Legume Genomics and Genetics 2026, Vol.17, No.1, 68-79 http://cropscipublisher.com/index.php/lgg 76 performance despite increased population size (Klimek-Kopyra et al., 2020). For instance, rainfall variability modulates the intensity of intraspecific competition—higher rainfall increases competition severity while drought reduces it by limiting overall growth (Klimek-Kopyra et al., 2020). Spatial arrangement also plays a role in regulating competition; uniform plant spacing reduces variability among individuals by minimizing dominance hierarchies within the canopy (Xu et al., 2021). Variable-density row arrangements have been tested but did not consistently improve yield over uniform high-density plantings in soybean (Ethridge et al., 2022). Optimizing both planting density and spatial distribution helps mitigate negative effects of intraspecific competition by balancing resource availability with population size. This regulation supports improved growth uniformity, physiological function, and yield stability across diverse environmental conditions. 7 Discussion 7.1 Mechanisms of differences in growth and yield under different densities Differences in soybean growth and yield under varying planting densities are primarily driven by changes in resource availability and plant physiological responses. Higher planting densities increase leaf area index (LAI) and aboveground biomass, which enhance light interception and photosynthetic capacity, ultimately boosting seed yield (Liao et al., 2022). However, increased density also intensifies competition among plants for water, nutrients, and light, which can reduce individual plant growth and seed size despite higher population yields (Liao et al., 2022; Xu et al., 2021). For example, at very high densities, soybean plants may exhibit reduced branch number and smaller stem diameter due to shading and resource limitations, affecting lodging resistance and yield stability (Xu et al., 2021; Xu et al., 2024). Physiological mechanisms such as chlorophyll content, photosynthetic rate, and root growth are also influenced by density. Increased density combined with adequate nitrogen fertilization and supplemental irrigation improves these parameters, enhancing water-nitrogen use efficiency and biomass accumulation (Liao et al., 2022). Conversely, excessive density without balanced nutrient or water supply can exacerbate stress conditions leading to diminished photosynthetic performance and yield penalties (Wang et al., 2023). Thus, the interplay between planting density and environmental factors regulates growth dynamics through both above- and below-ground processes that determine final yield outcomes. 7.2 Comparison with previous studies and interpretation The findings align with previous research demonstrating that moderate to high planting densities generally improve soybean yield by optimizing canopy light interception and dry matter accumulation (Xu et al., 2021; Carciochi et al., 2019). Uniform plant distribution at higher densities reduces variability among individual plants, contributing to more stable yields compared to non-uniform spacing (Xu et al., 2021). Additionally, the optimal agronomic plant density varies by environment; low-yield environments require higher densities than high-yield environments to maximize productivity (Carciochi et al., 2019). This variation reflects differences in resource availability and climatic conditions influencing plant competition intensity. Comparisons with intercropping systems reveal that shading stress from neighboring crops can reduce soybean stem lignin accumulation and lodging resistance at high densities, highlighting the importance of density management in mixed cropping scenarios (Wang et al., 2023). Moreover, cultivar-specific traits such as branching capacity affect how soybeans respond to density changes; cultivars with fewer branches tend to perform better under close planting due to higher tolerance of crowding. These insights emphasize the need for integrated management considering genotype-environment interactions when determining optimal planting densities. 7.3 Limitations of this study and future improvements This study’s limitations include its focus on a limited range of planting densities and environmental conditions, which may restrict the generalizability of results across diverse agroecosystems. The interaction effects of planting density with other agronomic factors such as row spacing, sowing date, and cultivar selection were not fully explored but are known to influence canopy structure and yield components significantly (Ran et al., 2023).
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