Soybean Yield Potential Research Articles

Assessing Soybean Yield Potential and Yield Gap in Different Agroecological Regions of India Using the DSSAT Model

The study used the DSSAT model to assess potential soybean yields in different regions of India and validated it under diverse agroecological conditions. The average simulated yield under irrigated conditions was 3794 kg ha−1 relative to the simulated average rainfed yield of 2446 kg ha−1, showing a 35.52% reduction in grain yield due to adverse moisture conditions under rainfed conditions. Relative to simulated yield, the average observed (actual) rainfed yield across 43 districts of India was 1025 kg ha−1, which was 2769 and 1421 kg ha−1 lower than irrigated and rainfed potential yield, respectively. A significant positive correlation was observed between simulated water non-limited yield and solar radiation (R2 = 0.55, p ≤ 0.05). The simulated rainfed grain yield (R2 = 0.66, p ≤ 0.05) had a significant, positive, and curvilinear relationship with growing season rainfall. On the other hand, the actual yield (R2 = 0.008) showed a non-significant relationship with mean crop seasonal rainfall across locations. The gap between simulated yield under irrigated and rainfed conditions is huge at locations with low seasonal rainfall and narrows with increasing rainfall. In addition, the gap between actual yield and simulated yield under rainfed conditions was larger, even in high seasonal rainfall areas. The yield gap under rainfed conditions is due to the non-adoption of improved crop management practices and could be reduced with proper interventions. This includes adapting drought-resistant varieties, conserving rainwater, changing land configuration, and adopting waterlogging-tolerant varieties using improved technology to reduce the soybean yield gap.

Management of Soybean Cyst Nematode and Sudden Death Syndrome with Nematode-Protectant Seed Treatments Across Multiple Environments in Soybean.

As soybean (Glycine max) production continues to expand in the United States and Canada, so do pathogens and pests that directly threaten soybean yield potential and economic returns for farmers. One such pathogen is the soybean cyst nematode (SCN; Heterodera glycines). SCN has traditionally been managed using SCN-resistant cultivars and rotation with nonhost crops, but the interaction of SCN with sudden death syndrome (SDS; caused by Fusarium virguliforme) in the field makes management more difficult. Nematode-protectant seed treatments have become options for SCN and SDS management. The objectives of this study were to evaluate nematode-protectant seed treatments for their effects on (i) early and full season SCN reproduction, (ii) foliar symptoms and root-rot caused by SDS, and (iii) soybean yield across environments accounting for the above factors. Using a standard protocol, field trials were implemented in 13 states and one Canadian province from 2019 to 2021 constituting 51 site-years. Six nematode-protectant seed treatment products were compared with a fungicide + insecticide base treatment and a nontreated check. Initial (at soybean planting) and final (at soybean harvest) SCN egg populations were enumerated, and SCN females were extracted from roots and counted at 30 to 35 days postplanting. Foliar disease index (FDX) and root rot caused by the SDS pathogen were evaluated, and yield data were collected for each plot. No seed treatment offered significant nematode control versus the nontreated check for in-season and full-season nematode response, no matter the initial SCN population or FDX level. Of all treatments, ILEVO (fluopyram) and Saltro (pydiflumetofen) provided more consistent increases in yield over the nontreated check in a broader range of SCN environments, even when FDX level was high.

Planting date and dicamba‐based herbicide programs influence soybean production in the Southern Great Plains

AbstractThe interplay of management decisions involving soybean (Glycine max L.) planting date, herbicide programs, and herbicide application timings is critical to optimize soybean performance and weed control in Southern Great Plains soybean production systems. This research sought to evaluate soybean yield potential and the level of weed control as influenced by early‐, delayed‐, and late‐ planting dates and various combinations of preemergence (PRE), early‐postemergence (EPOST), and mid‐postemergence (MPOST) weed management programs. A field study was established in Bixby, OK in 2017 and 2018 under irrigated conditions and in Perkins, OK in 2017 under dryland conditions, consisting of three planting windows (early, delayed, and late) of XtendFlex soybean, with or without a PRE (chlorimuron + flumioxazin + pyroxasulfone + glyphosate + dicamba) combined with EPOST or EPOST + MPOST (glyphosate + dicamba) versus no in‐season applications. The gap in late‐planted soybean yield potential, compared to early‐planted soybean, was exacerbated in the dryland systems (1346 kg ha−1) versus an irrigated system (2311 kg ha−1). Use of PRE provided 60% weed control until MPOST and increased yields by 657 kg ha−1 and 457 kg ha−1 for delayed and late‐planted soybean, respectively. Late‐planted soybean with EPOST + MPOST provided up to 50% weed control, but lack of biomass production for cultural control reduced weed control by 29% compared to early‐ and delayed‐planted soybean. From an agronomic management standpoint, the time of soybean planting is influential on the success of weed control measures and soybean yields in double‐cropping system in the Southern Great Plains, particularly with late‐planted soybean.

Negative synergistic effects of drought and heat during flowering and seed setting in soybean

Rising intense heat waves combined with lower precipitations are the new norms of current global scenarios. These altered climatic conditions negatively impact soybean yield potential and quality. Ten soybean cultivars were subjected to four different growing conditions: control, drought, heat, and combined drought and heat to understand the physiological, yield, quality and molecular changes. Stomatal conductance was reduced by 62% and 10% under drought and heat, respectively. This reduction was further exacerbated to 93% when exposed to combined stress. The highest canopy temperature was recorded at +8 °C with combined stress treatment, whereas drought and heat exhibited +2 °C and +5.4 °C, respectively. Furthermore, combined stress displayed a more pronounced negative impact on greenness-associated vegetative index; the gene expression analysis further corroborated these findings. Each degree Celsius increase in temperature during flowering and seed-filling reduced seed weight by approximately 7% and 4% with and without drought, respectively. The seed protein increased under drought, whereas the oil showed a converse trend under drought and combined stresses. Most physiological and yield traits showed no significant correlations between control and individual or combined stress. This suggests that selecting crops for combined stress tolerance may not be appropriate based on nonstress or individual stress performance. Thus, incorporating combined stress-resilient traits into elite soybean cultivars could significantly boost soybean production under hot and dry climatic conditions.

Impacts of aerosol meteorological feedback on China's yield potential of soybean

AbstractChina's severe particle pollution could affect the regional climate and weather conditions that consequently threaten local to global food security. Yet, the underlying mechanisms and quantitative assessment of aerosols on crop yields remain unknown. Here, by integrating a meteorology–chemistry model and a crop model, we show the impacts of atmospheric aerosols on China's meteorology and soybean yields. We find that the potential yields of soybean would decrease in most parts of China due to direct aerosol radiation effects, while showing diverse responses in parts of the Northeast and North China Plain. Moreover, because of the high sensitivity of soybean growth to water, potential yield fluctuations are closely related to aerosol‐induced precipitation changes in most soybean‐growing regions of China. In particular, aerosols play the most important role during soybean's pod‐filling stage, in which the influence of both precipitation perturbations and negative solar radiative forcing is about 5–10 times that of air temperature on crop yield. Our study thereby identifies aerosol mitigation can bring a notable increase in crop yields, highlighting the potential for important co‐benefits in food security across polluting developing countries.

Drought stress reduces the photosynthetic source of subtending leaves and the transit sink function of podshells, leading to reduced seed weight in soybean plants.

Drought stress is the key factor limiting soybean yield potential. Soybean seed formation involves a coordinated "subtending leaf-podshell-seed" process, but little is known about the assimilation and transport of photoassimilates in subtending leaves, podshells and seeds or their relationships with soybean seed formation under drought stress. To address these research gaps, two-year experiments with two soybean cultivars, Wandou 37 (drought tolerant) and Zhonghuang 13 (drought sensitive), were conducted under three soil water content (SWC) conditions in 2020 and 2021 based on the responses of their yield to drought. We analyzed the photosynthetic assimilation and translocation of photoassimilates in subtending leaves, podshells and seeds by stable isotope labeling. Compared with those under 75% SWC, 60% SWC and 45% SWC significantly decreased the Wandou 37 seed weight by 19.4% and 37.5%, respectively, and that of Zhonghuang 13 by 26.9% and 48.6%, respectively. Compared with those under 75% SWC, drought stress decreased the net photosynthetic rate and the activities of sucrose phosphate synthase (SPS) and sucrose synthase (SuSy), which in turn decreased the photosynthetic capacity of the subtending leaves. The podshells ensure the input of photoassimilates by increasing the SuSy activity, but the weakened source-sink relationship between podshells and seeds under drought stress leads to a decrease in the translocation of assimilates from podshells to seeds. The lack of assimilates under drought stress is an important factor restricting the development of soybean seeds. We conclude that the decrease in seed weight was caused by the decrease in the photosynthetic capacity of the subtending leaves and the decrease in the overall availability of photoassimilates; moreover, by a decrease in the translocation of assimilates from podshells to seeds.

Influence of planting date, maturity group, and harvest timing on soybean yield and seed quality

AbstractAs in other soybean‐producing regions in the United States, planting date and maturity group (MG) are two of the most important factors, along with variety selection and timely harvest, that can set the stage to optimize soybean yield potential in Louisiana. Limited data are available on the effect of these factors along with harvest timing on soybean seed quality. Field studies evaluated the influence of planting date, MG, and harvest timing on soybean yield and seed quality at the Louisiana State University AgCenter Northeast, Macon Ridge, and Dean Lee Research Stations in 2018–2020. Soybean yield was optimized when MG 4 and 5 soybean varieties were planted between mid‐April and mid‐May. Earlier and later planting dates did not result in maximum yield. Planting date effects on seed quality, however, were negligible. Greatest soybean quality was obtained when planting relative maturities (RM) 5.4–6.0 soybean; however, as indicated in the planting date study, yield was not maximized. Planting RM 3.0–4.4 soybean varieties in Louisiana resulted in lower seed quality. Soybean varieties within RM 4.5–5.3 resulted in acceptable seed quality and maximum yield in Louisiana, assuming plants are harvested at the optimum harvest timing (when seed reaches 13% moisture) and not delayed 14–28 days.

Canopy coverage phenotyping and field spatial variability adjustment as an efficient selection tool in soybean breeding

AbstractAccurate estimation of grain yield potential in soybean [Glycine max (L.) Merr.] progeny rows (PRs) by measuring yield itself is challenging due to the small number of seeds available. To obtain more precise estimates of soybean yield potential and control nongenetic sources of variability, soybean breeders in the United States use secondary traits, visual selection (VIS), adjustments for field spatial variation, pedigree (PED) information, and unmanned aerial systems–based plant phenotypes; however, there are limited comparisons among the different PR testing procedures. We conducted a selection experiment in 2018 PR populations developed for yield and diversity from four soybean breeding programs. Then, we compared the performance of the lines selected using 13 selection categories in 2019 preliminary yield trials (PYTs). The sources of information used across categories included spatially adjusted (SP) traits, PED information, the canopy of the plant measured by aerial and ground digital images, reproductive length (RL), and grain yield (YLD). SP trait covariates and canopy data were the information sources most highly associated with lower yield ranks and higher yield performance of PYT. The most effective secondary trait was average canopy coverage (ACC) measured by high‐throughput phenotyping (HTP) platforms. Our selection experiment shows that ACC used as a secondary trait in combination with SP trait covariates effectively selects high‐yielding lines from non‐replicated experiments. Based on the scenarios considered in this study, it may be possible to increase the gain from selection by phenotyping secondary traits using HTP and implementing spatial variation adjustments in PR trials, which could help enhance crop productivity.

Enhancing the Yield Potential of Soybean after Magneto-Priming: Detailed Study on Its Relation to Underlying Physiological Processes

Soybean (Glycine max) is one of the most important proteins and oilseed crops in the world due to a boom in its demand. In order to meet this demand, various modern agricultural methods are being employed, of which magneto-priming (treatment of seeds with magnetic field) is becoming the most popular technique owing to its efficiency and eco-friendly nature to improve seed vigour, growth and yield of soybean plants. Therefore, we conducted a field experiment to evaluate the impact of magneto-priming of seeds with static magnetic field on soybean var. JS-335 plants. We used static magnetic field (SMF) strengths of 150 mT (1 h) and 200 mT (1 h) for this study. Both the SMF treatments improved growth (shoot as well as root growth parameters), carbon fixation (PSII efficiency, gas exchange parameters, carbonic anhydrase activity) and nitrogen fixation (leghemoglobin content, total protein content, nitrate reductase activity). We observed an association between these parameters which contributed to biomass accumulation and hence to the enhanced crop yield. In addition, reduced levels of ASA (reduced form of ascorbate), MDA (malondialdehyde) and antioxidant enzymes suggest that magneto-priming alleviates oxidative stress in SMF-primed soybean plants. Field strength of 200 mT (1 h) proved to be more effective in improving all the parameters as compared to 150 mT. Our study suggested that pre-sowing SMF treatment can be efficaciously employed for improving the growth, development and production of soybean.

Prescient diagnostic analysis for boron nutritional status in soy crops

Boron is the most limiting micronutrient for soybean yield; therefore, accurate identification of its nutritional status is important for adequate fertilization management and maximize soybean yield potential. Currently, tools for nutritional status interpretation of B, such as the CND and DRIS are used; however, their efficacy is not considered to identify the true nutritional status of B. In this research, we investigated the efficacy of these methods to identify the nutritional status of B in 140 commercial soybean crops to obtain nutritional standards for the DRIS and CND methods. In addition, an experiment of B dose calibration (0, 300, 600, 1200 and 1800 g ha−1) was installed to assess the quality of nutritional diagnoses using the PDA. The experimental approach tested the limits of 0.25, 0.50, and 1.00 for the NRr and values of 1%, 5%, or 10% for YR. The DRIS method was more effective, and, on average, its variations increased yield by 27% compared to CND, with the best performance of DRIS when NRr = 1.00 was adopted with 10% for YR. This study highlights the need for reliable and accurate diagnostic methods with global implications for crop sustainability by improving the efficacy of B fertilization programs and crop yield.

Resilience of soybean cultivars to drought stress during flowering and early-seed setting stages

Drought stress during the reproductive stage and declining soybean yield potential raise concerns about yield loss and economic return. In this study, ten cultivars were characterized for 20 traits to identify reproductive stage (R1–R6) drought-tolerant soybean. Drought stress resulted in a marked reduction (17%) in pollen germination. The reduced stomatal conductance coupled with high canopy temperature resulted in reduced seed number (45%) and seed weight (35%). Drought stress followed by rehydration increased the hundred seed weight at the compensation of seed number. Further, soybean oil decreased, protein increased, and cultivars responded differently under drought compared to control. In general, cultivars with high tolerance scores for yield displayed lower tolerance scores for quality content and vice versa. Among ten cultivars, LS5009XS and G4620RX showed maximum stress tolerance scores for seed number and seed weight. The observed variability in leaf reflectance properties and their relationship with physiological or yield components suggested that leaf-level sensing information can be used for differentiating drought-sensitive soybean cultivars from tolerant ones. The study led to the identification of drought-resilient cultivars/promising traits which can be exploited in breeding to develop multi-stress tolerant cultivars.

Influence of a cereal rye cover crop on the critical period for weed control in soybean

AbstractSoybean is the world’s most widely grown leguminous crop and is an important source of oil and protein for food and feed in addition to other industrial uses. However, herbicide-resistant and troublesome weed control challenges limit yield potential and threaten conservation tillage (CT) systems. Cover crops have been widely adopted as an integrated pest management component in CT systems to suppress weeds and maintain soybean yield potential. A 3-yr field experiment was conducted to estimate the influence of a cereal rye cover crop following CT on the critical period for weed control (CPWC) in soybean. The experiment was implemented in a split-plot design in which main plots as CT following cover crop (CT + CC), CT following winter fallow (CT + WF), and conventional tillage (CVT), and subplots were multiple durations of weed-free and weed interference. Results showed that the estimated CPWC of CT + CC and CT + WF treatments was 0 wk and >7 wk, respectively, in 2018. In 2019, the estimated CPWC was 0 wk, 5.0 wk, and 1.3 wk under CT + CC, CT + WF, and CVT treatments, respectively. In 2020, the estimated CPWC was 3.5 wk, >6.2 wk, and 0 wk under CT + CC, CT + WF, and CVT treatments, respectively. The presence of a cover crop delayed the CTWR and caused an early beginning of the CWFP compared with CT + WF treatment, and hence shortened the CPWC in 2018 and 2019. In conclusion, the CT + WF system did not reduce the weed competition and subsequent yield loss in soybean compared to the CT + CC system.

​Phoma Blight of Soybean in Kashmir: Etiology, Relative Yield Losses and Critical Stage of Management Intervention

Background: Soybean leaf blight has been viewed as a possible biotic stress responsible for decreasing yield potential of soybean in Kashmir over the years. Therefore, its etiology and recording associated yield loss were deemed necessary corresponding to baseline findings for deciding any chemical or non-chemical intervention in disease management. Methods: Field and laboratory investigations were undertaken during crop periods of 2019 and 2020. Disease specimens were collected from various locations across valley and the pathogen was isolated on Potato Dextrose Agar medium. To identify the host range of soybean isolate, nine pulse crops were tested under controlled conditions (Tem. 22±3°C and RH greater than 80%). The relative yield loss and critical stage of chemical intervention were assessed by exposing soybean populations to disease at different phenological stages which created five different levels of disease in a field experiment laid in RBD with four replications. Result: Phoma sojicola (syn. Ascochyta sojicola) was associated pathogen of this disease of soybean in Kashmir. Typical disease symptoms on leaves comprised of roughly circular and brown lesions (up to 20 mm diameter) with concentric rings having interspersed pycnidia. Most often the diseased tissue fall apart and gives it a shot hole expression. Radial daily mycelial growth of the pathogen was 3.62 mm colony was grey olivaceous in the centre and light olivaceous towards periphery. Conidia were hyaline, oblong to ellipsoidal and 1-2 celled with average dimensions of 7.98 x 2.87 µ. Chlamydospores were brown olivaceous, globose to sub-globose with average dimensions of 16.89 x 9.30 µ. After artificial inoculation, Phaseolus vulgaris, Vigna sinensis, V. radiata, V. mungo, Cicer arietinum, Vicia faba and Cajanus cajan manifested disease symptoms after variable incubation periods of 8-13 days, while as Lens esculenta and Pisum sativum resisted the invasion. Early appearance of the Phoma blight (V-1 stage) in soybean can reach a terminal intensity of 67.16 per cent besides causing 51.72 per cent yield loss. Tolerable yield loss (5.63%) was achieved only when the crop was maintained disease free up to R-3 (beginning pod development) stage.

Assessing the impact of high-input management for reducing soybean yield gaps on high-productivity farms

To increase soybean actual yields (Ya), modern farmers are interested in exploring novel intensification options. We hypothesize that the inclusion of a high-input treatment in high-productivity systems may potentially reduce yield gaps (Yg), representing additional profits for farmers. Our objectives were to: (i) estimate Ya, water-limited yield potential (Ywlim), and Yg; (ii) evaluate a high-input treatment as a management option for reducing Yg; (iii) identify management and environmental factors associated to yield response to inputs and, (iv) determine the economic outcome of this high-input management on high-productivity soybean crops. We carried out 27 on-farm field experiments comparing a conventional management system versus a novel high-input treatment across the Central Pampas of Argentina. The conventional treatment was the most common management prescribed by farmers in the region. The high-input treatment included a set of inputs that were not usually applied and involved soil fertilizers with S and Zn, seeds treated with insecticides, fungicides, and inoculants, stress-reducing product, Ca and B foliar fertilizers and preventive insecticide. The Ywlim was estimated using crop simulation models. Yield gaps were calculated as the difference between Ywlim and Ya. Average Ya and Ywlim were 4571 and 5100 kg ha−1, respectively, with a Yg lower than 30%. High-input treatments promoted a yield response of 131 kg ha−1 across sites (p < 0.001), reducing Yg by 2.6%. Yield response to high-input treatment was positively correlated with Yg and soil pH, but negatively correlated with soil P. No positive economic outcomes were obtained with the high-input treatment. This study showed low benefits of the high-input treatments for reducing Yg in high-yielding soybeans managed by high-productivity farmers. Future yield increases in this type of systems would rely on genetic improvement of soybean yield potential and exploiting genotype x management x environment interactions.

Optimal Fertilization Level for Yield, Biological and Quality Traits of Soybean under Drip Irrigation System in the Arid Region of Northwest China

Soybean is one of the most important oilseed crops worldwide. Fertilization severely restricts the yield potential of soybean in the arid regions of Northwest China. A two-year field experiment was conducted to investigate the effects of fertilization on soybean yield in arid areas under a drip irrigation system. The treatment consisted of 14 fertilizer combinations comprising of four rates each of nitrogen (N) (0, 225, 450, and 675 kg ha−1), phosphorus (P) (0, 135, 270, and 405 kg ha−1), and potassium (K) (0, 75, 150, and 225 kg ha−1). The results revealed that grain yield was more sensitive to N fertilizer than to P and K fertilizers. The P and K fertilizers influenced harvest index and biomass, respectively. The optimized combination of fertilizers for high yield, as well as biological and quality traits was obtained by quadratic polynomial regression analysis. The theoretical grain yields based on the performed statistical calculations and plant biomass were greater than 7.21 tons ha−1 and 16.38 tons ha−1 with 300,000 plants ha−1 and were obtained under a fertilization combination of 411.62–418.39 kg ha−1 N, 153.97−251.03 kg ha−1 P2O5, and 117.77−144.73 kg ha−1 K2O. Thus, our findings will serve as a guideline for an effective fertilizer application in order to achieve a balance between grain yield and plant biomass as well as to contribute to the promotion of large-scale cultivation of soybean under drip irrigation.

Potencial de rendimento de cultivares de soja modernas sob níveis alto e baixo de insumos

Abstract The objective of this work was to evaluate the grain yield potential of modern soybean (Glycine max) cultivars subjected to high- and low-input management levels on different sowing dates, in the southwestern region of the state of Paraná, Brazil. The experiment was carried out in the 2017/2018 and 2018/2019 crop seasons in the municipality of Itapejara D’Oeste. Five soybean cultivars (BMX Zeus IPRO, BMX Ativa RR, BMX Lança IPRO, NS 5445 IPRO, and NA 5909 RG) were evaluated in four environments formed by the combination of input management levels (high and low) and sowing dates (first and second). The experimental design was a randomized complete block with three replicates. The evaluated traits were: grain yield potential (kg ha-1), in the R5 phenological stage; and grain yield (kg ha-1) and its components, in the R8 stage. Cultivar, sowing date, and input management are determinant for maximizing grain yield potential. In the first sowing date, in October, the BMX Zeus IPRO cultivar shows a better response to the high level management, with a higher yield potential in the R5 stage (19,682 kg ha-1) and a higher grain yield (8,248 kg ha-1), whereas NA 5909 RG shows the best results with the low input management.

Response of Several Soybean Varieties to Co-inoculation with Rhizobium and Mycorrhiza Biofertilizers in Dryland of East Lombok, Indonesia

In Indonesia, soybean is the most important legume crop, which can develop Rhizobium and mycorrhizal symbiosis for better nutrition, especially in dryland areas. A trial for investigating responses of several varieties of soybean to co-inoculation with Rhizobium and mycorrhiza biofertilizers has been carried out in East Lombok, Indonesia, from August to October 2022. The Randomized Block Design was used to arrange the two treatment factors tested, i.e. biofertilizer application (B0= without biofertilizer; B1= Rhizobium inoculant; B2: co-inoculation of soybean with Rhizobium and mycorrhiza biofertilizers) and soybean varieties (V1= Detap, V2: Biosoy-2, V3= Dena-1). The trial was made in three blocks (replications). The variables included plant height, trifoliate number, root volume, and biomass yield and pod number as a yield potential. Results indicated that co-inoculation several varieties of soybean with Rhizobium and mycorrhiza biofertilizer increased yield potential of soybean in dryland as indicated by higher nodule number, trifoliate number, pod number and biomass yield of soybean, especially of Detap (V1) and Dena-1 (V3) varieties under co-inoculation treatment (B2), compared to inoculation with Rhizobium only (B1) or unioculated control (B0). Further studies on more varieties of soybean need to be conducted in different types of soil to find out the most responsive varieties to co-inoculation with Rhizobium and mycorrhiza biofertilizer to increase soybean productivity especially in dryland areas.

Global warming and world soybean yields

The crop yield potential of world soybean from 2019 to 2028 has been projected using ARIMA model based on the yields from 1961 to 2018. Both annual global mean temperature and the yields of world soybean have been projected to rise during the ensuing decade 2019-2028. Projected average yields of world soybean varies from 2841 to 3276 kg ha-1 while 4324 to 4807 kg ha-1 in the case of top (national) yields of world soybean. Annual global mean temperatures may vary from 15.0 to 15.3oC and likely to exert positive impact on average yield (R squared = 0.80) while negative on top yield (R squared = 0.40) of world soybean. It may be concluded that for world soybean yields in 2019 to 2028, the opportunities for improving production should be dependent on both high and low-yielding countries as the yield remained between 30 and 70 per cent of potential limit i.e. in middle place around the turn-point of S-shaped curve in long-term trend partly affected by global warming.

Yield potential of soybean under palm oil trees

Research to assess soybean yields planted under palm oil trees was conducted in North Sumatera, Indonesia. This research aimed to provide information on soybean varieties that were most suitable for planting under palm trees. Two experiments were conducted in the palm tree areas i.e. under one-year-old (IP 1) and two years old (IP 2) of the palm tree. In each site, the experiment was arranged in a split-plot design with two replications. The main plot was spacing row arrangements, i.e. double-spacing (50 cm x (30 cm x 20 cm) and single-spacing (40 cm x 15 cm), whereas the subplot was soybean varieties consisted of Dega 1, Dena 1, Argomulyo, and Anjasmoro. Research results showed that the average seed yield obtained in IP 1 was higher than IP 2, and soybean planted in a single-spacing produced higher seed yield compared to double-spacing. Argomulyo variety was superior in IP 1 with a seed yield of 3.66 t/ha and Dena 1 was the most superior in IP 2 with a seed yield 2.17 t/ha, both in single-planting arrangements.

Effect of Source–Sink Ratio Manipulation on Growth, Flowering, and Yield Potential of Soybean

Trade-offs between growth and reproduction in soybean require resource availability manipulations. Decapitation and reducing sink strength through deflowering can affect the source–sink ratio that affects plant growth, development, and yield. The current study assesses the effect of decapitation (Decap) and removal of the two lowest racemes (R2LR) and their combination on growth, flowering, and yield capacity of soybean through controlling the source–sink ratio and inducing the “stay-green” phenotype. Two field experiments were conducted during 2018 and 2019 in the Agronomy Farm located at Mansoura University, Egypt. Decapitation was done at the V4 stage (35 days after sowing, DAS), during which four nodes on the main stem had fully developed leaves beginning with the unifoliolate nodes, whereas R2LR was performed at the R2 stage (50 DAS), during which the plants had one open flower at one of the two uppermost nodes on the main stem. Results indicated that Decap, R2LR, and their combination significantly increased seed yield per plant through increasing plant growth and flowering and improving biochemical attributes. The combination between Decap and R2LR was generally more effective in positively modulating plant vegetative, reproductive, and physiological capacity than either Decap or R2LR alone. Moreover, the number of branches as well as pods/plant and IAA content responded positively to Decap, whereas net assimilation rate, seed growth rate, number of flowers/node, and cytokinins content responded positively to R2LR. Decap and R2LR were interpreted in light of their effects on inducing the “stay-green” phenotype and altering the source–sink ratio. Based on the findings, it can be concluded that concealing the apical dominance in conjunction with reducing the sink strength through guided raceme removal would be beneficial for the reproductive potential in soybean.