Legume Genomics and Genetics 2026, Vol.17, No.1, 68-79 http://cropscipublisher.com/index.php/lgg 73 between environmental conditions within the canopy and plant water-nutrient status modulated by planting density. Optimizing these indices through appropriate density management supports improved gas exchange, photosynthesis, and ultimately yield. In summary, soybean planting density influences photosynthetic characteristics and physiological indices through modifications in canopy structure, light environment, and resource competition. Moderate increases in density enhance chlorophyll content, photosynthetic rate, light use efficiency, and favorable physiological responses such as higher SPAD values and balanced transpiration rates. However, excessively high densities can lead to shading stress that diminishes these benefits by reducing individual leaf function despite greater total canopy coverage. Optimal planting strategies should therefore balance population size with spatial arrangement to maximize photosynthetic performance and physiological health for sustainable yield improvement (Figure 3) (Liao et al., 2022). Figure 3 Schematic illustration of stomatal regulation and intercellular CO2 dynamics under optimal and excessive planting densities (Adopted from Liao et al., 2015) 5 Effects of Planting Density on Soybean Yield and Its Components 5.1 Variations in individual plant yield and population yield Planting density exerts contrasting effects on individual plant yield and overall population yield in soybean production. As density increases, the yield per individual plant typically decreases due to intensified competition for resources such as light, nutrients, and water. However, this reduction in per-plant productivity is often offset by a greater number of plants per unit area, leading to an increase in total population yield up to an optimal density (Yang et al., 2025). For example, research in the Huang-Huai-Hai Plain demonstrated that while individual-level relative productivity declined with increasing density, population-level seed yield peaked at around 315,000 plants per hectare, indicating that higher densities can compensate for lower individual yields through enhanced canopy development and light interception (Yang et al., 2025). Similarly, studies across North America found that low-yield environments required higher planting densities to maximize population yield compared to high-yield environments where lower densities sufficed (Carciochi et al., 2019). The balance between individual and population yield is influenced by environmental conditions and cultivar characteristics. In high-yield environments, plants tend to produce more seeds per plant at lower densities,
RkJQdWJsaXNoZXIy MjQ4ODYzNA==