Legume Genomics and Genetics 2024, Vol.15, No.6, 280-290 http://cropscipublisher.com/index.php/lgg 285 Conversely, lower plant densities can benefit from reduced fertilizer inputs, as the competition for nutrients is less intense. Research has indicated that lower plant densities can achieve adequate nutrient uptake with lower fertilizer rates, thereby reducing input costs and minimizing environmental impacts. For instance, a study demonstrated that lower plant densities combined with efficient nutrient management practices, such as the use of organic amendments and biological nitrogen fixation, resulted in improved nutrient uptake and yield (Luca et al., 2014). This suggests that adjusting fertilization strategies based on plant density can lead to more sustainable and cost-effective soybean production. 6 Strategies for Optimizing Soybean Plant Density and Nutrient Management 6.1 Site-specific management approaches Choosing optimal plant density and nutrient management strategies tailored to specific soil and climate conditions is crucial for maximizing soybean yield. Research indicates that higher planting densities can significantly enhance canopy light interception and dry matter accumulation, leading to increased soybean productivity. For instance, a study demonstrated that a higher planting density of 2.7×105 plants ha-¹ resulted in a 22.8% increase in seed yield compared to a normal planting density, primarily due to improved canopy light interception and uniform plant distribution (Xu et al., 2021). Additionally, site-specific nutrient management, such as the optimal application of nitrogen, phosphorus, and potassium, can further enhance yield. In Northeast China, the optimal planting density was found to be 45.37×104 plants/ha with specific nutrient applications, resulting in yields of up to 3 816.67 kg/ha (Hao et al., 2023). Moreover, the delineation of site-specific nutrient management zones using multivariate analysis and geostatistics can provide a practical and cost-effective approach to managing spatial soil fertility. This method allows for the identification of management zones within a field, optimizing nutrient application and improving yield outcomes. For example, a study in Brazil used principal component analysis and the fuzzy k-means algorithm to delineate management zones, resulting in a significant correlation between these zones and soybean yield (Martins et al., 2020). This approach ensures that nutrient management is tailored to the specific needs of different areas within a field, enhancing overall productivity. 6.2 Matching cultivar characteristics with management Different soybean cultivars have varying responses to plant density and nutrient regimes, making it essential to match cultivar characteristics with appropriate management practices. For instance, a study on soybean cultivar BRS 284 revealed that lower plant densities increased nodulation parameters and seed oil content, although protein content decreased slightly. Despite a 75% reduction in plant density, yield only decreased by 16% in one of the three cropping seasons, indicating the high plasticity of this cultivar to adapt to different densities (Luca et al., 2014). This suggests that selecting cultivars with high adaptability to varying densities can optimize yield without compromising plant health. Furthermore, the interaction between cultivar characteristics and nutrient management is critical. Research has shown that foliar application of macro- and micronutrients, such as zinc and boron, can significantly improve soybean yield and resource-use efficiency in semi-arid climates. For example, foliar-applied chelated zinc at 0.5% concentration increased seed yield by 18.5-37.8% compared to no foliar nutrition, highlighting the importance of matching nutrient management strategies with cultivar needs (Dass et al., 2022). This approach ensures that the specific nutrient requirements of different cultivars are met, optimizing growth and yield. 6.3 Integrated management and precision agriculture Utilizing precision agriculture technologies to optimize plant density and fertilization can significantly enhance soybean yield. Precision agriculture involves the use of advanced technologies, such as GPS and remote sensing, to monitor and manage crop production at a fine scale. For instance, the use of variable rate fertilization based on site-specific nutrient management zones can optimize nutrient application, reducing waste and improving yield. A study demonstrated that the delineation of management zones using geostatistics and principal component analysis resulted in a significant correlation between these zones and soybean yield, indicating the effectiveness of precision agriculture in nutrient management (Martins et al., 2020).
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