Growth and Yield Responses of Soybean to Row Spacing and Seeding Rate

Some growers in northern latitudes plant soybean [Glycine max (L.) Merr.] with a row crop planter in 0.38 m rows, but an economic analysis concluded that drilled soybean in rows <0.25 m was optimum in the North-Central United States. We planted two varieties in 0.19, 0.38, and 0.76 m rows at 321,000; 371,000; 420,000; and 469,000 seeds ha(-1) in New York in 2008 and 2009 to evaluate how soybean compensates to wide rows or low seeding rates in the Northeast United States. Soybean had limited compensation in biomass, pods, and seeds plant(-1) at wider rows so row spacing had linear responses for biomass accumulation (598, 554, and 497 g m(-2) in 0.19, 0.38. and 0.76 m rows, respectively) and leaf area index (LAI, 3.64, 3.47, and 3.16) at seed initiation; pod (1012, 935, and 875 pods m(-2)) and seed density (2272, 2230, and 2072 seeds m(-2), respectively) at harvest; and yield (3.37, 3.12, and 2.86 Mg ha(-1), respectively). Compensation in biomass, pods, and seeds plant(-1) at lower seeding rates resulted in similar biomass accumulation (528-570 g m(-2)), LAI (3.38-3.46), pod (921-965 pods m(-2)), and seed densities (2123 to 2234 seeds m(-2)) across seeding rates. Nevertheless, yield showed a quadratic response to seeding rate (3.04, 3.25, and 3.12 Mg ha(-1) at 321,000; 420,000; and 469,000 seeds ha(-1), respectively) with no row spacing interaction. Soybean compensated more at lower seeding rates than at wider rows, but field-scale studies are being conducted to evaluate the economics of both practices.