Legume Genomics and Genetics 2025, Vol.16, No.6, 253-269 http://cropscipublisher.com/index.php/lgg 254 interception rate and dry matter accumulation increased significantly, and the yield per unit area increased by 22.8% compared with the conventional density (Xu et al., 2021). Higher planting density is often used in high-yield practices: for example, Xinjiang once created a soybean yield record of 6,803 kg/hectare with a density of 300,000 plants per hectare. However, overcrowding may also lead to increased competition for nutrients and light, leggy plants, and increased risk of disease, so it is necessary to accurately grasp the critical balance point between density and yield. In terms of fertilization management, the unique nitrogen fixation ability of legumes determines that their demand for nitrogen fertilizer is different from that of cereals, but nutrients such as phosphorus and potassium are also essential for their growth, development and high yield. Studies have shown that the appropriate application of nitrogen, phosphorus and potassium compound fertilizers on soils with insufficient fertility can increase soybean yields by 5%-18% (Li et al., 2024). At the same time, China has long had problems with high fertilizer input and low utilization rate, and about 40% of fertilizer nutrients are not absorbed by crops and are lost. Excessive fertilization not only pushes up production costs, but also leads to soil compaction and environmental pollution, which is contrary to the goal of green agricultural development. Therefore, it is of great practical significance for high-yield cultivation of legumes to improve fertilizer utilization efficiency by optimizing fertilization structure and dosage, and to achieve fertilizer reduction without reducing production. There is also a significant interaction between the two factors of dense planting and fertilization: reasonable fertilization can alleviate the nutrient competition caused by dense planting and improve the group productivity; accordingly, appropriate planting density can give full play to the fertilizer benefits and avoid nutrient waste. Based on the field test results and literature reports on beans (mainly soybeans) at home and abroad in the past five years, this study systematically analyzes the impact mechanism of planting density and fertilization measures on crop growth, physiology and yield formation, focusing on the interaction and synergistic regulation effect between the two, and selects representative bean planting areas in the north and south (Zhumadian City, Henan Province and Qiqihar City, Heilongjiang Province) to carry out field experiments to verify the yield-increasing effect and applicability of dense planting and fertilization optimization strategies. By summarizing practical cases and farmer feedback from different regions, this study evaluates the agronomic and economic benefits of these technologies, and analyzes their feasibility of promotion and application in a larger area, providing theoretical basis and practical guidance for regionalized precision management and green high-yield cultivation of bean crops, and expects to contribute to improving China's bean self-sufficiency level, ensuring food security and promoting sustainable agricultural development. 2 Effects of Density on Growth and Yield 2.1 Changes in plant morphology The response of plant morphology to the environment directly affects photosynthetic efficiency and yield formation. Under dense planting conditions, legume crops often show a typical shade escape response: individuals quickly lengthen plant height and petioles in order to compete for light, stems become thinner, and the number of branches decreases. The experiment observed that the average plant height of soybeans under high density treatment increased by about 8.2% compared with conventional density; at the same time, due to limited space resources, the number of branches per plant decreased significantly, with a decrease of more than 40%. Fan et al. (2017) pointed out that under intercropping shading conditions, the functional leaves of soybeans became smaller and the stomatal density decreased, suggesting that the closure of the population caused by high-density planting may also inhibit leaf expansion and reduce the total leaf area of a single plant. However, due to the increase in the number of plants, the leaf area index (LAI) of high-density populations is often higher than that of low-density populations, especially in the middle and late stages of growth. In terms of canopy structure, dense planting can form a more closed canopy, which improves the interception of light by the upper leaf layer, but also leads to insufficient light and poor ventilation for the lower leaves. This change in the vertical structure of the canopy needs to be optimized through variety plant type and planting method. For example, a uniform and reasonable plant spacing layout helps to improve the light distribution of the densely planted canopy, reduce the height difference between plants and the uneven distribution of dry matter (Xue et al., 2015). The plant morphological
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