Row spacing and seeding rate effect on soybean seed yield in North Dakota

Abstract

North Dakota soybean [Glycine max (L.) Merr.] seeding rate and row spacing varies across the state due to climate factors. Eight soybean seeding rates (starting at 80,000 and increasing by 20,000 live seeds ac−1 increments) and row spacing (12 and 24 inches) were evaluated in 15 environments in 2017–2018 to quantify established plant densities, seed yield, and plant loss occurring during the season. Planting at a 12-inch row spacing yielded 2.7 bu ac−1 greater than 24-inch row spacing and provided $33 ac−1 greater net profit on average. Following plant establishment, 6.6% in-season plant loss occurred on average. Using 180,000 to 200,000 live seed ac−1 had higher yields than seeding rates of 120,000 or less. Maximum net partial profit based on seeding rate was 80,800, 105,300, and 167,500 live seed ac−1 for seed costs of $57.80, $50.80, and $33, respectively, for 140,000 seeds. North Dakota's current recommendation of 150,000 established plants ac−1 is in the range to optimize yield but will likely not optimize profit based on seed costs and current market values. North Dakota farmers are recommended to use 12-inch row spacing instead of 24 inches.