2024 Soybean Row Spacing and Population Studies for Coastal Soils

Summary: Three years of population studies have only shown little difference in population (60-180k), when planted early enough, however later planted  (double crop) beans may be safer at 120k or above. Planting in 15 inch rows can increase yields 5-10 bushels.

As soybean genetics have improved, national studies in planting populations are revealing that lower populations can still provide similar yields. We have performed studies over the past few years, including 2022 (Click for link) and 2023 (Click for link). For both of those years there was a 10-bushel advantage for narrower rows (15 vs 30”), 25 bushels for irrigation, but no differences between populations of 90 to 180,000 seeds per acre.

For 2024 we had three separate field sites, including two irrigated (full season and double crop) and a rainfed field (Table 1). For the full season, irrigated field (MG 4.2, planted 05/21/2024) there were no differences in populations between 60-180k, and potential 3-bushel bump for 15” rows (p-value = 0.1).

When planted behind wheat (06/20/2024) as irrigated double crop, 15-inch rows did provide an additional 5 bushels (27 vs 22 bushels). For this field we had space to include a very low rate of 40k seeds/acre, which did return the lowest yield of 19.4 bushels, with the 60k rate similar at 22.7 bushels. There wasn’t a lot of difference when rates were 120 to 180 seeds per acre.

For the full season, rainfed field there were also no differences between row spacing or population, however yields were about 20 bushels higher than the double crop field and only 10 bushels lower than the full season irrigated field. The double crop field did have some deer feeding early on which may have reduced yields.