Interaction of Soybean Maturity, Row Spacing, and Seeding Rate.

Several studies have been conducted examining the effect of soybean maturity, row spacing, and seeding rate, but few have facilitated exploration of interactions between all three factors in the western Corn Belt. The objective of this study was to optimize planting practices for non-irrigated soybeans. Field experiments were conducted in 2007-2009 near Manhattan, KS to compare the effect of maturity, row spacing, seeding rate, and their interactions on soybean yield. The MG 4.4 variety produced the greatest yield in 2007, and the MG 3.8 variety yielded most in 2008 and 2009. The MG 4.4 variety was less sensitive to changes in seeding rate than the MG 3.0 or 3.8 varieties. Row spacing did not influence yield and did not interact with maturity or seeding rate. Maximum yields resulted from seeding rates of 120,000 seeds acre^-1 and greater in 2008 and 2009 (64 bushels acre^-1) and 80,000 seeds acre^-1 or greater in 2007 (37 bushels acre^-1). The plant populations resulting from those seeding rates were approximately 79,000, 97,000, and 113,000 plants acre^-1 or greater in 2007, 2008, and 2009, respectively. Planting recommendations for northeast Kansas based on results of these experiments include planting a late MG 3 to early MG 4 variety at seeding rates that will result in 100,000 to 115,000 plants acre^-1 with no adjustments necessary for different row spacings.