Soybean Cultivar Responses to Row Spacing and Seeding Rates in Rainfed and Irrigated Environments

Abstract

Soybean [Glycine max (L.) Merr.] are grown under both irrigated and rainfed conditions in the western Corn Belt. We wanted to determine whether optimum row spacing and seeding rate were similar for different cultivars in different water regimes. A 3-yr field study at Clay Center, NE, and a 2-yr study near Oxford, NE, were conducted. We used a factorial combination of three row spacings (10, 20, and 30 in.), four seeding rates (45 000, 140 000, 230000, and 330 000 seeds/acre) and five cultivars with four replications planted in adjoining irrigated and rainfed fields at each site. Determinate cultivar yield increased 42% (11 bulacre) as seeding rate increased from 45 000 to 140 000 seeds/acre and then remained constant with increased seeding rate. Seeding rate generally did not affect indeterminate cultivar yield. The 20-in. row spacing consistently had the greatest yields or yields equal to the high-yielding row spacing. Yield of indeterminate cultivars in both water regimes and determinate cultivars with irrigation was greater with 20-in. rows than either 10- or 30-in. rows. Yield of determinate cultivars in rainfed was similar in 20- and 30-in. rows and less in 10-in. rows. The 20-in. row spacing also consistently produced the highest yield at all four seeding rates. This report goes beyond previous research findings by concluding that, with moisture stress, determinate cultivars in 20- and 30-in. rows may produce more than in 10-in. rows.