Above and below-ground responses to contrasting soil phosphorus distribution by mungbean (Vigna radiata L.) cultivars with diverse phenology

Above and below-ground responses to contrasting soil phosphorus distribution by mungbean (Vigna radiata L.) cultivars with diverse phenology | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Above and below-ground responses to contrasting soil phosphorus distribution by mungbean (Vigna radiata L.) cultivars with diverse phenology Vijaya Singh, Marisa Collins, Mike Bell This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3508080/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background and Aim Deep placement of fertiliser has been providing strong productivity responses in rainfed cropping systems on Vertisols soils in north-eastern Australia. However, genotypic differences in root system architecture (RSA) can play an important role in response to various P rates and placement strategies. In this study we tested for genetic variation in RSA and its impact on the ability to exploit deep P bands among four contrasting, early to late maturing mungbean varieties. Methods Differences in soil P status and distribution were established by varying rates of applied P and the volume of soil P enrichment in shallow (top 5cm) and deeper (20-25cm) profile layers in root observation chambers. Intact RSA was measured in the top 30cm and bottom 30cm sections of the soil profile. Results Shallower placement of P fertiliser resulted in a wider root growth angle compared with other P treatments, whereas deeper placements resulted in greater mean root diameter and total root volume. Deep banding and deeper P-enriched sub layer treatments tended to advance the flowering and increased the mungbean pod yield for the more responsive early maturing var. Berken, without influencing the total root surface area, P uptake or shoot P concentration. This cultivar showed the lowest shoot P concentrations, least P uptake and greatest internal phosphorus use efficiency. Conclusion The varietal differences in RSA and root functioning played a major role in response to P placement strategies, where the strongest P response was observed with the deep P band fertiliser treatment for crop performance. Deep banding phosphorus fertiliser root system architecture mungbean (Vigna radiata L) phosphorus use efficiency Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Introduction Inclusion of grain legumes in crop rotations can deliver many benefits, including a reduced environmental footprint, reduced use of synthetic nitrogen (N) due to biological N fixation and reduced soil pathogen populations through greater host plant diversity, while also improving food quality for livestock and human health through improved dietary intake of minerals, vitamins and fibre (Parida and Das 2005 ; Arnoldi et al. 2015 ; Vaz Patto et al. 2015 ). Mungbean ( Vigna radiata (L.) Wilczek) is the most widely grown grain legume after chickpea ( Cicer arietinum L) in northern Australia, with a very strong market demand and good prices. Both biotic and abiotic factors are important constraints to mungbean production, with phosphorus (P) deficiency one of the major limitations in major semi-arid growing regions of India and Australia (Araujo et al. 2015 ). Phosphorus plays critical roles in crop phenological development and the accumulation of biomass and grain yield, which has resulted in widespread application of fertilisers and soil amendments that supply plant-available P. Traditional application strategies involve application of P fertilisers to the surface soil layers, either with or without subsequent incorporation by tillage. While P is rapidly adsorbed to soil particles, surface P enrichment risks the movement of P and associated soil particles into nearby creeks and rivers during episodic rainfall events, potentially leading to eutrophication and deterioration of water quality (Kim and Li 2016 ; Yuan et al. 2018 ). In drier environments, this shallow P can also be effectively stranded in soil layers that quickly dry out, effectively limiting plant access to P for extended periods during crop growth (Eckert 1985 ; Howard and Tyler 1987 ; Jarvis and Bolland 1991 ; Mackay et al. 1999; Norrish et al 2003 ; Singh et al. 2005 ; Li-yun et al. 2014; Dang et al. 2015 ). Limited access to P via loss from the field as runoff or due to dry soil surface layers leads to reduced P availability for crop uptake and a loss of crop productivity. It is desirable to optimise P application rates and placement strategies to both maximise crop production and address growing environmental challenges (Kim and Li 2016 ). Deeper placement of P is a strategy that can allow landowners to better manage the P supply to crops as well as reducing the risk of environmental damage. Nkebiwe et al. ( 2016 ) conducted three meta-analysis studies that concluded that deep-placed (more than 10 cm deep) N and P were more effective for improving deep rooting, nutrient uptake and yield than equivalent broadcast applications from 1022 datasets from 40 field studies published from 1982 to 2015 (85% of studies were conducted since 2000). Collectively, deeper P fertiliser placement resulted in 3.7% higher yield than broadcast, and when co-location of N and P was combined with deep placement, yields were 27.3% (urea and soluble P) and 14.7% (ammonium and soluble P) higher than with conventional shallow placement. Given the greater prevalence of conservation farming practices, including reduced or zero tillage, this deeper placement typically occurs in concentrated bands that occupy relatively small proportions of the soil volume explored by roots. Root responses to encountering a zone of enhanced P availability, like a fertiliser band, typically involve a proliferation response in the vicinity of the band (Anghinoni and Barbaer 1980; Yao and Barber 1986 ; Sander and Eghball 1999 ; Grewal and Graham 1999 ; Trapeznikow et al. 2003 ; Chenet al. 2018 ; Ma et al. 2021 ), which maximises the root surface area available to exploit this scarce nutrient resource. Interestingly, Singh et al. ( 2005 ) and Ma et al. ( 2009 ) have also highlighted that deep application of nutrients like P can also encourage roots to grow deeper, increasing the exploitation of available moisture in deeper profile layers. The combination of an increased duration of P availability in subsoils that remain moist for longer and a deeper root system that can more efficiently extract water and nutrients like N from deep profile layers can substantially improve productivity and resilience of crops and pastures grown under variable seasonal conditions (Trapeznikow et al. 2003 ; Singh et al. 2012 ). Root system architecture (RSA), the combination of key root traits like length, angle, depth and branching capacity (Gregory et al. 2009 ; Wasson et al. 2012 , Rabbi et al. 2017 ), determines the spatial configuration of the plant root system and therefore is a key factor in the acquisition of water and nutrients (Fitter 1991 ; Lynch 1995 ). Root system architecture has been shown to respond to phosphorus availability, with the spatial distribution of roots able to influence the extent and timing of access to water and nutrients, thus impacting on yield potential (Lynch 1995 ; de Dorlodot et al. 2007 ; Liang et al. 2017 ; Ye et al. 2018 ). In a recent review, van der Bom et al. ( 2020 ) highlighted spatio-temporal trade-offs between efficient resource capture and pre-defined RSA, and advocated for a better understanding of how these trade-offs interact with genotype, environment and management. Under adverse soil or environmental conditions, RSA could be a critical factor in determining the nutrient acquisition, uptake and profitable crop production (Lynch 1995 ; de Dorlodot et al. 2007 ; Ye et al. 2018 ; Strock et al. 2019 ), particularly for the acquisition and uptake of P given its relative immobility in most soils (Barber 1995 ). Despite its importance, few studies have explored the implications of selection strategies targeting RSA traits (e.g. deep versus shallow root systems) for crop performance in soils with different P availability and profile distributions. Most recently, van der Bom et al. ( 2023 ) reported wheat genotypes with narrow root growth angle and deeper root systems increased deep soil exploration during early growth, with a tendency to more rapidly acquire P placed as a deep fertiliser band, whereas wide angle genotypes with shallower roots increased root growth in the topsoil. A better understanding of mungbean RSA may allow more targeted approaches to improve adaptation to water- and nutrient-limiting conditions that are currently constraining yields. However, genetic improvement of crop root systems requires knowledge of the intra-species variability in key root parameters and RSA and how these are controlled genetically (O' Toole and Bland 1987). An understanding of the relationships between RSA and plant productivity is also necessary before effective breeding and management strategies can be developed (Gowda et al. 2011 ; Henri et al. 2011; Joshi et al. 2016 ). Lawn and Rebetzke ( 2006 ) identified substantial variation in traits of potential agronomic, adaptive or taxonomic interest among 115 accessions of mungbean, mainly from Australia, West Timor, Papua New Guinea and India. Singh and Bell (2021) reported variability in RSA between contrasting early and late maturing mungbean varieties. However, genetic variation in RSA and its response to P application strategies with respect to plant growth and development in mungbean are largely unknown. Most commercially grown mungbean varieties are very quick to flower and begin pod addition, leading to cessation of further root growth (Singh and Bell 2021) that may affect root proliferation around deeper P bands and P acquisition. The main aims of this study were therefore to explore the interactions between RSA of contrasting mungbean varieties and the distribution of P fertiliser, with implications for contrasting P fertiliser application strategies. Materials and methods Plant material The experiment compared four commercial mungbean varieties from Australia, with contrasting growth characteristics and maturity classes. All varieties were produced by the National Mungbean Improvement Program, Queensland Department of Agriculture and Forestry (DAF), Australia, and have been described in detail by Singh and Bell (2021). Briefly, Jade-AU (3511-9 × VC 2768A, released in 2013) is an early maturing variety that dominates production in the Australian industry. It retains green leaf area until harvest, and so can respond to residual soil water and nitrogen. Berken (released 1975, a direct introduction from the USA with no pedigree history) is an early maturing, older variety with low yield potential that is highly susceptible to plant diseases. It is more determinate in growth pattern, with canopy senescence occurring during pod filling and grain maturation. Celera II-AU (M 773 × OAEM58-62, released 2015) is a recently released, early-intermediate maturing variety with short stature and resistance to the bacterial disease halo blight, caused by Pseudomonas savastanoi pv. Phaseolicola. Putland (Berken × CPI20141, released 1991) – is a longer season, photoperiod-sensitive variety that produces large biomass and is much later maturing than the other three varieties in the production environments of northeast Australia (i.e. maturing in 75–85 days after sowing, compared to 50–60 days after sowing for other varieties). Experimental site and unit The experiment was conducted in a temperature-controlled glasshouse at The University of Queensland, Brisbane, Australia (27°23’S, 153°06’E). Purpose-built root observation chambers were constructed from perspex sheets, with chamber dimensions being 60 cm high, 40 cm wide and 3 cm thick. Transparent perspex (8mm thick) sides were used to enable viewing and scanning of roots. The perspex sheets were screwed to the metal frame of the chamber and the backs of the chambers were lined with black plastic to allow easy removal at harvest. The chambers were wrapped in silver insulation to prevent exposure of the roots to light and to minimise fluctuations in soil temperature. Each chamber was filled with 9 kg air dried soil (Vertosol - Isbell 1986), which was collected in bulk from the 10-30cm cm layer of the soil profile from a commercial field on the central Darling Downs, near Jandowae (Queensland, Australia). This soil was characterised by a clay content of 35–40%, with key soil chemical characteristics determined using standard methods outlined in Rayment and Lyons ( 2010 ). Key physical and chemical properties of the soil are presented in Table 1 . The soil P status was considered marginal for crop growth, but there were no other deficiencies of macro or micronutrients. The soil was air dried and then crushed to 5mm size with a jaw crusher before being thoroughly mixed to provide a homogenous growing medium. The bulk density of the packed soil in the root observation chamber was estimated to be approximately 1.25 Mg/m 3 . Table 1 Chemical characteristics of the Vertisol soil used in the experiment Analyte Results Units pH (1:5 H 2 O) 7.5 pH (1:5 CaCl2) 6.3 Electrical conductivity (Sat. Ext) 1.2 dS/m Organic carbon 0.74 mg/kg Phosphorus (Colwell) 23 mg/kg PBI (Colwell) 110 Phosphorus (BSES) 33 mg/kg Cation Exchange Capacity 48.7 cmol (+)/kg Experimental design and P treatments The treatments consisted of four mungbean varieties and four P application methods or rates. Four replicate chambers of each combination of variety and P treatment were laid out in a randomised complete block design. The P treatments were (1) ‘Control’, with no additional P applied; (2) ‘Surface’, where an additional 30 mg P was mixed into soil in the top 5 cm.; (3) ‘Sub layer’, where an additional 30 mg P was mixed into a 5cm layer of soil from 20–25 cm depth.; (4) ‘Deep Band’, where an additional 30 mg P was applied in a band across the root chamber at 20 cm depth. Only 30 mg P/chamber was applied for each P treatment, except for the Control with no added P. The P was applied as monoammonium phosphate (MAP – 10:22:0 N:P:K). Since other basal nutrients were sufficient, no other nutrient applications were made. A diagrammatic representation of the P placement options is presented in the Fig. 1 . Growing conditions Soil in each chamber was slowly wet up over a period of 4–5 days, before being allowed to drain to near field capacity before sowing. At sowing, four seeds of one of the four chosen varieties were sown in each chamber and gradually thinned to one established plant 6 days after germination. The chambers were arranged on a stand that gave a plant-to-plant spacing of 20cm, and chambers were watered from the top every 10 days to return the soil to field capacity and avoid development of water stress. Measurements Before the harvesting of the plants at 50 days after emergence, plant height (from base to top of the stem) and total number of branches/node (at the nodes) were recorded. Plants were then destructively sampled by collecting the shoots of each plant above ground level and separating into stem, leaf and pod. The total number of leaves, number of fully expanded leaves, and leaf area (using a LICOR Planimeter (Li-3000 leaf area meter) were recorded. After removing the shoots, chambers were saturated with water overnight, after which each chamber was laid flat and the top perspex plate was removed. Purpose-built plywood pinboards that matched the chamber dimensions and fitted with 3 cm long black nails positioned in a 2×2 cm grid was then placed on top of the exposed soil. The moist soil allowed the nails to be easily pushed into the soil of the chamber, while preserving most of the intact root system architecture. The pinboards plus soil and roots were then held erect while the soil was washed from the pinboard using a very fine, low pressure water spray to minimise disturbance of the intact root system. The total number of nodules on the root system was recorded after root washing. The washed root system was then imaged with a digital camera (Canon, SX720 HS) mounted on a tripod and the images were converted to high-contrast black and white images using Adobe Photoshop software. Images were initially cropped to the same size and then image adjustment and threshold tools were used to convert the image into black and white. The average root angle of the first and second lateral branches was determined relative to the vertical axis using in-house software specifically designed for this purpose. After imaging, the roots were stored in 70% ethanol in a cold room (4 o C) for later detailed measurement. Dry matter of each plant part (stem, leaf, pods and roots) was obtained after drying in a dehydrator for four days at 70°C. Development of leaf area, root surface area, biomass, shoot mass (leaf + stem) and root mass were quantitatively determined. Macro and micronutrient analyses were performed on the composite shoot samples (which included stem + leaf + pods) from an analytical laboratory. Intact root characteristics Images of intact roots were analysed using WinRhizo Pro 2019 software ( https://regentinstruments.com/assets/winrhizo ). The image was acquired from the camera by electing the ‘origin’ setting in the software, and the following settings were chosen - image resolution was 600 dpi, the root background was changed to grey scale and calibration was performed by marking the length and width of the image (60 cm × 40 cm). The saved calibration was loaded onto each image before the start of the analysis. Before loading the calibration, the root diameter classes were changed into 10 different widths with a width interval of 0.25mm. The total root length (cm), total root surface area (cm 2 ), root surface area in top and bottom 30 cm of the chambers, mean root diameter (mm) and the number of root tips, forks and crossings were determined from image analysis. Images of intact roots were also analysed based on vertical distribution within the root chamber, with the top 30 cm and bottom 30 cm analysed separately. These analyses were conducted to determine whether varieties differed in their exploration of the shallow (top 0–30 cm) and deeper (30-60cm) parts of the soil profile with the different fertiliser P placements. Statistical analysis Analysis of variance (ANOVA) was performed using XLSTAT (2023.1.4. version). Data were statistically analysed using two-way ANOVA to understand the main treatment effects of fertiliser treatment and varieties. Normal distribution of data test and standardisation are automatically performed with the XLSTAT two-way ANOVA assessment. Fisher’s least significance differences test was used to compare the treatment means. Results Shoot and root growth of different varieties in response to P treatments Visual differences in the shoot and root growth of each variety grown in the deep ‘Band’ treatment are presented in the Fig. 2 . The late maturing variety Putland shows a relatively poor distribution of roots in the bottom soil profile layers, has thicker topsoil roots and has no pods, whereas the early maturing Jade and Berken and intermediate-maturity Celera II varieties show greater root proliferation in the bottom soil profile layers. Celera II also shows greater plant height and numbers of pods compared to the early maturing varieties Jade and Berken (Fig. 2 ). Differences between varieties and P treatments were observed for several shoot and root parameters. With the exception of pod yield, all above ground measured plant parameters did not show any overarching effects of P treatments, although there were significant interactions between P treatments and varieties for the below ground total root length and root surface area. However, there was a trend for deep banding to result in relatively greater total root volume, root surface area and plant biomass, followed by deeper sub layer P treatments, with the control or shallow P treatments recording the lowest root volume, root surface area and plant biomass. Phenological characteristics such as the leaf appearance rate and time to first flowering were not influenced by P treatments, but phenological differences were noted between early, intermediate and late maturing varieties as expected. Flowers were first recorded in the early maturing varieties Jade and Berken, followed by the intermediate variety Celera II. Putland had not flowered before the end of this experiment, which was in the pod development stages for the early and intermediate maturity varieties. Although there were no effects of P treatments that were consistent across varieties for the number of early flowers, there was a trend for a greater number of flowers (1.27 vs 1.06, or ~ 20% more) in the deep banded and deeper dispersed P layer treatments than in the control (no added P) and surface (shallow dispersed) P layer treatments. Plant biomass Plant biomass, a combination of pod mass, shoot mass (leaf + stem) and root mass, was not influenced by P treatment (Fig. 3 B) and there were no interactions between P treatment and variety. However, varietal differences in shoot mass, pod mass, root mass and total plant biomass were recorded (Fig. 3 A - P < 0.001). Celera II and Berken recorded significantly greater ( P < 0.001) plant biomass (12.6 g and 12.1 g, respectively), than either Jade (10.9g) or Putland (10.2g). The mass of vegetative material (leaf + stem) differed among the varieties (Fig. 3 A) in a fashion that was consistent with the duration of the pre-flowering period, with Putland (8.59g) and Celera II (8.00g) producing significantly ( P < 0.001) more vegetative shoot mass than either Jade (6.28g) or Berken (6.09g). The ratio of leaf mass to that of total vegetative matter was greatest for Putland (0.51), with the other three varieties varying between 0.44 and 0.46 ( P < 0.001). Root mass showed similar effects, with only varietal differences being statistically significant ( P < 0.001). Consistent with the time to flowering and cessation of vegetative growth, the late maturing variety Putland also had the highest root mass (1.60g), compared with the other three varieties (0.92 g to 1.1 g (Fig. 3 A). Unlike the responses in vegetative biomass, pod weight was influenced by both variety (Fig. 3 A) and to some extent P treatment (Fig. 3 B), although again there were no variety * P treatment interactions. Berken recorded the highest pod weight (5.31 g), compared with 4.14 g and 3.81g for Celera II and Jade respectively (Fig. 3 A), although the total number of pods was highest for Celera II (16), followed by Berken (12) and least for the Jade (8 - P < 0.001). The deep banded P treatment recorded the highest pod weight (4.8 g) while the surface P treatment recorded the lowest pod weight (4.1g; Fig. 3 B). Shoot P uptake and internal P use efficiency (iPUE) Significant ( P < 0.001) varietal differences in shoot P uptake, a product of shoot dry mass (leaf + stem + pods) and shoot P concentration, were recorded (Fig. 4 A). While the later maturing Putland showed the highest P concentrations in plant biomass (data not shown), total P uptake was greatest for Celera II (30.8 mg) and lowest for Berken (19.8 mg), with Jade and Putland intermediate. P treatments resulted in statistically significant effects on P uptake ( P = 0.049) and to some extent on iPUE ( P = 0.10) (Fig. 4 B). There was a trend for treatments enriched with P in deeper profile layers (either deep banded or dispersed in sub profile layers with or without topsoil P enrichment) to show greater shoot P uptake, although the lack of strong dry matter responses meant the iPUE in these treatments decreased compared with control or surface applied treatment (Fig. 4 B). Variety and P treatment effects on below ground root system architecture and root growth There were significant P treatment responses in both root growth angle and number of nodules (Fig. 5 ). The surface P treatment had relatively higher root growth angle (67°) than the other three P treatments (around 61°; Fig. 5 A). Root growth angle also differed among varieties, with the late-maturing Putland and intermediate maturity Celera II recording greater root growth angles (64°-67°) than the early-maturity Jade and Berken (59°- 61°; P = 0.015). Similarly, the number of nodules on mungbean roots were affected by both P treatment ( P = 0.038) and variety ( P = 0.05; Fig. 5 B). Deep banded and sub layer dispersed P treatments recorded the most nodules (> 90), compared with the surface P treatments with the lowest number of nodules (69 - Fig. 5 B). Among varieties, Celera II (102) and Berken (86) recorded more nodules than either Jade or Putland (80 and 74, respectively). Significant root trait responses to P treatments were observed for both mean root diameter and total root volume in the whole root chamber, with these two root traits also responding similarly for roots in the bottom 30cm of the root chambers (Fig. 6 ). Mean root diameter and total root volume were greatest with deep P applications (either a dispersed subsoil layer or a deep band), with no differences between the other P treatments (Fig. 6 A, B), with the same responses recorded in the bottom 30cm section (Fig. 6 C,D). The total root length and total root surface area exhibited significant interactions between variety and P treatments ( P = 0.033 and 0.002, respectively). Since the P treatment responses were similar for both the traits throughout the 60cm root chamber, we have illustrated this using root surface area responses (Fig. 7 ). Root surface area varied from around 1200 to 1800 cm 2 with no significant differences among varieties for the control and surface P treatments (Fig. 7 A). However, varieties appeared to respond differently to the deep sub layer and deep banded treatments. Jade and Berken showed significantly higher root surface areas (1630–1730 cm 2 ) in the deeper sub layer treatment than either Putland or Celera II (1200 cm 2 ). In contrast, Celera II showed higher root surface area (1800 cm 2 ) in the deep banded treatment compared with the Berken (1200 cm 2 ) and Putland (1450 cm 2 ). Separate analyses of root surface area in either the top or bottom sections showed highly significant interaction effects ( P = 0.003 and 0.014 respectively; Fig. 7 B-C). In the top 30 cm soil profile, P responses were like the whole soil profile with Jade and Berken showing higher root surface area in the top section compared with the Putland and Celera II, whereas Celera II showed highest root surface area compared with the deep banded treatment for Berken (Fig. 7 B). In the bottom 30 cm soil profile, Celera II had the highest root surface area with the deep banded treatment (979 cm 2 ), compared with the other P treatments (559–577 cm 2 ), while Jade had the highest root surface area with the deeper sub layer, compared with control or the surface P treatments (Fig. 7 Cd). There were clear varietal differences in root surface area in response to deep P treatments, with increases in root surface area in all compartments (whole chamber, top 30cm or bottom 30cm – Fig. 7 a, b, c) in response to deeper applied P in all varieties except Putland. Responsive varieties, however, differed in how they responded to deeper P treatments. For example, in the top compartment it was only Berken which showed significantly higher root surface area with the deeper sub layer P treatment compared with the control or surface P treatments (Fig. 7 B). However, in the bottom compartment higher root surface area was recorded in the deeper sub-layer P treatment for Jade while a similar response was recorded in Celera II for the deep banded treatment (Fig. 7 C). Discussion Above-ground growth responses to variety and fertiliser P treatments This study did not provide any evidence of interactions between fertiliser treatment and mungbean variety in terms of above ground growth and development, although there were significant differences between varieties and small growth responses to fertiliser P placement. Differences in phenological development (time to flowering) between varieties were observed in this study, along with the rate of flower addition once flowering had commenced, with differences consistent with expected varietal characteristics and previous studies (Singh and Bell, 2021). While Putland did not flower during this experiment, and continued vegetative growth for the duration, the early maturing Jade and Berken flowered slightly quicker and exhibited a greater number of early flowers than the intermediate maturity Celera II. Increasing the supply of P (comparing the Control treatment with all those with added P) had no statistically significant impact on above-ground biomass production in this study, possibly due to the combination of only moderately-low P status and a low P demand from the mungbean plant, given there was only a single mungbean plant grown in each rhizobox that contained 9 kg air dried soil. However, while there were no statistically significant increases in flower production in response to P addition, the deep-banded and deep sub soil layer P treatments had around 20% more flowers than the control or surface applied P treatments. This suggested that deep placement of P contributed to advancement and/or increased production of flowering in the early maturing varieties, and these effects were even stronger in terms of subsequent pod addition and growth. Increased flower production with increased P supply has been reported in many studies for various plant species (Kim and Li, 2016 ). While growth responses in above ground biomass were limited, there were significant differences in P accumulation in above ground biomass in response to both genotype and P treatment, with significant differences in iPUE also recorded. While the shallow P application did not result in increased P uptake compared to the unfertilised Control, consistent with the limited root development in those layers by all varieties, there were 14–16% increases in plant P uptake with the Deep P layer and Banded treatments, respectively. These differences were due to additive effects of small but not statistically significant increases in both crop biomass (8%) and biomass P concentration (6–8%), with these effects collectively representing P recovery efficiencies of only 6% (deep P layer) and 12% (deep P band) of applied P. The greater relative increase in P uptake compared to growth increase resulted in a 10% decline in internal iPUE for these treatments (Fig. 4 B). Differences in P uptake between varieties were much larger, with biomass P content in Celera II > Jade and Putland > Berken, with Berken (18.5 mg P) only acquiring 62% of the P taken up by Celera II (29.9 mg P). These varietal effects were due to contrasting differences in above-ground biomass (Celera II and Berken > Jade > Putland) and tissue P concentration (Jade, Putland and Celera II > Berken). Interestingly, the delayed flowering in Putland, which allowed a longer time for root growth and presumably nutrient accumulation, did not result in greater uptake of P due to the slower rate of growth and dry matter accumulation (Singh and Bell 2021). The low P recovery by the early maturity variety Berken is consistent with other studies that have shown lower tissue P concentrations in response to rapid growth rates. For example, De Bauw et al ( 2020 ) reported depleted shoot P concentrations induced by vigorous plant establishment in response to micro-doses of P placement in rice, while Vandamme et al ( 2016 ) reported low tissue P concentrations that occurred during periods of rapid growth of plants in an initially high P medium due to rapid depletion of soil solution P in the root zone. The differences in accumulation of plant P and biomass resulted in significant variation in iPUE between varieties, with Berken (602 mg DM/mg P uptake) > > Celera II, Jade and Putland (372–395 mg DM/mg P uptake). The reason for these differences could be related to differences in leaf area index, chlorophyll content and photosynthetic rate as reported for gluten free wheat varieties (Zhu et al 2012 ). In our studies, we didn’t directly measure these parameters, however, the early maturing varieties Berken and Jade showed greater rates of expansion of individual leaf area during early growth (Singh and Bell 2021), and both showed significantly greater dry matter accumulation per unit leaf area (1.8 g/cm 2 ) compared with the intermediate and late maturing varieties (1.0 g/cm 2 ) in this study. A greater dry matter per unit leaf area indicates greater photosynthetic rates for these varieties. A correlation coefficient matrix between iPUE and other key plant parameters also showed iPUE was significantly related to pod mass, specific leaf area (leaf area per unit leaf mass), plant biomass/leaf area, and calcium % (Supplementary Table 1). Irfan et al ( 2017 ) has also reported significant variability in the grain yield, P accumulation and iPUE among mungbean genotypes, with these observations suggesting there may be opportunities for further research to improve the efficiency of use of fertiliser P within existing mungbean varieties. Such experimentation would need to consider determination of leaf area expansion, shoot dry matter, tissue P concentration and iPUE at various growth stages for a larger set of mungbean varieties. Below-ground growth responses to variety and fertiliser P treatments While there was little difference between varieties in above ground biomass production, there were significant differences recorded in below ground parameters that are typically related to resource capture and nutrient supply, such as nodule numbers and root morphological traits such as root angle, root length, root surface area and root volume, with these traits only occasionally interacting with fertiliser P treatment. Greater nodule numbers were recorded in the intermediate maturing Celera II, which also exhibited the widest root angle and developed the largest total root volume, along with the early maturing Berken. Both Berken and Celera II supported the largest root volumes as a result of greater total root length with narrow root diameters, with the later maturing variety Putland unable to achieve similar metrics despite a longer period of root growth. Putland produced 16% less total root length, although these roots were significantly thicker than those of Berken and Celera II. Most previous studies have reported that a major portion of roots (> 70%) are present in the top 20–30 cm layers (e.g., Gao et al. 2010 ). In our study, total root length in the top 30 cm and bottom 30 cm sections were generally similar, but roots in the top 30cm compartment had a 12% greater mean root diameter. This resulted in around 10% greater root surface area and 22% greater root volume in the upper 30cm compartment in this study. Acquisition of water and nutrients are related to the ability of roots to exploit the available soil volume, and that ability is primarily governed by root length and root surface area in the various soil layers (Borkert and Barber 1983; Li et al. 2006 ). However, such broad adaptive traits are likely to be less effective for enhanced recovery of fertiliser P, which is typically applied in heterogeneous patches in soils with otherwise low background P fertility. Low soil solution P concentrations and a reliance on diffusive supply to replenish rapidly P-depleted rhizosphere soil volumes result in root P uptake occurring primarily near root tips that are exploring ‘new’ soil. An effective response to low soil P availability would therefore be expected to consist of enhanced root branching and proliferation responses that increase root length in the fertilised zone (Hill et al. 2005 ; Robinson 1996 ), and in particular, increases the production of root tips that can exploit undepleted soil solutions (Richardson et al. 2009 ). However, the deep banding treatment in which the largest increases in P uptake were recorded suggested the opposite actually occurred in these mungbean varieties, with 10–25% fewer root tips, forks and crossings (indicators of root proliferation in response to P fertilisation) than in the average of all other fertilised and unfertilised treatments (data not shown). Whilst there were occasionally significant interactions between P treatments and root parameters in either the top or bottom compartments (Fig. 7 B, C), there was no evidence of any increases in root length or proliferation in these mungbean varieties in response to P fertilisation, with the predominant response being a general increase in root surface area achieved through an increase in root diameter. This was most obvious in the P treatments applied into deeper soil layers. While root thickening has been recorded as characteristic of root development in some dicotyledonous species like bean (Lynch et al. 2011), root expansion is typically reduced in favour of continued root elongation under conditions of low P availability. While there is evidence for thinner roots in the unfertilised control and ineffective shallow P treatments (Fig. 6 A, C), the thicker roots found in the deep P band or layer treatments would seem to represent an ineffective response to enhance P acquisition that is reflected in the relatively small increases in tissue P concentration and plant P uptake. P availability can influence the root growth angle and root distribution in the soil profile Root growth angle has been noted to be the key indicator for a deep or shallow rooting genotype (Singh et al. 2011 ; Chen et al. 2017 ; Uga et al. 2013 ) and plays a major role in determining RSA. However, while root growth angle is primarily governed by plagiogravitropism (Nakamoto 1994 ), it can also be influenced by other factors such as soil strength, soil water, soil temperature and soil nutrition, especially phosphorus and nitrogen (Nakamoto, 1993 , 1994 ; Liao et al. 2001 ; Trachsel et al. 2013). Evidence from different crops has indicated that genotypes with narrow root growth angles are not only deep rooting, but they also tend to grow and develop more rapidly in both above and below-ground components, leading to early flowering and maturity (Singh et al 2011 ). Genetic variability in root growth angle, leading to development of relatively shallower or deeper root systems, were noted for the mungbean varieties grown under high fertility conditions in a previous study, where early maturing variety Jade and Berken showed relatively narrower root growth angle (Singh and Bell 2021). In the current study, in addition to the inherent varietal differences, P treatments also influenced the root growth angle. Shallower P treatment resulted in wider root growth angle and a shallower distribution of root system (even though this did not result in additional P uptake), whereas availability of relatively less P in the topsoil for the control P treatment or concentrated availability of P in the deep soil resulted in narrower root growth angle and deeper distribution of root system. Other studies have reported differential stimulation of shallower basal root growth angles in P-deficient environments (Liao et al 2001 ; Zhao et al 2004 ; Ao et al 2010). Lynch and Brown ( 2001 ) and Lynch ( 2011 ) reported that root growth angle has a dominant influence on P acquisition (6-fold) and yield of bean (3-fold), and Zhu et al ( 2005 ) reported 2-fold variation in P acquisition for maize genotypes, with these studies conducted in stratified soils where shallow root growth angle increased P acquisition by increasing topsoil foraging. P availability in shallower topsoil has been reported to control root branching, basal root length and adventitious roots for common bean (Miguel et al 2013 ), but our results show no similar response in mungbean to increased availability of P in the shallow topsoil layer. Responses were more pronounced in response to deep P bands or enriched layers, with these placements resulting in increased root diameter and surface area that appeared to differ somewhat between varieties. Differences in varietal response to P availability differed between the top and bottom soil root compartments for the early and intermediate maturity varieties, but not for Putland. The early maturing Jade and Berken showed significantly greater total root surface area for the deeper dispersed subsoil layer treatment, whereas the intermediate variety Celera II showed greatest total root surface area for the deep banded treatment. In both cases, effects were more prominent in the bottom compartment rather than in the top compartment where the P enrichment occurred. The lack of response to the enriched shallow topsoil in all mungbean varieties in this study may relate to the lack of strong lateral root development in that part of the soil profile. This is evident when comparing root images, showing no additional lateral root development in the surface applied P compared with the control (Supplementary Fig. 1). Proliferation of roots in P-enriched topsoil would therefore appear to be determined by genetic factors that influence root system architecture, in addition to a response to increased availability of P in the topsoil, as reported in other studies (Miguel et al. 2013 ; Chen et al. 2011 ; Chen et al. 2017 ). Zhu and Lynch ( 2004 ) have highlighted the genotypic variability in biomass investment by plants in response to P scarcity, with lateral root extension preferred due to the requirement for less biomass and P investment compared to extension of other root types. These authors suggested that enhanced lateral rooting in response to P stress may be harnessed as a useful trait for the selection and breeding of more P-efficient maize genotypes. Liao et al. ( 2001 ) reported basal roots of the P-inefficient common bean genotype extended deeper compared with those of the P-efficient genotype when experiencing P stress. In contrast, basal roots of the P-efficient genotype became shallower with P stress, while root growth angle reduced significantly, and roots became more horizontal (Liao et al. 2001 ). The extent to which such traits exist within mungbean germplasm should therefore be explored, particularly as mungbean is often grown in soil profiles that strongly P-stratified, and the short crop phenologies do not offer much opportunity to develop deep and well distributed root systems. Varietal differences in P acquisition and internal P use efficiency This study has found significant variability in P uptake and P use efficiency between varieties (Fig. 4 a), with no apparent relationship between P uptake and total root surface area. The variety Jade had the greatest total root length and root surface area compared to other varieties but shoot P uptake was the second lowest. The other three varieties (early or late maturing) had similar or relatively less total root surface area or volume compared with Jade, but with contrasting P uptake. For example, Berken, Putland and Celera II had the similar total root surface area and volume, but Berken had the lowest shoot P uptake, whereas the Celera II had the highest P uptake. While there are likely to be other factors that are important for determining varietal differences in total P uptake, it is the apparent compensatory ability of the variety Berken to overcome poor P acquisition by much more efficient utilisation of P within the plant to produce biomass that is of considerable interest. Rose et al. ( 2011 ) reported that internal P utilisation efficiency is often lower in plants with high P acquisition efficiency as a result of high tissue P concentration. In our study, late and intermediate maturing Putland and Celera II had high P acquisition and shoot P concentration, compared with the early maturing Berken, which had the highest iPUE. Hoad et al. ( 2001 ) and Romer ( 1986 ) reported that the nutrient requirements can vary considerably among varieties for other crop species. While relationships between P uptake and measured root traits were not recorded in our study, P uptake can also be influenced by the effective requirement of P during different stages of plant growth and development, which differed among the varieties. Singh and Bell (2021) have previously reported linear relationships between expanding total root surface area and leaf area obtained from sequential destructive sampling during early growth stages up to flowering for the same varieties used in the current study, but differences in phenology and the time to cessation of root growth between varieties would have potentially masked these effects when measured at a common harvest date. Root systems are known to be plastic in nature and can interact dynamically with soil physical, chemical and biological factors at different stages of a growing season (Lynch 1995 ; Wu et al. 2016 ; Chen et al. 2017 ). Development of roots occurs in synchrony with shoot growth (Wang et al. 2006 ), so characterisation of RSA over time is important to understand the interactions between RSA and shoot growth dynamics and nutrient uptake. The vigorous root growth and more rapid rates of root extension seen in the early maturing mungbean varieties appeared to be consistent with acquisition of enough water and nutrients to be able to support rapid shoot growth through increased dry matter accumulation per unit leaf area (Singh and Bell 2021), or increased leaf transpiration (Pang et al. 2017 ), and might have been correlated with early flowering and podding characteristics for the early maturing varieties studied (Singh and Bell 2021). Collectively, our data would suggest that further exploration of mungbean germplasm for variation in iPUE could provide opportunities to improve fertiliser use efficiency in this species. Conclusions The strongest P response in mungbean shoot and root traits and the greatest P uptake were observed with deeper placement of P fertiliser, especially when applied in a concentrated band compared to P applied in the shallow topsoil layers. The P responses in above-ground growth and development were most marked for reproductive development (flowering and podding), while below-ground responses were observed in key root traits such as mean root diameter and total root volume and root length and root surface area, all of which increased with deep banding relative to the unfertilised plants and those where P was applied in a shallow topsoil layer. The total root length and root surface area also increased when the same amount of P was applied in a less concentrated fashion across a larger soil volume in the deeper profile layer, and while these responses were recorded in both the soil compartment receiving the fertiliser and that below it, effects were confounded by significant varietal interactions. These are important findings for fertiliser P placement for mungbean crops that are typically grown in rainfed cropping systems under zero tillage conditions. Increases in root diameter and hence root surface area and volume that were observed in the deep band and enriched sub layer P treatments have been identified as anatomical traits that may be promising breeding targets for soil resource acquisition. However, these broad adaptive traits are not the most effective for enhanced recovery of fertiliser P applied in heterogeneous patches in soils with otherwise low background P fertility. Low soil solution P concentrations, root P uptake that occurs primarily near the root tips and a reliance on diffusive supply of P to replenish rapidly depleted rhizosphere soil volumes would suggest that a root proliferation response that maximises the exploitation of the fertilised soil volume would be more effective. The fact that mungbean plants showed no evidence of proliferation in P-enriched bands or soil layers in these studies is therefore consistent with the relatively small increases in tissue P concentration and plant uptake in response to fertiliser P application in soils with a moderate-low P fertility. Abbreviations RSA Root system architecture iPUE Internal phosphorus use efficiency MAP Mono Ammonium Phosphate Declarations Author Contributions Vijaya Singh contributed to the conceptualization of the research, experimental set up, data collection, result analysis and writing of the main manuscript text. Marissa Collins and Mike Bell contributed to the conceptualization of the research and interpretation of results, helped to improve the text and provided the financial support used to conduct the research. All authors contributed to the article and approved the submitted versions. Funding This project was supported by Grains Research Development Corporation through project UOQ-002RTX and UQ00063, and through funding contributions from the Sir Edwin Marsden Tooth Bequest and the School of Agriculture and Food Science, University of Queensland. Competing Interests The authors have no relevant financial or non-financial interests to disclose. References Anghinoni I, Barber SA (1980) Phosphorus application rate and distribution in the soil and phosphorus uptake by corn. Agron J 44:1041–1044 Adesemoye AO, Kloepper JW (2009) Plant-microbe interactions in enhanced fertilizer-use efficiency. Appl Microbiol Biotechnol 85:1–12 Araujo SS, Beebe S, Crespi M, Delbreli B, Gonzaliz EM, Gruber V et al (2015) Abiotic stress responses in legumes: strategies used to cope with environmental challenges. Crit Rev Plant Sci 34:237–280. 10.1080/07352689.2014.898450 Arnoldi A, Zanoni C, Lammi C, Boschin G (2015) The role of grain legumes in the prevention of hypercholesterolemia and hypertension. CRC Crit Rev Plant Sci 34:1–3. https://doi.org/10.1080/07352689.2014.897896 Barber SA (1995) Soil Nutrient Bioavailability: A Mechanistic Approach. 2nd Edn. John Wiley & Sons, New York Borkert CM, Barber SA (1985) Soybean shoot and root growth and phosphorus concentration as affected by phosphorus placement. Soil Sci Soc Am J 49:152–155 Chen X, Ding Q, Blaszkiewicz Z, Li Y (2017) Phenotyping for the dynamics of field wheat root system architecture. Sci Rep 7:37649 Chen Y, Dunbabin V, Diggle A, Siddique K, Rengel Z (2011) Development of a novel semi-hydroponic phenotyping system for studying root architecture. Funct Plant Biol 38(5):355–363 Chen Y, Ghanem ME, Siddique KHM (2017) Characterising root trait variability in chickpea ( Cicer arietinum L.) germplasm. J Exp Bot 68:1987–1999 Chen Y, Rengel Z, Palta J, Siddique KHM (2018) Efficient root systems for enhancing tolerance of crops to water and phosphorus limitation. Indian J Plant Physiol 23:689–696 Dang YP, Seymour NP, Walker SR, Bell MJ, Freebairn DM (2015) Strategic tillage in no-till farming systems in Australia’s northern grains growing regions: I. Drivers and implementation. Soil Till Res 152:104–114 De Bauw P, Mai TH, Schnepf A et al (2020) A functional structural model of upland rice root systems reveals the importance of laterals and growing root tips for phosphate uptake from wet and dry soils. Ann Bot 126:789–806. https://doi.org/10.1093/aob/mcaa120 De Bauw P, Smolders E, Verbeeck M, Senthilkumar K, Houben E, Vandamme E (2021) Micro-dose placement of phosphorus induces deep rooting of upland rice. Plant Soil 463:187–204. https://doi.org/10.1007/s11104-021-04914-z de Dorlodot S, Forster B, Pagés L, Price A, Tuberosa R, Draye X (2007) Root system architecture: opportunities and constraints for genetic improvement of crops. Trends Plant Sci 12:474–481 Eckert DJ (1985) Review: Effects of reduced tillage on the distribution of soil pH and nutrients in soil profiles. J Fert Issues 2:86–90 Fitter AH (1991) Characteristics and functions of root systems. In Plant Roots: The Hidden Half. 2nd edn. Eds. Y Waisel pp. 3–25. Marcel Dekker, New York, USA Gao Y, Duan A, Qiu X, Liu Z, Sun J, Zhang J, Wang H (2010) Distribution of roots and root length density in a maize/soybean strip intercropping system. Agric Water Manag 98(1):199–212. https://doi.org/10.1016/j.agwat.2010.08.021 Gowda VRPV, Henry A, Yamauchi A et al (2011) Root biology and genetic improvement for drought avoidance in rice. Field Crop Res 122:1–13. https://doi.org/10.1016/j.fcr.2011.03.001 Gu R, Chen F, Long L, …, Yuan L (2016) Enhancing phosphorus uptake efficiency through QTL-based selection for root system architecture in maize. J Genet Genomics 43(11):663–672. https://doi.org/10.1016/j.jgg.2016.11.002 Gregory PJ, Bengough AG, Grinev D, Schmidt S, Thomas WTB, Wojciechowski T, Young M (2009) Root phenomics of crops: opportunities and challenges. Funct Plant Biol 36:922–929 Grewal HS, Graham RD (1999) Residual effects of subsoil zinc and oilseed rape genotype on the grain yield and distribution of zinc in wheat. Plant Soil 207:29–36 Henry A, Gowda VRP, Torres RO, McNally KL, Serraj R (2011) Variation in root system architecture and drought response in rice (Oryza sativa): phenotyping of the OryzaSNP panel in rainfed lowland fields. Field Crops Res 120:205–214 Hill JO, Simpson RJ, Wood JT, Moore AD, Chapman DF (2005) The phosphorus and nitrogen requirements of temperate pasture species and their influence on grassland botanical composition. Aust J Agric Res 56:1027–1039. 10.1071/AR04279 Hoad SP, Russell G, Lucas ME, Bingham IJ (2001) The management of wheat, barley, and oat root systems. Adv Agron 74:193–246. https://doi.org/10.1016/S0065-2113(01)74034-5 Howard DD, Tyler DD (1987) Comparison of surface applied phosphorus and potassium rates and in-furrow fertiliser combinations for not-till corn. J Fert Issues 4:48–52 Irfan M, Shah JA, Abbas M (2017) Evaluating the performance of mungbean genotypes for grain yield, phosphorus accumulation and utilisation efficiency. J Plant Nutr 40:2709–2720. https://doi.org/10.1080/01904167.2017.1381718 Isbell R (2016) Australian Soil Classification. CSIRO Publishing Jarvis RJ, Bolland MDA (1991) Lupin grain yields and fertiliser effectiveness are increased by banding superphosphate below the seed. Aust J Exp Agric 31:357–366 Joshi D, Singh V, van Oosterom (2016) Erik, Mace, Emma, Jordan, David, and Hammer, Graeme Genetic manipulation of root system architecture to improve drought adaptation in sorghum. The sorghum genome. Edited by Sujay Rakshit and Yi-Hong Wang. Cham, Switzerland: Springer.207–226. https://doi.org/10.1007/978-3-319-47789-3_11 Kim H-J, Li X (2016) Effects of phosphorus on shoot and root growth, partitioning, and phosphorus utilization efficiency in Lantana. Hort Sci 51(8):1009–1009. 10.21273/HORTSCI.51.8.1001 Lawn RJ, Rebetzke G (2006) Variation among Australian accessions of the wild mungbean (Vigna radiata ssp. sublobata) for traits of agronomic, adaptive, or taxonomic interest. Aus J Agri Res 57:119–132 Li H, Ma Q, Li H, Zhang F, Rengel Z, Shen J (2014) Root morphological responses to localized nutrient supply differ among crop species with contrasting root traits. Plant Soil 376(1–2):151–163 Li L, Sun J, Zhang F, Guo T, Bao X, Smith A, Smith SE (2006) Root distribution and interactions between intercropped species. Oecologia 147:280–290 Liang C, Li A, Li YH, Liang W, Guo C S, et al (2017) Melatonin regulates root architecture by modulating auxin response in rice. Front Plant Sci 8:134. 10.3389/fpls.2017.00134 Liao H, Rubio G, Yan X, Cao A, Brown KM, Lynch JP (2001) Effect of phosphorus availability on basal root shallowness in common bean. Plant Soil 232:69–79 Lynch J (1995) Root architecture and plant productivity. Plant Physiol 109:7–13 Lynch J (2019) Root phenes for improved nutrient capture: an underexploited opportunity for global agriculture. New phytol 223:548–564 Lynch J (2011) Root phenes for enhanced soil exploration and phosphorus acquisition: tools for future crops. Plant Physiol 156:1041–1049. https://doi.org/10. 1104/ Lynch JP, Brown KM (2001) Topsoil foraging – an architectural adaptation of plants to low phosphorus availability. Plant Soil 237:225–237. https://doi.org/10. 1023/a: 10133 24727 040 Ma Q, Rengel Z, Rose T (2009) The effectiveness of deep placement of fertilisers is determined by crop species and edaphic conditions in Mediterranean-type environments: A review. Austr J Soil Res 47:19–32 Ma Q, Sun L, Tian H, Rengel Z, Shen J (2021) Deep banding of phosphorus and nitrogen enhances Rosa multiflora growth and nutrient accumulation by improving root spatial distribution. Sci Hort 277(109800). https://doi.org/10.1016/j.scienta.2020.109800 Mackay AD, Barber SA (1985) Soil moisture effects on root growth and phosphorus uptake by corn. Agron J 77:519–523 Miguel MA, Widrig A, Vieira RF, Brown KM, Lynch JP (2013) Basal root whorl number: a modulator of phosphorus acquisition in common bean (Phaseolus vulgaris). Ann Bot 112:973–982 Nakamoto T (1993) Effect of soil water content on the gravitropic behaviour of nodal roots in maize. Plant Soil 152:261–267 Nakamoto T (1994) Plagio-gravitropism of maize roots. Plant Soil 165:327–332 Nkebiwe PM, Weinmann M, Bar-Tal A, Muller T (2016) Fertilizer placement to improve crop nutrient acquisition and yield: A review and meta-analysis. Field Crops Res 196:389–401. http://dx.doi.org/10.1016/j.fcr.2016.07.018 Norrish SA, Cornish PS, Moody PW, Jessop RS (2003) Edaphic and environmental interactions controlling grain yield response to P fertiliser in dryland wheat crops of north-western NSW. Proceedings of 2nd International Symposium on Phosphorus Dynamics in the Soil-Plant Continuum, pp. 222–223, University of Western Australia: Perth, Australia O’Toole JC, Bland WL (1987) Genotypic variation in crop plant root systems. Adv Agron 41:91–145 Pang J, Zhao H, Bansal R, Bohuon E, Lambers H, Ryan MH, Siddique KHM (2017) Leaf transpiration plays a role in phosphorus acquisition among a large set of chickpea genotypes. Plant Cell Environ 41:2069–2079. https://doi.org/10.1111/pce.13139 Parida AK, Das AB (2005) Salt tolerance and salinity effects on plants: a review. Ecotoxicol Environ Saf 60:324–349. https://doi.org/10.1016/j.ecoenv.2004.06.010 Rabbi SMF, Guppy C, Flavel R, Tighe M, Young I (2017) Root plasticity not evident in N-enriched soil volumes for wheat ( Triticum aestivum L.) and barley ( Hordeum vulgare L.) varieties. Commun Soil Sci Plant Anal 48:2002–2012 Rayment GE, Lyons DJ (2010) Soil chemical methods-Australia. Australian Soil and Land Survey Handbooks Series. CSIRO Publishing Richardson AE, Hocking PJ, Simpson RJ, George TS (2009) Plant mechanisms to optimise access to soil phosphorus. Crop Past Sci 60:124–143. https://doi.org/10.1071/cp07125 Robinson D (1996) Resource capture by localised root proliferation: why do roots bother? Annal Bot 77:179–186. https://doi.org/10.1006/anbo.1996.0020 Romer W, Schilling G (1986) Phosphorus requirements of the wheat plant in various stages of the life cycle. Plant Soil 91:221–229 Rose TJ, Rose MT, Pariasca-Tanaka J, Heuer S, Wissuwa M (2011) The frustration with utilization: Why have improvements in internal phosphorus utilization efficiency in crops remained so elusive? Front Plant Sci 2:73 Sander DH, Eghball B (1999) Planting date and phosphorus fertiliser effects on winter wheat. Agron J 91:707–712 Singh DK, Sale PWG, Routley RR (2005) Increasing phosphorus supply in subsurface soil in northern Australia: Rationale for deep placement and the effects with various crops. Plant Soil 269:35–44 Singh V, van Oosterom EJ, Jordan DR, Hammer GL (2012) Genetic control of nodal root angle in sorghum and its implications on water extraction. Europ J Agron 42:3–10 Singh V, van Oosterom EJ, Jordan DR, Hunt CH, Hammer GL (2011) Genetic variability and control of nodal root angle in sorghum. Crop Sci 51:2011–2020 Strock CF, Burridge J, Massas ASF et al (2019) Seedling root architecture and its relationship with seed yield across diverse environments in Phaseolus vulgaris. Field Crops Res 237:53–64 Trachsel S, Kaeppler SM, Brown KM, Lynch JP (2011) Shovelomics: high throughput phenotyping of maize ( Zea mays L.) root architecture in the field. Plant Soil 341:75–87 Trapeznikow VK, Ivanov II, Kudoyarova GR (2003) Effect of heterogeneous distribution of nutrients on root growth, ABA content and drought resistance of wheat plants. Plant Soil 252(2):207–214. 10.1023/A:1024734310214 Uga Y, Sugimoto K, Ogawa S, Rane J, Ishitani M, Hara N et al (2013) Control of root system architecture by DEEPER ROOTING 1 increases rice yield under drought conditions. Nat Genet 45:1097–1102. 10.1038/ng.2725) Vandamme E, Rose T, Saito K et al (2016) Integration of P acquisition efficiency, P utilization efficiency and low grain P concentrations into P-efficient rice genotypes for specific target environments. Nutr Cycl Agroecosyst 104:413–427. https://doi.org/10.1007/s10705-015-9716-3 Van der Bom FJT, Williams A, Bell MJ (2020) Root architecture for improved resource capture: trade-offs in complex environments. J Exp Bot 71:5752–5763. 10.1093/jxb/eraa324 Van der Bom FJT, Williams A, Raymond NS, Alahmad S, Hickey LT, Singh V, Bell MJ (2023) Root angle, phosphorus, and water: Interactions and effects on durum wheat genotype performance in drought-prone environments. Plant Soil. https://doi.org/10.1007/s11104-023-05966-z Vaz Patto MC, Amarowicz R, Aryee ANA, Boye JI, Chung HJ, Martín Cabrejas MA, Domoney C (2015) Achievements and challenges in improving the nutritional quality of food legumes. Crit Rev Plant Sci 34:1–3. https://doi.org/10.1080/07352689.2014.897896 Wang H, Inukai Y, Yamauchi A (2006) Root development and nutrient uptake. Crit Rev Plant Sci 25:279–301 Wasson AP, Richards RA, Chatrath R, Misra SC, Prasad SV, Rebetzke GJ, Kirkegaard JA, Christopher J, Watt M (2012) Traits and selection strategies to improve root systems and water uptake in water-limited wheat crops. J Exp Bot 63:3485–3498 Wu Q, Pages L, Wu J (2016) Relationships between root diameter, root length and root branching along lateral roots in adult, field-grown maize. Ann Bot 117:379–390 Yao J, Barber SA (1986) Effect of one phosphorus rate placed in different soil volumes on P uptake and growth of wheat. Commun Soil Sci Plant Anal 17:819–827 Ye H, Roorkiwal M, Valliyodan B, Zhou L, Chen P, Varshney RK, Nguyen HT (2018) Genetic diversity of root system architecture in response to drought stress in grain legumes. J Exp Bot 69:3267–3232. 10.1093/jxb/ery082 Yuan Z, Jiang S, Sheng H et al (2018) Human perturbation of the global phosphorus cycle: changes and consequences. Environ Sci Technol 52:2438–2450 [DOI:. 10.1021/acs.est.7b03910]( Yuan M, Fernandez FG, Pittelkow CM, Greer KD, Schaefer D (2018) Tillage and fertilizer management effects on phosphorus runoff from minimal slope fields. J Environ Qual 47:462–470. 10.2134/jeq2017.07.0271 Zhao J, Fu J, Liao H, He Y, Nian Hai, Yan X (2004) Characterization of root architecture in an applied core collection for phosphorus efficiency of soybean germplasm. Chin Sci Bull 49:1611–1620 Zhu J, Lynch JP (2004) The contribution of lateral rooting to phosphorus acquisition efficiency in maize ( Zea mays ) seedlings. Funct Plant Biol 31:949–958. https://doi.org/10.1071/FP04046 Zhu J, Kaeppler S, Lynch JP (2005) Topsoil foraging and phosphorus acquisition efficiency in maize ( Zea mays L). Funct Plant Biol 32:749–762 Zhu X, Li C, Jiang Z, Huang L (2012) Responses of phosphorus use efficiency, grain yield, and quality to phosphorus application amount of weak-gluten wheat. J Integr Agric 11(7):1103–1110. 10.1016/S2095-3119(12)60103-8 Supplementary Files SupplementaryTablesandFigures.pdf Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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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-3508080","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":245756699,"identity":"f50c4fd7-52df-4410-9e77-ebd1bc564453","order_by":0,"name":"Vijaya Singh","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAzElEQVRIiWNgGAWjYJCCA0AkB2bxkKLFmDQtIF2JDURrMTjA/vBwwa876RuOJzA+eNvGIG9wgKAWHoPDM/ue5W4484DZcG4bg+EGQlokG3gYDvP2HM7dcCOBTZq3jYGRCC3sD0Ba0g1uJLD/BmqxJ6iFH+i2wzw/DicAtbAxA7UkEtbCDPQLb8Nhw5lnHjZLzjknkTyTkBY29vbHn3n+HJbnO5588MObMhvbPkJaGJiBmLENxAJHjQQh9TDwB0QkEKt6FIyCUTAKRhoAAKwzRjtDQpd7AAAAAElFTkSuQmCC","orcid":"","institution":"","correspondingAuthor":true,"prefix":"","firstName":"Vijaya","middleName":"","lastName":"Singh","suffix":""},{"id":245756700,"identity":"337a8b49-6576-4f06-9cc8-c224f07c808d","order_by":1,"name":"Marisa Collins","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Marisa","middleName":"","lastName":"Collins","suffix":""},{"id":245756701,"identity":"1e88f276-5823-4c59-b0bc-e756432a91e1","order_by":2,"name":"Mike Bell","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Mike","middleName":"","lastName":"Bell","suffix":""}],"badges":[],"createdAt":"2023-10-29 17:18:59","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3508080/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3508080/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":46048793,"identity":"c272c9ae-7b5e-406a-b858-6564f9136168","added_by":"auto","created_at":"2023-11-07 23:15:37","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":327378,"visible":true,"origin":"","legend":"\u003cp\u003eAdded phosphorus treatments (A) ‘Surface’ mixed in the top 5 cm, (B) ‘Sub layer’ deep dispersed layer at 20-25 cm depth, and (C) ‘Band’ deep banded at 20 cm depth\u003c/p\u003e","description":"","filename":"F1.png","url":"https://assets-eu.researchsquare.com/files/rs-3508080/v1/db633f3b9d6c84599acf4cef.png"},{"id":46048520,"identity":"269d1aac-6bf6-4067-b947-a75c7408cf85","added_by":"auto","created_at":"2023-11-07 23:07:37","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":543575,"visible":true,"origin":"","legend":"\u003cp\u003eVisual differences in shoot and root morphology for varieties (A) Jade, (B) Putland, (C) Berken and (D) Celera II for deep banded phosphorus treatment\u003c/p\u003e","description":"","filename":"F2.png","url":"https://assets-eu.researchsquare.com/files/rs-3508080/v1/7247de7318aab6523a38cd05.png"},{"id":46048016,"identity":"9595f586-994c-4d33-815d-fb2c0a88b401","added_by":"auto","created_at":"2023-11-07 22:59:36","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":30315,"visible":true,"origin":"","legend":"\u003cp\u003eMain effects of varieties (A) and P treatments (B) on the distribution of dry matter between plant parts (shoot, pods, and roots). Letters in the specific shaded portion of the bars represent Fisher’s least significant differences (5%)\u003c/p\u003e","description":"","filename":"F3.png","url":"https://assets-eu.researchsquare.com/files/rs-3508080/v1/4fac0fd9184df0dbd9709f3c.png"},{"id":46048019,"identity":"01fb4617-2b12-4946-af19-e2db43df8e8d","added_by":"auto","created_at":"2023-11-07 22:59:36","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":47972,"visible":true,"origin":"","legend":"\u003cp\u003eDifferences in shoot P uptake and internal P use efficiency (iPUE) in response to (a) varieties, and (b) P treatments. Letters represent Fisher’s least significant differences (5%)\u003c/p\u003e","description":"","filename":"F4.png","url":"https://assets-eu.researchsquare.com/files/rs-3508080/v1/6da9be3fc55caa555f4dcca5.png"},{"id":46048022,"identity":"4239bdca-8af1-46e3-ab1a-1e8274c63e99","added_by":"auto","created_at":"2023-11-07 22:59:37","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":39555,"visible":true,"origin":"","legend":"\u003cp\u003ePhosphorus treatment effects on root growth parameters (A) root growth angle and (B) number of nodules for Control, Surface, Sub layer, and Deep Band treatments. Different letters on the columns indicate significant differences (lsd, 0.05) between those P treatments\u003c/p\u003e","description":"","filename":"F5.png","url":"https://assets-eu.researchsquare.com/files/rs-3508080/v1/e6bb48809cea426683222396.png"},{"id":46048018,"identity":"2c963770-28d1-4d68-9125-64c598c514bc","added_by":"auto","created_at":"2023-11-07 22:59:36","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":13664,"visible":true,"origin":"","legend":"\u003cp\u003ePhosphorus treatment effects on root growth parameters in whole root chamber (A) mean root diameter and total root volume (B), in bottom 30 cm root chamber (C) bottom mean root diameter and (D) bottom root volume for Control, Surface, Sub layer, and Deep Band treatments. Different letters on the columns indicate significant differences (lsd, 0.05) between those P treatments\u003c/p\u003e","description":"","filename":"F6.png","url":"https://assets-eu.researchsquare.com/files/rs-3508080/v1/8d28d4919b0599742776de1a.png"},{"id":46048518,"identity":"d2cb340c-b82d-484b-82c5-86d58e92edd7","added_by":"auto","created_at":"2023-11-07 23:07:37","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":20682,"visible":true,"origin":"","legend":"\u003cp\u003eInteraction effect between varieties and phosphorus treatments on (A) total root surface area, (B) root surface area in top 30cm section, and (C) root surface area in bottom 30cm\u003c/p\u003e","description":"","filename":"F7.png","url":"https://assets-eu.researchsquare.com/files/rs-3508080/v1/69a9c7c7e8be33a93d6b8825.png"},{"id":51587087,"identity":"83a9a4fc-f0b0-4250-84ce-2f89aa233027","added_by":"auto","created_at":"2024-02-24 14:39:17","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1311272,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3508080/v1/371f5c8c-0991-4f8a-9456-0188ca4d6c8c.pdf"},{"id":46048024,"identity":"5422fad7-8d73-455b-8b2b-35acddb43866","added_by":"auto","created_at":"2023-11-07 22:59:37","extension":"pdf","order_by":6,"title":"","display":"","copyAsset":false,"role":"supplement","size":460024,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryTablesandFigures.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3508080/v1/a83c495fc7607392a80c5b43.pdf"}],"financialInterests":"","formattedTitle":"Above and below-ground responses to contrasting soil phosphorus distribution by mungbean (Vigna radiata L.) cultivars with diverse phenology","fulltext":[{"header":"Introduction","content":"\u003cp\u003eInclusion of grain legumes in crop rotations can deliver many benefits, including a reduced environmental footprint, reduced use of synthetic nitrogen (N) due to biological N fixation and reduced soil pathogen populations through greater host plant diversity, while also improving food quality for livestock and human health through improved dietary intake of minerals, vitamins and fibre (Parida and Das \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e2005\u003c/span\u003e; Arnoldi et al. \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Vaz Patto et al. \u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Mungbean (\u003cem\u003eVigna radiata\u003c/em\u003e (L.) Wilczek) is the most widely grown grain legume after chickpea (\u003cem\u003eCicer arietinum\u003c/em\u003e L) in northern Australia, with a very strong market demand and good prices. Both biotic and abiotic factors are important constraints to mungbean production, with phosphorus (P) deficiency one of the major limitations in major semi-arid growing regions of India and Australia (Araujo et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2015\u003c/span\u003e).\u003c/p\u003e \u003cp\u003ePhosphorus plays critical roles in crop phenological development and the accumulation of biomass and grain yield, which has resulted in widespread application of fertilisers and soil amendments that supply plant-available P. Traditional application strategies involve application of P fertilisers to the surface soil layers, either with or without subsequent incorporation by tillage. While P is rapidly adsorbed to soil particles, surface P enrichment risks the movement of P and associated soil particles into nearby creeks and rivers during episodic rainfall events, potentially leading to eutrophication and deterioration of water quality (Kim and Li \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Yuan et al. \u003cspan citationid=\"CR75\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). In drier environments, this shallow P can also be effectively stranded in soil layers that quickly dry out, effectively limiting plant access to P for extended periods during crop growth (Eckert \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e1985\u003c/span\u003e; Howard and Tyler \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e1987\u003c/span\u003e; Jarvis and Bolland \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e1991\u003c/span\u003e; Mackay et al. 1999; Norrish et al \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2003\u003c/span\u003e; Singh et al. \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e2005\u003c/span\u003e; Li-yun et al. 2014; Dang et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Limited access to P via loss from the field as runoff or due to dry soil surface layers leads to reduced P availability for crop uptake and a loss of crop productivity. It is desirable to optimise P application rates and placement strategies to both maximise crop production and address growing environmental challenges (Kim and Li \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2016\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eDeeper placement of P is a strategy that can allow landowners to better manage the P supply to crops as well as reducing the risk of environmental damage. Nkebiwe et al. (\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2016\u003c/span\u003e) conducted three meta-analysis studies that concluded that deep-placed (more than 10 cm deep) N and P were more effective for improving deep rooting, nutrient uptake and yield than equivalent broadcast applications from 1022 datasets from 40 field studies published from 1982 to 2015 (85% of studies were conducted since 2000). Collectively, deeper P fertiliser placement resulted in 3.7% higher yield than broadcast, and when co-location of N and P was combined with deep placement, yields were 27.3% (urea and soluble P) and 14.7% (ammonium and soluble P) higher than with conventional shallow placement. Given the greater prevalence of conservation farming practices, including reduced or zero tillage, this deeper placement typically occurs in concentrated bands that occupy relatively small proportions of the soil volume explored by roots.\u003c/p\u003e \u003cp\u003eRoot responses to encountering a zone of enhanced P availability, like a fertiliser band, typically involve a proliferation response in the vicinity of the band (Anghinoni and Barbaer 1980; Yao and Barber \u003cspan citationid=\"CR72\" class=\"CitationRef\"\u003e1986\u003c/span\u003e; Sander and Eghball \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e1999\u003c/span\u003e; Grewal and Graham \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e1999\u003c/span\u003e; Trapeznikow et al. \u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e2003\u003c/span\u003e; Chenet al. \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Ma et al. \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), which maximises the root surface area available to exploit this scarce nutrient resource. Interestingly, Singh et al. (\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e2005\u003c/span\u003e) and Ma et al. (\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2009\u003c/span\u003e) have also highlighted that deep application of nutrients like P can also encourage roots to grow deeper, increasing the exploitation of available moisture in deeper profile layers. The combination of an increased duration of P availability in subsoils that remain moist for longer and a deeper root system that can more efficiently extract water and nutrients like N from deep profile layers can substantially improve productivity and resilience of crops and pastures grown under variable seasonal conditions (Trapeznikow et al. \u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e2003\u003c/span\u003e; Singh et al. \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e2012\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eRoot system architecture (RSA), the combination of key root traits like length, angle, depth and branching capacity (Gregory et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Wasson et al. \u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e2012\u003c/span\u003e, Rabbi et al. \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2017\u003c/span\u003e), determines the spatial configuration of the plant root system and therefore is a key factor in the acquisition of water and nutrients (Fitter \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e1991\u003c/span\u003e; Lynch \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e1995\u003c/span\u003e). Root system architecture has been shown to respond to phosphorus availability, with the spatial distribution of roots able to influence the extent and timing of access to water and nutrients, thus impacting on yield potential (Lynch \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e1995\u003c/span\u003e; de Dorlodot et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Liang et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Ye et al. \u003cspan citationid=\"CR73\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). In a recent review, van der Bom et al. (\u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e2020\u003c/span\u003e) highlighted spatio-temporal trade-offs between efficient resource capture and pre-defined RSA, and advocated for a better understanding of how these trade-offs interact with genotype, environment and management. Under adverse soil or environmental conditions, RSA could be a critical factor in determining the nutrient acquisition, uptake and profitable crop production (Lynch \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e1995\u003c/span\u003e; de Dorlodot et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Ye et al. \u003cspan citationid=\"CR73\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Strock et al. \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e2019\u003c/span\u003e), particularly for the acquisition and uptake of P given its relative immobility in most soils (Barber \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e1995\u003c/span\u003e). Despite its importance, few studies have explored the implications of selection strategies targeting RSA traits (e.g. deep versus shallow root systems) for crop performance in soils with different P availability and profile distributions. Most recently, van der Bom et al. (\u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) reported wheat genotypes with narrow root growth angle and deeper root systems increased deep soil exploration during early growth, with a tendency to more rapidly acquire P placed as a deep fertiliser band, whereas wide angle genotypes with shallower roots increased root growth in the topsoil.\u003c/p\u003e \u003cp\u003eA better understanding of mungbean RSA may allow more targeted approaches to improve adaptation to water- and nutrient-limiting conditions that are currently constraining yields. However, genetic improvement of crop root systems requires knowledge of the intra-species variability in key root parameters and RSA and how these are controlled genetically (O' Toole and Bland 1987). An understanding of the relationships between RSA and plant productivity is also necessary before effective breeding and management strategies can be developed (Gowda et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Henri et al. 2011; Joshi et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Lawn and Rebetzke (\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2006\u003c/span\u003e) identified substantial variation in traits of potential agronomic, adaptive or taxonomic interest among 115 accessions of mungbean, mainly from Australia, West Timor, Papua New Guinea and India. Singh and Bell (2021) reported variability in RSA between contrasting early and late maturing mungbean varieties. However, genetic variation in RSA and its response to P application strategies with respect to plant growth and development in mungbean are largely unknown. Most commercially grown mungbean varieties are very quick to flower and begin pod addition, leading to cessation of further root growth (Singh and Bell 2021) that may affect root proliferation around deeper P bands and P acquisition. The main aims of this study were therefore to explore the interactions between RSA of contrasting mungbean varieties and the distribution of P fertiliser, with implications for contrasting P fertiliser application strategies.\u003c/p\u003e"},{"header":"Materials and methods","content":"\u003cp\u003ePlant material\u003c/p\u003e \u003cp\u003eThe experiment compared four commercial mungbean varieties from Australia, with contrasting growth characteristics and maturity classes. All varieties were produced by the National Mungbean Improvement Program, Queensland Department of Agriculture and Forestry (DAF), Australia, and have been described in detail by Singh and Bell (2021).\u003c/p\u003e \u003cp\u003eBriefly, Jade-AU (3511-9 \u0026times; VC 2768A, released in 2013) is an early maturing variety that dominates production in the Australian industry. It retains green leaf area until harvest, and so can respond to residual soil water and nitrogen.\u003c/p\u003e \u003cp\u003eBerken (released 1975, a direct introduction from the USA with no pedigree history) is an early maturing, older variety with low yield potential that is highly susceptible to plant diseases. It is more determinate in growth pattern, with canopy senescence occurring during pod filling and grain maturation.\u003c/p\u003e \u003cp\u003eCelera II-AU (M 773 \u0026times; OAEM58-62, released 2015) is a recently released, early-intermediate maturing variety with short stature and resistance to the bacterial disease halo blight, caused by \u003cem\u003ePseudomonas savastanoi\u003c/em\u003e pv. \u003cem\u003ePhaseolicola.\u003c/em\u003e\u003c/p\u003e \u003cp\u003ePutland (Berken \u0026times; CPI20141, released 1991) \u0026ndash; is a longer season, photoperiod-sensitive variety that produces large biomass and is much later maturing than the other three varieties in the production environments of northeast Australia (i.e. maturing in 75\u0026ndash;85 days after sowing, compared to 50\u0026ndash;60 days after sowing for other varieties).\u003c/p\u003e \u003cp\u003eExperimental site and unit\u003c/p\u003e \u003cp\u003eThe experiment was conducted in a temperature-controlled glasshouse at The University of Queensland, Brisbane, Australia (27\u0026deg;23\u0026rsquo;S, 153\u0026deg;06\u0026rsquo;E). Purpose-built root observation chambers were constructed from perspex sheets, with chamber dimensions being 60 cm high, 40 cm wide and 3 cm thick. Transparent perspex (8mm thick) sides were used to enable viewing and scanning of roots. The perspex sheets were screwed to the metal frame of the chamber and the backs of the chambers were lined with black plastic to allow easy removal at harvest. The chambers were wrapped in silver insulation to prevent exposure of the roots to light and to minimise fluctuations in soil temperature.\u003c/p\u003e \u003cp\u003eEach chamber was filled with 9 kg air dried soil (Vertosol - Isbell 1986), which was collected in bulk from the 10-30cm cm layer of the soil profile from a commercial field on the central Darling Downs, near Jandowae (Queensland, Australia). This soil was characterised by a clay content of 35\u0026ndash;40%, with key soil chemical characteristics determined using standard methods outlined in Rayment and Lyons (\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). Key physical and chemical properties of the soil are presented in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The soil P status was considered marginal for crop growth, but there were no other deficiencies of macro or micronutrients. The soil was air dried and then crushed to 5mm size with a jaw crusher before being thoroughly mixed to provide a homogenous growing medium. The bulk density of the packed soil in the root observation chamber was estimated to be approximately 1.25 Mg/m\u003csup\u003e3\u003c/sup\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\u003eChemical characteristics of the Vertisol soil used in the experiment\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAnalyte\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eResults\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eUnits\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003epH (1:5 H\u003csub\u003e2\u003c/sub\u003eO)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003epH (1:5 CaCl2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eElectrical conductivity (Sat. Ext)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003edS/m\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOrganic carbon\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.74\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003emg/kg\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePhosphorus (Colwell)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003emg/kg\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePBI (Colwell)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e110\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePhosphorus (BSES)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003emg/kg\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCation Exchange Capacity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e48.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003ecmol (+)/kg\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\u003eExperimental design and P treatments\u003c/p\u003e \u003cp\u003eThe treatments consisted of four mungbean varieties and four P application methods or rates. Four replicate chambers of each combination of variety and P treatment were laid out in a randomised complete block design. The P treatments were (1) \u0026lsquo;Control\u0026rsquo;, with no additional P applied; (2) \u0026lsquo;Surface\u0026rsquo;, where an additional 30 mg P was mixed into soil in the top 5 cm.; (3) \u0026lsquo;Sub layer\u0026rsquo;, where an additional 30 mg P was mixed into a 5cm layer of soil from 20\u0026ndash;25 cm depth.; (4) \u0026lsquo;Deep Band\u0026rsquo;, where an additional 30 mg P was applied in a band across the root chamber at 20 cm depth. Only 30 mg P/chamber was applied for each P treatment, except for the Control with no added P. The P was applied as monoammonium phosphate (MAP \u0026ndash; 10:22:0 N:P:K). Since other basal nutrients were sufficient, no other nutrient applications were made. A diagrammatic representation of the P placement options is presented in the Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eGrowing conditions\u003c/p\u003e \u003cp\u003eSoil in each chamber was slowly wet up over a period of 4\u0026ndash;5 days, before being allowed to drain to near field capacity before sowing. At sowing, four seeds of one of the four chosen varieties were sown in each chamber and gradually thinned to one established plant 6 days after germination. The chambers were arranged on a stand that gave a plant-to-plant spacing of 20cm, and chambers were watered from the top every 10 days to return the soil to field capacity and avoid development of water stress.\u003c/p\u003e \u003cp\u003eMeasurements\u003c/p\u003e \u003cp\u003eBefore the harvesting of the plants at 50 days after emergence, plant height (from base to top of the stem) and total number of branches/node (at the nodes) were recorded. Plants were then destructively sampled by collecting the shoots of each plant above ground level and separating into stem, leaf and pod. The total number of leaves, number of fully expanded leaves, and leaf area (using a LICOR Planimeter (Li-3000 leaf area meter) were recorded.\u003c/p\u003e \u003cp\u003eAfter removing the shoots, chambers were saturated with water overnight, after which each chamber was laid flat and the top perspex plate was removed. Purpose-built plywood pinboards that matched the chamber dimensions and fitted with 3 cm long black nails positioned in a 2\u0026times;2 cm grid was then placed on top of the exposed soil. The moist soil allowed the nails to be easily pushed into the soil of the chamber, while preserving most of the intact root system architecture. The pinboards plus soil and roots were then held erect while the soil was washed from the pinboard using a very fine, low pressure water spray to minimise disturbance of the intact root system. The total number of nodules on the root system was recorded after root washing. The washed root system was then imaged with a digital camera (Canon, SX720 HS) mounted on a tripod and the images were converted to high-contrast black and white images using Adobe Photoshop software. Images were initially cropped to the same size and then image adjustment and threshold tools were used to convert the image into black and white. The average root angle of the first and second lateral branches was determined relative to the vertical axis using in-house software specifically designed for this purpose. After imaging, the roots were stored in 70% ethanol in a cold room (4\u003csup\u003eo\u003c/sup\u003eC) for later detailed measurement.\u003c/p\u003e \u003cp\u003eDry matter of each plant part (stem, leaf, pods and roots) was obtained after drying in a dehydrator for four days at 70\u0026deg;C. Development of leaf area, root surface area, biomass, shoot mass (leaf\u0026thinsp;+\u0026thinsp;stem) and root mass were quantitatively determined. Macro and micronutrient analyses were performed on the composite shoot samples (which included stem\u0026thinsp;+\u0026thinsp;leaf\u0026thinsp;+\u0026thinsp;pods) from an analytical laboratory.\u003c/p\u003e \u003cp\u003eIntact root characteristics\u003c/p\u003e \u003cp\u003eImages of intact roots were analysed using WinRhizo Pro 2019 software (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://regentinstruments.com/assets/winrhizo\u003c/span\u003e\u003cspan address=\"https://regentinstruments.com/assets/winrhizo\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e). The image was acquired from the camera by electing the \u0026lsquo;origin\u0026rsquo; setting in the software, and the following settings were chosen - image resolution was 600 dpi, the root background was changed to grey scale and calibration was performed by marking the length and width of the image (60 cm \u0026times; 40 cm). The saved calibration was loaded onto each image before the start of the analysis. Before loading the calibration, the root diameter classes were changed into 10 different widths with a width interval of 0.25mm. The total root length (cm), total root surface area (cm\u003csup\u003e2\u003c/sup\u003e), root surface area in top and bottom 30 cm of the chambers, mean root diameter (mm) and the number of root tips, forks and crossings were determined from image analysis. Images of intact roots were also analysed based on vertical distribution within the root chamber, with the top 30 cm and bottom 30 cm analysed separately. These analyses were conducted to determine whether varieties differed in their exploration of the shallow (top 0\u0026ndash;30 cm) and deeper (30-60cm) parts of the soil profile with the different fertiliser P placements.\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis\u003c/h2\u003e \u003cp\u003eAnalysis of variance (ANOVA) was performed using XLSTAT (2023.1.4. version). Data were statistically analysed using two-way ANOVA to understand the main treatment effects of fertiliser treatment and varieties. Normal distribution of data test and standardisation are automatically performed with the XLSTAT two-way ANOVA assessment. Fisher\u0026rsquo;s least significance differences test was used to compare the treatment means.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eShoot and root growth of different varieties in response to P treatments\u003c/p\u003e \u003cp\u003eVisual differences in the shoot and root growth of each variety grown in the deep \u0026lsquo;Band\u0026rsquo; treatment are presented in the Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The late maturing variety Putland shows a relatively poor distribution of roots in the bottom soil profile layers, has thicker topsoil roots and has no pods, whereas the early maturing Jade and Berken and intermediate-maturity Celera II varieties show greater root proliferation in the bottom soil profile layers. Celera II also shows greater plant height and numbers of pods compared to the early maturing varieties Jade and Berken (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eDifferences between varieties and P treatments were observed for several shoot and root parameters. With the exception of pod yield, all above ground measured plant parameters did not show any overarching effects of P treatments, although there were significant interactions between P treatments and varieties for the below ground total root length and root surface area. However, there was a trend for deep banding to result in relatively greater total root volume, root surface area and plant biomass, followed by deeper sub layer P treatments, with the control or shallow P treatments recording the lowest root volume, root surface area and plant biomass.\u003c/p\u003e \u003cp\u003ePhenological characteristics such as the leaf appearance rate and time to first flowering were not influenced by P treatments, but phenological differences were noted between early, intermediate and late maturing varieties as expected. Flowers were first recorded in the early maturing varieties Jade and Berken, followed by the intermediate variety Celera II. Putland had not flowered before the end of this experiment, which was in the pod development stages for the early and intermediate maturity varieties. Although there were no effects of P treatments that were consistent across varieties for the number of early flowers, there was a trend for a greater number of flowers (1.27 vs 1.06, or ~\u0026thinsp;20% more) in the deep banded and deeper dispersed P layer treatments than in the control (no added P) and surface (shallow dispersed) P layer treatments.\u003c/p\u003e \u003cp\u003ePlant biomass\u003c/p\u003e \u003cp\u003ePlant biomass, a combination of pod mass, shoot mass (leaf\u0026thinsp;+\u0026thinsp;stem) and root mass, was not influenced by P treatment (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eB) and there were no interactions between P treatment and variety. However, varietal differences in shoot mass, pod mass, root mass and total plant biomass were recorded (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA - P\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Celera II and Berken recorded significantly greater (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001) plant biomass (12.6 g and 12.1 g, respectively), than either Jade (10.9g) or Putland (10.2g).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe mass of vegetative material (leaf\u0026thinsp;+\u0026thinsp;stem) differed among the varieties (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA) in a fashion that was consistent with the duration of the pre-flowering period, with Putland (8.59g) and Celera II (8.00g) producing significantly (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001) more vegetative shoot mass than either Jade (6.28g) or Berken (6.09g). The ratio of leaf mass to that of total vegetative matter was greatest for Putland (0.51), with the other three varieties varying between 0.44 and 0.46 (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001).\u003c/p\u003e \u003cp\u003eRoot mass showed similar effects, with only varietal differences being statistically significant (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Consistent with the time to flowering and cessation of vegetative growth, the late maturing variety Putland also had the highest root mass (1.60g), compared with the other three varieties (0.92 g to 1.1 g (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA).\u003c/p\u003e \u003cp\u003eUnlike the responses in vegetative biomass, pod weight was influenced by both variety (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA) and to some extent P treatment (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eB), although again there were no variety * P treatment interactions. Berken recorded the highest pod weight (5.31 g), compared with 4.14 g and 3.81g for Celera II and Jade respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA), although the total number of pods was highest for Celera II (16), followed by Berken (12) and least for the Jade (8 - \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001). The deep banded P treatment recorded the highest pod weight (4.8 g) while the surface P treatment recorded the lowest pod weight (4.1g; Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eB).\u003c/p\u003e \u003cp\u003eShoot P uptake and internal P use efficiency (iPUE)\u003c/p\u003e \u003cp\u003eSignificant (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001) varietal differences in shoot P uptake, a product of shoot dry mass (leaf\u0026thinsp;+\u0026thinsp;stem\u0026thinsp;+\u0026thinsp;pods) and shoot P concentration, were recorded (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eA). While the later maturing Putland showed the highest P concentrations in plant biomass (data not shown), total P uptake was greatest for Celera II (30.8 mg) and lowest for Berken (19.8 mg), with Jade and Putland intermediate. P treatments resulted in statistically significant effects on P uptake (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.049) and to some extent on iPUE (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.10) (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eB). There was a trend for treatments enriched with P in deeper profile layers (either deep banded or dispersed in sub profile layers with or without topsoil P enrichment) to show greater shoot P uptake, although the lack of strong dry matter responses meant the iPUE in these treatments decreased compared with control or surface applied treatment (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eB).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eVariety and P treatment effects on below ground root system architecture and root growth\u003c/p\u003e \u003cp\u003eThere were significant P treatment responses in both root growth angle and number of nodules (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). The surface P treatment had relatively higher root growth angle (67\u0026deg;) than the other three P treatments (around 61\u0026deg;; Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eA). Root growth angle also differed among varieties, with the late-maturing Putland and intermediate maturity Celera II recording greater root growth angles (64\u0026deg;-67\u0026deg;) than the early-maturity Jade and Berken (59\u0026deg;- 61\u0026deg;; \u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.015). Similarly, the number of nodules on mungbean roots were affected by both P treatment (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.038) and variety (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.05; Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eB). Deep banded and sub layer dispersed P treatments recorded the most nodules (\u0026gt;\u0026thinsp;90), compared with the surface P treatments with the lowest number of nodules (69 - Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eB). Among varieties, Celera II (102) and Berken (86) recorded more nodules than either Jade or Putland (80 and 74, respectively).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eSignificant root trait responses to P treatments were observed for both mean root diameter and total root volume in the whole root chamber, with these two root traits also responding similarly for roots in the bottom 30cm of the root chambers (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). Mean root diameter and total root volume were greatest with deep P applications (either a dispersed subsoil layer or a deep band), with no differences between the other P treatments (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eA, B), with the same responses recorded in the bottom 30cm section (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eC,D).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe total root length and total root surface area exhibited significant interactions between variety and P treatments (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.033 and 0.002, respectively). Since the P treatment responses were similar for both the traits throughout the 60cm root chamber, we have illustrated this using root surface area responses (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e). Root surface area varied from around 1200 to 1800 cm\u003csup\u003e2\u003c/sup\u003e with no significant differences among varieties for the control and surface P treatments (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eA). However, varieties appeared to respond differently to the deep sub layer and deep banded treatments. Jade and Berken showed significantly higher root surface areas (1630\u0026ndash;1730 cm\u003csup\u003e2\u003c/sup\u003e) in the deeper sub layer treatment than either Putland or Celera II (1200 cm\u003csup\u003e2\u003c/sup\u003e). In contrast, Celera II showed higher root surface area (1800 cm\u003csup\u003e2\u003c/sup\u003e) in the deep banded treatment compared with the Berken (1200 cm\u003csup\u003e2\u003c/sup\u003e) and Putland (1450 cm\u003csup\u003e2\u003c/sup\u003e). Separate analyses of root surface area in either the top or bottom sections showed highly significant interaction effects (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.003 and 0.014 respectively; Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eB-C). In the top 30 cm soil profile, P responses were like the whole soil profile with Jade and Berken showing higher root surface area in the top section compared with the Putland and Celera II, whereas Celera II showed highest root surface area compared with the deep banded treatment for Berken (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eB). In the bottom 30 cm soil profile, Celera II had the highest root surface area with the deep banded treatment (979 cm\u003csup\u003e2\u003c/sup\u003e), compared with the other P treatments (559\u0026ndash;577 cm\u003csup\u003e2\u003c/sup\u003e), while Jade had the highest root surface area with the deeper sub layer, compared with control or the surface P treatments (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eCd).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThere were clear varietal differences in root surface area in response to deep P treatments, with increases in root surface area in all compartments (whole chamber, top 30cm or bottom 30cm \u0026ndash; Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ea, b, c) in response to deeper applied P in all varieties except Putland. Responsive varieties, however, differed in how they responded to deeper P treatments. For example, in the top compartment it was only Berken which showed significantly higher root surface area with the deeper sub layer P treatment compared with the control or surface P treatments (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eB). However, in the bottom compartment higher root surface area was recorded in the deeper sub-layer P treatment for Jade while a similar response was recorded in Celera II for the deep banded treatment (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eC).\u003c/p\u003e"},{"header":"Discussion","content":"\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eAbove-ground growth responses to variety and fertiliser P treatments\u003c/h2\u003e \u003cp\u003eThis study did not provide any evidence of interactions between fertiliser treatment and mungbean variety in terms of above ground growth and development, although there were significant differences between varieties and small growth responses to fertiliser P placement. Differences in phenological development (time to flowering) between varieties were observed in this study, along with the rate of flower addition once flowering had commenced, with differences consistent with expected varietal characteristics and previous studies (Singh and Bell, 2021). While Putland did not flower during this experiment, and continued vegetative growth for the duration, the early maturing Jade and Berken flowered slightly quicker and exhibited a greater number of early flowers than the intermediate maturity Celera II.\u003c/p\u003e \u003cp\u003eIncreasing the supply of P (comparing the Control treatment with all those with added P) had no statistically significant impact on above-ground biomass production in this study, possibly due to the combination of only moderately-low P status and a low P demand from the mungbean plant, given there was only a single mungbean plant grown in each rhizobox that contained 9 kg air dried soil. However, while there were no statistically significant increases in flower production in response to P addition, the deep-banded and deep sub soil layer P treatments had around 20% more flowers than the control or surface applied P treatments. This suggested that deep placement of P contributed to advancement and/or increased production of flowering in the early maturing varieties, and these effects were even stronger in terms of subsequent pod addition and growth. Increased flower production with increased P supply has been reported in many studies for various plant species (Kim and Li, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2016\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eWhile growth responses in above ground biomass were limited, there were significant differences in P accumulation in above ground biomass in response to both genotype and P treatment, with significant differences in iPUE also recorded. While the shallow P application did not result in increased P uptake compared to the unfertilised Control, consistent with the limited root development in those layers by all varieties, there were 14\u0026ndash;16% increases in plant P uptake with the Deep P layer and Banded treatments, respectively. These differences were due to additive effects of small but not statistically significant increases in both crop biomass (8%) and biomass P concentration (6\u0026ndash;8%), with these effects collectively representing P recovery efficiencies of only 6% (deep P layer) and 12% (deep P band) of applied P. The greater relative increase in P uptake compared to growth increase resulted in a 10% decline in internal iPUE for these treatments (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eB).\u003c/p\u003e \u003cp\u003eDifferences in P uptake between varieties were much larger, with biomass P content in Celera II\u0026thinsp;\u0026gt;\u0026thinsp;Jade and Putland\u0026thinsp;\u0026gt;\u0026thinsp;Berken, with Berken (18.5 mg P) only acquiring 62% of the P taken up by Celera II (29.9 mg P). These varietal effects were due to contrasting differences in above-ground biomass (Celera II and Berken\u0026thinsp;\u0026gt;\u0026thinsp;Jade\u0026thinsp;\u0026gt;\u0026thinsp;Putland) and tissue P concentration (Jade, Putland and Celera II\u0026thinsp;\u0026gt;\u0026thinsp;Berken). Interestingly, the delayed flowering in Putland, which allowed a longer time for root growth and presumably nutrient accumulation, did not result in greater uptake of P due to the slower rate of growth and dry matter accumulation (Singh and Bell 2021). The low P recovery by the early maturity variety Berken is consistent with other studies that have shown lower tissue P concentrations in response to rapid growth rates. For example, De Bauw et al (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2020\u003c/span\u003e) reported depleted shoot P concentrations induced by vigorous plant establishment in response to micro-doses of P placement in rice, while Vandamme et al (\u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e2016\u003c/span\u003e) reported low tissue P concentrations that occurred during periods of rapid growth of plants in an initially high P medium due to rapid depletion of soil solution P in the root zone.\u003c/p\u003e \u003cp\u003eThe differences in accumulation of plant P and biomass resulted in significant variation in iPUE between varieties, with Berken (602 mg DM/mg P uptake)\u0026thinsp;\u0026gt;\u0026thinsp;\u0026gt;\u0026thinsp;Celera II, Jade and Putland (372\u0026ndash;395 mg DM/mg P uptake). The reason for these differences could be related to differences in leaf area index, chlorophyll content and photosynthetic rate as reported for gluten free wheat varieties (Zhu et al \u003cspan citationid=\"CR79\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). In our studies, we didn\u0026rsquo;t directly measure these parameters, however, the early maturing varieties Berken and Jade showed greater rates of expansion of individual leaf area during early growth (Singh and Bell 2021), and both showed significantly greater dry matter accumulation per unit leaf area (1.8 g/cm\u003csup\u003e2\u003c/sup\u003e) compared with the intermediate and late maturing varieties (1.0 g/cm\u003csup\u003e2\u003c/sup\u003e) in this study. A greater dry matter per unit leaf area indicates greater photosynthetic rates for these varieties. A correlation coefficient matrix between iPUE and other key plant parameters also showed iPUE was significantly related to pod mass, specific leaf area (leaf area per unit leaf mass), plant biomass/leaf area, and calcium % (Supplementary Table\u0026nbsp;1). Irfan et al (\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2017\u003c/span\u003e) has also reported significant variability in the grain yield, P accumulation and iPUE among mungbean genotypes, with these observations suggesting there may be opportunities for further research to improve the efficiency of use of fertiliser P within existing mungbean varieties. Such experimentation would need to consider determination of leaf area expansion, shoot dry matter, tissue P concentration and iPUE at various growth stages for a larger set of mungbean varieties.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eBelow-ground growth responses to variety and fertiliser P treatments\u003c/h3\u003e\n\u003cp\u003eWhile there was little difference between varieties in above ground biomass production, there were significant differences recorded in below ground parameters that are typically related to resource capture and nutrient supply, such as nodule numbers and root morphological traits such as root angle, root length, root surface area and root volume, with these traits only occasionally interacting with fertiliser P treatment. Greater nodule numbers were recorded in the intermediate maturing Celera II, which also exhibited the widest root angle and developed the largest total root volume, along with the early maturing Berken. Both Berken and Celera II supported the largest root volumes as a result of greater total root length with narrow root diameters, with the later maturing variety Putland unable to achieve similar metrics despite a longer period of root growth. Putland produced 16% less total root length, although these roots were significantly thicker than those of Berken and Celera II. Most previous studies have reported that a major portion of roots (\u0026gt;\u0026thinsp;70%) are present in the top 20\u0026ndash;30 cm layers (e.g., Gao et al. \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). In our study, total root length in the top 30 cm and bottom 30 cm sections were generally similar, but roots in the top 30cm compartment had a 12% greater mean root diameter. This resulted in around 10% greater root surface area and 22% greater root volume in the upper 30cm compartment in this study.\u003c/p\u003e \u003cp\u003eAcquisition of water and nutrients are related to the ability of roots to exploit the available soil volume, and that ability is primarily governed by root length and root surface area in the various soil layers (Borkert and Barber 1983; Li et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2006\u003c/span\u003e). However, such broad adaptive traits are likely to be less effective for enhanced recovery of fertiliser P, which is typically applied in heterogeneous patches in soils with otherwise low background P fertility. Low soil solution P concentrations and a reliance on diffusive supply to replenish rapidly P-depleted rhizosphere soil volumes result in root P uptake occurring primarily near root tips that are exploring \u0026lsquo;new\u0026rsquo; soil. An effective response to low soil P availability would therefore be expected to consist of enhanced root branching and proliferation responses that increase root length in the fertilised zone (Hill et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2005\u003c/span\u003e; Robinson \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e1996\u003c/span\u003e), and in particular, increases the production of root tips that can exploit undepleted soil solutions (Richardson et al. \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). However, the deep banding treatment in which the largest increases in P uptake were recorded suggested the opposite actually occurred in these mungbean varieties, with 10\u0026ndash;25% fewer root tips, forks and crossings (indicators of root proliferation in response to P fertilisation) than in the average of all other fertilised and unfertilised treatments (data not shown).\u003c/p\u003e \u003cp\u003eWhilst there were occasionally significant interactions between P treatments and root parameters in either the top or bottom compartments (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eB, C), there was no evidence of any increases in root length or proliferation in these mungbean varieties in response to P fertilisation, with the predominant response being a general increase in root surface area achieved through an increase in root diameter. This was most obvious in the P treatments applied into deeper soil layers. While root thickening has been recorded as characteristic of root development in some dicotyledonous species like bean (Lynch et al. 2011), root expansion is typically reduced in favour of continued root elongation under conditions of low P availability. While there is evidence for thinner roots in the unfertilised control and ineffective shallow P treatments (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eA, C), the thicker roots found in the deep P band or layer treatments would seem to represent an ineffective response to enhance P acquisition that is reflected in the relatively small increases in tissue P concentration and plant P uptake.\u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eP availability can influence the root growth angle and root distribution in the soil profile\u003c/h2\u003e \u003cp\u003eRoot growth angle has been noted to be the key indicator for a deep or shallow rooting genotype (Singh et al. \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Chen et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Uga et al. \u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e2013\u003c/span\u003e) and plays a major role in determining RSA. However, while root growth angle is primarily governed by plagiogravitropism (Nakamoto \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e1994\u003c/span\u003e), it can also be influenced by other factors such as soil strength, soil water, soil temperature and soil nutrition, especially phosphorus and nitrogen (Nakamoto, \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e1993\u003c/span\u003e, \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e1994\u003c/span\u003e; Liao et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2001\u003c/span\u003e; Trachsel et al. 2013). Evidence from different crops has indicated that genotypes with narrow root growth angles are not only deep rooting, but they also tend to grow and develop more rapidly in both above and below-ground components, leading to early flowering and maturity (Singh et al \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). Genetic variability in root growth angle, leading to development of relatively shallower or deeper root systems, were noted for the mungbean varieties grown under high fertility conditions in a previous study, where early maturing variety Jade and Berken showed relatively narrower root growth angle (Singh and Bell 2021). In the current study, in addition to the inherent varietal differences, P treatments also influenced the root growth angle. Shallower P treatment resulted in wider root growth angle and a shallower distribution of root system (even though this did not result in additional P uptake), whereas availability of relatively less P in the topsoil for the control P treatment or concentrated availability of P in the deep soil resulted in narrower root growth angle and deeper distribution of root system. Other studies have reported differential stimulation of shallower basal root growth angles in P-deficient environments (Liao et al \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2001\u003c/span\u003e; Zhao et al \u003cspan citationid=\"CR76\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; Ao et al 2010). Lynch and Brown (\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2001\u003c/span\u003e) and Lynch (\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2011\u003c/span\u003e) reported that root growth angle has a dominant influence on P acquisition (6-fold) and yield of bean (3-fold), and Zhu et al (\u003cspan citationid=\"CR78\" class=\"CitationRef\"\u003e2005\u003c/span\u003e) reported 2-fold variation in P acquisition for maize genotypes, with these studies conducted in stratified soils where shallow root growth angle increased P acquisition by increasing topsoil foraging.\u003c/p\u003e \u003cp\u003eP availability in shallower topsoil has been reported to control root branching, basal root length and adventitious roots for common bean (Miguel et al \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2013\u003c/span\u003e), but our results show no similar response in mungbean to increased availability of P in the shallow topsoil layer. Responses were more pronounced in response to deep P bands or enriched layers, with these placements resulting in increased root diameter and surface area that appeared to differ somewhat between varieties. Differences in varietal response to P availability differed between the top and bottom soil root compartments for the early and intermediate maturity varieties, but not for Putland. The early maturing Jade and Berken showed significantly greater total root surface area for the deeper dispersed subsoil layer treatment, whereas the intermediate variety Celera II showed greatest total root surface area for the deep banded treatment. In both cases, effects were more prominent in the bottom compartment rather than in the top compartment where the P enrichment occurred.\u003c/p\u003e \u003cp\u003eThe lack of response to the enriched shallow topsoil in all mungbean varieties in this study may relate to the lack of strong lateral root development in that part of the soil profile. This is evident when comparing root images, showing no additional lateral root development in the surface applied P compared with the control (Supplementary Fig.\u0026nbsp;1). Proliferation of roots in P-enriched topsoil would therefore appear to be determined by genetic factors that influence root system architecture, in addition to a response to increased availability of P in the topsoil, as reported in other studies (Miguel et al. \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Chen et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Chen et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Zhu and Lynch (\u003cspan citationid=\"CR77\" class=\"CitationRef\"\u003e2004\u003c/span\u003e) have highlighted the genotypic variability in biomass investment by plants in response to P scarcity, with lateral root extension preferred due to the requirement for less biomass and P investment compared to extension of other root types. These authors suggested that enhanced lateral rooting in response to P stress may be harnessed as a useful trait for the selection and breeding of more P-efficient maize genotypes. Liao et al. (\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2001\u003c/span\u003e) reported basal roots of the P-inefficient common bean genotype extended deeper compared with those of the P-efficient genotype when experiencing P stress. In contrast, basal roots of the P-efficient genotype became shallower with P stress, while root growth angle reduced significantly, and roots became more horizontal (Liao et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2001\u003c/span\u003e). The extent to which such traits exist within mungbean germplasm should therefore be explored, particularly as mungbean is often grown in soil profiles that strongly P-stratified, and the short crop phenologies do not offer much opportunity to develop deep and well distributed root systems.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eVarietal differences in P acquisition and internal P use efficiency\u003c/h3\u003e\n\u003cp\u003eThis study has found significant variability in P uptake and P use efficiency between varieties (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea), with no apparent relationship between P uptake and total root surface area. The variety Jade had the greatest total root length and root surface area compared to other varieties but shoot P uptake was the second lowest. The other three varieties (early or late maturing) had similar or relatively less total root surface area or volume compared with Jade, but with contrasting P uptake. For example, Berken, Putland and Celera II had the similar total root surface area and volume, but Berken had the lowest shoot P uptake, whereas the Celera II had the highest P uptake. While there are likely to be other factors that are important for determining varietal differences in total P uptake, it is the apparent compensatory ability of the variety Berken to overcome poor P acquisition by much more efficient utilisation of P within the plant to produce biomass that is of considerable interest. Rose et al. (\u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e2011\u003c/span\u003e) reported that internal P utilisation efficiency is often lower in plants with high P acquisition efficiency as a result of high tissue P concentration. In our study, late and intermediate maturing Putland and Celera II had high P acquisition and shoot P concentration, compared with the early maturing Berken, which had the highest iPUE.\u003c/p\u003e \u003cp\u003eHoad et al. (\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2001\u003c/span\u003e) and Romer (\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e1986\u003c/span\u003e) reported that the nutrient requirements can vary considerably among varieties for other crop species. While relationships between P uptake and measured root traits were not recorded in our study, P uptake can also be influenced by the effective requirement of P during different stages of plant growth and development, which differed among the varieties. Singh and Bell (2021) have previously reported linear relationships between expanding total root surface area and leaf area obtained from sequential destructive sampling during early growth stages up to flowering for the same varieties used in the current study, but differences in phenology and the time to cessation of root growth between varieties would have potentially masked these effects when measured at a common harvest date. Root systems are known to be plastic in nature and can interact dynamically with soil physical, chemical and biological factors at different stages of a growing season (Lynch \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e1995\u003c/span\u003e; Wu et al. \u003cspan citationid=\"CR71\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Chen et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Development of roots occurs in synchrony with shoot growth (Wang et al. \u003cspan citationid=\"CR69\" class=\"CitationRef\"\u003e2006\u003c/span\u003e), so characterisation of RSA over time is important to understand the interactions between RSA and shoot growth dynamics and nutrient uptake. The vigorous root growth and more rapid rates of root extension seen in the early maturing mungbean varieties appeared to be consistent with acquisition of enough water and nutrients to be able to support rapid shoot growth through increased dry matter accumulation per unit leaf area (Singh and Bell 2021), or increased leaf transpiration (Pang et al. \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2017\u003c/span\u003e), and might have been correlated with early flowering and podding characteristics for the early maturing varieties studied (Singh and Bell 2021). Collectively, our data would suggest that further exploration of mungbean germplasm for variation in iPUE could provide opportunities to improve fertiliser use efficiency in this species.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eThe strongest P response in mungbean shoot and root traits and the greatest P uptake were observed with deeper placement of P fertiliser, especially when applied in a concentrated band compared to P applied in the shallow topsoil layers. The P responses in above-ground growth and development were most marked for reproductive development (flowering and podding), while below-ground responses were observed in key root traits such as mean root diameter and total root volume and root length and root surface area, all of which increased with deep banding relative to the unfertilised plants and those where P was applied in a shallow topsoil layer. The total root length and root surface area also increased when the same amount of P was applied in a less concentrated fashion across a larger soil volume in the deeper profile layer, and while these responses were recorded in both the soil compartment receiving the fertiliser and that below it, effects were confounded by significant varietal interactions.\u003c/p\u003e \u003cp\u003eThese are important findings for fertiliser P placement for mungbean crops that are typically grown in rainfed cropping systems under zero tillage conditions. Increases in root diameter and hence root surface area and volume that were observed in the deep band and enriched sub layer P treatments have been identified as anatomical traits that may be promising breeding targets for soil resource acquisition. However, these broad adaptive traits are not the most effective for enhanced recovery of fertiliser P applied in heterogeneous patches in soils with otherwise low background P fertility. Low soil solution P concentrations, root P uptake that occurs primarily near the root tips and a reliance on diffusive supply of P to replenish rapidly depleted rhizosphere soil volumes would suggest that a root proliferation response that maximises the exploitation of the fertilised soil volume would be more effective. The fact that mungbean plants showed no evidence of proliferation in P-enriched bands or soil layers in these studies is therefore consistent with the relatively small increases in tissue P concentration and plant uptake in response to fertiliser P application in soils with a moderate-low P fertility.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eRSA\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;Root system architecture\u003c/p\u003e\n\u003cp\u003eiPUE\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Internal phosphorus use efficiency\u003c/p\u003e\n\u003cp\u003eMAP \u0026nbsp; \u0026nbsp; \u0026nbsp; Mono Ammonium Phosphate\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAuthor Contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eVijaya Singh contributed to the conceptualization of the research, experimental set up, data collection, result analysis and writing of the main manuscript text. Marissa Collins and Mike Bell contributed to the conceptualization of the research and interpretation of results, helped to improve the text and provided the financial support used to conduct the research. All authors contributed to the article and approved the submitted versions.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis project was supported by Grains Research Development Corporation through project UOQ-002RTX and UQ00063, and through funding contributions from the Sir Edwin Marsden Tooth Bequest and the School of Agriculture and Food Science, University of Queensland.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting Interests\u003c/strong\u003e The authors have no relevant financial or non-financial interests to disclose.\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAnghinoni I, Barber SA (1980) Phosphorus application rate and distribution in the soil and phosphorus uptake by corn. Agron J 44:1041\u0026ndash;1044\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAdesemoye AO, Kloepper JW (2009) Plant-microbe interactions in enhanced fertilizer-use efficiency. Appl Microbiol Biotechnol 85:1\u0026ndash;12\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAraujo SS, Beebe S, Crespi M, Delbreli B, Gonzaliz EM, Gruber V et al (2015) Abiotic stress responses in legumes: strategies used to cope with environmental challenges. Crit Rev Plant Sci 34:237\u0026ndash;280. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1080/07352689.2014.898450\u003c/span\u003e\u003cspan address=\"10.1080/07352689.2014.898450\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eArnoldi A, Zanoni C, Lammi C, Boschin G (2015) The role of grain legumes in the prevention of hypercholesterolemia and hypertension. CRC Crit Rev Plant Sci 34:1\u0026ndash;3. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1080/07352689.2014.897896\u003c/span\u003e\u003cspan address=\"10.1080/07352689.2014.897896\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBarber SA (1995) Soil Nutrient Bioavailability: A Mechanistic Approach. 2nd Edn. John Wiley \u0026amp; Sons, New York\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBorkert CM, Barber SA (1985) Soybean shoot and root growth and phosphorus concentration as affected by phosphorus placement. Soil Sci Soc Am J 49:152\u0026ndash;155\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChen X, Ding Q, Blaszkiewicz Z, Li Y (2017) Phenotyping for the dynamics of field wheat root system architecture. Sci Rep 7:37649\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChen Y, Dunbabin V, Diggle A, Siddique K, Rengel Z (2011) Development of a novel semi-hydroponic phenotyping system for studying root architecture. Funct Plant Biol 38(5):355\u0026ndash;363\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChen Y, Ghanem ME, Siddique KHM (2017) Characterising root trait variability in chickpea (\u003cem\u003eCicer arietinum\u003c/em\u003e L.) germplasm. J Exp Bot 68:1987\u0026ndash;1999\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChen Y, Rengel Z, Palta J, Siddique KHM (2018) Efficient root systems for enhancing tolerance of crops to water and phosphorus limitation. Indian J Plant Physiol 23:689\u0026ndash;696\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDang YP, Seymour NP, Walker SR, Bell MJ, Freebairn DM (2015) Strategic tillage in no-till farming systems in Australia\u0026rsquo;s northern grains growing regions: I. Drivers and implementation. Soil Till Res 152:104\u0026ndash;114\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDe Bauw P, Mai TH, Schnepf A et al (2020) A functional structural model of upland rice root systems reveals the importance of laterals and growing root tips for phosphate uptake from wet and dry soils. Ann Bot 126:789\u0026ndash;806. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1093/aob/mcaa120\u003c/span\u003e\u003cspan address=\"10.1093/aob/mcaa120\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDe Bauw P, Smolders E, Verbeeck M, Senthilkumar K, Houben E, Vandamme E (2021) Micro-dose placement of phosphorus induces deep rooting of upland rice. Plant Soil 463:187\u0026ndash;204. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s11104-021-04914-z\u003c/span\u003e\u003cspan address=\"10.1007/s11104-021-04914-z\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ede Dorlodot S, Forster B, Pag\u0026eacute;s L, Price A, Tuberosa R, Draye X (2007) Root system architecture: opportunities and constraints for genetic improvement of crops. Trends Plant Sci 12:474\u0026ndash;481\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eEckert DJ (1985) Review: Effects of reduced tillage on the distribution of soil pH and nutrients in soil profiles. J Fert Issues 2:86\u0026ndash;90\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFitter AH (1991) Characteristics and functions of root systems. In Plant Roots: The Hidden Half. 2nd edn. Eds. Y Waisel pp.\u0026nbsp;3\u0026ndash;25. Marcel Dekker, New York, USA\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGao Y, Duan A, Qiu X, Liu Z, Sun J, Zhang J, Wang H (2010) Distribution of roots and root length density in a maize/soybean strip intercropping system. Agric Water Manag 98(1):199\u0026ndash;212. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.agwat.2010.08.021\u003c/span\u003e\u003cspan address=\"10.1016/j.agwat.2010.08.021\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGowda VRPV, Henry A, Yamauchi A et al (2011) Root biology and genetic improvement for drought avoidance in rice. Field Crop Res 122:1\u0026ndash;13. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.fcr.2011.03.001\u003c/span\u003e\u003cspan address=\"10.1016/j.fcr.2011.03.001\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGu R, Chen F, Long L, \u0026hellip;, Yuan L (2016) Enhancing phosphorus uptake efficiency through QTL-based selection for root system architecture in maize. J Genet Genomics 43(11):663\u0026ndash;672. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.jgg.2016.11.002\u003c/span\u003e\u003cspan address=\"10.1016/j.jgg.2016.11.002\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGregory PJ, Bengough AG, Grinev D, Schmidt S, Thomas WTB, Wojciechowski T, Young M (2009) Root phenomics of crops: opportunities and challenges. Funct Plant Biol 36:922\u0026ndash;929\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGrewal HS, Graham RD (1999) Residual effects of subsoil zinc and oilseed rape genotype on the grain yield and distribution of zinc in wheat. Plant Soil 207:29\u0026ndash;36\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHenry A, Gowda VRP, Torres RO, McNally KL, Serraj R (2011) Variation in root system architecture and drought response in rice (Oryza sativa): phenotyping of the OryzaSNP panel in rainfed lowland fields. Field Crops Res 120:205\u0026ndash;214\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHill JO, Simpson RJ, Wood JT, Moore AD, Chapman DF (2005) The phosphorus and nitrogen requirements of temperate pasture species and their influence on grassland botanical composition. Aust J Agric Res 56:1027\u0026ndash;1039. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1071/AR04279\u003c/span\u003e\u003cspan address=\"10.1071/AR04279\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHoad SP, Russell G, Lucas ME, Bingham IJ (2001) The management of wheat, barley, and oat root systems. Adv Agron 74:193\u0026ndash;246. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/S0065-2113(01)74034-5\u003c/span\u003e\u003cspan address=\"10.1016/S0065-2113(01)74034-5\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHoward DD, Tyler DD (1987) Comparison of surface applied phosphorus and potassium rates and in-furrow fertiliser combinations for not-till corn. J Fert Issues 4:48\u0026ndash;52\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eIrfan M, Shah JA, Abbas M (2017) Evaluating the performance of mungbean genotypes for grain yield, phosphorus accumulation and utilisation efficiency. J Plant Nutr 40:2709\u0026ndash;2720. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1080/01904167.2017.1381718\u003c/span\u003e\u003cspan address=\"10.1080/01904167.2017.1381718\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eIsbell R (2016) Australian Soil Classification. CSIRO Publishing\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJarvis RJ, Bolland MDA (1991) Lupin grain yields and fertiliser effectiveness are increased by banding superphosphate below the seed. Aust J Exp Agric 31:357\u0026ndash;366\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJoshi D, Singh V, van Oosterom (2016) Erik, Mace, Emma, Jordan, David, and Hammer, Graeme Genetic manipulation of root system architecture to improve drought adaptation in sorghum. The sorghum genome. Edited by Sujay Rakshit and Yi-Hong Wang. Cham, Switzerland: Springer.207\u0026ndash;226.\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/978-3-319-47789-3_11\u003c/span\u003e\u003cspan address=\"10.1007/978-3-319-47789-3_11\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKim H-J, Li X (2016) Effects of phosphorus on shoot and root growth, partitioning, and phosphorus utilization efficiency in Lantana. Hort Sci 51(8):1009\u0026ndash;1009. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.21273/HORTSCI.51.8.1001\u003c/span\u003e\u003cspan address=\"10.21273/HORTSCI.51.8.1001\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLawn RJ, Rebetzke G (2006) Variation among Australian accessions of the wild mungbean (Vigna radiata ssp. sublobata) for traits of agronomic, adaptive, or taxonomic interest. Aus J Agri Res 57:119\u0026ndash;132\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi H, Ma Q, Li H, Zhang F, Rengel Z, Shen J (2014) Root morphological responses to localized nutrient supply differ among crop species with contrasting root traits. Plant Soil 376(1\u0026ndash;2):151\u0026ndash;163\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi L, Sun J, Zhang F, Guo T, Bao X, Smith A, Smith SE (2006) Root distribution and interactions between intercropped species. Oecologia 147:280\u0026ndash;290\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLiang C, Li A, Li YH, Liang W, Guo C S, et al (2017) Melatonin regulates root architecture by modulating auxin response in rice. Front Plant Sci 8:134. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.3389/fpls.2017.00134\u003c/span\u003e\u003cspan address=\"10.3389/fpls.2017.00134\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLiao H, Rubio G, Yan X, Cao A, Brown KM, Lynch JP (2001) Effect of phosphorus availability on basal root shallowness in common bean. Plant Soil 232:69\u0026ndash;79\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLynch J (1995) Root architecture and plant productivity. Plant Physiol 109:7\u0026ndash;13\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLynch J (2019) Root phenes for improved nutrient capture: an underexploited opportunity for global agriculture. New phytol 223:548\u0026ndash;564\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLynch J (2011) Root phenes for enhanced soil exploration and phosphorus acquisition: tools for future crops. Plant Physiol 156:1041\u0026ndash;1049. https://doi.org/10. 1104/\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLynch JP, Brown KM (2001) Topsoil foraging \u0026ndash; an architectural adaptation of plants to low phosphorus availability. Plant Soil 237:225\u0026ndash;237. https://doi.org/10. 1023/a: 10133 24727 040\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMa Q, Rengel Z, Rose T (2009) The effectiveness of deep placement of fertilisers is determined by crop species and edaphic conditions in Mediterranean-type environments: A review. Austr J Soil Res 47:19\u0026ndash;32\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMa Q, Sun L, Tian H, Rengel Z, Shen J (2021) Deep banding of phosphorus and nitrogen enhances Rosa multiflora growth and nutrient accumulation by improving root spatial distribution. Sci Hort 277(109800). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.scienta.2020.109800\u003c/span\u003e\u003cspan address=\"10.1016/j.scienta.2020.109800\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMackay AD, Barber SA (1985) Soil moisture effects on root growth and phosphorus uptake by corn. Agron J 77:519\u0026ndash;523\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMiguel MA, Widrig A, Vieira RF, Brown KM, Lynch JP (2013) Basal root whorl number: a modulator of phosphorus acquisition in common bean (Phaseolus vulgaris). Ann Bot 112:973\u0026ndash;982\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNakamoto T (1993) Effect of soil water content on the gravitropic behaviour of nodal roots in maize. Plant Soil 152:261\u0026ndash;267\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNakamoto T (1994) Plagio-gravitropism of maize roots. Plant Soil 165:327\u0026ndash;332\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNkebiwe PM, Weinmann M, Bar-Tal A, Muller T (2016) Fertilizer placement to improve crop nutrient acquisition and yield: A review and meta-analysis. Field Crops Res 196:389\u0026ndash;401. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://dx.doi.org/10.1016/j.fcr.2016.07.018\u003c/span\u003e\u003cspan address=\"10.1016/j.fcr.2016.07.018\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNorrish SA, Cornish PS, Moody PW, Jessop RS (2003) Edaphic and environmental interactions controlling grain yield response to P fertiliser in dryland wheat crops of north-western NSW. Proceedings of 2nd International Symposium on Phosphorus Dynamics in the Soil-Plant Continuum, pp.\u0026nbsp;222\u0026ndash;223, University of Western Australia: Perth, Australia\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eO\u0026rsquo;Toole JC, Bland WL (1987) Genotypic variation in crop plant root systems. Adv Agron 41:91\u0026ndash;145\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePang J, Zhao H, Bansal R, Bohuon E, Lambers H, Ryan MH, Siddique KHM (2017) Leaf transpiration plays a role in phosphorus acquisition among a large set of chickpea genotypes. Plant Cell Environ 41:2069\u0026ndash;2079. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1111/pce.13139\u003c/span\u003e\u003cspan address=\"10.1111/pce.13139\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eParida AK, Das AB (2005) Salt tolerance and salinity effects on plants: a review. Ecotoxicol Environ Saf 60:324\u0026ndash;349. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.ecoenv.2004.06.010\u003c/span\u003e\u003cspan address=\"10.1016/j.ecoenv.2004.06.010\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRabbi SMF, Guppy C, Flavel R, Tighe M, Young I (2017) Root plasticity not evident in N-enriched soil volumes for wheat (\u003cem\u003eTriticum aestivum\u003c/em\u003e L.) and barley (\u003cem\u003eHordeum vulgare\u003c/em\u003e L.) varieties. Commun Soil Sci Plant Anal 48:2002\u0026ndash;2012\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRayment GE, Lyons DJ (2010) Soil chemical methods-Australia. Australian Soil and Land Survey Handbooks Series. CSIRO Publishing\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRichardson AE, Hocking PJ, Simpson RJ, George TS (2009) Plant mechanisms to optimise access to soil phosphorus. Crop Past Sci 60:124\u0026ndash;143. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1071/cp07125\u003c/span\u003e\u003cspan address=\"10.1071/cp07125\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRobinson D (1996) Resource capture by localised root proliferation: why do roots bother? Annal Bot 77:179\u0026ndash;186. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1006/anbo.1996.0020\u003c/span\u003e\u003cspan address=\"10.1006/anbo.1996.0020\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRomer W, Schilling G (1986) Phosphorus requirements of the wheat plant in various stages of the life cycle. Plant Soil 91:221\u0026ndash;229\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRose TJ, Rose MT, Pariasca-Tanaka J, Heuer S, Wissuwa M (2011) The frustration with utilization: Why have improvements in internal phosphorus utilization efficiency in crops remained so elusive? Front Plant Sci 2:73\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSander DH, Eghball B (1999) Planting date and phosphorus fertiliser effects on winter wheat. Agron J 91:707\u0026ndash;712\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSingh DK, Sale PWG, Routley RR (2005) Increasing phosphorus supply in subsurface soil in northern Australia: Rationale for deep placement and the effects with various crops. Plant Soil 269:35\u0026ndash;44\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSingh V, van Oosterom EJ, Jordan DR, Hammer GL (2012) Genetic control of nodal root angle in sorghum and its implications on water extraction. Europ J Agron 42:3\u0026ndash;10\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSingh V, van Oosterom EJ, Jordan DR, Hunt CH, Hammer GL (2011) Genetic variability and control of nodal root angle in sorghum. Crop Sci 51:2011\u0026ndash;2020\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eStrock CF, Burridge J, Massas ASF et al (2019) Seedling root architecture and its relationship with seed yield across diverse environments in Phaseolus vulgaris. Field Crops Res 237:53\u0026ndash;64\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTrachsel S, Kaeppler SM, Brown KM, Lynch JP (2011) Shovelomics: high throughput phenotyping of maize (\u003cem\u003eZea mays\u003c/em\u003e L.) root architecture in the field. Plant Soil 341:75\u0026ndash;87\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTrapeznikow VK, Ivanov II, Kudoyarova GR (2003) Effect of heterogeneous distribution of nutrients on root growth, ABA content and drought resistance of wheat plants. Plant Soil 252(2):207\u0026ndash;214. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1023/A:1024734310214\u003c/span\u003e\u003cspan address=\"10.1023/A:1024734310214\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eUga Y, Sugimoto K, Ogawa S, Rane J, Ishitani M, Hara N et al (2013) Control of root system architecture by DEEPER ROOTING 1 increases rice yield under drought conditions. Nat Genet 45:1097\u0026ndash;1102. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1038/ng.2725)\u003c/span\u003e\u003cspan address=\"10.1038/ng.2725)\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eVandamme E, Rose T, Saito K et al (2016) Integration of P acquisition efficiency, P utilization efficiency and low grain P concentrations into P-efficient rice genotypes for specific target environments. Nutr Cycl Agroecosyst 104:413\u0026ndash;427. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s10705-015-9716-3\u003c/span\u003e\u003cspan address=\"10.1007/s10705-015-9716-3\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eVan der Bom FJT, Williams A, Bell MJ (2020) Root architecture for improved resource capture: trade-offs in complex environments. J Exp Bot 71:5752\u0026ndash;5763. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1093/jxb/eraa324\u003c/span\u003e\u003cspan address=\"10.1093/jxb/eraa324\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eVan der Bom FJT, Williams A, Raymond NS, Alahmad S, Hickey LT, Singh V, Bell MJ (2023) Root angle, phosphorus, and water: Interactions and effects on durum wheat genotype performance in drought-prone environments. Plant Soil. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s11104-023-05966-z\u003c/span\u003e\u003cspan address=\"10.1007/s11104-023-05966-z\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eVaz Patto MC, Amarowicz R, Aryee ANA, Boye JI, Chung HJ, Mart\u0026iacute;n Cabrejas MA, Domoney C (2015) Achievements and challenges in improving the nutritional quality of food legumes. Crit Rev Plant Sci 34:1\u0026ndash;3. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1080/07352689.2014.897896\u003c/span\u003e\u003cspan address=\"10.1080/07352689.2014.897896\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang H, Inukai Y, Yamauchi A (2006) Root development and nutrient uptake. Crit Rev Plant Sci 25:279\u0026ndash;301\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWasson AP, Richards RA, Chatrath R, Misra SC, Prasad SV, Rebetzke GJ, Kirkegaard JA, Christopher J, Watt M (2012) Traits and selection strategies to improve root systems and water uptake in water-limited wheat crops. J Exp Bot 63:3485\u0026ndash;3498\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWu Q, Pages L, Wu J (2016) Relationships between root diameter, root length and root branching along lateral roots in adult, field-grown maize. Ann Bot 117:379\u0026ndash;390\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYao J, Barber SA (1986) Effect of one phosphorus rate placed in different soil volumes on P uptake and growth of wheat. Commun Soil Sci Plant Anal 17:819\u0026ndash;827\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYe H, Roorkiwal M, Valliyodan B, Zhou L, Chen P, Varshney RK, Nguyen HT (2018) Genetic diversity of root system architecture in response to drought stress in grain legumes. J Exp Bot 69:3267\u0026ndash;3232. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1093/jxb/ery082\u003c/span\u003e\u003cspan address=\"10.1093/jxb/ery082\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYuan Z, Jiang S, Sheng H et al (2018) Human perturbation of the global phosphorus cycle: changes and consequences. Environ Sci Technol 52:2438\u0026ndash;2450 [DOI:. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1021/acs.est.7b03910](\u003c/span\u003e\u003cspan address=\"10.1021/acs.est.7b03910](\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYuan M, Fernandez FG, Pittelkow CM, Greer KD, Schaefer D (2018) Tillage and fertilizer management effects on phosphorus runoff from minimal slope fields. J Environ Qual 47:462\u0026ndash;470. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.2134/jeq2017.07.0271\u003c/span\u003e\u003cspan address=\"10.2134/jeq2017.07.0271\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhao J, Fu J, Liao H, He Y, Nian Hai, Yan X (2004) Characterization of root architecture in an applied core collection for phosphorus efficiency of soybean germplasm. Chin Sci Bull 49:1611\u0026ndash;1620\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhu J, Lynch JP (2004) The contribution of lateral rooting to phosphorus acquisition efficiency in maize (\u003cem\u003eZea mays\u003c/em\u003e) seedlings. Funct Plant Biol 31:949\u0026ndash;958. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1071/FP04046\u003c/span\u003e\u003cspan address=\"10.1071/FP04046\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhu J, Kaeppler S, Lynch JP (2005) Topsoil foraging and phosphorus acquisition efficiency in maize (\u003cem\u003eZea mays\u003c/em\u003e L). Funct Plant Biol 32:749\u0026ndash;762\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhu X, Li C, Jiang Z, Huang L (2012) Responses of phosphorus use efficiency, grain yield, and quality to phosphorus application amount of weak-gluten wheat. J Integr Agric 11(7):1103\u0026ndash;1110. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/S2095-3119(12)60103-8\u003c/span\u003e\u003cspan address=\"10.1016/S2095-3119(12)60103-8\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Deep banding, phosphorus fertiliser, root system architecture, mungbean (Vigna radiata L), phosphorus use efficiency","lastPublishedDoi":"10.21203/rs.3.rs-3508080/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3508080/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cem\u003eBackground and Aim\u003c/em\u003e Deep placement of fertiliser has been providing strong productivity responses in rainfed cropping systems on Vertisols soils in north-eastern Australia. However, genotypic differences in root system architecture (RSA) can play an important role in response to various P rates and placement strategies. In this study we tested for genetic variation in RSA and its impact on the ability to exploit deep P bands among four contrasting, early to late maturing mungbean varieties.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eMethods \u003c/em\u003eDifferences in soil P status and distribution were established by varying rates of applied P and the volume of soil P enrichment in shallow (top 5cm) and deeper (20-25cm) profile layers in root observation chambers. Intact RSA was measured in the top 30cm and bottom 30cm sections of the soil profile.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eResults \u003c/em\u003eShallower placement of P fertiliser resulted in a wider root growth angle compared with other P treatments, whereas deeper placements resulted in greater mean root diameter and total root volume. Deep banding and deeper P-enriched sub layer treatments tended to advance the flowering and increased the mungbean pod yield for the more responsive early maturing var. Berken, without influencing the total root surface area, P uptake or shoot P concentration. This cultivar showed the lowest shoot P concentrations, least P uptake and greatest internal phosphorus use efficiency.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eConclusion\u003c/em\u003e The varietal differences in RSA and root functioning played a major role in response to P placement strategies, where the strongest P response was observed with the deep P band fertiliser treatment for crop performance.\u003c/p\u003e","manuscriptTitle":"Above and below-ground responses to contrasting soil phosphorus distribution by mungbean (Vigna radiata L.) cultivars with diverse phenology","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2023-11-07 22:59:31","doi":"10.21203/rs.3.rs-3508080/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"4789962b-bb82-40b9-8219-4f6bfacb49c6","owner":[],"postedDate":"November 7th, 2023","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-02-24T14:31:09+00:00","versionOfRecord":[],"versionCreatedAt":"2023-11-07 22:59:31","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-3508080","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3508080","identity":"rs-3508080","version":["v1"]},"buildId":"_2-kVJe1T_tPrBINL-cwx","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}