Soybean overcome differences in row spacing and seeding rate to maintain stable yield

Abstract

Soybean [Glycine max (L.) Merr.] is a crucial crop for global food, feed, and biofuel industries, with its yield influenced by agronomic practices such as row spacing and seeding rate. This study aimed to evaluate the effects of these practices on soybean yield across 7 years (2016–2023) in Iowa. Using a split-split-plot design, we examined three row spacings (15, 20, and 30 inches) and varying seeding rates at two experimental sites. The research was conducted under typical Iowa conditions with different soybean cultivars and soil types. Grain yield data were standardized to 13% moisture and analyzed using ANOVA to assess the interactions between row spacing, seeding rate, and cultivar. Results indicated the effects of row spacing and seeding rate on yield were inconsistent across years and locations. Narrower row spacings (15 and 20 inches) tended to improve yield in high-productivity environments, while wider spacing (30 inches) performed better in some low-yielding environments. The seeding rate response varied, with no clear pattern across site-years, suggesting that soybean plants can compensate for lower planting densities by adjusting branching and pod set. These findings highlight the adaptability of soybean to different planting practices, offering farmers flexibility in optimizing seeding rates and row spacings without significant yield loss. This research provides valuable insights into potentially reducing input costs while maintaining productivity in soybean production.