantly stimulated (p ≤ 0.05) populations of bacteria, fungi, and dehydrogenase activity measured at day 10 and 20 after insecticide application. Nevertheless, at day 30 after application, population levels and dehydrogenase in the control and insecticide amended soils returned to levels observed at the beginning of the study. Cypermethrin levels in soil reported by Gundi et al. ( 2005 ) were again higher than levels observed in the current study (Fig. 4 ). The calculated TERs have demonstrated a possible chronic exposure risk to cypermethrin (Table 4 ). Since numerous studies show that the impacts of cypermethrin are short-lived (as is evident in studies conducted by Rangaswamy et al. ( 1994 ), Gundi et al. ( 2005 ), Tedaja et al. (2015) ) further testing of the impact of cypermethrin to non-target organisms is not a priority for soil ecotoxicity. This especially since the concentrations leading to the potential for chronic risk stem from a spot soil application of cypermethrin at planting (that is application into the pit). As such, only a small proportion of the total planted area is treated (an area of approximately 1% of a hectare). Moreover, owing to its high adsorption coefficient (Katayama et al. 2010 ) it is likely that the bioavailability of cypermethrin residues will be reduced under field conditions. However, field studies would need to confirm the bioavailability or lack thereof, and therefore the actual impact of cypermethrin in soil for extended periods as recorded in this study. 3.2.3 Fungicides No information could be cited relating to the soil fate of azoxystrobin and tebuconazole when applied in a forestry context. As such, use was made of literature mainly from agriculture and laboratory studies. (i) Azoxystrobin Following the application of azoxystrobin (applied at 0.10 kg a.i. ha − 1 ) and tebuconazole (applied at 0.17 kg a.i. ha − 1 ) in November 2020 as a foliar spray, azoxystrobin residues were detected only in soils collected at 0 to 10 cm and only at 35 DAT (0.042 mg kg − 1 ). At 81 and 117 DAT azoxystrobin residues were BDL in all soil samples. The results in this study indicate that azoxystrobin has limited persistence and mobility under the tested soil and climatic conditions and use patterns. A wide range of azoxystrobin DT 50 soil values have been reported from azoxystrobin fate studies conducted in the field and laboratory (DT 50 values ranging from 0.3 to 180.7 days) (such as Sopeña and Bending ( 2013 ) , Herrero-Hernandez et al. ( 2015 ), Edwards et al. ( 2016 )). From literature, results suggest that in tropical, subtropical and warm temperate climates azoxystrobin dissipation is rapid with DT 50 values ranging from 4.9 to 26.9 days, irrespective of application rates (up to 2.02 kg a.i. ha − 1 tested) and frequency of applications (up to five times at 15-day intervals) (as seen in Gajbhiye at el. 2011 , Huan et al. 2013 , Wang et al. 2013 , Hou et al. 2016 , Dubey et al. 2017 , Wang et al. 2017 , Saha et al. 2020 ). Photodegradation and microbial degradation are the main dissipation pathways of azoxystrobin in soils, hence the rapid dissipation in warmer climates (Purnama et al. 2015 , Feng et al. 2020 ). It can therefore be expected that azoxystrobin applied within subtropical forestry regions of SA will dissipate more rapidly than observed in the present (warm temperate) study. In addition to the effects of photodegradation and microbial degradation, it is also possible that the rapid dissipation of azoxystrobin in the present study was facilitated by rainfall. A total of 33.5 mm of rain occurred within nine days of the fungicide application. In a study investigating the fate and transport of azoxystrobin (108.5 g ha − 1 ) and propiconazole (93.8 g ha − 1 ) in corn and soybean fields established in United States (Illinois), Edwards et al. ( 2016 ) found that rainfall (and thus runoff) occurring soon after azoxystrobin application in 2014 (within 12 hours, amount of rain not specified) contributed to reduced peak concentrations (concentrations < 0.05 mg kg − 1 ) of azoxystrobin reported in soil. Studies similar to the present study, have reported limited vertical movement (leaching) of azoxystrobin in soils, possibly due its low water solubility (6.7 mg L − 1 ) ( Online Resource 4 , Lewis et al. 2016 ). In a laboratory-based study aiming to understand the leaching of azoxystrobin, Dagar and Kumari ( 2014 ) applied the fungicide at 50 and 100 µg in a sandy loam soil under continuous and discontinuous flow conditions. They found that more than 80% and 77.36% of azoxystrobin concentrations were retained in the top 10 cm of soil, respectively. Herrero-Hernandez et al. ( 2015 ) also observed higher concentrations of azoxystrobin (data not specified) in the top 20 cm of the sandy clay loam soil following azoxystrobin application at 0.25 and 1.25 kg ha − 1 . No studies could be citied regarding leaching of azoxystrobin in clayey soils. Despite the rapid degradation of azoxystrobin measured in the current study, these results cannot be readily extrapolated to all SA forestry sites as the fate of azoxystrobin is complex and is influenced by soil and climatic conditions. Although azoxystrobin is a non-ionic compound, soil pH plays a major role in the fate of azoxystrobin, together with the moisture status of the soil and OC content ( Singh and Singh 2010 ) . Bending et al. ( 2006 ) and Sopeña and Bending ( 2013 ) observed more rapid azoxystrobin degradation under alkaline pH conditions. Organic matter or OC produces contrasting results for degradation of azoxystrobin, depending on the soil type. Singh and Singh ( 2010 ) found that azoxystrobin was more persistent in compost-amended silt loams, whereas compost enhanced degradation in sandy loam soils. Ecotoxicity of azoxystrobin within the soil environment Guo et al. ( 2015 ) studied the effect of azoxystrobin on fungi, bacteria and actinomycetes biomass, on soil respiration and soil enzymatic activities in black soil (clay loam; OC: 2.65%; pH: 6.8), and found that azoxystrobin significantly reduced microbial communities, even at azoxystrobin soil concentrations of 0.1 mg kg − 1 . Han et al. ( 2014 ) and Xu et al. ( 2021 ) suggest that azoxystrobin is potentially toxic to earthworms in soil. Azoxystrobin caused oxidative stress and DNA damage, even at low concentrations of 0.1 mg kg − 1 and 1 mg kg − 1 (Han et al. 2014 ; Xu et al. 2021 ). Azoxystrobin concentrations recorded in this study were lower than the levels reported to cause adverse effects in previous research (Han et al. 2014 ; Guo et al. 2015 ; Xu et al. 2021 ). Therefore, its use in SA forest plantations is not expected to result in significant environmental harm. Azoxystrobin also has relatively high acute LD 50 and EC 50 values for earthworms (≥ 42.0 mg a.i. kg − 1 dry weight of natural soil) (Wang et al. 2012 ; Leitão et al. 2014 ; Lewis et al. 2016 ), and the calculated TER values are well above trigger values (Table 4 ). (ii) Tebuconazole Following the application of tebuconazole in November 2020 as a foliar spray (Table 1 ), tebuconazole residues were detected only in soils collected at 0 to 10 cm (Fig. 5 ). Tebuconazole concentrations were BDL in all soil samples collected at 117 DAT. The results in this study show tebuconazole as being persistent in soils, but having limited mobility under the tested soil, climatic conditions and use patterns. Tebuconazole has a high adsorption affinity ( Koc of 1 035.16 ml g-1) ( Online Resource 4 ) and strongly adsorbs to clay and OM ( FAO 1994 , Čadková et al. 2013 , Tchaikovskaya et al. 2016 ). Tebuconazole has been reported to exhibit limited vertical movement (leaching) (FAO 1994) , which supports the observations in the present study. Approximately 80% of tebuconazole residues were found at the 0 to 5 cm soil depth in a laboratory-based study by Aldana et al. ( 2011 ) investigating the leaching behaviour of tebuconazole and oxadyxil in soil (OC: 2.35%; clay: 35.39%) (duration of the study not specified). A tebuconazole fate field study carried out in La Rioja (Spain) on a sandy clay loam soil (OC: 1.31%; clay: 17.1%) (application rates of 0.25 and 1.25 kg ha − 1 ) found that throughout the study period (355 days), tebuconazole residues occurred predominately at the 0 to 10 cm depth (% and/or quantities not specified) compared to concentrations reported in the lower soil depth/s (up to 50 cm) ( Herrero-Hernández et al. 2011 ). The risk of tebuconazole leaching is therefore negligible in soils with high clay and high OM content ( Gámiz et al. 2016 ). Although clay and OM are considered important for tebuconazole adsorption, other minerals in the soil can play an important role. For instance, Čadková et al. ( 2012 ) found that soil minerals such as ferrihydrite, birnessite, illite and goethite also adsorb tebuconazole. As such leaching might be countered in soils with low OM/low clay but high in other minerals. The persistence of tebuconazole in the present study was expected due to the high adsorption affinity and the nature of the dissipation pattern of tebuconazole. Adsorption and dissipation often show an inverse relationship ( Kah et al. 2007 ) as adsorbed pesticides are often unavailable for degradation and/or dissipation processes ( Koskinen et al. 2001 ). Several studies have shown that tebuconazole exhibits a biphasic dissipation pattern in field and laboratory, meaning it undergoes initial rapid degradation and/or dissipation but as tebuconazole adsorption to mineral and organic surfaces increases over time, degradation and/or dissipation slows down thus leading to persistence (for instance as shown in Papadopoulou et al. 2016 ). Ecotoxicity of tebuconazole within the soil environment From the few field-based studies that could be cited on the impact of tebuconazole to soil biota that were carried out across variable climatic and soil conditions and use patterns, it was found that the application of tebuconazole either causes no impact to soil biota, or if toxic impacts to soil biota do occur, their impacts are short-lived. For instance, Herrero-Hernández et al. ( 2011 ) found that tebuconazole had no impact on soil dehydrogenase activity. In a study investigating the impacts of tebuconazole applied at 187.5 (Field rate (FR)), 375 (2xFR (2FR)) and 1 875 g a.i. ha − 1 (10xFR (10FR)) in subtropical Junagadh (India), Saha et al. ( 2016 ) reported that the FR and 2FR inhibited soil microbial parameters such as microbial biomass carbon, soil ergosterol and dehydrogenase activity. However, a recovery over time was observed. Microbial biomass recovered after 7 days and 15 days for the FR and 2FR, respectively. Soil ergosterol recovered after 15 days for the FR and 45 days for the 2FR, and at 60 days for dehydrogenase activity for both the FR and 2FR (Saha et al. 2016 ). The calculated TERs showed a low acute and low chronic exposure risk of non-target soil organisms to tebuconazole (Table 4 ). It is therefore expected that tebuconazole, as used within SA forest plantations, will pose an insignificant risk to non-target soil organisms. 4. Conclusion This study investigated the soil fate (persistence and vertical movement) of pesticides used within South African (SA) forest plantations and the risk posed by their use to non-target soil organisms. The study was implemented on a site considered representative of typical SA forestry environmental conditions. The most noteworthy result from this study was that glyphosate, the most important herbicide for the SA forestry industry which accounts for 97% of the total herbicide use by the industry, was below the detection limit (< 0.01 mg kg -1 ) in all soil samples collected over the study period. This, despite the repeated applications of glyphosate occurring across different seasons (summer and winter). The rapid degradation and the low risk posed to the soil organisms observed in this study is similar to conclusions obtained from literature regarding the use of glyphosate within forest plantations globally. Azoxystrobin and foliar applied cypermethrin also degraded rapidly in the present study, possibly due to favourable conditions for photodegradation and microbial degradation. In contrast, triclopyr, tebuconazole, and especially metazachlor and soil applied cypermethrin, persisted for extended periods (> 90 days). This was possibly due to various factors such as: reduced microbial degradation in the cooler winter months; reduced sunlight exposure and thus photodegradation (for soil applied cypermethrin); and limited degradation due to high adsorption (tebuconazole and cypermethrin). The pesticides applied in this study showed limited vertical movement (thus low susceptibility to leaching). This was often associated with high adsorption coefficients and/or moderate to low water solubilities. The limited vertical movement observed is similar to observations made in other studies investigating the soil fate of the pesticides applied. Although pesticides can affect the homeostasis of the soil, the limited number of field-based studies and laboratory studies (mainly) reporting the impacts of pesticides to soil indicate that pesticide concentrations reported in this study posed a low risk to the soil environment. As pesticides are applied infrequently within SA forest plantations, any impacts that would occur to the soil environment as a result of their application are likely to be short-lived. While these results are largely positive for the SA forestry industry, they should be interpreted with caution, as they are based on a single study conducted in one region over a single growing season. Additionally, this study does not account for the environmental fate of pesticide degradation products or their potential risks to non-target soil organisms. Furthermore, most importantly, it does not consider the additive, antagonistic, or synergistic effects of pesticide mixtures on non-target organisms as this aspect was beyond the scope of this study. Declarations Acknowledgements This study was conducted as part of Noxolo’s PhD research at Nelson Mandela University. NCT Forestry, the Timber Industry Working Group (through Forestry South Africa), the Fibre Processing and Manufacturing Sector Education and Training Authority and Nelson Mandela University are highly acknowledged for funding this work. NCT Forestry is also thanked for providing the land and labor used to complete the study. Funding This work was funded by NCT Forestry, the Timber Industry Working Group (through Forestry South Africa), the Fibre Processing and Manufacturing Sector Education and Training Authority and Nelson Mandela University. Author contribution Ndlovu N. prepared the manuscript, tables and figures. Rolando C., Baillie B., and Little K. all reviewed the manuscript, tables and figures. References Ahmad I, Malloch D (1995) Interaction of soil microflora with the bioherbicide phosphinothricin. Agric Ecosyst Environ 54:165–174. Aldana M, De Prado R, Martínez MJ (2011) Leaching of oxadyxil and tebuconazole in Colombian soil. Commun. Agric. Appl. Biol. Sci 76:909–914. 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Assess 185:7757–7761. Wang Y, Wu S, Chen L, Wu C, Yu R, Wang Q, Zhao X (2012) Toxicity assessment of 45 pesticides to the epigeic earthworm Eisenia fetida . Chemosphere 88:484–491. Warburton ML, Schulze RE, Jewitt GPW (2010) Confirmation of ACRU model results for applications in land use and climate change studies. Hydrol Earth Syst Sci 14:2399–2414. Włodarczyk M (2014) Influence of formulation on mobility of metazachlor in soil. Environ. Monit. Assess 186:3503–3509. World Health Organization, Food and Agriculture Organization of the United Nations (2019) Global situation of pesticide management in agriculture and public health: Report of a 2018 WHO–FAO survey. World Health Organization, Geneva; Food and Agriculture Organization of the United Nations, Rome, Italy. Xie W, Zhou J, Wang H, Chen X, Lu Z, Yu J, Chen X (2009) Short-term effects of copper, cadmium and cypermethrin on dehydrogenase activity and microbial functional diversity in soils after long-term mineral or organic fertilization. Agric Ecosyst Environ 129:450–456. Xu Y, Li B, Hou K, Du Z, Allen SC, Zhu L, Li W, Zhu L, Wang J, Wang J (2021) Ecotoxicity evaluation of azoxystrobin on Eisenia fetida in different soils. Environ. Res 194:110705. Zubizarreta M, Arana-Landín G, Wolff S, Egiluz Z (2023) Assessing the economic impacts of forest certification in Spain: A longitudinal study. Ecol Econ 204:107630. Table 3 Table 3 is available in the Supplementary Files section. Additional Declarations No competing interests reported. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6886614","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":496058008,"identity":"3ecbc301-da8e-4da3-96a4-ca68341945a1","order_by":0,"name":"Noxolo Ndlovu","email":"","orcid":"","institution":"Nelson Mandela University","correspondingAuthor":false,"prefix":"","firstName":"Noxolo","middleName":"","lastName":"Ndlovu","suffix":""},{"id":496058010,"identity":"84b0309c-86fb-4148-8a31-fecb9c4ab03c","order_by":1,"name":"Carol Rolando","email":"data:image/png;base64,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","orcid":"","institution":"Scion","correspondingAuthor":true,"prefix":"","firstName":"Carol","middleName":"","lastName":"Rolando","suffix":""},{"id":496058011,"identity":"3523b5d2-28be-4081-97f7-f42af52c32ca","order_by":2,"name":"Brenda Baillie","email":"","orcid":"","institution":"Ministry for Primary Industries","correspondingAuthor":false,"prefix":"","firstName":"Brenda","middleName":"","lastName":"Baillie","suffix":""},{"id":496058020,"identity":"82e5e39c-d26d-4ea0-b8fe-a32a15edf80b","order_by":3,"name":"Keith Little","email":"","orcid":"","institution":"Nelson Mandela University","correspondingAuthor":false,"prefix":"","firstName":"Keith","middleName":"","lastName":"Little","suffix":""}],"badges":[],"createdAt":"2025-06-13 09:08:15","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6886614/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6886614/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s11056-026-10162-9","type":"published","date":"2026-02-02T15:57:36+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":88571796,"identity":"6b0f03c4-9ffa-4e9e-bc13-4350be8c8ad0","added_by":"auto","created_at":"2025-08-07 23:05:08","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1219643,"visible":true,"origin":"","legend":"\u003cp\u003ePhysical characteristics and position of sample plots in a trial investigating the environmental fate of pesticides during establishment of trees in South African forest plantations. (a) soil form (\u003cstrong\u003eSoil Classification Working Group 1991\u003c/strong\u003e) and soil depth; (b) slope; (c) aspect\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6886614/v1/a2385149d4f8d2632aaf11d6.png"},{"id":88572070,"identity":"23c1202b-adee-475b-abbb-365879cc5d7c","added_by":"auto","created_at":"2025-08-07 23:21:08","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":112063,"visible":true,"origin":"","legend":"\u003cp\u003eNinety-seventh percentile concentrations of triclopyr in soil after a pre-plant broadcast spray for weed control in January 2020 and a post-plant weed management coning spray operation in May 2020 in a trial investigating the environmental fate of pesticides in South African forest plantations\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6886614/v1/bc9054fc65e8a5a54a0f62f2.png"},{"id":88571801,"identity":"4beafa7a-db4b-42bf-bcfd-099dd991f0d9","added_by":"auto","created_at":"2025-08-07 23:05:08","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":86267,"visible":true,"origin":"","legend":"\u003cp\u003eNinety-seventh percentile concentrations of metazachlor in soil after pesticide application in January 2020 for the management of pre-emergent weeds in a trial investigating the environmental fate of pesticides in South African forest plantations\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6886614/v1/c3630e3e0d9a8cb93a523bfd.png"},{"id":88571798,"identity":"052e80fc-30db-44d0-8af8-c362adca011f","added_by":"auto","created_at":"2025-08-07 23:05:08","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":84396,"visible":true,"origin":"","legend":"\u003cp\u003eNinety-seventh percentile concentrations of cypermethrin in soil following application in January 2020 for the management of soil-borne pests in a trial investigating the environmental fate of pesticides in South African forest plantations\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-6886614/v1/eae88281c401c49b59f489ec.png"},{"id":88571809,"identity":"1eb276ac-b90a-449a-963f-31b89c0d39fa","added_by":"auto","created_at":"2025-08-07 23:05:08","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":85437,"visible":true,"origin":"","legend":"\u003cp\u003eNinety-seventh percentile concentrations of tebuconazole in soil following application in November 2020 for the management of foliar pathogens in a trial investigating the environmental fate of pesticides in South African forest plantations\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-6886614/v1/5cde71a29bda5119545ed19d.png"},{"id":102233995,"identity":"7c389b2e-7c25-4d7f-80c0-dd4aa2857a06","added_by":"auto","created_at":"2026-02-09 16:02:34","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4160572,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6886614/v1/f283af91-7fdb-476d-9d41-772e3b1e0c2e.pdf"},{"id":88571799,"identity":"b1387b5f-087f-47ae-b739-72b278bcc26e","added_by":"auto","created_at":"2025-08-07 23:05:08","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":145591,"visible":true,"origin":"","legend":"","description":"","filename":"Ndlovuetal2025Supplementarymaterial.docx","url":"https://assets-eu.researchsquare.com/files/rs-6886614/v1/246ae99cff3de783186bc98c.docx"},{"id":88571794,"identity":"0264d4a7-4bf6-43a2-8078-b33c53dac2dc","added_by":"auto","created_at":"2025-08-07 23:05:08","extension":"docx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":18168,"visible":true,"origin":"","legend":"","description":"","filename":"Table3.docx","url":"https://assets-eu.researchsquare.com/files/rs-6886614/v1/acc938e357f3061bef08507b.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Understanding the environmental fate of pesticides in South African planted forests: Part 1 – concentrations of pesticides in soil and risk posed to non-target soil organisms","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eForestry is an important contributor to the South African (SA) economy, with forest plantations covering approximately 1% of the total land area of the country. The sector contributes 1.07% to the national Gross Domestic Product (GDP) and supports an estimated 648 000 livelihoods (\u003cb\u003eOberholzer 2021\u003c/b\u003e). Forest plantations occur predominantly within the summer rainfall region of the country, with only 3.6% found within the winter rainfall region (Godsmark \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). A significant portion (57%) of forest plantations are established within the warm temperate (WT) climatic region, followed by cool temperate (CT) (33%) and subtropical (ST) (10%) (South African Site Classification Database \u003cspan citationid=\"CR117\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). The mean annual temperature (MAT) and mean annual precipitation (MAP) ranges for the different climatic zones are: \u0026lt;14 to 16 ⁰C and \u0026lt;\u0026thinsp;725 to \u0026gt;\u0026thinsp;925 mm for CT; 16 to 19 ⁰C and \u0026lt;\u0026thinsp;850 to 1 000 mm for WT; and 19 to 22 ⁰C and \u0026lt;\u0026thinsp;925 to \u0026gt;\u0026thinsp;1075 mm for ST regions. \u003cem\u003ePinus\u003c/em\u003e spp. (48.6%), \u003cem\u003eEucalyptus\u003c/em\u003e spp. (44.2%) and \u003cem\u003eAcacia mearnsii\u003c/em\u003e De Wild. (6.8%) are the main species grown, mainly, for pulpwood (57.2%) and sawtimber (37.7%) (\u003cb\u003eOberholzer 2021\u003c/b\u003e).\u003c/p\u003e\u003cp\u003eThe productivity and sustainability of forest plantations in SA is compromised by pests (including weeds) and pathogens/diseases (Greyling et al. \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2016\u003c/span\u003e, Little et al. \u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e2018\u003c/span\u003e, Roux et al. \u003cspan citationid=\"CR101\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Biological, cultural and chemical (pesticides) control methods are often used to manage pests and pathogens to economically acceptable levels (Mead \u003cspan citationid=\"CR74\" class=\"CitationRef\"\u003e2001\u003c/span\u003e). Although pesticides (herbicides, insecticides and fungicides) are used as a last resort, they remain necessary for the management of some economically important pests and pathogens (Ndlovu et al. \u003cspan citationid=\"CR80\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). For instance, the effective and efficient management of some difficult to kill weeds, like \u003cem\u003eSetaria\u003c/em\u003e grass spp. (Letaoana \u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e2018\u003c/span\u003e), \u003cem\u003eGonipterus\u003c/em\u003e spp. at high altitudes (Tribe \u003cspan citationid=\"CR130\" class=\"CitationRef\"\u003e2005\u003c/span\u003e), white grubs and cutworms at establishment (Sivparsad et al. \u003cspan citationid=\"CR114\" class=\"CitationRef\"\u003e2020\u003c/span\u003e) is still reliant on pesticide-use in SA forest plantations.\u003c/p\u003e\u003cp\u003eThe SA forestry industry is a minor pesticide user (Roberts et al. \u003cspan citationid=\"CR93\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), constituting 4% of the total pesticide use in the country (Gous \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2014\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e. Pesticides are used infrequently, with up to seven applications over a rotation of 7 to 25 years (Roberts et al. \u003cspan citationid=\"CR95\" class=\"CitationRef\"\u003e2016\u003c/span\u003e, Rolando et al. \u003cspan citationid=\"CR96\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). The highest quantity of herbicides in forestry are applied between the pre-plant and canopy closure period (Roberts et al. \u003cspan citationid=\"CR93\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), due to the heightened vulnerability of young trees to competition (Wagner et al. \u003cspan citationid=\"CR135\" class=\"CitationRef\"\u003e2006\u003c/span\u003e). Roberts et al. (\u003cspan citationid=\"CR93\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), in a study estimating herbicide use in SA forestry, found that an average of 1.67 kg a.i. ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is applied during this period while 0.27 kg a.i. ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is applied post-canopy closure. The time to canopy closure is influenced by various factors such as the genus planted and climate (Little and Rolando \u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e2008\u003c/span\u003e, Rolando and Little \u003cspan citationid=\"CR97\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). For instance, canopy closure of \u003cem\u003eEucalyptus\u003c/em\u003e in ST regions occurs at 9 to 12 months, whereas it takes approximately 18 months in WT, and 24 months in CT regions (Little and Rolando \u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e2008\u003c/span\u003e). All post-planting herbicide applications are directed sprays (spot sprays) which result in reduced pesticide quantities used and area treated than aerial or broadcast applications (Roberts et al. \u003cspan citationid=\"CR93\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). There are often fewer and more sporadic insecticide and fungicide applications in response to a pest or pathogen outbreak, at any stage of tree growth (Thompson \u003cspan citationid=\"CR127\" class=\"CitationRef\"\u003e2011\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e. Silvicultural operations in SA forestry, including pesticide applications, are mostly carried out manually (Ramantswana et al. \u003cspan citationid=\"CR90\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eIn the last decade of the 20th century, various industries including forestry have been under pressure to reduce reliance on pesticides (Little et al. \u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e2006\u003c/span\u003e, Joemat-Pettersson \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e2010\u003c/span\u003e, \u003cb\u003eWorld Health Organization (WHO) and Food and Agriculture Organization of the United Nations (FAO) 2019\u003c/b\u003e). This is due to the potential harm posed by their use to human health, and aquatic and terrestrial environments (Joemat-Pettersson \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e2010\u003c/span\u003e, Mensah et al. \u003cspan citationid=\"CR75\" class=\"CitationRef\"\u003e2013\u003c/span\u003e, Dabrowski \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). This pressure in forestry was further driven by national legislation (Joemat-Pettersson \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e2010\u003c/span\u003e) and the voluntary compliance with forest certification standards (Rolando et al. \u003cspan citationid=\"CR98\" class=\"CitationRef\"\u003e2011\u003c/span\u003e); which facilitate access to global markets (Zubizarreta et al. \u003cspan citationid=\"CR145\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). More than 80% of forest plantations in SA are certified through the Forest Stewardship Council (FSC) scheme (\u003cb\u003eFSC 2017\u003c/b\u003e), with approximately 58% certified through the Programme for the Endorsement of Forest Certification (Sustainable African Forest Assurance Scheme \u003cspan citationid=\"CR121\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Forest certification schemes have similar goals related to responsible pesticide-use which includes the need to avoid the use of highly hazardous pesticides, reduce and, where possible, eliminate the use of pesticides (\u003cb\u003eFSC 2017\u003c/b\u003e, Sustainable African Forest Assurance Scheme \u003cspan citationid=\"CR121\" class=\"CitationRef\"\u003e2024\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe SA forestry industry has a mandate to ensure that all activities conducted within forest plantations preserve and protect environmental values\u0026mdash;both aquatic and terrestrial\u0026mdash;and safeguard the wellbeing of people working or living within plantations, as well as those affected by plantation practices, such as downstream water users \u003cb\u003e(Forestry South Africa (FSA) 2019\u003c/b\u003e). Since pesticides are chemical compounds with a potential to cause harm, it is imperative that relevant data is available to guide responsible pesticide use and/or the application of risk mitigation (where necessary) (Ndlovu et al. \u003cspan citationid=\"CR80\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Ndlovu et al. (\u003cspan citationid=\"CR80\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), in a study evaluating environmental fate studies of pesticides relevant to the SA forestry industry, found that no studies have been implemented within SA forest plantations to understand the impact of the SA forestry pesticide use to the environment and human health. The study found that numerous pesticide environmental fate studies have been carried out in forest plantations abroad and in the SA agricultural industry (Ndlovu et al. \u003cspan citationid=\"CR80\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Although these studies provide insights into the environmental fate and risk posed by pesticide use, the observations made and/or conclusions from these studies cannot be readily transferable to the SA forestry landscape due to differences in climatic and physiographic conditions, pesticides used and pesticide-use patterns (rates, methods and frequencies) (Ndlovu et al. \u003cspan citationid=\"CR80\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe purpose of this field-based study was therefore to determine the environmental fate of pesticides within SA forest plantations, as used operationally, and the risk posed by their use to non-target environments and human health. This study covered two components: (1) the soil fate of pesticides and the risk posed by their use to non-target soil organisms; and (2) the aquatic fate of pesticides and the risk posed by their use to non-target aquatic organisms and human health. This paper presents the soil fate component which studies the persistence and potential leaching (vertical movement) of pesticides in soil. Pesticide in this study refers to the active ingredient, and not the pesticide product formulation. As no previous research had been conducted on the environmental fate (soil and water) and risk of pesticides used under typical operational practice within SA forest plantations (Ndlovu et al. \u003cspan citationid=\"CR80\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), a benchmark study which would represent a \u0026lsquo;worst-case scenario\u0026rsquo; for environmental contamination by pesticides was preferred.\u003c/p\u003e"},{"header":"2. Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1 Study location and site characteristics\u003c/h2\u003e\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eThe field study was carried out at Natal Co-operative Timbers\u0026rsquo; (NCT) Ingwe Farm in the KwaZulu-Natal (KZN) Midlands, South Africa (29˚24'S; 30˚06'E). A 16.6 hectare (ha) compartment was selected as the trial site, situated within a 386 ha drainage basin in the Lions River Water Management Unit of the Umngeni Catchment (Warburton et al. \u003cspan citationid=\"CR140\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). The site was located within a warm temperate summer rainfall region, with an altitude range between 1 165 meters and 1 210 meters above sea level (m a.s.l.), an MAT of 16˚C and MAP between 976 to 1 024 mm. Although rain can occur throughout the year, most of the precipitation occurs during spring/summer thunderstorm events (September to March). Dolerite (approximately\u0026thinsp;\u0026gt;\u0026thinsp;90%) and shale were the dominant geologies (Heathman \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e1994\u003c/span\u003e), with humic ferralsol as the main soil form. The site was previously planted with \u003cem\u003eEucalyptus smithii\u003c/em\u003e R.T. Baker at a density of 1 667 stems per hectare, managed on a 10-year pulpwood rotation. The stand was clearfelled in August 2019 and subsequently replanted with seedlings of the same species and at the same density in January/February 2020. The study site was considered representative of typical SA forestry climatic and soil conditions, as well as the commonly planted genus and intended end-product. The site also represented a worst-case scenario for environmental contamination by pesticides since: (1) it was established on an ex-eucalypt stand meaning more herbicides would be required to kill the stumps of the previous rotation; (2) burning was the harvest residue management method employed; (3) the study was completed over a period of 24 months, covering the period from pre-plant to canopy closure. This is considered the period of the most intensive pesticide application in forest plantations; and (4) pesticides were intentionally the only intervention or method used to manage pests and pathogens.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003ePrior to planting, harvest residues from the previous rotation were windrowed within every fifth row along contours and then burned on 20 November 2019. This is a common practice in SA forest plantations (Ross \u003cspan citationid=\"CR99\" class=\"CitationRef\"\u003e2004\u003c/span\u003e). Following the prescribed burn a wild fire occurred on the site on 30 November 2020. The prescribed burn and wild fire resulted in minimal organic matter (OM) remaining on the site (0.73 tons ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e of harvest residues post fire events), creating a worst-case scenario for environmental contamination as OM can mitigate or minimize the risk of pesticides leaching down the soil profile (Garrett et al. \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2015\u003c/span\u003e) and pesticide runoff from the site (Cawson et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2012\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe physical characteristics of the site (e.g. slope, aspect, soil type and depth) were evaluated prior to strategically establishing four sample plots (40x20 m plot\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) that were representative of the study area (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). These four sample plots formed the main sampling units for further site description (pH, soil texture, organic carbon (OC), and bulk density) and subsequent soil sampling for investigating or quantifying the persistence of any pesticide (active ingredients) following their application to the soil, and potential to leach down the soil profile. All pesticide applications were completed within a day or two (in the case of cypermethrin at planting) within the four sample plots whereas pesticide application over the whole site occurred over numerous days and sometimes over a couple of weeks due to the manual nature of the work and limited labour force. This paper will present pesticide applications and findings specific to the four sample plots (Tables\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e and \u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eAn iWeather\u0026reg; automatic weather station (AWS) (iWeather SA, 26 Brick Rd, George Industria, George, 6536, SA) was installed approximately 450 m from the trial site to record temperature, wind speed, wind direction, rainfall, vapour pressure deficit, humidity, solar radiation and evapotranspiration. Data was recorded at 10-minute intervals and summarised daily. The rain gauge of the AWS experienced periodic technical faults. Substitute rainfall data was obtained daily after rainfall events from a funnel rain gauge approximately 370 m from the trial site. Refer to \u003cb\u003eOnline Resource 1\u003c/b\u003e for a summary of the weather data recorded throughout the study period.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2 Pesticide application\u003c/h2\u003e\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eDepending on the pesticide and rationale for application, pesticides were applied either as a broadcast spray and/or broadcast spray with planted trees protected with cones, or over the top of the planted trees, or within the planting pit (a manually prepared planting hole 25 cm wide and 25 cm deep made prior to planting the seedlings) (Tables\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e and \u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). All pesticides were applied manually using a 16 L Matabi knapsack backsprayer, with the exception of the insecticide applied at planting which was directly poured into the planting hole (within the planting pit). All pesticides were applied according to label recommendations, and as per standard operational practice for SA forest plantations.\u003c/p\u003e\u003cp\u003eFor each pesticide application, the quantity of product used (and volumes of water used) within each sample plot and for trial site was recorded (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). From this the quantity of a.i. applied could be determined on a sample plot and hectare\u003csup\u003e-1\u003c/sup\u003e basis.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003ePre-plant broadcast herbicide application\u003c/strong\u003e\u003cp\u003eOn 21 January 2020 the four soil plots received a broadcast pre-plant spray with the non-selective herbicide glyphosate (Roundup WeatherMAX\u0026reg;, glyphosate at 660 g a.i. L\u003csup\u003e-1\u003c/sup\u003e, Bayer, 27 Wrench Road, Isando, 1600, SA ) and selective herbicide triclopyr (Triclon\u0026reg;, triclopyr at 480 g a.i. L\u003csup\u003e-1\u003c/sup\u003e, Arysta LifeScience, 7 Sunbury Office Park, La Lucia Park, La Lucia Ridge, 4019, SA ) to ensure the site was free of competing vegetation prior to the planting of seedlings (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Glyphosate and triclopyr were applied at 7.9 and 1.32 kg ha\u003csup\u003e-1\u003c/sup\u003e over the four plots (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The combined glyphosate/triclopyr treatment targeted the vigorous coppicing of the stumps remaining from harvest and the high glyphosate rate was necessary for the control of \u003cem\u003eRubus cuneifolius\u003c/em\u003e Pursh. (bramble).\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003cem\u003eInsecticides for soil-borne pests at planting: Eucalyptus smithii\u003c/em\u003e seedlings were planted on 22 and 23 January 2020. Each seedling received 1 L of water which was poured into the planting pit immediately prior to the placement of the seedling thereafter covering the pit with soil (known in SA as puddle planting). To prevent damage to the seedlings from soil-borne pests, 1.25 ml of the insecticide Kemprin\u0026reg; 200 EC (cypermethrin at 200 g a.i. L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, Arysta LifeScience, 7 Sunbury Office Park, La Lucia Park, La Lucia Ridge, 4019, SA), at a rate of 0.42 kg ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, was incorporated into each 1 L water (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003cstrong\u003ePost-planting herbicide application\u003c/strong\u003e\u003cp\u003eFor the short-term suppression of grasses and some broadleaf weed seeds, a pre-emergent herbicide metazachlor (Claw\u0026reg; 500 EC, metazachlor at 500 g a.i. L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, Arysta LifeScience, 7 Sunbury Office Park, La Lucia Park, La Lucia Ridge, 4019, SA), at a rate of 1.0 kg a.i. ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, was applied as a banded 1 m line spray (0.5 m on either side of the tree) over the planted seedlings (24 January 2020) (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Although some of the herbicide was intercepted by the newly planted seedlings, most was evenly distributed over the soil within this 1 m swathe.\u003c/p\u003e\u003c/p\u003e\u003cp\u003eTo prevent interspecific competition, the weeds on the trial site were controlled on two more occasions (14 May 2020 and 13 November 2020) (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). In May 2020, glyphosate (Roundup WeatherMAX\u0026reg;, glyphosate at 540 g a.i. L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, Bayer, 27 Wrench Road, Isando, 1600, SA) was applied at 2.16 kg ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and triclopyr (Triclon\u0026reg;), was applied at 0.79 kg ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, in a broadcast spray operation (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The seedlings were protected by inverted cones during this operation, known as a coning vegetation management operation or broadcast coning spray operation in SA forest plantations. The operators did apply additional herbicide to woody weeds and coppice regrowth to ensure improved cover and hence control. As such, higher amounts of herbicide were applied in areas with more woody weeds and it is expected that herbicide runoff off from the foliage to the soil will be higher than the rest of the inter- and intra-row. In May 2020, the site had minimal vegetation, with \u003cem\u003eEucalyptus\u003c/em\u003e coppice constituting the main vegetation type controlled.\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eIn November 2020 the coppice regrowth was inadvertently removed (manually by labourers using machetes). As such only glyphosate (Roundup WeatherMAX\u0026reg;) was applied as a broadcast coning spray for the November 2020 weeding event at 2.81 kg a.i. ha\u003csup\u003e-1\u003c/sup\u003e (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003ePost-planting insecticide and fungicide application\u003c/strong\u003e\u003cp\u003eDue to high seedling mortality (41.9% in February and 28.9% in October 2020) dead seedlings were replaced (blanking) in February to April and October 2020, with the total cypermethrin applied, over the 16.6 ha trial site, being 2.9 kg a.i. ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 2 kg a.i. ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e in February to April and October 2020, respectively (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The seedlings were replanted in a similar manner as they were planted in January 2020 \u0026ndash; puddle planting with 1.25 ml Kemprin\u0026reg; added to the 1 L of water. Following blanking, nursey tags were placed around the seedlings that were replaced. This was to prevent the sampling of planting pits that had received more than one application of cypermethrin. Nevertheless, due to frequent rainfall events most of the tags got washed away.\u003c/p\u003e\u003c/p\u003e\u003cp\u003eAlthough only limited numbers of \u003cem\u003eGonipterus\u003c/em\u003e spp. larvae and adults were observed on the site and no other pathogens observed, to fulfil the study objectives to assess the environmental fate of all pesticides that may be used during re-establishment, an insecticide and fungicide were applied to the foliage of the trees (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). These were applied in early summer, the time of year when climatic conditions become conducive to an increase in insect pest and pathogen incidence. On the 12 November 2020, a tank-mix containing cypermethrin (Kemprin\u0026reg; 200 EC) at a rate of 0.02 kg a.i. ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e as well as and the fungicides azoxystrobin and tebuconazole (Custodia\u0026reg; 320 SC, azoxystrobin and tebuconazole at 120 and 200 g a.i. L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, ADAMA, 99 Jip de Jager Drive, Belville, 7530, SA) were manually applied as a banded 1 m line spray (0.5 m on either side of the tree) over the planted seedlings. Azoxystrobin and tebuconazole were applied at 0.1 and 0.2 kg ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eDetails of pesticide application in a trial investigating the environmental fate of pesticides in South African forest plantations. Soil sample plot area\u0026thinsp;=\u0026thinsp;800 m\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"8\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePesticide application operation\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eDate of operation\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eActive ingredient (a.i.)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePesticide (a.i.) applied plot\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Values within bracket shows the amount of product\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eWater volume (L ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eTargeted rate of application for the trial site\u003c/p\u003e\u003cp\u003e(kg a.i. ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003eMean application rate ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for sample plots (kg a.i. ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) (standard deviation)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c8\"\u003e\u003cp\u003eActual rate of application for trial site\u003c/p\u003e\u003cp\u003e(kg a.i. ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"7\" rowspan=\"8\"\u003e\u003cp\u003ePre-plant:\u003c/p\u003e\u003cp\u003eWeed management spray (broadcast application)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\" morerows=\"7\" rowspan=\"8\"\u003e\u003cp\u003e21/01/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003eglyphosate (660 g a.i. L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 1: 693.0 g (1.05 L)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\" morerows=\"7\" rowspan=\"8\"\u003e\u003cp\u003e404.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e3\u0026ndash;5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e7.9 (0.06)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e5.85\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 2: 640.2 g (0.97 L)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 3: 646.8 g (0.98 L)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 4: 547.8 g (0.83 L)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c3\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003etriclopyr (480 g a.i. L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 1: 120.0 g (0.250 L)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e\u0026ndash;\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e1.32 (0.01)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e0.97\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 2: 101.3 g (0.211 L)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 3: 107.5 g (0.224 L)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 4: 93.6 g (0.195 L)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003eAt planting:\u003c/p\u003e\u003cp\u003eSoil-borne insect pests management (within planting pit)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e22\u0026amp;23/01/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003ecypermethrin (200 g a.i. L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 1: 33.0 g (0.165 L)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e1667\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e0.01\u0026ndash;0.02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e0.42 (0.001)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e0.41\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 2: 32.0 g (0.160 L)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 3: 34.6 g (0.173 L)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 4: 34.8 g (0.174 L)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003eAt planting:\u003c/p\u003e\u003cp\u003ePre-emergent weed management spray (line spray)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e24/01/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003emetazachlor (500 g a.i. L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 1: 102.5 g (0.205 L)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e105.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e0.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e1.0 (0.02)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e0.56\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 2: 77.5 g (0.155 L)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 3: 74.5 g (0.149 L)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 4: 67.0 g (0.134 L)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBlanking (replacement of dead seedlings)\u003csup\u003e1\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e02/2020\u0026ndash;04/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003ecypermethrin (200 g a.i. L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e2.9\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"7\" rowspan=\"8\"\u003e\u003cp\u003ePost-plant:\u003c/p\u003e\u003cp\u003eWeed management (broadcast coning operation)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\" morerows=\"7\" rowspan=\"8\"\u003e\u003cp\u003e14 May 2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003eglyphosate (540 g a.i. L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 1: 137.3 g (0.208 L)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\" morerows=\"7\" rowspan=\"8\"\u003e\u003cp\u003e239\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003eVaries dependent upon on vegetation type and abundance\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e2.16 (0.03)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e1.62\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 2: 159.7 g (0.242 L)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 3: 185.5 g (0.281 L)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 4: 208.6 g (0.316 L)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c3\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003etriclopyr (480 g a.i. L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 1: 49.9 g (0.104 L)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003eVaries dependent upon on vegetation type and abundance\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e0.79 (0.01)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e0.59\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 2: 58.1 g (0.121 L)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 3: 67.7 g (0.141 L)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 4: 75.8 g (0.158 L)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBlanking (replacement of dead seedlings)1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e10/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003ecypermethrin (200 g a.i. L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e2.0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"11\" rowspan=\"12\"\u003e\u003cp\u003ePost-plant:\u003c/p\u003e\u003cp\u003eFoliar insect pests and disease management (line spray)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\" morerows=\"11\" rowspan=\"12\"\u003e\u003cp\u003e12 Nov 2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003ecypermethrin (200 g a.i. L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 1: 1.2 g (0.006 L)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\" morerows=\"11\" rowspan=\"12\"\u003e\u003cp\u003e109.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e0.01\u0026ndash;0.02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e0.02 (0.0002)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e0.02\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 2: 1.2 g (0.006 L)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 3: 1.6 g (0.008 L)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 4: 1.6 g (0.008 L)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c3\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003eazoxystrobin (120 g a.i. L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 1: 7.4 g (0.062 L)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e0.06\u0026ndash;0.12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e0.10 (0.001)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e0.10\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 2: 6.8 g (0.057 L)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 3: 9.1 g (0.076 L)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 4: 9.0 g (0.075 L)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c3\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003etebuconazole (200 g a.i. L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 1: 12.4 g (0.062 L)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e0.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e0.17 (0.002)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e0.16\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 2: 11.4 g (0.057 L)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 3: 15.2 g (0.076 L)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 4: 15.0 g (0.075 L)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003ePost-plant:\u003c/p\u003e\u003cp\u003eWeed management (broadcast coning operation)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e13 Nov 2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003eglyphosate (540 g a.i. L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 1: 194.7 g (0.295 L)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e221.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003eVaries dependent upon on vegetation type and abundance\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e2.81 (0.05)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e2.28\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 2: 235.0 g (0.356 L)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 3: 293.7 g (0.445 L)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePlot 4: 175.6 g (0.266 L)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"8\"\u003e\u003csup\u003e1\u003c/sup\u003eBlanking (replacement of dead seedlings) occurred over 16.6 ha.\u003csup\u003e2\u003c/sup\u003eThis was calculated by dividing the total active ingredient quantities applied (derived from the total product applied) by the trial area (16.6 ha). Pesticide applications within the trial site were completed over several days and sometimes weeks, whereas in the four sample plots applications were completed within a day or two (as was for the cypermethrin application at planting)\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3 Soil sampling for pesticide analysis\u003c/h2\u003e\u003cp\u003eSoil sampling commenced prior to the application of any pesticides for the new rotation (12 August 2019) and extended over 24 months (until 12 August 2021) with a total of 12 sampling events carried out over the study period. To understand pesticide-specific persistence sampling was planned to occur at the following periods: \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\frac{DT50\\:\\left(days\\right)}{2}\\)\u003c/span\u003e\u003c/span\u003e; \u0026#119863;\u0026#119879;50 (\u0026#119889;\u0026#119886;\u0026#119910;\u0026#119904;); and \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:DT50+\\:\\left(\\frac{DT50\\:\\left(days\\right)}{2}\\right)\\)\u003c/span\u003e\u003c/span\u003e, following pesticide application. DT\u003csub\u003e50\u003c/sub\u003e indicates the time taken for 50% of the initial dose to degrade/dissipate (Navarro et al. \u003cspan citationid=\"CR79\" class=\"CitationRef\"\u003e2007\u003c/span\u003e). The DT\u003csub\u003e50\u003c/sub\u003e values for each pesticide are listed in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eFor each pesticide (active ingredient), three soil sampling events were initially planned following its application. However, since some pesticides were analyzed using the same procedures, additional analyses were possible beyond the originally planned three. Although the degradation of tebuconazole and azoxystrobin are different, due to budget constraints tebuconazole soil sampling and analysis was carried out based on the degradation period of azoxystrobin. While soil sampling for each pesticide at the proposed periods was not always feasible, sampling occurred as close to the proposed time as was possible (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eAn additional soil sample was taken from the pit at 568 DAT to determine whether cypermethrin was still detectable months following its last application. This was especially important since pesticide analysis results showed that cypermethrin levels in the pit did not reach undetectable levels at the third soil sampling event (that is, at 33 to 34 days after the first application of cypermethrin within the pit at planting) and there were additional cypermethrin applications during blanking events.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eSoil sampling for pesticide analysis in a trial investigating the environmental fate of pesticides in South African forest plantations\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"8\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOperation\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eActive ingredient\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eDT\u003csub\u003e50\u003c/sub\u003e (days)\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eApplication date\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003ePlanned sampling\u003csup\u003e3\u003c/sup\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eActual soil sampling date\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003eDays after treatment\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c8\"\u003e\u003cp\u003eSampling point\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePre-pesticide application\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e12/09/2019\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eWithin interrow\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"5\" rowspan=\"6\"\u003e\u003cp\u003ePre-plant:\u003c/p\u003e\u003cp\u003eWeed management spray\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003eglyphosate\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003e23.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003e21/01/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e02/02/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003eWithin interrow\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e24\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e14/02/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e24\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e36\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e25/02/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e35\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003etriclopyr\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003e30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003e21/01/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e02/02/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003eWithin interrow\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e14/02/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e24\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e45\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e25/02/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e35\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003eAt planting:\u003c/p\u003e\u003cp\u003eSoil-borne insect pest management (at planting)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003ecypermethrin\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e22.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e22\u0026amp;23/01/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e02/02/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e10\u0026ndash;11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003eWithin pit\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e22\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e14/02/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e22\u0026ndash;23\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e33\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e25/02/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e33\u0026ndash;34\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e12/08/2021*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e567\u0026ndash;568\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"7\" rowspan=\"8\"\u003e\u003cp\u003ePost-plant:\u003c/p\u003e\u003cp\u003ePre-emergent weed management spray\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\" morerows=\"7\" rowspan=\"8\"\u003e\u003cp\u003emetazachlor\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\" morerows=\"7\" rowspan=\"8\"\u003e\u003cp\u003e6.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\" morerows=\"7\" rowspan=\"8\"\u003e\u003cp\u003e24/01/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e27/01/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003eWithin pit\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNo samples taken\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eNo samples taken\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e02/02/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e9\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e14/02/2020*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e21\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\" morerows=\"4\" rowspan=\"5\"\u003e\u003cp\u003eWithin interrow\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e25/02/2020*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e32\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e26/11/2020*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e307\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e08/12/2020*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e319\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e17/12/2020*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e328\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBlanking (replacement of dead seedlings)\u003csup\u003e1\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ecypermethrin\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e22.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e02/2020 to 04/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"8\" rowspan=\"9\"\u003e\u003cp\u003ePost-plant:\u003c/p\u003e\u003cp\u003eWeed management (coning operation)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003eglyphosate\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003e23.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003e14/05/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e29/05/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003eWithin interrow\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e24\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e12/06/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e29\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e36\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e29/06/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e46\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\" morerows=\"5\" rowspan=\"6\"\u003e\u003cp\u003etriclopyr\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\" morerows=\"5\" rowspan=\"6\"\u003e\u003cp\u003e30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\" morerows=\"5\" rowspan=\"6\"\u003e\u003cp\u003e14/05/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e29/05/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\" morerows=\"5\" rowspan=\"6\"\u003e\u003cp\u003eWithin interrow\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e12/06/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e29\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e45\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e29/06/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e46\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e26/11/2020*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e196\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e08/12/2020*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e208\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e17/12/2020*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e217\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBlanking (replacement of dead seedlings)\u003csup\u003e1\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ecypermethrin\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e22.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e10/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"5\" rowspan=\"6\"\u003e\u003cp\u003ePost-plant:\u003c/p\u003e\u003cp\u003eFoliar insect pests and disease management\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003ecypermethrin\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003e22.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003e12/11/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e26/11/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e13\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003eWithin interrow\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e22\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e08/12/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e25\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e33\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e17/12/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e35\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003eazoxystrobin \u0026amp; tebuconazole\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003e78 \u0026amp; 47.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003e12/11/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e39\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e17/12/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e35\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003eWithin interrow\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e78\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e02/02/2021\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e81\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e117\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e09/03/2021\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e117\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003ePost-plant:\u003c/p\u003e\u003cp\u003eWeed management (coning operation)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003eglyphosate\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003e23.79\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003e13/11/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e26/11/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e14\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003eWithin interrow\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e24\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e08/12/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e24\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e36\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e17/12/2020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e34\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003csup\u003e1\u003c/sup\u003eBlanking (replacement of dead seedlings) occurred over the 16.6 ha.\u003c/p\u003e\u003cp\u003e\u003csup\u003e2\u003c/sup\u003eLewis KA, Tzilivakis J, Warner D, Green A. 2016. An international database for pesticide risk assessments and management. \u003cem\u003eHuman and Ecological Risk Assessment: An International Journal\u003c/em\u003e 22: 1050\u0026ndash;1064.\u003c/p\u003e\u003cp\u003e\u003csup\u003e3\u003c/sup\u003eDays after treatment\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003e*Additional soil sampling events\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eSamples were collected from within the pit, or interrow depending on how the pesticide was applied (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Each of the four sample plots were divided into four quadrants, with soil samples obtained from three quadrants at each sampling event, thus leaving one quadrant undisturbed. An area of 0.1 m\u003csup\u003e2\u003c/sup\u003e was first cleared of any slash and/or litter, with samples collected at two depths (0 to 10 cm and 10 to 50 cm) using graduated stainless-steel cores. When sampling soil within the planting pit three seedlings were randomly selected within a quadrant. Previously sampled pits were avoided on subsequent sampling events. During earlier sampling events (February 2020) it was easier to identify planting pits that were sampled in previous events as the soil sampling \u0026lsquo;hole\u0026rsquo; was still evident. Also, during earlier sampling events the nursey tags showing blanked/replanted were still in place. As such, blanked trees were not sampled.\u003c/p\u003e\u003cp\u003eThe sampling depths were chosen to assess pesticide persistence in the topsoil (0 to 10 cm) and the potential for leaching into the subsoil (10 to 50 cm). At each soil sampling event a total of 48 individual soil samples were collected. Since soil properties can be more variable within topsoil soil layers compared to subsoil layers, a higher number of soil samples were collected within the topsoil compared to the subsoil. In each of the four sample plots, a total of nine topsoil (three from each quadrant) and three subsoil (one from each quadrant) samples were collected plot\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and combined to form two composite samples (one topsoil and one subsoil sample plot\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e). These were placed on ice in a cooler box before decanted into sealed 100 ml amber glass bottles and stored in a refrigerator at 4˚ C (\u003cb\u003eUnited States Environmental Protection Agency (US EPA) 2007\u003c/b\u003e). The samples were transported overnight (chilled) to Bureau Veritas M \u0026amp; L Laboratory Services (40 Modulus Rd, Ormonde, 2091, Johannesburg, SA) for pesticide analysis.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.4 Pesticide extraction and analysis\u003c/h2\u003e\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003ePesticide extraction and analysis in soil samples was carried out using the QueCHERs method based on EN 15662 for pesticide extraction and clean-up (European Standards \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Following the use of QueCHERs glyphosate, triclopyr, tebuconazole and azoxystrobin were analyzed using Liquid Chromatography\u0026ndash;Mass Spectrometry (LC-MS) whereas cypermethrin and metazachlor were analyzed using Gas Chromatography\u0026ndash;Mass Spectrometry (GC-MS). Detection limits were 0.01 mg kg\u003csup\u003e-1\u003c/sup\u003e for all pesticides analysed in soil and pesticide recoveries were between 70 to 120%.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003e2.5 Risk posed by pesticides to non-target soil organisms\u003c/h2\u003e\u003cp\u003eThe potential risk posed by pesticide use to non-target soil organisms was assessed by comparing the measured pesticide concentrations in soil to toxicity values derived for standard soil ecotoxicity test species (like earthworms) and/or concentrations reported to impact soil microbial functioning. To approximate a worst-case scenario, the 97th percentile concentrations were used rather than mean pesticide concentrations. The 97th percentile concentrations were calculated using a formula by Rumsey (\u003cspan citationid=\"CR103\" class=\"CitationRef\"\u003e2011\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e. In this study, the 97th percentile concentration coincided with the maximum pesticide concentration observed across the four sample plots, at each sampling event.\u003c/p\u003e\u003cp\u003eAlthough various species (such as \u003cem\u003eCollembola\u003c/em\u003e spp.) can be used to evaluate the risk posed by pesticides to non-target soil organisms, this study predominantly used pesticide ecotoxicity data derived for earthworms. Earthworms are the most studied soil organisms in pesticide ecotoxicity (Gunstone et al. \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) and are more sensitive to pesticides tested in this study compared to \u003cem\u003eCollembola\u003c/em\u003e spp. (Lewis et al. \u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Standard soil ecotoxicity values were obtained mainly from the Pesticide Properties Database (PPDB) (Lewis et al. \u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e2016\u003c/span\u003e. \u003cb\u003eOnline Resources 2\u0026ndash;4\u003c/b\u003e) and any observations made in literature, especially in field studies.\u003c/p\u003e\u003cp\u003eAlthough there is a large amount of pesticide toxicology data (of many tiers) available, the PPDB was consulted since it an extensive, open-access, database with consolidated pesticide risk data from a wide range of sources (\u003cb\u003eOnline Resources 2\u0026ndash;4\u003c/b\u003e, Lewis et al. \u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e2016\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eIn addition, toxicity exposure ratios (TERs), which are widely used in pesticide ecotoxicology studies as indicators of the risk posed by pesticides to non-target soil organisms, were calculated to assess the potential ecotoxicity risk (European Commission \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2002\u003c/span\u003e, Mu et al. \u003cspan citationid=\"CR77\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Toxicity exposure ratios were calculated for short-term or acute (using the LC\u003csub\u003e50\u003c/sub\u003e concentration of the most sensitive soil organism) and long-term or chronic (using the No Observed Effects Concentration (NOEC)) exposure risk. LC50 and NOEC values were sourced from the PPDB (\u003cb\u003eOnline Resources 2\u0026ndash;4\u003c/b\u003e). Pesticides are considered high risk if the TER is below the trigger value of 10 for acute and 5 for chronic exposure (European Commission \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2002\u003c/span\u003e). Worst-case TERs were calculated by using 97th percentile pesticide concentrations measured in the topsoil (0 to 10 cm). The use of worst-case 97th percentile pesticide concentrations, especially for calculating TER (chronic), is precautionary since non-target soil organisms are unlikely to be exposed to the measured (topsoil) 97th percentile pesticide concentrations for extended periods because of pesticide dissipation over time.\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:TER\\:\\left(acute\\right)\\frac{LC50\\:of\\:the\\:most\\:sensitive\\:soil\\:organism\\:(mg/kg)}{Measured\\:concentration\\:of\\:the\\:pesticide\\:in\\:soil\\:(mg/kg)\\:}$$\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Equb\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equb\" name=\"EquationSource\"\u003e\n$$\\:TER\\:\\left(chronic\\right)\\frac{NOEC\\:of\\:the\\:most\\:sensitive\\:soil\\:organism\\:(mg/kg)}{Measured\\:concentration\\:of\\:the\\:pesticide\\:in\\:soil\\:(mg/kg)\\:}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\n \u003ch2\u003e3.1 Soil characteristics\u003c/h2\u003e\n \u003cp\u003eThe soils on the site were acidic (pH (KCl): 4 to 5.8) and clayey in texture (topsoil and subsoil), with bulk density ranging between 1.08 to 1.48 g cm\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e (Table \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e). Organic carbon (OC) was higher in the topsoil (0 to 10 cm) (average OC in 0 to 10 cm soil depth: 4.9%); compared with 3.5% for the 10 to 50 cm sub-soil depth) (Table \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\n \u003ch2\u003e3.2 Pesticide concentrations in soil and risk posed to non-target soil organisms\u003c/h2\u003e\n \u003cp\u003eBefore the trial commenced in August 2019, residual pesticide concentrations in soil samples from the previous rotation were below the detection limit (BDL) (\u0026lt;\u0026thinsp;0.01 mg kg⁻\u0026sup1;). Therefore, only pesticide concentrations in soil following application events from January 2020 onward are discussed.\u003c/p\u003e\n \u003cdiv id=\"Sec11\" class=\"Section3\"\u003e\n \u003ch2\u003e3.2.1 Herbicides\u003c/h2\u003e\n \u003cp\u003e\u003cem\u003e(i) Glyphosate\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003eGlyphosate concentrations were BDL (\u0026lt;\u0026thinsp;0.01 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) in all soil samples collected at 0 to 10 cm and 10 to 50 cm soil depths, irrespective of repeated applications over a period of varying climatic conditions. This finding is significant for the SA forestry industry, as glyphosate is the most widely used herbicide, accounting for 97% of total herbicide applications (Roberts et al. \u003cspan class=\"CitationRef\"\u003e2021\u003c/span\u003e). The results observed in this study may in part be due to the application of glyphosate during the summer rainfall period where runoff from rainfall events occurring soon after pesticide application are considered an important mode of pesticide transport from the site (Screpanti et al. \u003cspan class=\"CitationRef\"\u003e2005\u003c/span\u003e, Boithias et al. \u003cspan class=\"CitationRef\"\u003e2014\u003c/span\u003e). For example, following the January 2020 broadcast glyphosate application (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e), there was a cumulative rainfall total of 19.5 mm before the first soil sampling event (12 days after treatment (DAT), data not shown). Similarly, following the broadcast (coning) glyphosate application in November 2020 (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e), there was a cumulative total of 38.4 mm before the first soil sampling event (14 DAT, data not shown), possibly resulting in the movement of majority of glyphosate from the soil prior to sampling.\u003c/p\u003e\n \u003cp\u003eIt is also possible that some glyphosate leached down preferential flow paths in the soil profile due to the presence of root channels from previous rotations. Reviews by Vereecken (\u003cspan class=\"CitationRef\"\u003e2005\u003c/span\u003e\u003cstrong\u003e) and Borggard and Gimsing (2008)\u003c/strong\u003e on glyphosate environmental fate and leaching in agricultural soils and soils under multiple land-use suggest that leaching risk is higher in well-structured, macroporous soils, particularly when rainfall occurs soon after application. However, in this study, glyphosate dissipation via leaching is likely minimal. This is because many pesticide-fate studies conducted within forest plantations have reported negligible leaching of glyphosate in forestry soils (Roy et al. \u003cspan class=\"CitationRef\"\u003e1989\u003c/span\u003e, Feng and Thompson \u003cspan class=\"CitationRef\"\u003e1990\u003c/span\u003e, Newton et al. \u003cspan class=\"CitationRef\"\u003e1994\u003c/span\u003e, Thompson et al. \u003cspan class=\"CitationRef\"\u003e2000\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eLeaching and runoff are not the only plausible explanations for the rapid dissipation or undetectable levels of glyphosate observed in this study, as even with minimal rainfall following glyphosate application that occurred in May 2020 (\u003cstrong\u003eOnline Resource 1\u003c/strong\u003e), concentrations remained below the detection limit. No rainfall occurred between the May 2020 application of glyphosate (1.62 kg ha⁻\u0026sup1;) and the first two soil sampling events (15 and 29 DAT). A total of 7.5 mm was recorded at 35 DAT, with no further rainfall until the third sampling event at 46 DAT.\u003c/p\u003e\n \u003cp\u003eRapid dissipation of glyphosate following application has been reported in numerous publications (such as Roy et al. \u003cspan class=\"CitationRef\"\u003e1989\u003c/span\u003e, Veiga et al. \u003cspan class=\"CitationRef\"\u003e2001\u003c/span\u003e, Guijarro et al. \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e). Glyphosate environmental fate studies conducted in South America and Europe have reported DT\u003csub\u003e50\u003c/sub\u003e values in the range of 8.6 to 17.5 days (Screpanti et al. \u003cspan class=\"CitationRef\"\u003e2005\u003c/span\u003e, Simonsen et al. \u003cspan class=\"CitationRef\"\u003e2008\u003c/span\u003e, Guijarro et al. \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e). Glyphosate dissipation is mainly through microbial pathways (Sviridov et al. \u003cspan class=\"CitationRef\"\u003e2015\u003c/span\u003e, Singh et al. \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e) with warm and moist conditions increasing the rate of microbial activity (Bento et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e, Silva et al. \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e). The low glyphosate concentration levels detected following the January 2020 and November 2020 applications may have also been due to warm summer temperatures (mean daily temperatures for January/February: 18˚C; November/December 2020: 17˚C), and high moisture contents (total rain for January/February 2020: 264.1 mm; November/December 2020: 236.2 mm) (\u003cstrong\u003eOnline Resource 1\u003c/strong\u003e) facilitating rapid breakdown.\u003c/p\u003e\n \u003cp\u003e\u003cem\u003e(ii) Triclopyr\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003eFollowing the broadcast pre-plant herbicide application in January 2020 (Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e), triclopyr was detected in soil samples taken after application on three occasions in February 2020 \u003cstrong\u003e(\u003c/strong\u003eFig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e) in both the 0 to 10 cm and 10 to 50 cm depth, with the concentrations at 10 to 50 cm sampling depth consistently lower (Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e). Rapid triclopyr dissipation occurred during the January/February 2020 period (Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e), with triclopyr concentrations below detectable levels at 35 DAT in all but one of the 10 to 50 cm depth soil samples (Plot 2\u0026thinsp;=\u0026thinsp;0.02 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e). Concentrations in samples collected at 0 to 10 cm remained above the detection limit, albeit at a 97th percentile concentration of 0.122 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eFollowing the second triclopyr and glyphosate application in May 2020 (Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e), triclopyr residues were again detected in all soil samples collected at the 0 to 10 and 10 to 50 cm soil depth (Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e). Similar to the January 2020 pre-plant operation, triclopyr residues were consistently lower within the 10 to 50 cm soil sampling depth (Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e). Overall, triclopyr concentrations in soil samples collected shortly after the May 2020 broadcast coning event were higher (9.433 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) than triclopyr concentrations recorded in February 2020 (1.495 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) after the January 2020 application, despite the lower application rate (1.32 kg a.i. ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e vs 0.79 kg a.i. ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e).\u003c/p\u003e\n \u003cp\u003eTriclopyr residues were below the detection limit in all soil samples collected at 0 to 10 cm and 10 to 50 cm at 196, 208 and 217 days after the last application of triclopyr on 14 May 2020. The only exception was a 0 to 10 cm soil sample in Plot 1 (at 196 days), which had a concentration of 0.035 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003eTriclopyr residues are often detected in soils following triclopyr application (Johnson et al. \u003cspan class=\"CitationRef\"\u003e1995\u003c/span\u003e). Thompson et al. (\u003cspan class=\"CitationRef\"\u003e2000\u003c/span\u003e) reported triclopyr in soil following its application in an Acadian Forest (Canada). The peak concentrations reported by Thompson et al. (\u003cspan class=\"CitationRef\"\u003e2000\u003c/span\u003e) were, however, higher than those found in this study (11.72 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e versus maximum 97th percentile concentration of 9.433 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e in this study). The differences were possibly due to the higher application rate applied in the study by Thompson et al. (\u003cspan class=\"CitationRef\"\u003e2000\u003c/span\u003e) (3.98 kg ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e versus the 1.32 and 0.79 kg a.i. ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e used in this study).\u003c/p\u003e\n \u003cp\u003eMicrobial breakdown and photodegradation are the main degradation pathways for triclopyr in soil (Ganapathy \u003cspan class=\"CitationRef\"\u003e1997\u003c/span\u003e, Tu et al. \u003cspan class=\"CitationRef\"\u003e2001\u003c/span\u003e). The rapid degradation of triclopyr following the broadcast pre-plant application (January 2020) could be a result of the warm, moist conditions that occurred during the summer months (\u003cstrong\u003eOnline Resource 1\u003c/strong\u003e), and the increased duration and intensity of sunlight facilitating rapid microbial degradation and photodegradation (Tu et al. \u003cspan class=\"CitationRef\"\u003e2001\u003c/span\u003e, Sanchez-Bayo and Hyne \u003cspan class=\"CitationRef\"\u003e2011\u003c/span\u003e\u003cstrong\u003e)\u003c/strong\u003e.\u003c/p\u003e\n \u003cp\u003eTotal rainfall following the 21 January 2020 herbicide application to 25 February 2020 (last soil sampling event, 35 DAT) was 114.8 mm compared to 7.5 mm received between 14 May (day of herbicide application) and 29 June 2020 (day of soil sampling at 46 DAT). In a review comparing the fate of pesticides in tropical and non-tropical environments Sanchez-Bayo and Hyne (\u003cspan class=\"CitationRef\"\u003e2011\u003c/span\u003e\u003cstrong\u003e)\u003c/strong\u003e indicated that rainfall events contribute to the dissipation of pesticides in soil (through runoff). Similarly, Berisford et al. (\u003cspan class=\"CitationRef\"\u003e2006\u003c/span\u003e) reported higher triclopyr persistence during periods with reduced rainfall. They hypothesized that the lower degradation rates were associated with lower microbial activity due to reduced available soil moisture (Berisford et al. \u003cspan class=\"CitationRef\"\u003e2006\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eDuring the first spraying event (broadcast pre-plant treatment), herbicides were evenly sprayed over the entire area, whereas some localised (more intense) application of herbicide occurred during the treatment of woody weeds (including coppice regrowth) during the second spraying event (broadcast coning event). Although not measured, it is possible that soils during the May/June 2020 sampling were collected from these areas with potentially higher herbicide concentrations.\u003c/p\u003e\n \u003cp\u003eDespite the lower triclopyr application rate in May 2020 (0.79 vs. 1.32 kg a.i. ha⁻\u0026sup1; in January) (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e), soil triclopyr concentrations were higher than those detected after the January 2020 broadcast pre-plant spray. This could be attributed to a combination of factors, including: (1) the cumulative effect of both applications. It is possible that residues from the January application had not fully degraded by the time of the May treatment, resulting in elevated concentrations due to accumulation; (2) reduced rainfall; (3) lower temperatures; and (4) the manner in which the herbicides were applied.\u003c/p\u003e\n \u003cp\u003eThe movement of triclopyr down the soil profile was expected as triclopyr is considered moderately mobile (water solubility of 440 mg L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) (\u003cstrong\u003eOnline Resource 2\u003c/strong\u003e, Lewis et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e), with previous studies testing triclopyr on different textured soils and/or properties recording vertical mobility (Stephenson et al. \u003cspan class=\"CitationRef\"\u003e1990\u003c/span\u003e, Newton et al. \u003cspan class=\"CitationRef\"\u003e1990\u003c/span\u003e, Johnson et al. \u003cspan class=\"CitationRef\"\u003e1995\u003c/span\u003e). Similar to this study, most studies reported lower triclopyr concentrations in soil lower down the profile compared with the topsoil concentrations (Stephenson et al. \u003cspan class=\"CitationRef\"\u003e1990\u003c/span\u003e, Newton et al. \u003cspan class=\"CitationRef\"\u003e1990\u003c/span\u003e, Johnson et al. \u003cspan class=\"CitationRef\"\u003e1995\u003c/span\u003e, Berisford et al. \u003cspan class=\"CitationRef\"\u003e2006\u003c/span\u003e). Berisford et al. (\u003cspan class=\"CitationRef\"\u003e2006\u003c/span\u003e) compared the persistence and leaching of four herbicides (including triclopyr applied at 3.5 kg ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) on four sites with variable soil properties. They concluded that, although mobile, triclopyr at the levels detected in their study (\u0026lt;\u0026thinsp;6 \u0026micro;g L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) was unlikely to leach to concentrations which would be considered detrimental to aquatic species (\u003cem\u003eDaphni\u003c/em\u003ea O.E Miller; bluegill sunfish (\u003cem\u003eLepomis macrochirus\u003c/em\u003e Rafinesque, rainbow trout (\u003cem\u003eOncorhynchus mykiss\u003c/em\u003e Walbaum)), or render water unsafe for drinking.\u003c/p\u003e\n \u003cp\u003e\u003cem\u003eEcotoxicity of triclopyr within the soil environment\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003eTriclopyr concentrations in soil of the present study (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e) were \u0026gt;\u0026thinsp;100-fold lower than the acute LC\u003csub\u003e50\u003c/sub\u003e concentrations for earthworms (\u003cstrong\u003eOnline Resource 2\u003c/strong\u003e, Lewis et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e). Studies investigating the use of triclopyr in North American forest plantations with higher application rates and slower dissipation/degradation rates than in this SA study indicate that triclopyr as currently used (mostly aerial application of triclopyr at rates between 1.65 to 3.98 kg a.i. ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) is unlikely to be of concern (such as Newton et al. \u003cspan class=\"CitationRef\"\u003e1990\u003c/span\u003e, Stephenson et al. \u003cspan class=\"CitationRef\"\u003e1990\u003c/span\u003e, Thompson et al. \u003cspan class=\"CitationRef\"\u003e2000\u003c/span\u003e). This is because the reported triclopyr residues in soil were consistently below concentrations considered detrimental to soil organisms (\u0026lt;\u0026thinsp;100 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) (Newton et al. \u003cspan class=\"CitationRef\"\u003e1990\u003c/span\u003e, Stephenson et al. \u003cspan class=\"CitationRef\"\u003e1990\u003c/span\u003e, Thompson et al. \u003cspan class=\"CitationRef\"\u003e2000\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eBusse et al. (\u003cspan class=\"CitationRef\"\u003e2004\u003c/span\u003e) tested the influence of three herbicides, including triclopyr applied at 4.5 and 9 kg a.i. ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, on soils with differing clay and OM contents on ectomycorrhizae of conifer species. Observations made three to four months after herbicide application, indicated no impact to soil microbial biomass and activity. Souza-Alonso et al. (\u003cspan class=\"CitationRef\"\u003e2013\u003c/span\u003e) investigated the impact of triclopyr as a spot application on the soil microbial community (enzymatic activity and soil respiration) and native species diversity in a \u003cem\u003ePinus pinaster\u003c/em\u003e Aiton forest in Spain. Over the initial six-month sampling period, no significant differences in soil microbial responses were detected between the control treatment and triclopyr treated plots (total quantity of a.i. ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e not specified). However, there was evidence of changes in bacterial community structure at one year, but the bacterial richness, density, and diversity were not impacted (Souza-Alonso et al. \u003cspan class=\"CitationRef\"\u003e2015\u003c/span\u003e). They also detected no changes in the fungal community over the same sampling period.\u003c/p\u003e\n \u003cp\u003eNolte and Fulbright (\u003cspan class=\"CitationRef\"\u003e1997\u003c/span\u003e\u003cstrong\u003e)\u003c/strong\u003e investigated plant, small mammal, and avian diversity following the use of a mixture of picloram and triclopyr (each applied at 1.9 kg a.i. ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) for the control of honey mesquite (\u003cem\u003eProsopis glandulosa\u003c/em\u003e Torr.) in humid, subtropical Texas. They observed no difference in plant and vertebrate species richness between herbicide treated plots and control plots over a two-year period.\u003c/p\u003e\n \u003cp\u003eAccording to the calculated TERs, triclopyr concentrations at the trial site posed a low acute risk to non-target soil organisms (Table \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e\u003cstrong\u003e).\u003c/strong\u003e However, a high chronic exposure risk was identified \u003cstrong\u003e(\u003c/strong\u003eTable \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e). A TER below the relevant trigger value signals a need for further testing such as conducting field tests to determine the ecological significance of the exposure to the pesticide identified as a high exposure risk pesticide (European Commission \u003cspan class=\"CitationRef\"\u003e2002\u003c/span\u003e). Nevertheless, since short- and long-term field studies have indicated that triclopyr effects to soil organisms are negligible (such as Potter et al. \u003cspan class=\"CitationRef\"\u003e1990\u003c/span\u003e, Busse et al. \u003cspan class=\"CitationRef\"\u003e2004\u003c/span\u003e, Souza-Alonso et al. \u003cspan class=\"CitationRef\"\u003e2013\u003c/span\u003e) the same result is expected within SA forest plantations and therefore further testing is not a priority.\u003c/p\u003e\n \u003ctable id=\"Tab4\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003ePesticide toxicity exposure ratios (TERs) for acute and chronic exposure risk of non-target soil organisms in a trial investigating the environmental fate of pesticides in South African forest plantations. Values in bold represent values below the trigger value of 10 for acute risk exposure and 5 for chronic risk exposure\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003ePesticide\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMaximum 97th percentile pesticide concentrations (mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) at 0\u0026ndash;10 cm depth\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eTER (acute)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eTER (chronic)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eglyphosate\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026lt;\u0026thinsp;0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e560 000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2 131\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003etriclopyr\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e9.43\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e55.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.6\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003emetazachlor\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.97\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e83.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.4\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ecypermethrin (soil applied)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.37\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e22.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e1.2\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ecypermethrin (foliar applied)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026lt;\u0026thinsp;0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e10 000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e530\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eazoxystrobin\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6 910.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e73.2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003etebuconazole\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.09\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e15 293.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e110.7\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003e\u003cem\u003e(iii) Metazachlor\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003eFollowing the application of the pre-emergent herbicide metazachlor (at 1.0 kg ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) as a 1 m line spray (centered on tree rows) in January 2020, the active ingredient was detected in all soil samples up to 32 DAT (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e). Concentrations of metazachlor were higher in the 0 to 10 cm soil depth than at 10 to 50 cm soil depth (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e). Despite a single application at planting, metazachlor was still detected at 307 DAT in the 0 to 10 cm soil samples, albeit at a low 97th percentile concentration of 0.087 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (data not shown). At subsequent sampling events (319 and 328 DAT) concentrations in all samples were BDL (\u0026lt;\u0026thinsp;0.01 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e).\u003c/p\u003e\n \u003cp\u003eIn a study investigating the differences in dissipation of metazachlor (0.5 kg a.i. ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) and clomazone (0.096 kg a.i. ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) under field and laboratory conditions in Greece, Szpyrka et al. (\u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e) also reported metazachlor residues in the topsoil following application. Although the study had a similar application rate and similar soil texture to this study, Szpyrka et al. (\u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e) reported lower metazachlor concentrations (range of average concentrations at 0 to 20 cm of 0.05 to 0.52 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) compared to the current study (range of concentrations at 0 to 10 cm of 1.597 and 5.974 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e). This was possibly due to the dilution effect of increasing sample depth. Concentrations in Szpyrka et al. (\u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e) were less than 0.1 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e after 30 days of application. More rapid dissipation was expected in the present study compared to the Szpyrka et al. (\u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e) study due to a combination of the high rainfall following application, clay textured soils, and higher levels of OM (range\u0026thinsp;=\u0026thinsp;3.63 to 5.25% compared to 0.87% for the Greece study), especially as high clay and OM content facilitate increased metazachlor degradation (Mamy et al. \u003cspan class=\"CitationRef\"\u003e2005\u003c/span\u003e, Sadowski et al. \u003cspan class=\"CitationRef\"\u003e2012\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eIt is also possible that the differences in metazachlor dissipation between the present study and that reported by Szpyrka et al. (\u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e), could in part be related to the prevailing temperatures over the sampling period. Temperatures ranged from 12 to 27˚C, which were higher than those recorded in this study in the first 34 days after metazachlor application (13 to 22˚C). Increased soil temperatures result in a more rapid breakdown of metazachlor (Mantzos et al. \u003cspan class=\"CitationRef\"\u003e2016a\u003c/span\u003e), with Walker and Brown (\u003cspan class=\"CitationRef\"\u003e1985\u003c/span\u003e\u003cstrong\u003e)\u003c/strong\u003e recording a reduction in metazachlor half-life from 77 to 29.2 to 11.6 days with an increase in soil temperature from 5 to 15 to 25\u0026deg;C (at a constant humidity of 12% w/w).\u003c/p\u003e\n \u003cp\u003eHowever, microbial degradation is a main pathway of metazachlor degradation (Mamy et al. \u003cspan class=\"CitationRef\"\u003e2005\u003c/span\u003e), with slower degradation rates observed in cooler winter months (Rouchaud et al. \u003cspan class=\"CitationRef\"\u003e1992\u003c/span\u003e). Detectable levels of metazachlor in the months following application in this study were likely due to slower degradation rates over the winter period (April/May to August/September).\u003c/p\u003e\n \u003cp\u003eDespite being relatively mobile (water solubility of 450 mg L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) (\u003cstrong\u003eOnline Resource 2\u003c/strong\u003e, Lewis et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e), in laboratory and field studies metazachlor was observed to exhibit limited vertical movement in soil (European Food Safety Authority \u003cspan class=\"CitationRef\"\u003e2017\u003c/span\u003e, Jurs\u0026iacute;k et al. \u003cspan class=\"CitationRef\"\u003e2019\u003c/span\u003e). The results in this study are consistent with observations reported by Mantzos et al. (\u003cspan class=\"CitationRef\"\u003e2016a\u003c/span\u003e) where metazachlor residues were lower in subsoil layers. Mamy et al. (\u003cspan class=\"CitationRef\"\u003e2008\u003c/span\u003e) \u003cstrong\u003eand\u003c/strong\u003e Mantzos et al. (\u003cspan class=\"CitationRef\"\u003e2016a\u003c/span\u003e) reported increased vertical movement of metazachlor in the presence of preferential flow paths or during intense rainfall events, especially if these occurred shortly following metazachlor application (Włodarczyk \u003cspan class=\"CitationRef\"\u003e2014\u003c/span\u003e). In the present study, the vertical movement of metazachlor could have been facilitated by the presence of preferential flow paths through root channels still present from previous crops, together with diffusion that likely occurred following the rainfall event of 12 mm, two days following metazachlor application.\u003c/p\u003e\n \u003cp\u003e\u003cem\u003eEcotoxicity of metazachlor within the soil environment\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003eMetazachlor concentrations in this study were below the threshold of 7.5 mg kg⁻\u0026sup1;, which is reported to have no significant impact on soil microorganisms (such as nitrogen and carbon mineralization) and below the LC\u003csub\u003e50\u003c/sub\u003e value (500 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) for earthworms (Lewis et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e, \u003cstrong\u003eOnline Resource 2\u003c/strong\u003e). Beulke and Malkomes (\u003cspan class=\"CitationRef\"\u003e2001\u003c/span\u003e\u003cstrong\u003e)\u003c/strong\u003e studied the effects of metazachlor in a laboratory on the soil microflora and degradation and adsorption of metazachlor under different temperature and soil conditions. They found that metazachlor applied at 1.5 kg ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e inhibited dehydrogenase activity (indicator of microbial biomass) and substrate-induced short-term respiration (indicator of potentially active soil microbial biomass) but stimulated nitrogen mineralisation. The degree of inhibition was more pronounced in soils incubated at 20˚C than those incubated at 30˚C (although not statistically significant). Due to the lower application rates used in SA forestry, metazachlor impacts on soil microorganisms are likely to be lower or insignificant.\u003c/p\u003e\n \u003cp\u003eA greenhouse pot trial by Gyamfi et al. (\u003cspan class=\"CitationRef\"\u003e2002\u003c/span\u003e) reported minor impacts of metazachlor (application rate of 1 kg a.i.) on eubacterial and \u003cem\u003ePseudomonas\u003c/em\u003e rhizosphere community structures. Eubacterial and \u003cem\u003ePseudomonas\u003c/em\u003e communities play a key role in soil fertility and thus plant growth, and the breakdown of environmental pollutants in soil (such as pesticides) (Ahmad and Malloch \u003cspan class=\"CitationRef\"\u003e1995\u003c/span\u003e, Mandelbaum et al. \u003cspan class=\"CitationRef\"\u003e1995\u003c/span\u003e, Kriete and Broer \u003cspan class=\"CitationRef\"\u003e1996\u003c/span\u003e\u003cstrong\u003e)\u003c/strong\u003e. Their study showed that the impacts of metazachlor on eubacterial and \u003cem\u003ePseudomonas\u003c/em\u003e communities were short-lived, with negative impacts detected at 42 days after application, but not at 104 days (Gyamfi et al. \u003cspan class=\"CitationRef\"\u003e2002\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eMetazachlor accounts for less than 2% of herbicides used within SA forestry (Roberts et al. \u003cspan class=\"CitationRef\"\u003e2021\u003c/span\u003e), however, to ascertain protection and preservation of key soil microorganism communities in areas where the herbicide is used, field testing of the effects of metazachlor on non-target soil organisms under conditions relevant to SA forest plantations is recommended. This is important since metazachlor was persistent on the site, the maximum 97th percentile concentrations (5.974 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) were above the chronic NOEC of \u0026gt;\u0026thinsp;2.31 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and the calculated chronic TER in this study identified a possible high risk of exposure to non-target soil organisms (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec12\" class=\"Section3\"\u003e\n \u003ch2\u003e3.2.2 Insecticides\u003c/h2\u003e\n \u003cp\u003e\u003cem\u003e(i) Cypermethrin\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003eCypermethrin within the planting pits was detected at both the 0 to 10 and 10 to 50 cm sampling depths up to 568 DAT (Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e) and was regarded as persistent as it was detected 10 months after the last application in October 2020 (that is, on soil samples taken on 12 August 2021 (568 DAT). Cypermethrin concentrations within the soil decreased marginally between 11 DAT and 34 DAT (Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e) but increased at both soil depths 568 DAT (Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eFollowing the foliar application of cypermethrin in November 2020, for the management of foliar insect pests, cypermethrin concentrations in all soil samples collected at 13, 25 and 35 DAT were consistently BDL. The soil samples collected to determine cypermethrin concentrations following foliar application were taken along the tree lines where cypermethrin was sprayed (not within the planting pit as with samples collected after the application of cypermethrin into the planting pit for the management of soil-borne insect pests).\u003c/p\u003e\n \u003cp\u003eThe high cypermethrin concentration reported at 568 DAT in soil samples collected in the planting pit were most likely a function of sampling from planting pits that had been replanted. Early tree growth across the site was variable, with some degree of difficulty in terms of separating the replanted (blanked) versus the original seedlings, especially at the later sampling dates. As a relatively high number of plants were replanted, resulting in three times the quantity of cypermethrin in these pits, it is likely that soil samples (at 568 DAT) were also taken from these pits. It is unlikely that the foliar application of cypermethrin caused the increase in concentrations in planting pits at 568 DAT given that post-application samples were BDL.\u003c/p\u003e\n \u003cp\u003eAcross a range of application rates tested under varying soil and climatic conditions in field studies, foliar-applied cypermethrin has been shown to dissipate rapidly in soil following application (Battu et al. \u003cspan class=\"CitationRef\"\u003e2009\u003c/span\u003e; Mukherjee et al. \u003cspan class=\"CitationRef\"\u003e2012\u003c/span\u003e; Mantzos et al. \u003cspan class=\"CitationRef\"\u003e2016b\u003c/span\u003e). For example, in a study carried out in chilli (\u003cem\u003eCapsicum annuum\u003c/em\u003e L.) fields in Ludhiana (India) where cypermethrin and chlorpyrifos were applied at 15-day intervals and at rates higher than those in the current study (0.05 and 0.1 kg a.i. ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e versus 0.02 kg a.i. ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), Jyot et al. (\u003cspan class=\"CitationRef\"\u003e2013\u003c/span\u003e) found that fifteen days following the last of three applications, cypermethrin concentrations in 0 to 15 cm soil samples were BDL of 0.01 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Although selected soil properties were reported (sand\u0026thinsp;=\u0026thinsp;78%; silt\u0026thinsp;=\u0026thinsp;10.2%; clay\u0026thinsp;=\u0026thinsp;11.8%; pH\u0026thinsp;=\u0026thinsp;8; OC\u0026thinsp;=\u0026thinsp;0.3%), no weather data was provided, nor were possible reasons given for this rapid dissipation (Jyot et al. \u003cspan class=\"CitationRef\"\u003e2013\u003c/span\u003e). In another study, Mohapatra (\u003cspan class=\"CitationRef\"\u003e2014\u003c/span\u003e\u003cstrong\u003e)\u003c/strong\u003e investigated the fate of foliar applied cypermethrin (and chlorpyrifos) applied twice, at two-week intervals, at two rates (0.25 and 0.5 kg a.i. ha\u003csup\u003e\u0026minus;\u0026thinsp;1)\u003c/sup\u003e on a sandy loam (OC\u0026thinsp;=\u0026thinsp;0.4%) pomegranate cultivated research field in Bangalore, India. Cypermethrin concentrations were BDL limit (\u0026lt;\u0026thinsp;0.05 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) in 0 to 15 cm soil samples after one month.\u003c/p\u003e\n \u003cp\u003eThe slower degradation of cypermethrin in the soil pits could be attributed to a combination of: 1) lack of sunlight exposure; 2) higher application rates (0.42 versus 0.02 kg a.i. ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for foliar application); 3) repeated applications of cypermethrin in planting pits; 4) reduced likelihood of surface runoff following rainfall events; and 5) the high clay (\u0026gt;\u0026thinsp;40%) and OC (2.18 to 5.25%) content. There is consensus within the literature that due to the high adsorption affinity of cypermethrin (\u003cstrong\u003eOnline Resource 3\u003c/strong\u003e), dissipation is slower in soils with high levels of OM and/or clay (Chapman and Harris \u003cspan class=\"CitationRef\"\u003e1981\u003c/span\u003e, Cycoń and Piotrowska-Seget \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eIn addition to hydrolysis and microbial degradation, photolysis is also considered an important dissipation pathway for cypermethrin in soil (Takahashi et al. \u003cspan class=\"CitationRef\"\u003e1985\u003c/span\u003e; Class \u003cspan class=\"CitationRef\"\u003e1992\u003c/span\u003e; Raikwar and Nag \u003cspan class=\"CitationRef\"\u003e2006\u003c/span\u003e). Rafique and Tariq (\u003cspan class=\"CitationRef\"\u003e2015\u003c/span\u003e\u003cstrong\u003e)\u003c/strong\u003e reported a photodegradation half-life of 0.64 hours for alpha-cypermethrin (a compound closely related to cypermethrin) under laboratory conditions. Chai and Zaidel (\u003cspan class=\"CitationRef\"\u003e2011\u003c/span\u003e\u003cstrong\u003e)\u003c/strong\u003e concluded that differences in cypermethrin dissipation rates observed at three sites in Malaysia were due to differences in the amount and intensity of sunlight recorded. Therefore, any cypermethrin on, or near the soil surface, or on leaves, following foliar application in this study may have been exposed to and broken down by solar radiation and/or sunlight.\u003c/p\u003e\n \u003cp\u003eStudies by Jin and Webster (\u003cspan class=\"CitationRef\"\u003e1998\u003c/span\u003e\u003cstrong\u003e) and\u003c/strong\u003e Gu et al. (\u003cspan class=\"CitationRef\"\u003e2008\u003c/span\u003e) reported faster soil dissipation at lower cypermethrin application rates compared to higher doses, possibly due to the inhibitory effects of higher concentrations on microbial communities (Eneyi et al. \u003cspan class=\"CitationRef\"\u003e2021\u003c/span\u003e). In addition to the higher application rate, the soil-applied treatment was concentrated over a smaller area (planting pits of 25\u0026times;25 cm), whereas the foliar application was distributed over a 1 m swathe. Consequently, soil microorganisms in treated pits were exposed to higher concentrations, potentially inhibiting their ability to degrade the pesticide efficiently.\u003c/p\u003e\n \u003cp\u003eAlthough cypermethrin adsorbs strongly to soil, some can be transported off-site during rainfall events (Jergentz et al. \u003cspan class=\"CitationRef\"\u003e2005\u003c/span\u003e). As a cumulative total of 33.5 mm of rain occurred within nine days of the foliar cypermethrin application, it is possible that runoff could have also contributed to the rapid dissipation following application.\u003c/p\u003e\n \u003cp\u003eCypermethrin has been found to exhibit limited vertical movement (leaching) in soils with variable properties (Sakata et al. \u003cspan class=\"CitationRef\"\u003e1986\u003c/span\u003e, Chai and Zaidel \u003cspan class=\"CitationRef\"\u003e2011\u003c/span\u003e, Rani et al. \u003cspan class=\"CitationRef\"\u003e2014\u003c/span\u003e, Mantzos et al. \u003cspan class=\"CitationRef\"\u003e2016b\u003c/span\u003e). This has been attributed to the hydrophobic nature and high adsorption affinity (\u003cem\u003eKoc\u003c/em\u003e of 307 558 ml g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) of cypermethrin (\u003cstrong\u003eOnline Resource 3\u003c/strong\u003e, Lewis et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e). In the present study, however, cypermethrin residues were detected at the 10 to 50 cm soil depth, in all soil samples collected from within the planting pit (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e). The detection of cypermethrin at the lower soil depth (10 to 50 cm) may not necessarily be as a result of leaching but could be attributed to the application method. Cypermethrin was applied into the planting pit, to a depth of approximately 25 cm. Therefore, soil collected for determining the fate of cypermethrin at 10 to 50 cm by default contained and/or incorporated soil initially contaminated by cypermethrin. It is therefore difficult to determine whether cypermethrin moved below the 25 cm depth at which it was applied.\u003c/p\u003e\n \u003cp\u003e\u003cem\u003eEcotoxicity of cypermethrin within the soil environment\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003eNo field-based studies on the influence of cypermethrin on soil functioning could be cited, as such use was made of laboratory studies to interpret the environmental risk likely to be posed by cypermethrin use within SA forest plantations.\u003c/p\u003e\n \u003cp\u003eMost studies have found that cypermethrin enhances soil biota enzymatic activities (such as Xie et al. \u003cspan class=\"CitationRef\"\u003e2009\u003c/span\u003e, Butt \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e). A laboratory-based study investigating the impact of insecticides (including cypermethrin) on soil enzymatic activity (dehydrogenase and protease) found a directly proportional positive relationship between cypermethrin-dose (2.5 kg a.i. ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e up to 10 kg a.i. ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) and enzymatic activity (Rangaswamy et al. \u003cspan class=\"CitationRef\"\u003e1994\u003c/span\u003e). The impact was, however, short-lived as no stimulation was observed beyond day 30. Application rates within the study by Rangaswamy et al. (\u003cspan class=\"CitationRef\"\u003e1994\u003c/span\u003e) were higher than those applied within the present study. Under laboratory conditions, Gundi et al. (\u003cspan class=\"CitationRef\"\u003e2005\u003c/span\u003e) testing three insecticides (including cypermethrin) applied alone or in combination, found that cypermethrin (applied on its own as an aqueous solution added to soil) in concentrations ranging from 5 to 25 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e of soil significantly stimulated (p\u0026thinsp;\u0026le;\u0026thinsp;0.05) populations of bacteria, fungi, and dehydrogenase activity measured at day 10 and 20 after insecticide application. Nevertheless, at day 30 after application, population levels and dehydrogenase in the control and insecticide amended soils returned to levels observed at the beginning of the study. Cypermethrin levels in soil reported by Gundi et al. (\u003cspan class=\"CitationRef\"\u003e2005\u003c/span\u003e) were again higher than levels observed in the current study (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eThe calculated TERs have demonstrated a possible chronic exposure risk to cypermethrin (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e). Since numerous studies show that the impacts of cypermethrin are short-lived (as is evident in studies conducted by Rangaswamy et al. (\u003cspan class=\"CitationRef\"\u003e1994\u003c/span\u003e), Gundi et al. (\u003cspan class=\"CitationRef\"\u003e2005\u003c/span\u003e), \u003cstrong\u003eTedaja et al. (2015)\u003c/strong\u003e) further testing of the impact of cypermethrin to non-target organisms is not a priority for soil ecotoxicity. This especially since the concentrations leading to the potential for chronic risk stem from a spot soil application of cypermethrin at planting (that is application into the pit). As such, only a small proportion of the total planted area is treated (an area of approximately 1% of a hectare). Moreover, owing to its high adsorption coefficient (Katayama et al. \u003cspan class=\"CitationRef\"\u003e2010\u003c/span\u003e) it is likely that the bioavailability of cypermethrin residues will be reduced under field conditions. However, field studies would need to confirm the bioavailability or lack thereof, and therefore the actual impact of cypermethrin in soil for extended periods as recorded in this study.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec13\" class=\"Section3\"\u003e\n \u003ch2\u003e3.2.3 Fungicides\u003c/h2\u003e\n \u003cp\u003eNo information could be cited relating to the soil fate of azoxystrobin and tebuconazole when applied in a forestry context. As such, use was made of literature mainly from agriculture and laboratory studies.\u003c/p\u003e\n \u003cp\u003e\u003cem\u003e(i) Azoxystrobin\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003eFollowing the application of azoxystrobin (applied at 0.10 kg a.i. ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) and tebuconazole (applied at 0.17 kg a.i. ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) in November 2020 as a foliar spray, azoxystrobin residues were detected only in soils collected at 0 to 10 cm and only at 35 DAT (0.042 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e). At 81 and 117 DAT azoxystrobin residues were BDL in all soil samples. The results in this study indicate that azoxystrobin has limited persistence and mobility under the tested soil and climatic conditions and use patterns.\u003c/p\u003e\n \u003cp\u003eA wide range of azoxystrobin DT\u003csub\u003e50\u003c/sub\u003e soil values have been reported from azoxystrobin fate studies conducted in the field and laboratory (DT\u003csub\u003e50\u003c/sub\u003e values ranging from 0.3 to 180.7 days) (such as Sope\u0026ntilde;a and Bending (\u003cspan class=\"CitationRef\"\u003e2013\u003c/span\u003e\u003cstrong\u003e)\u003c/strong\u003e, Herrero-Hernandez et al. (\u003cspan class=\"CitationRef\"\u003e2015\u003c/span\u003e), Edwards et al. (\u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e)). From literature, results suggest that in tropical, subtropical and warm temperate climates azoxystrobin dissipation is rapid with DT\u003csub\u003e50\u003c/sub\u003e values ranging from 4.9 to 26.9 days, irrespective of application rates (up to 2.02 kg a.i. ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e tested) and frequency of applications (up to five times at 15-day intervals) (as seen in \u003cstrong\u003eGajbhiye at el. 2011\u003c/strong\u003e, Huan et al. \u003cspan class=\"CitationRef\"\u003e2013\u003c/span\u003e, Wang et al. \u003cspan class=\"CitationRef\"\u003e2013\u003c/span\u003e, Hou et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e, Dubey et al. \u003cspan class=\"CitationRef\"\u003e2017\u003c/span\u003e, Wang et al. \u003cspan class=\"CitationRef\"\u003e2017\u003c/span\u003e, Saha et al. \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e). Photodegradation and microbial degradation are the main dissipation pathways of azoxystrobin in soils, hence the rapid dissipation in warmer climates (Purnama et al. \u003cspan class=\"CitationRef\"\u003e2015\u003c/span\u003e, Feng et al. \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e). It can therefore be expected that azoxystrobin applied within subtropical forestry regions of SA will dissipate more rapidly than observed in the present (warm temperate) study.\u003c/p\u003e\n \u003cp\u003eIn addition to the effects of photodegradation and microbial degradation, it is also possible that the rapid dissipation of azoxystrobin in the present study was facilitated by rainfall. A total of 33.5 mm of rain occurred within nine days of the fungicide application. In a study investigating the fate and transport of azoxystrobin (108.5 g ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) and propiconazole (93.8 g ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) in corn and soybean fields established in United States (Illinois), Edwards et al. (\u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e) found that rainfall (and thus runoff) occurring soon after azoxystrobin application in 2014 (within 12 hours, amount of rain not specified) contributed to reduced peak concentrations (concentrations\u0026thinsp;\u0026lt;\u0026thinsp;0.05 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) of azoxystrobin reported in soil.\u003c/p\u003e\n \u003cp\u003eStudies similar to the present study, have reported limited vertical movement (leaching) of azoxystrobin in soils, possibly due its low water solubility (6.7 mg L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) (\u003cstrong\u003eOnline Resource 4\u003c/strong\u003e, Lewis et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e). In a laboratory-based study aiming to understand the leaching of azoxystrobin, Dagar and Kumari (\u003cspan class=\"CitationRef\"\u003e2014\u003c/span\u003e\u003cstrong\u003e)\u003c/strong\u003e applied the fungicide at 50 and 100 \u0026micro;g in a sandy loam soil under continuous and discontinuous flow conditions. They found that more than 80% and 77.36% of azoxystrobin concentrations were retained in the top 10 cm of soil, respectively. Herrero-Hernandez et al. (\u003cspan class=\"CitationRef\"\u003e2015\u003c/span\u003e) also observed higher concentrations of azoxystrobin (data not specified) in the top 20 cm of the sandy clay loam soil following azoxystrobin application at 0.25 and 1.25 kg ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. No studies could be citied regarding leaching of azoxystrobin in clayey soils.\u003c/p\u003e\n \u003cp\u003eDespite the rapid degradation of azoxystrobin measured in the current study, these results cannot be readily extrapolated to all SA forestry sites as the fate of azoxystrobin is complex and is influenced by soil and climatic conditions. Although azoxystrobin is a non-ionic compound, soil pH plays a major role in the fate of azoxystrobin, together with the moisture status of the soil and OC content \u003cstrong\u003e(\u003c/strong\u003eSingh and Singh \u003cspan class=\"CitationRef\"\u003e2010\u003c/span\u003e\u003cstrong\u003e)\u003c/strong\u003e. Bending et al. (\u003cspan class=\"CitationRef\"\u003e2006\u003c/span\u003e) \u003cstrong\u003eand\u003c/strong\u003e Sope\u0026ntilde;a and Bending (\u003cspan class=\"CitationRef\"\u003e2013\u003c/span\u003e\u003cstrong\u003e)\u003c/strong\u003e observed more rapid azoxystrobin degradation under alkaline pH conditions. Organic matter or OC produces contrasting results for degradation of azoxystrobin, depending on the soil type. Singh and Singh (\u003cspan class=\"CitationRef\"\u003e2010\u003c/span\u003e) found that azoxystrobin was more persistent in compost-amended silt loams, whereas compost enhanced degradation in sandy loam soils.\u003c/p\u003e\n \u003cp\u003e\u003cem\u003eEcotoxicity of azoxystrobin within the soil environment\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003eGuo et al. (\u003cspan class=\"CitationRef\"\u003e2015\u003c/span\u003e) studied the effect of azoxystrobin on fungi, bacteria and actinomycetes biomass, on soil respiration and soil enzymatic activities in black soil (clay loam; OC: 2.65%; pH: 6.8), and found that azoxystrobin significantly reduced microbial communities, even at azoxystrobin soil concentrations of 0.1 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Han et al. (\u003cspan class=\"CitationRef\"\u003e2014\u003c/span\u003e) \u003cstrong\u003eand\u003c/strong\u003e Xu et al. (\u003cspan class=\"CitationRef\"\u003e2021\u003c/span\u003e) suggest that azoxystrobin is potentially toxic to earthworms in soil. Azoxystrobin caused oxidative stress and DNA damage, even at low concentrations of 0.1 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 1 mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (Han et al. \u003cspan class=\"CitationRef\"\u003e2014\u003c/span\u003e; Xu et al. \u003cspan class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eAzoxystrobin concentrations recorded in this study were lower than the levels reported to cause adverse effects in previous research (Han et al. \u003cspan class=\"CitationRef\"\u003e2014\u003c/span\u003e; Guo et al. \u003cspan class=\"CitationRef\"\u003e2015\u003c/span\u003e; Xu et al. \u003cspan class=\"CitationRef\"\u003e2021\u003c/span\u003e). Therefore, its use in SA forest plantations is not expected to result in significant environmental harm. Azoxystrobin also has relatively high acute LD\u003csub\u003e50\u003c/sub\u003e and EC\u003csub\u003e50\u003c/sub\u003e values for earthworms (\u0026ge;\u0026thinsp;42.0 mg a.i. kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e dry weight of natural soil) (Wang et al. \u003cspan class=\"CitationRef\"\u003e2012\u003c/span\u003e; Leit\u0026atilde;o et al. \u003cspan class=\"CitationRef\"\u003e2014\u003c/span\u003e; Lewis et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e), and the calculated TER values are well above trigger values (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003e\u003cem\u003e(ii) Tebuconazole\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003eFollowing the application of tebuconazole in November 2020 as a foliar spray (Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e), tebuconazole residues were detected only in soils collected at 0 to 10 cm (Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e). Tebuconazole concentrations were BDL in all soil samples collected at 117 DAT. The results in this study show tebuconazole as being persistent in soils, but having limited mobility under the tested soil, climatic conditions and use patterns.\u003c/p\u003e\n \u003cp\u003eTebuconazole has a high adsorption affinity (\u003cem\u003eKoc\u003c/em\u003e of 1 035.16 ml g-1) (\u003cstrong\u003eOnline Resource 4\u003c/strong\u003e) and strongly adsorbs to clay and OM (\u003cstrong\u003eFAO 1994\u003c/strong\u003e, Čadkov\u0026aacute; et al. \u003cspan class=\"CitationRef\"\u003e2013\u003c/span\u003e, Tchaikovskaya et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e). Tebuconazole has been reported to exhibit limited vertical movement (leaching) \u003cstrong\u003e(FAO 1994)\u003c/strong\u003e, which supports the observations in the present study. Approximately 80% of tebuconazole residues were found at the 0 to 5 cm soil depth in a laboratory-based study by Aldana et al. (\u003cspan class=\"CitationRef\"\u003e2011\u003c/span\u003e) investigating the leaching behaviour of tebuconazole and oxadyxil in soil (OC: 2.35%; clay: 35.39%) (duration of the study not specified). A tebuconazole fate field study carried out in La Rioja (Spain) on a sandy clay loam soil (OC: 1.31%; clay: 17.1%) (application rates of 0.25 and 1.25 kg ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) found that throughout the study period (355 days), tebuconazole residues occurred predominately at the 0 to 10 cm depth (% and/or quantities not specified) compared to concentrations reported in the lower soil depth/s (up to 50 cm) \u003cstrong\u003e(\u003c/strong\u003eHerrero-Hern\u0026aacute;ndez et al. \u003cspan class=\"CitationRef\"\u003e2011\u003c/span\u003e). The risk of tebuconazole leaching is therefore negligible in soils with high clay and high OM content \u003cstrong\u003e(\u003c/strong\u003eG\u0026aacute;miz et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e). Although clay and OM are considered important for tebuconazole adsorption, other minerals in the soil can play an important role. For instance, Čadkov\u0026aacute; et al. (\u003cspan class=\"CitationRef\"\u003e2012\u003c/span\u003e) found that soil minerals such as ferrihydrite, birnessite, illite and goethite also adsorb tebuconazole. As such leaching might be countered in soils with low OM/low clay but high in other minerals.\u003c/p\u003e\n \u003cp\u003eThe persistence of tebuconazole in the present study was expected due to the high adsorption affinity and the nature of the dissipation pattern of tebuconazole. Adsorption and dissipation often show an inverse relationship \u003cstrong\u003e(\u003c/strong\u003eKah et al. \u003cspan class=\"CitationRef\"\u003e2007\u003c/span\u003e) as adsorbed pesticides are often unavailable for degradation and/or dissipation processes \u003cstrong\u003e(\u003c/strong\u003eKoskinen et al. \u003cspan class=\"CitationRef\"\u003e2001\u003c/span\u003e). Several studies have shown that tebuconazole exhibits a biphasic dissipation pattern in field and laboratory, meaning it undergoes initial rapid degradation and/or dissipation but as tebuconazole adsorption to mineral and organic surfaces increases over time, degradation and/or dissipation slows down thus leading to persistence (for instance as shown in Papadopoulou et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003e\u003cem\u003eEcotoxicity of tebuconazole within the soil environment\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003eFrom the few field-based studies that could be cited on the impact of tebuconazole to soil biota that were carried out across variable climatic and soil conditions and use patterns, it was found that the application of tebuconazole either causes no impact to soil biota, or if toxic impacts to soil biota do occur, their impacts are short-lived. For instance, Herrero-Hern\u0026aacute;ndez et al. (\u003cspan class=\"CitationRef\"\u003e2011\u003c/span\u003e) found that tebuconazole had no impact on soil dehydrogenase activity. In a study investigating the impacts of tebuconazole applied at 187.5 (Field rate (FR)), 375 (2xFR (2FR)) and 1 875 g a.i. ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (10xFR (10FR)) in subtropical Junagadh (India), Saha et al. (\u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e) reported that the FR and 2FR inhibited soil microbial parameters such as microbial biomass carbon, soil ergosterol and dehydrogenase activity. However, a recovery over time was observed. Microbial biomass recovered after 7 days and 15 days for the FR and 2FR, respectively. Soil ergosterol recovered after 15 days for the FR and 45 days for the 2FR, and at 60 days for dehydrogenase activity for both the FR and 2FR (Saha et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eThe calculated TERs showed a low acute and low chronic exposure risk of non-target soil organisms to tebuconazole (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e). It is therefore expected that tebuconazole, as used within SA forest plantations, will pose an insignificant risk to non-target soil organisms.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eThis study investigated the soil fate (persistence and vertical movement) of pesticides used within South African (SA) forest plantations and the risk posed by their use to non-target soil organisms. The study was implemented on a site considered representative of typical SA forestry environmental conditions.\u003c/p\u003e\u003cp\u003eThe most noteworthy result from this study was that glyphosate, the most important herbicide for the SA forestry industry which accounts for 97% of the total herbicide use by the industry, was below the detection limit (\u0026lt;\u0026thinsp;0.01 mg kg\u003csup\u003e-1\u003c/sup\u003e) in all soil samples collected over the study period. This, despite the repeated applications of glyphosate occurring across different seasons (summer and winter). The rapid degradation and the low risk posed to the soil organisms observed in this study is similar to conclusions obtained from literature regarding the use of glyphosate within forest plantations globally.\u003c/p\u003e\u003cp\u003eAzoxystrobin and foliar applied cypermethrin also degraded rapidly in the present study, possibly due to favourable conditions for photodegradation and microbial degradation. In contrast, triclopyr, tebuconazole, and especially metazachlor and soil applied cypermethrin, persisted for extended periods (\u0026gt;\u0026thinsp;90 days). This was possibly due to various factors such as: reduced microbial degradation in the cooler winter months; reduced sunlight exposure and thus photodegradation (for soil applied cypermethrin); and limited degradation due to high adsorption (tebuconazole and cypermethrin).\u003c/p\u003e\u003cp\u003eThe pesticides applied in this study showed limited vertical movement (thus low susceptibility to leaching). This was often associated with high adsorption coefficients and/or moderate to low water solubilities. The limited vertical movement observed is similar to observations made in other studies investigating the soil fate of the pesticides applied.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eAlthough pesticides can affect the homeostasis of the soil, the limited number of field-based studies and laboratory studies (mainly) reporting the impacts of pesticides to soil indicate that pesticide concentrations reported in this study posed a low risk to the soil environment. As pesticides are applied infrequently within SA forest plantations, any impacts that would occur to the soil environment as a result of their application are likely to be short-lived.\u003c/p\u003e\u003cp\u003eWhile these results are largely positive for the SA forestry industry, they should be interpreted with caution, as they are based on a single study conducted in one region over a single growing season. Additionally, this study does not account for the environmental fate of pesticide degradation products or their potential risks to non-target soil organisms. Furthermore, most importantly, it does not consider the additive, antagonistic, or synergistic effects of pesticide mixtures on non-target organisms as this aspect was beyond the scope of this study.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eAcknowledgements\u003c/p\u003e\n\u003cp\u003eThis study was conducted as part of Noxolo\u0026rsquo;s PhD research at Nelson Mandela University. NCT Forestry, the Timber Industry Working Group (through Forestry South Africa), the Fibre Processing and Manufacturing Sector Education and Training Authority and Nelson Mandela University are highly acknowledged for funding this work. NCT Forestry is also thanked for providing the land and labor used to complete the study.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eFunding\u003c/p\u003e\n\u003cp\u003eThis work was funded by NCT Forestry, the Timber Industry Working Group (through Forestry South Africa), the Fibre Processing and Manufacturing Sector Education and Training Authority and Nelson Mandela University.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;Author contribution\u003c/p\u003e\n\u003cp\u003eNdlovu N. prepared the manuscript, tables and figures. Rolando C., Baillie B., and Little K. all reviewed the manuscript, tables and figures.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAhmad I, Malloch D (1995) Interaction of soil microflora with the bioherbicide phosphinothricin. Agric Ecosyst Environ 54:165\u0026ndash;174.\u003c/li\u003e\n\u003cli\u003eAldana M, De Prado R, Mart\u0026iacute;nez MJ (2011) Leaching of oxadyxil and tebuconazole in Colombian soil. Commun. Agric. Appl. Biol. 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Ecol Econ 204:107630.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Table 3","content":"\u003cp\u003eTable 3 is available in the Supplementary Files section.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"new-forests","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"nefo","sideBox":"Learn more about [New Forests](http://link.springer.com/journal/11056)","snPcode":"11056","submissionUrl":"https://submission.nature.com/new-submission/11056/3","title":"New Forests","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"forest plantations, glyphosate, pesticide risk, pesticide-use, soil, South Africa","lastPublishedDoi":"10.21203/rs.3.rs-6886614/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6886614/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003ePesticides are used within forest plantations to manage the negative impacts caused by pests (including weeds) and pathogens. However, these chemicals have the potential to negatively affect the environment, including non-target soil organisms such as earthworms and microorganisms. It is therefore imperative that relevant pesticide environmental fate data is available to guide responsible pesticide use and/or the application of risk mitigation measures (where necessary). To this end, a 24-month field study, covering the period from pre-plant to canopy closure, was conducted to investigate the soil fate of commonly used pesticides in South African forest plantations and assess the risk they pose to non-target soil organisms. The trial was established in a \u003cem\u003eEucalyptus\u003c/em\u003e stand managed for pulpwood production in the KwaZulu-Natal Midlands, South Africa. Pesticides were applied at different stages of stand development according to standard operational practices. Pesticides (active ingredients) applied included glyphosate, triclopyr, metazachlor, cypermethrin, azoxystrobin, and tebuconazole. Following each application, soil samples were collected at pre-determined intervals (based on the DT₅₀ value of each pesticide) from two depths (0\u0026ndash;10 cm and 10\u0026ndash;50 cm) to evaluate persistence and leaching potential. The results were largely positive. Glyphosate, azoxystrobin, and foliar-applied cypermethrin degraded rapidly and posed a low risk to non-target soil organisms. While triclopyr, tebuconazole, metazachlor, and soil-applied cypermethrin persisted for more than 90 days, their concentrations either remained below risk thresholds or require further investigation to fully determine their ecological impact.\u003c/p\u003e","manuscriptTitle":"Understanding the environmental fate of pesticides in South African planted forests: Part 1 – concentrations of pesticides in soil and risk posed to non-target soil organisms","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-07 23:05:03","doi":"10.21203/rs.3.rs-6886614/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-11-12T14:43:47+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-11-05T02:03:14+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"220350005703530107918689947796463008804","date":"2025-10-23T15:42:23+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"22430101228216377612343447483962673371","date":"2025-08-05T13:41:57+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-08-05T13:16:55+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-06-25T16:21:37+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-06-18T11:20:02+00:00","index":"","fulltext":""},{"type":"submitted","content":"New Forests","date":"2025-06-13T08:56:21+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"new-forests","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"nefo","sideBox":"Learn more about [New Forests](http://link.springer.com/journal/11056)","snPcode":"11056","submissionUrl":"https://submission.nature.com/new-submission/11056/3","title":"New Forests","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"1f199124-de32-49d5-86e7-fd7ee5a3c8d5","owner":[],"postedDate":"August 7th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-02-09T16:00:48+00:00","versionOfRecord":{"articleIdentity":"rs-6886614","link":"https://doi.org/10.1007/s11056-026-10162-9","journal":{"identity":"new-forests","isVorOnly":false,"title":"New Forests"},"publishedOn":"2026-02-02 15:57:36","publishedOnDateReadable":"February 2nd, 2026"},"versionCreatedAt":"2025-08-07 23:05:03","video":"","vorDoi":"10.1007/s11056-026-10162-9","vorDoiUrl":"https://doi.org/10.1007/s11056-026-10162-9","workflowStages":[]},"version":"v1","identity":"rs-6886614","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6886614","identity":"rs-6886614","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}