Legume Genomics and Genetics 2026, Vol.17, No.1, 68-79 http://cropscipublisher.com/index.php/lgg 75 Ventilation within dense canopies is also affected by planting density, as tighter spacing can restrict air movement, increasing humidity and potentially promoting disease development. Adjusting spatial arrangements such as row spacing can improve airflow and reduce microclimate stress within the canopy. Studies on maize and cotton similarly show that moderate densities optimize canopy structure to balance light interception with adequate ventilation, supporting healthier growth and yield stability (Zhang et al., 2021; Zhai et al., 2024). Thus, managing planting density alongside spatial configuration is crucial for maintaining optimal light distribution and ventilation in soybean canopies. 6.2 Water and nutrient use efficiency Water use efficiency (WUE) and nutrient use efficiency (NUE) are closely linked to planting density through their effects on root competition, canopy transpiration, and nutrient uptake dynamics. Moderate increases in planting density enhance resource capture by increasing total leaf area and root volume per unit land area, thereby improving precipitation use efficiency (PUE) and NUE up to an optimal point (Figure 4) (Duan et al., 2025). However, excessively high densities may reduce individual plant access to water and nutrients due to intensified competition, leading to diminished WUE and NUE despite higher total biomass production (Zhang et al., 2021). Research in semiarid environments indicates that moderate planting densities combined with density-tolerant cultivars achieve better balance between resource uptake and utilization efficiency than very high densities (Zhang et al., 2021). Similarly, studies on cotton demonstrate that increased planting density improves nutrient uptake correlated with higher leaf area index but only up to a threshold beyond which efficiency gains plateau or decline (Zhai et al., 2024). In soybean, uniform plant distribution at higher densities enhances dry matter accumulation without additional inputs by optimizing resource use across the population (Xu et al., 2021). Therefore, careful management of planting density is essential for maximizing water and nutrient use efficiencies while avoiding detrimental competition effects. Figure 4 AV-19LQ total solar radiation sensor (Adopted from Duan et al., 2025) 6.3 Regulation of intraspecific competition under different densities Intraspecific competition among soybean plants intensifies with increasing planting density as individuals compete for limited resources such as light, water, and nutrients. This competition affects plant growth plasticity, architecture, nitrogen accumulation, and ultimately yield potential (Klimek-Kopyra et al., 2020). Studies show that low to moderate densities reduce competitive stress allowing plants to express their productive potential fully; however, at very high densities or under favorable moisture conditions, strong competition can limit individual
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