Soybean plant population density recommendations across the United States

Rising production costs and declining commodity prices have compelled farmers to reassess their input and management strategies. Soybean [Glycine max (L.) Merr] seed costs, in particular, have continued to increase due to advances in biotechnology, higher-yielding germplasm, and available seed treatments, accounting for 32–35% of the total operational expenses in current soybean production systems. Optimizing seeding rate is therefore one area of consideration for improving profitability and maximizing return on investment. However, soybean yield response to plant population density is influenced by the combination of several factors, including water availability, temperature, radiation interception, planting practices, and crop growth and development. Unlike many other crops, soybean exhibits high phenotypic plasticity, allowing plants to adjust their growth and yield components (e.g., number of pods and seeds per plant) in response to varying plant population densities. As a result, the literature has shown that soybean can produce comparable yields across a wide range of plant population densities. The objectives of this management guide were to (i) provide an overview of factors influencing soybean yield response to seeding rate and plant population density and (ii) summarize recommendations by land grant university Extension agronomists across soybean-producing states in the United States.