Potential allelopathic effects of selected shade tree species on cocoa (Theobroma cacao)

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This research sought to determine the effect of aqueous extract from selected shade trees cultivated on cocoa farms on germination and growth of cocoa seedlings. Mature leaves and roots of commonly used shade trees ( Khaya anthotheca , Triplochiton scleroxylon , Melicia excelsa and Terminalia superba ) were collected separately and grounded into powder. Aqueous extracts of shade trees of different concentrations (15g/lit., 30g/lit. and 45g/lit) were formulated and applied to seeds and seedlings of cocoa. The study was carried out in a greenhouse which mimic field conditions. The study revealed that germination of cocoa seeds declined with increasing concentrations of K. anthotheca , M. excelsa and T. scleroxlon , however, T. superba generally did not result in further decline in germination. Higher concentrations of T. superba reduced dry biomass whiles that of T. scleroxylon increased root length with respect to the control. Farmers ranked T. superba as their most preferred shade species which contradicts with the findings which preferably suggest the use of T. scleroxylon and M. excelsa as shade trees in cocoa agroforestry. allelopathy seedlings aqueous extracts germination shoot length dry biomass root length Figures Figure 1 Introduction Cocoa is of significant economic importance for both producing and consuming countries. It generates export revenues, income and employment. Cocoa is an important ingredient in the confectionery, and food and beverage industries, and, more recently, in the pharmaceutical and cosmetics industries (UNCTAD, 2016). Historically, cocoa has been established as an understory tree which is naturally existing or intentionally planted (Klein et al., 2002; Anim-Kwarpong, 2003). Cocoa has been cultivated for decades in the tropics by small and marginal farmers in the shade of main and secondary forest trees (Anim-Kwarpong, 2003). Shade is always recommended for cocoa production and usually reduced progressively as the cocoa trees mature (World Cocoa Foundation, 2016). Cocoa trees need a certain level of shade, specifically in the initial stages of growth (Conservation Alliance, 2013). This is to shield cocoa seedlings from the sun and wind to enable them flourish. Generally, 12–18 shade trees per hectare which results in a canopy cover of 30–40% is recommended (Asare and Anders, 2016). Shade trees provide a range of benefits to cocoa trees, soils , ecosystems and people including (i) provision of shade for cocoa trees (Asare and Anders, 2016), (ii) conservation of native trees (Asigbaase et al. , 2019), (iii) provision of food and fruits for farmers (Tscharntke et al. , 2011), (iv) enhanced farm resilience and carbon sequestration (Asigbaase et al. 2021a), (v) increased soil and water quality (Tscharntke et al. , 2011) and (vi) nutrient recycling through litterfall (Asigbaase et al. 2021b). Nonetheless, research studies exploring the interactions between commonly used shade tree species and cocoa trees in relation to potential allelopathy are rare (Asare, 2005). The planting of both shade trees and cocoa plants together on the same piece of land could potentially result in an interaction where one of these plants will moderate the growth of the associated plants in a condition known as allelopathy (Fritz et al., 2007). Allelo-chemicals are relinquished through the immediate surroundings which interfere in multiple physiological processes that change certain organisms' growth dynamics (Kil & Shim, 2006). Allelochemicals influence respiration, photosynthesis, enzymatic activities, water interactions, stomach opening, rates of hormones, mineral accessibility, cell splitting, elongation, cell membranes and walls, and their structure and permeation (Reigosa et al., 1999; more refs here since many effects are listed). Allelopathic substances may be influenced by biochemical physiological processes such as the stomatal opening and closure, photosynthesis, and respiration. These substances in the soil may also intrude on the uptake of nutrients (Doughari, 2015) There are several merit and demerit relationships that have been suggested for the tree and crop constituents of agroforestry systems, and the direction and magnitude of these interactions are determined by the patterns of resource sharing (Gillsepie et al., 2000). In order to accomplish sustainable agriculture, the ecological connection within a given agroecosystem must be recognized (Qasem and Foy, 2001). Therefore, to ensure the sustainability of cocoa production it is important to have a better understanding of the interaction between shade trees and cocoa. This will particularly ensure that cocoa farming becomes a more viable source of livelihoods for farmers and guarantee a sustainable global cocoa economy. Researchers have reported on the allelopathic potential of species by examining the effect of aqueous extracts on plumule and radicle length of the species (Arif, 2015; Siyar, 2018; Hachani et al. 2019). It is surmised that if species affect the growth of associated crops at the seedling or initial stages of growth, it would ultimately affect its overall performance. Currently, Triplochiton scleroxylon , Khaya anthotheca , Melicia excelsa and Terminalia superba have been promoted in cocoa plantations as shade trees, however, their potential allelopathic effects are not well understood. Therefore, we investigated the allelopathic effects of selected shade trees on cocoa seed germination and seedling growth. Our work will provide robust data on the compatibility of shade trees with cocoa, which is critical for sustainable cocoa production. Land use systems involving trees and crops are complex because a lot of complex interactions occur between the various components (Abugre et al., 2011). These interactions, which includes allelopathy, either promote or inhibit growth and development of the components (El khatib, 1997). In order to eliminate extraneous factors and yet mimic field conditions, the research was conducted in a greenhouse facility. Materials and Methods Description of the Study Area This research was carried out from March, 2019 to July, 2019 in a greenhouse of the Ministry of Food and Agriculture of Ghana (MOFA) at Fiapre near Sunyani. Fiapre -Sunyani has a tropical climate with an average annual temperature of 25.7 ° C and an annual average rainfall of 1189 mm. The rainfall pattern is bimodal, with a major rainfall between April and July, followed by a short dry spell, and the minor rainfall occurs between September and October, followed by a dry season (between November and mid-March). The study area for the greenhouse is located on Latitude 7°20'54.13"N and Longitude 2°20'35.2"W (Figure 1). Experimental Design and Treatments The experiment was laid using Randomized Complete Block Design with three (3) replications. Each shade tree ( Triplochiton scleroxylon , Khaya anthotheca , Melicia excelsa and Terminalia superba ) was tested at four levels (control, 15, 30, 45 grams) and at two level of plant parts (Leaves and Roots). Eventhough litter of leaves and roots are inseparable, it is important it is important to know the plant part which affects most. The average temperature of the greenhouse was 26.7 ° C. Source of plants used Leaves and roots part of Khaya anthotheca , Triplochiton scleroxylon , Melicia excelsa and Terminalia superba ) were obtained from Modified ‘Taungya’ plantations located in the Sunyani Forest District. Extraction of aqueous leaf and root solutions Fresh mature leaves (near abscission) and roots of Triplochiton scleroxylon , Khaya anthotheca , Melicia excelsa and Terminalia superba were collected from the Asukese Forest Reserve ( Latitude 7° 9' 16.2" North and Longitude 2° 29' 56.6" West) which is found in a moist semi-deciduous vegetation in the Sunyani Municipality of Bono Region. Seeds of hybrid cocoa were purchased from the Cocoa Research Institute of Ghana at Goaso. The collected dry, mature leaves and roots of T. scleroxylon , K. anthotheca , M. excelsa and T. superba were dried in an oven at 70 °C for 48 hours. The dried leaves and roots of the shade trees were ground and passed through a 40 mm mesh screen. Using an electronic balance, 15g, 30g and 45g of the powdered leaves and roots of each tree species ( T. scleroxylon, K. anthotheca, M. excelsa and T. superba ) were weighed into separate and sterilized conical flasks. These concentrations were chosen based on similar studies by Maharjan et al. (2007) where effects were realized at these concentrations. The samples were mixed with 100 ml of purified water and stirred for 5 minutes. The mixtures were preserved for 48 hours at room temperature of 25 ºC. The aqueous extracts of the leaves and roots were then made using pressure pumps. Both solutions from leaves and roots at different concentration were kept in a dark cupboard according to the procedure used by Maharjan et al. (2007) and Abugre et al. (2011). Germination Test Twenty planted seeds were watered with the different aqueous plant extracts from leaves (L) and roots (R) at different concentrations (i.e. control, 15, 30, and 45 grams in 100 litres of water) of the four shade tree species. The planted seeds were watered twice a day till the seeds germinated fully. The average values (germination and growth parameters) for both leaves and roots extracts were then computed to establish the effect of the shade tree species. Growth Performance Test Five cocoa seedlings of five months established in poly pots were randomly selected for data collection from all the treatment concentration in each replication. Seedlings shoot length and total root length were measured and analyzed at the end of three months. Dry biomass was obtained after placing the roots and shoots in an oven at 70 o C for 48 hours. Our technique for assessing growth performance is consistent with Maharjan et al. (2007). Farmer's preference for shade tree species Factors that influence the preference of a farmer's choice of species were conducted in diverse cocoa Districts of the Brong-Ahafo Region of Ghana. Simple random sampling was employed to choose the cocoa-growing districts in the Region. After this, purposive sampling was employed to choose farmers who have benefited from the supply of shade trees species supplied by the Forestry Commission of Ghana. Questionnaires were issued to 150 farmers from the 5 districts of the cocoa production sample. Data analysis Data were analyzed using one-way variance (ANOVA) employing R version i386 3.6.0 software. Analysis of variance (ANOVA) was utilized to establish significant diffrences aomg the treatments. Treatment means were separated by using the Least Significant Difference (LSD) at p = 0.05. Results Effect of different extracts concentrations of T. scleroxylon , K. anthotheca , M. excelsa, and T. superba on germination of cocoa seedlings Compared to the control, aqueous extracts of all the selected shade tree species significantly reduced cocoa seedling germination ( p < 0.05) but the pattern of their effect on cocoa germination differed (Table 1). Whereas increased concentrations of K. anthotheca, M. excelsa and T. scleroxylon aqueous extract resulted in significant declines in cocoa seed germination ( p < 0.05), that of T. superba did not differ among the aqueous extracts, even though all differed from the control (Table 1). Plant part (root verses leaves) did not have any significant effect on cocoa seed germination ( p > 0.05) (Table 1). Effect of different extracts concentrations of T. scleroxylon, K. anthotheca, M. excelsa , and T. superba on growth parameters of cocoa seedlings Aqueous extract of T. superba had significant effect on shoot length and dry biomass of cocoa seedling (Table 2). Higher concentrations of T. superba significantly (p < 0.05) reduced shoot length of the cocoa seedlings. Similarly, aqueous extracts of K. anthotheca also resulted in reduced shoot length and dry biomass of the cocoa seedlings (Table 3). On the contrary, the different concentrations of the aqueous extracts of T. scleroxylon did not affect shoot length and dry biomass of cocoa seedlings (Table 4; p > 0.05). On the other hand, aqueous extract of M. excelsa influenced root length and dry biomass of cocoa seedlings (Table 5). Generally, plant part of the various test tree species did not significantly influence shoot length, root length and dry biomass of cocoa seedlings. Farmers’ preference for shade tree species in cocoa farms Out of the 150 farmers interviewed, the majority (67%) had shade trees growing on their cocoa farms, and (33%) were without shade trees on their farms. The majority of farmers (66%) planted different tree species on their farms with seedlings from the forestry department and (34%) were trees left on the farm during land preparation. The ranking of shade tree species by farmers from first to the fourth choice showed that majority of farmers (64%) preferred T. superba as shade trees on their cocoa farms, 24%, and 12% of farmers selected K. anthotheca and M. excelsa as their second and third preferred shade tree species on their farms respectively. Triplochiton scleroxylon was the least preferred by farmers as the majority of farmers (90%) selected it for the fourth choice. The majority of farmers preferred shade tree species in the order of Terminalia superba , Khaya anthotheca , Melicia excelsa and Triplochiton scleroxylon (Table 6). Farmers’ perception of the effects of shade trees on cocoa The majority of farmers indicated that they maintained shade trees on their farms mainly (i) to provide shade for cocoa seedlings (54%), (ii) to improve microclimatic conditions (12%) and (iii) to improve soil fertility (10%) (Table 7). The major concern of the farmers about shade trees were, reduced sunlight and air circulation (30 %), allelopathic effects (26 %), reduced yield (20%) and host for pests and disease (16%) (Table 8). Discussion Effect of Aqueous Extract on germination of cocoa seeds The aqueous extracts of Khaya anthotheca (Mahogany), T. superba , Triplochiton scleroxylon (Wawa) and Melicia Excelsa (Odum) hindered the germination of cocoa seeds but the degree and pattern of their effect depend on their concentration. Allelopathic compounds inhibit seed germination by inhibiting hydrolyzation of reserve food and cell division (Rice, 1984 ). According to Oyewale and Khadijat ( 2019 ) the presence of saponins, tannins, and polyphenolics in plants could account for suppression of germination and growth in plants. Furthermore, many plants emit saponins into the rhizosphere, which may act as allelopathic substances that suppress the growth of surrounding plants, thus reducing competition for resources (Moses et al., 2014 ). T. scleroxylon contains 12.67% tannins, flavonoids, 0.69% of phenols and 2.23% of saponins (Prohp and Onoagbe, 2012 ) which could have caused the decline in cocoa germination. This is therefore consistent with the choices made by farmers where Triplochiton scleroxylon was the least preferred species. Moreover, Abugre et al. ( 2014 ) reported that the extracts of T. scleroxylon inhibited the germination of three crops, namely, tomato (Lycopersicum esculentum), pepper (Capsicum annuum) and garden egg (Solanummelongena). Aqueous extracts of roots, stems-bark and leaves of Melicia excelsa contain flavonoids, saponins, cardiac glycoside, terpenoid and tannins (Bayani et al., 2009 ; Areola et al., 2015 ). Terpenoids which make up the largest and most functionally complex group play a significant role in plant interactions (Chen et al. 2011 ; Cheng et al. 2007 ). Germination of seeds depends on the concentration of aqueous extracts, with greater concentrations expressing greater allelopathic potency than the lower concentrations (Siddiqui et al., 2009 ). Khan et al. ( 2008 ) also showed that aqueous extracts at concentrations of 10, 15 and 20% had an inhibitory effect on wheat germination. Therefore, the decline in cocoa seed germination treated with aqueous extracts of K. anthotheca , T. scleroxylon, T. superba and M. excelsa may be related to the existence of allelochemicals which suppressed the seed germination cycle. El-Khatib ( 1997 ) suggested that the inverse relationship between seed germination and allelopathic inhibition may be due to reduced water uptake. The lower germination of cocoa seedlings treated with aqueous extracts from the selected shade tree may be partly attributable to the inhibition of water uptake by the presence of some allelochemicals, which prevented the growth of the seed embryo or caused its death (El-Khatib, 1997 ; Abugre et al., 2011 ). That notwithstanding, Abugre et al. ( 2011 ) reported that leaf extracts of T. superba promoted germination of seeds of Zea mays by 2.5%; our results on the effects of aqueous extracts of T. superba on cocoa seed germination are contrary to this, possibly because allelopathic effects are species-specific. T. scleroxylon is the most inhibiting species as it recorded the lowest level of germination compared to the other three species selected for this study. Higher concentrations (45 g / lit.) resulted in the highest suppression of cocoa seed germination. The decrease in cocoa seed germination due to allelopathic stress of various aqueous extracts may be attributed to numerous defects of metabolic function, the seed imbibition capacity, and embryonic defects (Maharjan et al., 2007 ; Chon and Nelson, 2010 ). The effect of aqueous extract of the various concentrations of shade trees on the growth of cocoa seedlings Effects on dry biomass aqueous extracts of T. superba reduced dry biomass with increasing concentration as reported by Bhatt et al. ( 1997 ) and Sisodia and Siddiqui ( 2009 ). Specifically, Bhatt et al. ( 1997 ) found that the aqueous extracts from Terminalia spp . suppressed the growth of Eleusine coracana, Brassica campestris, Horduem vulgare , and Glycine max and their dry biomass whiles Sisodia and Siddiqui ( 2009 ) reported that germination and growth inhibition efficiency increased with increasing amounts of various aqueous extracts. Naeem et al. ( 2012 ), Oudhia ( 2001 ) and Scrivanti ( 2010 ) attributed suppression in seed germination and growth of seedlings of the crops they investigated to allelochemicals in plant extracts. Seedling growth inhibition could probably be due to the induction of growth-inhibiting hormones. Bhatt et al. ( 1997 ) suggested that the presence of gallic acid, ellagic acid, ethyl gallate, galloyl glucose and chebulagic acid in the aqueous extracts of Terminalia spp. inhibited the growth of the crop seedlings they assessed and this resulted in reduced dry biomass. It is therefore possible that the aqueous extracts of T. superba contained growth inhibitors which hindered the growth of cocoa seedlings and this resulted in reduced dry biomass. Several authors (Ali-Smith, 2009 and Bukar et al., 2009 ) have suggested that leaves of certain plants contain allelochemicals such as tannins, saponin, steroids which inhibits plant growth. Azza ( 2016 ) also established that the leaf extracts of R. stricta inhibited the height of Viciafaba, Triticum aestivum , and Hordeum vulgare. Furthermore, Randhawa et al. ( 2002 ) reported that the root and shoot length of Trianthema portulacastrum was decreased by a greater concentration of sorghum aqueous extracts. T. scleroxylon and M. excelsa aqueous extracts did not affect the dry biomass of cocoa seedlings even though they significantly affected germination of cocoa, possibly because allelochemicals are organ-specific and species-specific. Effects on root growth the aqueous extracts of T. scleroxylon increased the root length of cocoa seedlings. This finding is consistent with Abugre and Quashie-sam ( 2010 ) who reported that maize root and stem length increased with increasing concentrations of aqueous extracts. Allelopathic interactions can produce beneficial effects as it is the case in our finding that T. scleroxylon extracts promoted root growth. This finding also converges with Tefera ( 2002 ), who suggested that Parthenium hysterophorus aqueous leaf, tribal, heart, and flower extracts stimulated the development of the Eragrostis tef seedling. Since roots are sensitive to chemical processes, they can react more quickly. Enhanced root growth may be attributed to increased cell replication and growth hormone enhancement or supply of limiting nutrients. The allelochemicals possibly triggered the production and synthesis of growth specific hormones such as auxins. The radicle, which grows into the main root, allows the seed to absorb and transport water and salts to the shoot and leaves of the seedlings for photosynthesis and growth. The positive effects of T. scleroxylon extracts on the roots of cocoa seedlings may enhance their early establishment, survival and growth. Generally, in aqueous extract experiments, the reported inhibitory effect is due to pH modification, which raises questions about allelopathy and its ecological nature and significance (Conway et al., 2002 ; Sisodia, 2008 ). On the other hand, the root length of cocoa seedlings was not significantly affected by aqueous extracts of K. anthotheca, M. excelsa , and T. superba ; this is contrary to the findings of Abugre et al. ( 2011 ) who reported that root and leaf extracts of T. superba hindered radicle growth of Vigna unguiculata, Lycopersicon esculentum and Zea mays . Our results also diverge from Khan et al. ( 2008 ), which showed that aqueous extracts at concentrations of 10, 15, and 20% had inhibitory effect on some agricultural crops. Furthermore, Khan et al. ( 2012 ) reported that the aqueous extracts from various seedlings of Parthenium hysterophorus had significant inhibitory consequences on the root and stem lengths of four wheat cultivars. Allelochemicals are both species-specific and organ-specific; different allelochemicals have different sites of action in different parts of a plant hence different species and organs vary in their sensitivity to allelochemicals (Mahajan et al ., 2007; Macias et al. , 2004). Moreover, the extent of allelopathic inhibition depends on the concentration of the plant extracts. This accounts of the varied response of the roots of cocoa seedlings to the aqueous extracts of the selected shade tree species. Effects on shoot length the aqueous extracts of Khaya anthotheca reduced the shoot length of cocoa seedlings and higher concentrations of its aqueous extracts had similar effects on the shoot length of cocoa seedlings (Table 4). The inhibitory effects of some plant extracts on plumule or radicle length may be associated with the occurrence of allelochemicals such as tannins, wax, flavonoids, and phenolic acids (Fag and Stewart, 1994; Mahajan et al ., 2007; Macias et al. , 2004). Randhawa et al. ( 2002 ) reported that high concentration of sorghum aqueous extracts decreased Trianthema portulacastrum root and shoot length. Ashrafi et al., ( 2008 ) also stated that allelopathic impact in all sunflower aqueous extracts accelerated as the concentration increased. Our results also partly agree with the findings of Khan et al. ( 2008 ) who showed that an increase in aqueous extract concentrations increased the inhibitory effect on some agricultural crops. A decrease in shoot length of cocoa seedlings can be deduced from the occurrence of phytotoxic compounds in these aqueous extracts from tree species and the display of inhibitor impact on the growth parameter (Javaid and Anjum, 2006 ). Therefore, the presence of allelochemicals in the extracts of Khaya anthotheca were possibly able to inhibit the synthesis of growth hormones, thus, limited cell division and differentiation resulting in reduced shoot growth. Generally, aqueous extracts of T. scleroxylon, T. superba and M. excelsa at all concentrations under this study did not affect the shoot length, except at higher concentrations (45g/lit) and lower concentrations (15g/lit) for T. superba and M. excelsa , respectively, where reduced shoot length growth was observed (Table 4). Our results diverge from Abugre et al. ( 2014 ) who indicated that aqueous extracts of T. scleroxylon adversely affected the shoot growth of tomato (Lycopersicum esculentum), pepper (Capsicum annuum) and garden egg (Solanummelongena). Furthermore, our findings are in contrast with previous researchers such as Tefera ( 2002 ), Yawer et al. ( 2007 ), Sisodia and Siddiqui ( 2009 ) and Khan et al. ( 2011 ) who found that greater degree of inhibition ensued with the leaves extracts at higher concentrations. That notwithstanding, our results are not entirely different from these authors since at the highest treatment level of 45g/lit, the aqueous extracts of T. superba suppressed the growth (shoot) of cocoa seedlings. Farmers’ perception of shade trees in cocoa farms Farmers had a mixed perception about shade trees on cocoa farms. They perceived shade trees as being important for three key ecosystem services namely, shade for cocoa, microclimate amelioration and maintenance of soil fertility possibly through litterfall and decomposition (Asare and Anders, 2016 ; Tscharntke et al., 2011 ; Asigbaase et al., 2021b ). On the other hand, farmers viewed shade trees as having negative effects on light penetration and air circulation and cocoa yield (Asare 2005 ; Asare and Anders, 2016 ). Ong et al. ( 2004 ) reported that shade trees are considered to have a detrimental impact on cocoa plant growth and yields; a view the farmers in our study also held. Additionally, they perceived shade trees as having allelopathic effects and being hosts for pest and disease (Anim-Kwarpong, 2003 ; Asare 2005 ; Asare and Anders, 2016 ). Consistent with this perception, Akrofi et al. ( 2003 ) who found out that excessive shade has negative allelopathic effects on cocoa farm influences disease and pest status of cocoa farms. Vandenbelt et al. ( 1990 ) showed that tree roots often exploit the crop root region for nutrients and water. This could be mainly so for shade tree species whose roots are shallow with the horizontal distribution. According to Vandenbelt et al. ( 1990 ), the basic model depicted in most agroforestry literature of trees as complementary and interconnected with other crops and plants may be used with caution. The combinations of trees and crops may display more extensive niche differentiation than would be anticipated from their rooting forms in monoculture because of reactions to reduced water and nutrient obtainability in upper soil layers as a result of resource consumption by companion crops (Sinclair et al. , 1994). Contrary to the assertions of Vandenbelt et al. ( 1990 ) and Sinclair et al. (1994), farmers in our study did not view competition with cocoa trees for water and nutrients as a major issue. Notwithstanding farmers’ mixed perception about shade trees, they were willing to integrate shade trees into their cocoa farms as they requested, received and planted shade tree seedlings supplied by the Forestry Commission of Ghana. This willingness may be a reflection of the perception that the positive effects of shade trees may compensate for or outweigh their negative effects. The most preferred shade by the farmers was Terminalia superba yet our results show that aqueous extracts from this tree species resulted in reduced cocoa seed germination and biomass (Tables 2 and 5). This calls for further research and interventions to ensure recommended or preferred species are indeed beneficial for sustainable cocoa production. Conclusions Based on the findings, we concluded that Khaya anthotheca, Melicia excelsa, Terminalia superba and Triplochiton scleroxylon suppressed the germination of cocoa and higher concentrations showed mixed results, which are always lower than the control. Higher concentrations of K. anthotheca reduced cocoa seed germination while higher concentrations of T. scleroxylon, M. excelsa , and T. superba generally did not increase inhibition of the germination of cocoa seeds. Whereas the aqueous extracts of T. superba reduced the dry biomass of cocoa seedlings and the aqueous extracts of K. anthotheca hindered the shoot growth of cocoa, the aqueous extracts of T. scleroxylon enhanced the growth of the root length of cocoa seedlings. Generally, the aqueous extracts of M. excelsa did not adversely affect the dry biomass, shoot length and root length of cocoa seedlings. Farmers at the research areas preferred Terminalia superba on their farms to other species. Their reason being that it has a positive effect on cocoa seedlings. Farmers keep shade trees on their farms purposely to provide shade for cocoa seedlings. We recommend the use of T. scleroxylon and M. excelsa on cococa farms as these species either promoted or had no adverse effects cocoa seedling growth. Declarations Acknowledgement We are very grateful to staff of the Forestry Commission for assisting in the administration of questionnaire on farmer preferences. Funding Statement No funding was secured for the study. Ethics Statement and Consent to participate No ethical approval was sought for the study, however, ethical issues were addressed during the research. No formal permission was sought in obtaining the plant species from Modified ‘Taungya’ Plantations established by the Forestry Commission. One of the authors was a Manager of these plantations and also a staff of the Forestry Commission. Farmers who participated in the study were informed of the importance of the study and their right not to participate. A verbal consent was obtained from participants before administration of the questionnaire. Consent to publish declaration The authors grant permission for the publication of their manuscript. Competing interest The authors declare that there is no competing interest. Data Availability Statement The datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request. Clinical Trial number This is not applicable Author Contribution 1) S. A. Conceived the idea, designed the analysis, wrote the manuscript, laid the experiment, contributed to analysis and the lead2) E. A. Collected the data, wrote the paper, contributed data and analysis tools, contributed to laying of experiment3) S. N. Contributed data analysis and Laying of experiment4) M. A. Performed the analysis, reading of manuscript5) A. A. A. Performed the analysis, reading of manuscript References Abugre S, Quashie-sam SJ. Evaluating the allelopathic effect of Jatrophacurcas aqueous extract on germination, radicle and plumule length of crops. Int J Agric Biol. 2010;12:769–72. Abugre S, Apetorgbor AK, Antwiwaa A, Apetorgbor MM. Allelopathic effects of ten tree species on germination and growth of four traditional food crops in Ghana. J Agric Technol. 2011;7(3):825–34. Abugre S, Apetorgbor MM, Abebrese IK, Apetorgbor AK, Amoako PK. 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Allelopathic potentialities of different concentration of aqueous leaf extracts of some arable trees on germination and radicle growth of Cicer arietinum var.– C-235. Global J Mol Sci. 2009;4(2):91–5. Sinclair FL, Verinumbe I and Hall. J. B. The role of tree domestication in agroforestry. In: Leakey RRB, Newton AC, editors. Tropical Trees: The Potential for Domestication and the Rebuilding of Forest Resources. London: HMSO; 1994. pp. 124–36. Sisodia S. Allelopathic effect of Croton bonplandianum Baill. towards some weed and crop plants Department of Botany. Aligarh: Aligarh Muslim University; 2008. pp. 181–94. Sisodia S, Siddiqui MB. Allelopathic potential of rhizosphere soil of Croton bonplandianum on growth and establishment of some crop and weed plants. Afr J Agric Res. 2009;4(5):461–7. Sisodia S, Siddiqui MB. Allelopathic effect by aqueous extracts of different parts of Croton bonplandianum Baill. on some crop and weed plants. J Agric Ext Rural Dev. 2010;2:022–8. Siyar S, Abdul Majeed A, Muhammad Z, Ali H, Inayat H, N. Allelopathic effect of aqueous extracts of three weed species on the growth and leaf chlorophyll content of bread wheat. Acta Ecol Sin. 2018. https://doi.org/10.1016/j.chnaes.2018.05.007 . Tefera T. Allelopathic effects of Partheniumhysterophorus extracts on seed germination and seedling growth of Eragro stistef (Zucc.) Trotter. J Agron Crop Sci. 2002;188(5):306–10. Tscharntke T, Clough Y, Shonil A, Bhagwat AS, Buchori D, Faust H, et al. Multifunctional shadetree management in tropical agroforestry landscape—a review. J Appl Ecol. 2011;48:619–29. UNCTAD. Cocoa industry: integrating small farmers into the global value chain. New York, Geneva: United Nations; 2016. Vandenbelt RJ, Brenner AJ, Sinclair FL. (1990). The tree/crop interactions in agroforestry systems. Proceedings 19th IUFRO World Congress, Montreal, Canada, 5–9 August, 1990, pp. 292–303. World Cocoa Foundation. Manual for Cocoa extension in Ghana. USAID, Cocoa Health and Extension Division (CHED), Sustainable Trade Initiative; 2016. Yawer MA, Ahmed E, Malik A, Ashraf M, Rasool MA, Aziza W. New lipoxygenasein habiting constituents from Calligonum polygonoides. Chem Biodivers. 2007;4(7):1578–85. Tables Tables 1 to 8 are available in the Supplementary Files section. Additional Declarations No competing interests reported. Supplementary Files Tables.docx 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-6984171","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":486186962,"identity":"91f26d33-a478-4a0a-a392-3d7289650a0b","order_by":0,"name":"Simon Abugre","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABAElEQVRIiWNgGAWjYDACZgiVACY/QAUl4CKEtDDOIEoLA5IWZh5itMi3cyc+LmCwyzM4v/bhY9s2mzzzBuaDt3kYavNwaTE4zLvZeAZDcrHBjefGxrltacUyB9iSrXkYjhfj1MLMu02ah4E5ccONY2zSuW2HE2cw8JgBRY4lNuByWDNYSz1IC/tvy7b/QC383/BqYTgM1nI4ccP5NjZmxrYDIFvYgCI1OLWA/cJjcLxY8gYbs2TPueTEGcxsxpZzDA7gdlj/2Y2PeSqq8/jOH2P88KPMLnEGe/PDG28q6nA7DGIXEEskQDnMENvxaoAA/gMo3DoitIyCUTAKRsEIAQDqdFH0iah8UAAAAABJRU5ErkJggg==","orcid":"","institution":"UENR","correspondingAuthor":true,"prefix":"","firstName":"Simon","middleName":"","lastName":"Abugre","suffix":""},{"id":486186963,"identity":"9b0f2836-eb0a-4561-9e5d-93e7e40db4b0","order_by":1,"name":"Eric Asare","email":"","orcid":"","institution":"UENR","correspondingAuthor":false,"prefix":"","firstName":"Eric","middleName":"","lastName":"Asare","suffix":""},{"id":486186964,"identity":"e2310d04-1788-4aa1-9cb3-aa37a842391a","order_by":2,"name":"Samuel Novor","email":"","orcid":"","institution":"University of Energy and Natural Resources","correspondingAuthor":false,"prefix":"","firstName":"Samuel","middleName":"","lastName":"Novor","suffix":""},{"id":486186966,"identity":"4e2545d2-2390-4f99-8f1c-9d2422130548","order_by":3,"name":"Michael Asigbaase","email":"","orcid":"","institution":"University of Energy and Natural Resources","correspondingAuthor":false,"prefix":"","firstName":"Michael","middleName":"","lastName":"Asigbaase","suffix":""},{"id":486186968,"identity":"44e4e383-c9a1-43b7-979b-8e130ed475f5","order_by":4,"name":"Alex Amerh Agbeshie","email":"","orcid":"","institution":"UENR","correspondingAuthor":false,"prefix":"","firstName":"Alex","middleName":"Amerh","lastName":"Agbeshie","suffix":""}],"badges":[],"createdAt":"2025-06-26 14:08:22","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6984171/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6984171/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":87089778,"identity":"9075298b-6289-41fe-ac12-41812db409b3","added_by":"auto","created_at":"2025-07-19 08:02:30","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":246341,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eThe map of the cocoa growing districts\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6984171/v1/983be3bec283a0b47db9e7b2.png"},{"id":87749471,"identity":"8b20f468-c683-48c1-80a4-b61d6e359e04","added_by":"auto","created_at":"2025-07-28 14:47:21","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1130515,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6984171/v1/8efc5829-fa21-4146-86fe-0ef6190fe5ac.pdf"},{"id":87089782,"identity":"84158ccf-57a4-4394-929c-a0be7551fa91","added_by":"auto","created_at":"2025-07-19 08:02:30","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":49060,"visible":true,"origin":"","legend":"","description":"","filename":"Tables.docx","url":"https://assets-eu.researchsquare.com/files/rs-6984171/v1/bbfd43db41a95c87b43a26f3.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Potential allelopathic effects of selected shade tree species on cocoa (Theobroma cacao)","fulltext":[{"header":"Introduction","content":"\u003cp\u003eCocoa is of significant economic importance for both producing and consuming countries. It generates export revenues, income and employment. Cocoa is an important ingredient in the confectionery, and food and beverage industries, and, more recently, in the pharmaceutical and cosmetics industries (UNCTAD, 2016).\u003c/p\u003e\n\u003cp\u003eHistorically, cocoa has been established as an understory tree which is naturally existing or intentionally planted (Klein \u003cem\u003eet al.,\u003c/em\u003e 2002; Anim-Kwarpong, 2003). Cocoa has been cultivated for decades in the tropics by small and marginal farmers in the shade of main and secondary forest trees (Anim-Kwarpong, 2003). Shade is always recommended for cocoa production and usually reduced progressively as the cocoa trees mature (World Cocoa Foundation, 2016). Cocoa trees need a certain level of shade, specifically in the initial stages of growth (Conservation Alliance, 2013). This is to shield cocoa seedlings from the sun and wind to enable them flourish.\u0026nbsp;Generally, 12\u0026ndash;18 shade trees \u003cem\u003eper\u003c/em\u003e hectare which results in a canopy cover of 30\u0026ndash;40% is recommended (Asare and Anders, 2016).\u003c/p\u003e\n\u003cp\u003eShade trees provide a range of benefits to cocoa trees, soils , ecosystems and people including (i) provision of shade for cocoa trees (Asare and Anders, 2016), (ii) conservation of native trees (Asigbaase \u003cem\u003eet al.\u003c/em\u003e, 2019), (iii) provision of food and fruits for farmers (Tscharntke \u003cem\u003eet al.\u003c/em\u003e, 2011), (iv) enhanced farm resilience and carbon sequestration (Asigbaase \u003cem\u003eet al. \u003c/em\u003e2021a), (v) increased soil and water quality (Tscharntke \u003cem\u003eet al.\u003c/em\u003e, 2011) and (vi) nutrient recycling through litterfall (Asigbaase \u003cem\u003eet al. \u003c/em\u003e2021b). Nonetheless, research studies exploring the interactions between commonly used shade tree species and cocoa trees in relation to potential allelopathy are rare (Asare, 2005).\u003c/p\u003e\n\u003cp\u003eThe planting of both shade trees and cocoa plants together on the same piece of land could potentially result in an interaction where one of these plants will moderate the growth of the associated plants in a condition known as allelopathy (Fritz \u003cem\u003eet al.,\u003c/em\u003e 2007). Allelo-chemicals are relinquished through the immediate surroundings which interfere in multiple physiological processes that change certain organisms' growth dynamics (Kil \u0026amp; Shim, 2006). Allelochemicals influence respiration, photosynthesis, enzymatic activities, water interactions, stomach opening, rates of hormones, mineral accessibility, cell splitting, elongation, cell membranes and walls, and their structure and permeation (Reigosa \u003cem\u003eet al.,\u003c/em\u003e 1999; more refs here since many effects are listed). Allelopathic substances may be influenced by biochemical physiological processes such as the stomatal opening and closure, photosynthesis, and respiration. These substances in the soil may also intrude on the uptake of nutrients (Doughari, 2015)\u003c/p\u003e\n\u003cp\u003eThere are several merit and demerit relationships that have been suggested for the tree and crop constituents of agroforestry systems, and the direction and magnitude of these interactions are determined by the patterns of resource sharing (Gillsepie \u003cem\u003eet al., \u003c/em\u003e2000). In order to accomplish sustainable agriculture, the ecological connection within a given agroecosystem must be recognized (Qasem and Foy, 2001). Therefore, to ensure the sustainability of cocoa production it is important to have a better understanding of the interaction between shade trees and cocoa. This will particularly ensure that cocoa farming becomes a more viable source of livelihoods for farmers and guarantee a sustainable global cocoa economy.\u003c/p\u003e\n\u003cp\u003eResearchers have reported on the allelopathic potential of species by examining the effect of aqueous extracts on plumule and radicle length of the species (Arif, 2015; Siyar, 2018; Hachani et al. 2019). It is surmised that if species affect the growth of associated crops at the seedling or initial stages of growth, it would ultimately affect its overall performance. Currently, \u003cem\u003eTriplochiton scleroxylon\u003c/em\u003e, \u003cem\u003eKhaya\u003c/em\u003e\u003cem\u003eanthotheca\u003c/em\u003e, \u003cem\u003eMelicia excelsa\u003c/em\u003e and \u003cem\u003eTerminalia superba\u003c/em\u003e have been promoted in cocoa plantations as shade trees, however, their potential allelopathic effects are not well understood. Therefore, we investigated the allelopathic effects of selected shade trees on cocoa seed germination and seedling growth. Our work will provide robust data on the compatibility of shade trees with cocoa, which is critical for sustainable cocoa production. Land use systems involving trees and crops are complex because a lot of complex interactions occur between the various components (Abugre et al., 2011). These interactions, which includes allelopathy, either promote or inhibit growth and development of the components (El khatib, 1997). In order to eliminate extraneous factors and yet mimic field conditions, the research was conducted in a greenhouse facility.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003ch2\u003eDescription of the Study Area\u003c/h2\u003e\n\u003cp\u003eThis research was carried out from March, 2019 to July, 2019 in a greenhouse of the Ministry of Food and Agriculture of Ghana (MOFA) at Fiapre near Sunyani. Fiapre -Sunyani has a tropical climate with an average\u0026nbsp;annual temperature of 25.7 \u0026deg; C and an annual average rainfall of 1189 mm. The rainfall pattern is bimodal, with a major rainfall between April and July, followed by a short dry spell, and the minor rainfall occurs between September and October, followed by a dry season (between November and mid-March). The study area for the greenhouse is located on Latitude 7\u0026deg;20'54.13\"N and Longitude 2\u0026deg;20'35.2\"W (Figure 1).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eExperimental Design and Treatments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe experiment was laid using Randomized Complete Block Design with three (3) replications. Each shade tree (\u003cem\u003eTriplochiton scleroxylon\u003c/em\u003e, \u003cem\u003eKhaya\u003c/em\u003e\u003cem\u003eanthotheca\u003c/em\u003e, \u003cem\u003eMelicia excelsa\u003c/em\u003e and \u003cem\u003eTerminalia superba\u003c/em\u003e) was tested at four levels (control, 15, 30, 45 grams) and at two level of plant parts (Leaves and Roots). Eventhough litter of leaves and roots are inseparable, it is important it is important to know the plant part which affects most. The average temperature of the greenhouse was 26.7 \u0026deg; C.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSource of plants used\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eLeaves and roots part of\u003cem\u003e Khaya\u003c/em\u003e\u003cem\u003eanthotheca\u003c/em\u003e, \u003cem\u003eTriplochiton scleroxylon\u003c/em\u003e, \u003cem\u003eMelicia excelsa\u003c/em\u003e and \u003cem\u003eTerminalia superba\u003c/em\u003e) were obtained from Modified \u0026lsquo;Taungya\u0026rsquo; plantations located in the Sunyani Forest District.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eExtraction of aqueous leaf and root solutions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFresh mature leaves (near abscission) and roots of \u003cem\u003eTriplochiton scleroxylon\u003c/em\u003e, \u003cem\u003eKhaya\u003c/em\u003e\u003cem\u003eanthotheca\u003c/em\u003e, \u003cem\u003eMelicia excelsa\u003c/em\u003e and \u003cem\u003eTerminalia superba\u003c/em\u003e were collected from the Asukese Forest Reserve ( Latitude 7\u0026deg; 9' 16.2\" North and Longitude 2\u0026deg; 29' 56.6\" West) which is found in a moist semi-deciduous vegetation in the Sunyani Municipality of Bono Region. Seeds of hybrid cocoa were purchased from the Cocoa Research Institute of Ghana at Goaso.\u003c/p\u003e\n\u003cp\u003eThe collected dry, mature leaves and roots of \u003cem\u003eT. scleroxylon\u003c/em\u003e, \u003cem\u003eK.\u003c/em\u003e\u003cem\u003eanthotheca\u003c/em\u003e, \u003cem\u003eM. excelsa\u003c/em\u003e and \u003cem\u003eT. superba\u003c/em\u003e were dried in an oven at 70 \u0026deg;C for 48 hours. The dried leaves and roots of the shade trees were ground and passed through a 40 mm mesh screen.\u003c/p\u003e\n\u003cp\u003eUsing an electronic balance, 15g, 30g and 45g of the powdered leaves and roots of each tree species (\u003cem\u003eT. scleroxylon, K. anthotheca, M. excelsa\u0026nbsp;\u003c/em\u003eand\u003cem\u003e T. superba\u003c/em\u003e) were weighed into separate and sterilized conical flasks. These concentrations were chosen based on similar studies by Maharjan \u003cem\u003eet al.\u003c/em\u003e (2007) where effects were realized at these concentrations. The samples were mixed with 100 ml of purified water and stirred for 5 minutes. The mixtures were preserved for 48 hours at room temperature of 25 \u0026ordm;C. The aqueous extracts of the leaves and roots were then made using pressure pumps. Both solutions from leaves and roots at different concentration were kept in a dark cupboard according to the procedure used by Maharjan \u003cem\u003eet al.\u003c/em\u003e (2007) and Abugre \u003cem\u003eet al.\u003c/em\u003e (2011).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eGermination Test\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTwenty planted seeds were watered with the different aqueous plant extracts from leaves (L) and roots (R) at different concentrations (i.e. control, 15, 30, and 45 grams in 100 litres of water) of the four shade tree species. The planted seeds were watered twice a day till the seeds germinated fully. The average values (germination and growth parameters) for both leaves and roots extracts were then computed to establish the effect of the shade tree species.\u003c/p\u003e\n\u003ch3\u003e\u003cstrong\u003eGrowth Performance Test\u003c/strong\u003e\u003c/h3\u003e\n\u003cp\u003eFive cocoa seedlings of five months established in poly pots were randomly selected for data collection from all the treatment concentration in each replication. Seedlings shoot length and total root length were measured and analyzed at the end of three months. Dry biomass was obtained after placing the roots and shoots in an oven at 70\u003csup\u003eo\u003c/sup\u003eC for 48 hours. Our technique for assessing growth performance is consistent with Maharjan \u003cem\u003eet al.\u003c/em\u003e (2007).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFarmer's preference for shade tree species\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFactors that influence the preference of a farmer's choice of species were conducted in diverse cocoa Districts of the Brong-Ahafo Region of Ghana. Simple random sampling was employed to choose the cocoa-growing districts in the Region. After this, purposive sampling was employed to choose farmers who have benefited from the supply of shade trees species supplied by the Forestry Commission of Ghana. Questionnaires were issued to 150 farmers from the 5 districts of the cocoa production sample.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData analysis\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eData were analyzed using one-way variance (ANOVA) employing R version i386 3.6.0 software. Analysis of variance\u0026nbsp;(ANOVA) was utilized to establish significant diffrences aomg the treatments. Treatment means were separated by using the Least Significant Difference (LSD) at \u003cem\u003ep \u003c/em\u003e= 0.05.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003e\u003cstrong\u003eEffect of different extracts concentrations of \u003cem\u003eT. scleroxylon\u003c/em\u003e,\u003cem\u003e K.\u003c/em\u003e\u003cem\u003eanthotheca\u003c/em\u003e, \u003cem\u003eM. excelsa,\u003c/em\u003e and \u003cem\u003eT. superba\u0026nbsp;\u003c/em\u003e on germination of cocoa seedlings\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eCompared to the control, aqueous extracts of all the selected shade tree species significantly reduced cocoa seedling germination (\u003cem\u003ep \u003c/em\u003e\u0026lt; 0.05) but the pattern of their effect on cocoa germination differed (Table 1). Whereas increased concentrations of \u003cem\u003eK.\u003c/em\u003e\u003cem\u003eanthotheca, M. excelsa\u003c/em\u003e and \u003cem\u003eT. scleroxylon\u003c/em\u003e aqueous extract resulted in significant declines in cocoa seed germination (\u003cem\u003ep \u003c/em\u003e\u0026lt; 0.05), that of \u003cem\u003eT. superba\u003c/em\u003e did not differ among the aqueous extracts, even though all differed from the control (Table 1). Plant part (root verses leaves) did not have any significant effect on cocoa seed germination (\u003cem\u003ep \u003c/em\u003e\u0026gt; 0.05) (Table 1).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEffect of different extracts concentrations of \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003eT. scleroxylon, K. anthotheca, M. excelsa\u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e\u003cem\u003e, and T. superba \u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003eon growth parameters of cocoa seedlings\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAqueous extract of \u003cem\u003eT. superba\u003c/em\u003e had significant effect on shoot length and dry biomass of cocoa seedling (Table 2). Higher concentrations of \u003cem\u003eT. superba\u003c/em\u003e significantly (p \u0026lt; 0.05) reduced shoot length of the cocoa seedlings. Similarly, aqueous extracts of \u003cem\u003eK. anthotheca\u003c/em\u003e also resulted in reduced shoot length and dry biomass of the cocoa seedlings (Table 3). On the contrary, the different concentrations of the aqueous extracts of \u003cem\u003eT. scleroxylon \u003c/em\u003edid not affect shoot length and dry biomass of cocoa seedlings (Table 4; \u003cem\u003ep \u003c/em\u003e\u0026gt; 0.05). On the other hand, aqueous extract of \u003cem\u003eM. excelsa\u003c/em\u003e influenced root length and dry biomass of cocoa seedlings (Table 5).\u003c/p\u003e\n\u003cp\u003eGenerally, plant part of the various test tree species did not significantly influence shoot length, root length and dry biomass of cocoa seedlings.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFarmers\u0026rsquo; preference for shade tree species in cocoa farms\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eOut of the 150 farmers interviewed, the majority (67%) had shade trees growing on their cocoa farms, and (33%) were without shade trees on their farms. The majority of farmers (66%) planted different tree species on their farms with seedlings from the forestry department and (34%) were trees left on the farm during land preparation.\u003c/p\u003e\n\u003cp\u003eThe ranking of shade tree species by farmers from first to the fourth choice showed that majority of farmers (64%) preferred \u003cem\u003eT. superba\u003c/em\u003e\u0026nbsp;as shade trees on their cocoa farms, 24%, and 12% of farmers selected \u003cem\u003eK.\u003c/em\u003e\u003cem\u003eanthotheca\u003c/em\u003e and \u003cem\u003eM. excelsa\u003c/em\u003e as their second and third preferred shade tree species on their farms respectively.\u003cem\u003e Triplochiton scleroxylon\u003c/em\u003e was the least preferred by farmers as the majority of farmers (90%) selected it for the fourth choice. The majority of farmers preferred shade tree species in the order of \u003cem\u003eTerminalia superba\u003c/em\u003e, \u003cem\u003eKhaya\u003c/em\u003e\u003cem\u003eanthotheca\u003c/em\u003e, \u003cem\u003eMelicia excelsa \u003c/em\u003eand \u003cem\u003eTriplochiton scleroxylon\u003c/em\u003e (Table 6).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFarmers\u0026rsquo; perception of the effects of shade trees on cocoa\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe majority of farmers indicated that they maintained shade trees on their farms mainly (i) to provide shade for cocoa seedlings (54%), (ii) to improve microclimatic conditions (12%) and (iii) to improve soil fertility (10%) (Table 7). The major concern of the farmers about shade trees were, reduced sunlight and air circulation (30 %), allelopathic effects (26 %), reduced yield (20%) and host for pests and disease (16%) (Table 8).\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003e\u003cb\u003eEffect of Aqueous Extract on germination of cocoa seeds\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe aqueous extracts of \u003cem\u003eKhaya anthotheca\u003c/em\u003e (Mahogany), \u003cem\u003eT. superba\u003c/em\u003e, \u003cem\u003eTriplochiton scleroxylon\u003c/em\u003e (Wawa) and \u003cem\u003eMelicia Excelsa\u003c/em\u003e (Odum) hindered the germination of cocoa seeds but the degree and pattern of their effect depend on their concentration. Allelopathic compounds inhibit seed germination by inhibiting hydrolyzation of reserve food and cell division (Rice, \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e1984\u003c/span\u003e). According to Oyewale and Khadijat (\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) the presence of saponins, tannins, and polyphenolics in plants could account for suppression of germination and growth in plants. Furthermore, many plants emit saponins into the rhizosphere, which may act as allelopathic substances that suppress the growth of surrounding plants, thus reducing competition for resources (Moses et al., \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). \u003cem\u003eT. scleroxylon\u003c/em\u003e contains 12.67% tannins, flavonoids, 0.69% of phenols and 2.23% of saponins (Prohp and Onoagbe, \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2012\u003c/span\u003e) which could have caused the decline in cocoa germination. This is therefore consistent with the choices made by farmers where \u003cem\u003eTriplochiton scleroxylon\u003c/em\u003e was the least preferred species. Moreover, Abugre et al. (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2014\u003c/span\u003e) reported that the extracts of \u003cem\u003eT. scleroxylon\u003c/em\u003e inhibited the germination of three crops, namely, tomato (Lycopersicum esculentum), pepper (Capsicum annuum) and garden egg (Solanummelongena). Aqueous extracts of roots, stems-bark and leaves of \u003cem\u003eMelicia excelsa\u003c/em\u003e contain flavonoids, saponins, cardiac glycoside, terpenoid and tannins (Bayani et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Areola et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Terpenoids which make up the largest and most functionally complex group play a significant role in plant interactions (Chen et al. \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Cheng et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2007\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eGermination of seeds depends on the concentration of aqueous extracts, with greater concentrations expressing greater allelopathic potency than the lower concentrations (Siddiqui et al., \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). Khan et al. (\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2008\u003c/span\u003e) also showed that aqueous extracts at concentrations of 10, 15 and 20% had an inhibitory effect on wheat germination. Therefore, the decline in cocoa seed germination treated with aqueous extracts of \u003cem\u003eK. anthotheca\u003c/em\u003e, \u003cem\u003eT. scleroxylon, T. superba\u003c/em\u003e and \u003cem\u003eM. excelsa\u003c/em\u003e may be related to the existence of allelochemicals which suppressed the seed germination cycle. El-Khatib (\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e1997\u003c/span\u003e) suggested that the inverse relationship between seed germination and allelopathic inhibition may be due to reduced water uptake. The lower germination of cocoa seedlings treated with aqueous extracts from the selected shade tree may be partly attributable to the inhibition of water uptake by the presence of some allelochemicals, which prevented the growth of the seed embryo or caused its death (El-Khatib, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e1997\u003c/span\u003e; Abugre et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). That notwithstanding, Abugre et al. (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2011\u003c/span\u003e) reported that leaf extracts of \u003cem\u003eT. superba\u003c/em\u003e promoted germination of seeds of \u003cem\u003eZea mays\u003c/em\u003e by 2.5%; our results on the effects of aqueous extracts of \u003cem\u003eT. superba\u003c/em\u003e on cocoa seed germination are contrary to this, possibly because allelopathic effects are species-specific.\u003c/p\u003e\u003cp\u003e\u003cem\u003eT. scleroxylon\u003c/em\u003e is the most inhibiting species as it recorded the lowest level of germination compared to the other three species selected for this study. Higher concentrations (45 g / lit.) resulted in the highest suppression of cocoa seed germination. The decrease in cocoa seed germination due to allelopathic stress of various aqueous extracts may be attributed to numerous defects of metabolic function, the seed imbibition capacity, and embryonic defects (Maharjan et al., \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Chon and Nelson, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2010\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003cb\u003eThe effect of aqueous extract of the various concentrations of shade trees on the growth of cocoa seedlings\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eEffects on dry biomass\u003c/strong\u003e\u003cp\u003eaqueous extracts of \u003cem\u003eT. superba\u003c/em\u003e reduced dry biomass with increasing concentration as reported by Bhatt et al. (\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e1997\u003c/span\u003e) and Sisodia and Siddiqui (\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). Specifically, Bhatt et al. (\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e1997\u003c/span\u003e) found that the aqueous extracts from \u003cem\u003eTerminalia spp\u003c/em\u003e. suppressed the growth of \u003cem\u003eEleusine coracana, Brassica campestris, Horduem vulgare\u003c/em\u003e, and \u003cem\u003eGlycine max\u003c/em\u003e and their dry biomass whiles Sisodia and Siddiqui (\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e2009\u003c/span\u003e) reported that germination and growth inhibition efficiency increased with increasing amounts of various aqueous extracts. Naeem et al. (\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2012\u003c/span\u003e), Oudhia (\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2001\u003c/span\u003e) and Scrivanti (\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2010\u003c/span\u003e) attributed suppression in seed germination and growth of seedlings of the crops they investigated to allelochemicals in plant extracts. Seedling growth inhibition could probably be due to the induction of growth-inhibiting hormones. Bhatt et al. (\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e1997\u003c/span\u003e) suggested that the presence of gallic acid, ellagic acid, ethyl gallate, galloyl glucose and chebulagic acid in the aqueous extracts of \u003cem\u003eTerminalia spp.\u003c/em\u003e inhibited the growth of the crop seedlings they assessed and this resulted in reduced dry biomass. It is therefore possible that the aqueous extracts of \u003cem\u003eT. superba\u003c/em\u003e contained growth inhibitors which hindered the growth of cocoa seedlings and this resulted in reduced dry biomass. Several authors (Ali-Smith, 2009 and Bukar et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2009\u003c/span\u003e) have suggested that leaves of certain plants contain allelochemicals such as tannins, saponin, steroids which inhibits plant growth. Azza (\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2016\u003c/span\u003e) also established that the leaf extracts of \u003cem\u003eR. stricta\u003c/em\u003e inhibited the height of \u003cem\u003eViciafaba, Triticum aestivum\u003c/em\u003e, and \u003cem\u003eHordeum vulgare.\u003c/em\u003e Furthermore, Randhawa et al. (\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2002\u003c/span\u003e) reported that the root and shoot length of \u003cem\u003eTrianthema portulacastrum\u003c/em\u003e was decreased by a greater concentration of sorghum aqueous extracts. \u003cem\u003eT. scleroxylon\u003c/em\u003e and \u003cem\u003eM. excelsa\u003c/em\u003e aqueous extracts did not affect the dry biomass of cocoa seedlings even though they significantly affected germination of cocoa, possibly because allelochemicals are organ-specific and species-specific.\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eEffects on root growth\u003c/strong\u003e\u003cp\u003ethe aqueous extracts of \u003cem\u003eT. scleroxylon\u003c/em\u003e increased the root length of cocoa seedlings. This finding is consistent with Abugre and Quashie-sam (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2010\u003c/span\u003e) who reported that maize root and stem length increased with increasing concentrations of aqueous extracts. Allelopathic interactions can produce beneficial effects as it is the case in our finding that \u003cem\u003eT. scleroxylon\u003c/em\u003e extracts promoted root growth. This finding also converges with Tefera (\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e2002\u003c/span\u003e), who suggested that \u003cem\u003eParthenium hysterophorus\u003c/em\u003e aqueous leaf, tribal, heart, and flower extracts stimulated the development of the \u003cem\u003eEragrostis tef\u003c/em\u003e seedling. Since roots are sensitive to chemical processes, they can react more quickly. Enhanced root growth may be attributed to increased cell replication and growth hormone enhancement or supply of limiting nutrients. The allelochemicals possibly triggered the production and synthesis of growth specific hormones such as auxins. The radicle, which grows into the main root, allows the seed to absorb and transport water and salts to the shoot and leaves of the seedlings for photosynthesis and growth. The positive effects of \u003cem\u003eT. scleroxylon\u003c/em\u003e extracts on the roots of cocoa seedlings may enhance their early establishment, survival and growth. Generally, in aqueous extract experiments, the reported inhibitory effect is due to pH modification, which raises questions about allelopathy and its ecological nature and significance (Conway et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2002\u003c/span\u003e; Sisodia, \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2008\u003c/span\u003e). On the other hand, the root length of cocoa seedlings was not significantly affected by aqueous extracts of \u003cem\u003eK. anthotheca, M. excelsa\u003c/em\u003e, and \u003cem\u003eT. superba\u003c/em\u003e; this is contrary to the findings of Abugre et al. (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2011\u003c/span\u003e) who reported that root and leaf extracts of \u003cem\u003eT. superba\u003c/em\u003e hindered radicle growth of \u003cem\u003eVigna unguiculata, Lycopersicon esculentum\u003c/em\u003e and \u003cem\u003eZea mays\u003c/em\u003e. Our results also diverge from Khan et al. (\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2008\u003c/span\u003e), which showed that aqueous extracts at concentrations of 10, 15, and 20% had inhibitory effect on some agricultural crops. Furthermore, Khan et al. (\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2012\u003c/span\u003e) reported that the aqueous extracts from various seedlings of \u003cem\u003eParthenium hysterophorus\u003c/em\u003e had significant inhibitory consequences on the root and stem lengths of four wheat cultivars. Allelochemicals are both species-specific and organ-specific; different allelochemicals have different sites of action in different parts of a plant hence different species and organs vary in their sensitivity to allelochemicals (Mahajan \u003cem\u003eet al\u003c/em\u003e., 2007; Macias \u003cem\u003eet al.\u003c/em\u003e, 2004). Moreover, the extent of allelopathic inhibition depends on the concentration of the plant extracts. This accounts of the varied response of the roots of cocoa seedlings to the aqueous extracts of the selected shade tree species.\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eEffects on shoot length\u003c/strong\u003e\u003cp\u003ethe aqueous extracts of \u003cem\u003eKhaya anthotheca\u003c/em\u003e reduced the shoot length of cocoa seedlings and higher concentrations of its aqueous extracts had similar effects on the shoot length of cocoa seedlings (Table\u0026nbsp;4). The inhibitory effects of some plant extracts on plumule or radicle length may be associated with the occurrence of allelochemicals such as tannins, wax, flavonoids, and phenolic acids (Fag and Stewart, 1994; Mahajan \u003cem\u003eet al\u003c/em\u003e., 2007; Macias \u003cem\u003eet al.\u003c/em\u003e, 2004). Randhawa et al. (\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2002\u003c/span\u003e) reported that high concentration of sorghum aqueous extracts decreased \u003cem\u003eTrianthema portulacastrum\u003c/em\u003e root and shoot length. Ashrafi et al., (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2008\u003c/span\u003e) also stated that allelopathic impact in all sunflower aqueous extracts accelerated as the concentration increased. Our results also partly agree with the findings of Khan et al. (\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2008\u003c/span\u003e) who showed that an increase in aqueous extract concentrations increased the inhibitory effect on some agricultural crops. A decrease in shoot length of cocoa seedlings can be deduced from the occurrence of phytotoxic compounds in these aqueous extracts from tree species and the display of inhibitor impact on the growth parameter (Javaid and Anjum, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2006\u003c/span\u003e). Therefore, the presence of allelochemicals in the extracts of \u003cem\u003eKhaya anthotheca\u003c/em\u003e were possibly able to inhibit the synthesis of growth hormones, thus, limited cell division and differentiation resulting in reduced shoot growth.\u003c/p\u003e\u003c/p\u003e\u003cp\u003eGenerally, aqueous extracts of \u003cem\u003eT. scleroxylon, T. superba\u003c/em\u003e and \u003cem\u003eM. excelsa\u003c/em\u003e at all concentrations under this study did not affect the shoot length, except at higher concentrations (45g/lit) and lower concentrations (15g/lit) for \u003cem\u003eT. superba\u003c/em\u003e and \u003cem\u003eM. excelsa\u003c/em\u003e, respectively, where reduced shoot length growth was observed (Table\u0026nbsp;4). Our results diverge from Abugre et al. (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2014\u003c/span\u003e) who indicated that aqueous extracts of \u003cem\u003eT. scleroxylon\u003c/em\u003e adversely affected the shoot growth of tomato (Lycopersicum esculentum), pepper (Capsicum annuum) and garden egg (Solanummelongena). Furthermore, our findings are in contrast with previous researchers such as Tefera (\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e2002\u003c/span\u003e), Yawer et al. (\u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e2007\u003c/span\u003e), Sisodia and Siddiqui (\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e2009\u003c/span\u003e) and Khan et al. (\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2011\u003c/span\u003e) who found that greater degree of inhibition ensued with the leaves extracts at higher concentrations. That notwithstanding, our results are not entirely different from these authors since at the highest treatment level of 45g/lit, the aqueous extracts of \u003cem\u003eT. superba\u003c/em\u003e suppressed the growth (shoot) of cocoa seedlings.\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eFarmers\u0026rsquo; perception of shade trees in cocoa farms\u003c/b\u003e\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eFarmers had a mixed perception about shade trees on cocoa farms. They perceived shade trees as being important for three key ecosystem services namely, shade for cocoa, microclimate amelioration and maintenance of soil fertility possibly through litterfall and decomposition (Asare and Anders, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Tscharntke et al., \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Asigbaase et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2021b\u003c/span\u003e). On the other hand, farmers viewed shade trees as having negative effects on light penetration and air circulation and cocoa yield (Asare \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2005\u003c/span\u003e; Asare and Anders, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Ong et al. (\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2004\u003c/span\u003e) reported that shade trees are considered to have a detrimental impact on cocoa plant growth and yields; a view the farmers in our study also held. Additionally, they perceived shade trees as having allelopathic effects and being hosts for pest and disease (Anim-Kwarpong, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2003\u003c/span\u003e; Asare \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2005\u003c/span\u003e; Asare and Anders, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Consistent with this perception, Akrofi et al. (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2003\u003c/span\u003e) who found out that excessive shade has negative allelopathic effects on cocoa farm influences disease and pest status of cocoa farms.\u003c/p\u003e\u003cp\u003eVandenbelt et al. (\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e1990\u003c/span\u003e) showed that tree roots often exploit the crop root region for nutrients and water. This could be mainly so for shade tree species whose roots are shallow with the horizontal distribution. According to Vandenbelt et al. (\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e1990\u003c/span\u003e), the basic model depicted in most agroforestry literature of trees as complementary and interconnected with other crops and plants may be used with caution. The combinations of trees and crops may display more extensive niche differentiation than would be anticipated from their rooting forms in monoculture because of reactions to reduced water and nutrient obtainability in upper soil layers as a result of resource consumption by companion crops (Sinclair \u003cem\u003eet al.\u003c/em\u003e, 1994). Contrary to the assertions of Vandenbelt et al. (\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e1990\u003c/span\u003e) and Sinclair \u003cem\u003eet al.\u003c/em\u003e (1994), farmers in our study did not view competition with cocoa trees for water and nutrients as a major issue.\u003c/p\u003e\u003cp\u003eNotwithstanding farmers\u0026rsquo; mixed perception about shade trees, they were willing to integrate shade trees into their cocoa farms as they requested, received and planted shade tree seedlings supplied by the Forestry Commission of Ghana. This willingness may be a reflection of the perception that the positive effects of shade trees may compensate for or outweigh their negative effects. The most preferred shade by the farmers was \u003cem\u003eTerminalia superba\u003c/em\u003e yet our results show that aqueous extracts from this tree species resulted in reduced cocoa seed germination and biomass (Tables\u0026nbsp;2 and 5). This calls for further research and interventions to ensure recommended or preferred species are indeed beneficial for sustainable cocoa production.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eBased on the findings, we concluded that \u003cem\u003eKhaya anthotheca, Melicia excelsa, Terminalia superba\u003c/em\u003e and \u003cem\u003eTriplochiton scleroxylon\u003c/em\u003e suppressed the germination of cocoa and higher concentrations showed mixed results, which are always lower than the control. Higher concentrations of \u003cem\u003eK. anthotheca\u003c/em\u003e reduced cocoa seed germination while higher concentrations of \u003cem\u003eT. scleroxylon, M. excelsa\u003c/em\u003e, and \u003cem\u003eT. superba\u003c/em\u003e generally did not increase inhibition of the germination of cocoa seeds. Whereas the aqueous extracts of \u003cem\u003eT. superba\u003c/em\u003e reduced the dry biomass of cocoa seedlings and the aqueous extracts of \u003cem\u003eK. anthotheca\u003c/em\u003e hindered the shoot growth of cocoa, the aqueous extracts of \u003cem\u003eT. scleroxylon\u003c/em\u003e enhanced the growth of the root length of cocoa seedlings. Generally, the aqueous extracts of \u003cem\u003eM. excelsa\u003c/em\u003e did not adversely affect the dry biomass, shoot length and root length of cocoa seedlings. Farmers at the research areas preferred \u003cem\u003eTerminalia superba\u003c/em\u003e on their farms to other species. Their reason being that it has a positive effect on cocoa seedlings. Farmers keep shade trees on their farms purposely to provide shade for cocoa seedlings. We recommend the use of \u003cem\u003eT. scleroxylon\u003c/em\u003e and \u003cem\u003eM. excelsa\u003c/em\u003e on cococa farms as these species either promoted or had no adverse effects cocoa seedling growth.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe are very grateful to staff of the Forestry Commission for assisting in the administration of questionnaire on farmer preferences.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding Statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo funding was secured for the study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics Statement and Consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo ethical approval was sought for the study, however, ethical issues were addressed during the research. No formal permission was sought in obtaining the plant species from Modified \u0026lsquo;Taungya\u0026rsquo; Plantations established by the Forestry Commission. One of the authors was a Manager of these plantations and also a staff of the Forestry Commission. Farmers who participated in the study were informed of the importance of the study and their right not to participate. A verbal consent was obtained from participants before administration of the questionnaire.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to publish declaration\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors grant permission for the publication of their manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that there is no competing interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData Availability Statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical Trial number\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis is not applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contribution\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e1) S. A. Conceived the idea, designed the analysis, wrote the manuscript, laid the experiment, contributed to analysis and the lead2) E. A. Collected the data, wrote the paper, contributed data and analysis tools, contributed to laying of experiment3) S. N. Contributed data analysis and Laying of experiment4) M. A. Performed the analysis, reading of manuscript5) A. A. A. Performed the analysis, reading of manuscript\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAbugre S, Quashie-sam SJ. Evaluating the allelopathic effect of Jatrophacurcas aqueous extract on germination, radicle and plumule length of crops. Int J Agric Biol. 2010;12:769\u0026ndash;72.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAbugre S, Apetorgbor AK, Antwiwaa A, Apetorgbor MM. Allelopathic effects of ten tree species on germination and growth of four traditional food crops in Ghana. 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Chem Biodivers. 2007;4(7):1578\u0026ndash;85.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTables 1 to 8 are available in the Supplementary Files section.\u003c/p\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":"allelopathy, seedlings, aqueous extracts, germination, shoot length, dry biomass, root length","lastPublishedDoi":"10.21203/rs.3.rs-6984171/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6984171/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eShade trees on cocoa farms have been recommended without properly understanding the potential of some shade trees to release chemicals which could be injurious to cocoa. This research sought to determine the effect of aqueous extract from selected shade trees cultivated on cocoa farms on germination and growth of cocoa seedlings. Mature leaves and roots of commonly used shade trees (\u003cem\u003eKhaya anthotheca\u003c/em\u003e, \u003cem\u003eTriplochiton scleroxylon\u003c/em\u003e, \u003cem\u003eMelicia excelsa\u003c/em\u003e and \u003cem\u003eTerminalia superba\u003c/em\u003e) were collected separately and grounded into powder. Aqueous extracts of shade trees of different concentrations (15g/lit., 30g/lit. and 45g/lit) were formulated and applied to seeds and seedlings of cocoa. The study was carried out in a greenhouse which mimic field conditions. The study revealed that germination of cocoa seeds declined with increasing concentrations of \u003cem\u003eK. anthotheca\u003c/em\u003e, \u003cem\u003eM. excelsa\u003c/em\u003e and \u003cem\u003eT. scleroxlon\u003c/em\u003e, however, \u003cem\u003eT. superba\u003c/em\u003e generally did not result in further decline in germination. Higher concentrations of \u003cem\u003eT. superba\u003c/em\u003e reduced dry biomass whiles that of \u003cem\u003eT. scleroxylon\u003c/em\u003e increased root length with respect to the control. Farmers ranked \u003cem\u003eT. superba\u003c/em\u003e as their most preferred shade species which contradicts with the findings which preferably suggest the use of \u003cem\u003eT. scleroxylon\u003c/em\u003e and \u003cem\u003eM. excelsa\u003c/em\u003e as shade trees in cocoa agroforestry.\u003c/p\u003e","manuscriptTitle":"Potential allelopathic effects of selected shade tree species on cocoa (Theobroma cacao)","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-07-19 08:02:25","doi":"10.21203/rs.3.rs-6984171/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":"0d6c683c-571d-4566-ab29-de017f4b7f21","owner":[],"postedDate":"July 19th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-07-28T14:39:10+00:00","versionOfRecord":[],"versionCreatedAt":"2025-07-19 08:02:25","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6984171","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6984171","identity":"rs-6984171","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}