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Soybean [Glycine max (L.) Merr.] seeding rate research across North America is typically conducted in small geo-political regions where environmental effects on the seeding rate × yield relationship are minimized. Data from 211 individual field studies (∼21,000 data points, 2007-2017) were combined from across North America ranging in yield from 1,000-7,500 kg ha −1 . Cluster analysis was used to stratify each individual field study into similar environmental (soil × climate) clusters and into high (HYL), medium (MYL), and low (LYL) yield levels. Agronomically optimal seeding rates (AOSR) were calculated and Monte Carlo risk analysis was implemented. Within the two northern most clusters the AOSR was higher in the LYL followed by the MYL and then HYL. Within the farthest south cluster, a relatively Abbreviations: AOSR, agronomically optimal seeding rate; CIPAR, cumulatively intercepted photosynthetically active radiation; HYL, high yield level; LYL, low yield level; MYL, medium yield level; NCCPI, national commodity crop productivity index; PAR, photosynthetically active radiation; VRS, variable rate seeding.This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

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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.