Soybean yield and profitability are affected by the spatial distribution of seeds in rows and seeding rate

Soybean [Glycine max (L.) Merr.] yield and profitability can be affected by plant-to-plant spatial uniformity and sowing rate. This study aimed to evaluate the agronomic and economic performance of soybean in relation to the spatial distribution of seeds in rows and seeding rates. A field experiment was conducted during the 2018-2019 and 2019-2020 growing seasons in Londrina, Parana state, Brazil. We evaluated three coefficients of variation of seed distribution in rows (coefficient of variation of seeds distribution (VDS): 0%, 50%, and 100%) and four seeding rates (350,000, 262,500, 175,000, and 87,500 seeds ha-1), which corresponded to 100%, 75%, 50%, and 25% of the recommended seeding rate of the cultivar BRS 1003 IPRO, respectively. Sowing was performed manually to ensure that seed distribution accurately adhered to the experimental setup. Soybean yield components, yield, and profitability were then evaluated. The lower VDS improved the yield by 374 kg ha-1 compared to the higher VDS and increased the profitability by $334.7 ha-1 in 2019-2020. A seeding rate of 262,500 seeds ha-1 yielded the highest grain yield. The highest soybean profitability was achieved at a seeding rate 6.5% lower than that which produced the highest yield. Branching is essential in compensating for lower seeding rates and plants with uneven spatial distributions. The present study shows that equidistant distribution of seeds in rows optimizes grain yield. Plant-to-plant spatial uniformity increases soybean yield and profitability.Reduced soybean seeding rate increases profitability.Branching is the most important phenotypically plastic mechanism in soybean.