Planting Soybean with a Grain Drill Inconsistently Increases Yield and Profit.

Growers can plant soybean [Glycine max( L.) Merr.] with a grain drill or row crop planter, which can affect seed and weed control costs and yield. Farmers planted soybean with a drill in 0.19 m rows and row crop planter in 0.38 and 0.76 m rows at two seeding rates (420,000 and 321,000 seeds ha^-1) in two field-scale studies in New York to obtain agronomic information and conduct partial budget analyses to aid in future planter selection and purchase decisions.  Soybean intercepted more light at flowering in 0.19 (65-70%) compared with 0.76 m rows (50-55%), despite lower early plant establishment (~70 and ~85%, respectively) at both locations.  At a no-till location, 0.76 m rows compared with narrower rows had greater weed density at full pod stage (19.7 vs. 6.3 and 5.1 weeds m^-2) and weed biomass at harvest (13.7 vs. 6.6 and 7.3 g m^-2, respectively) but similar yield (~3.30 Mg ha^-1). At a chisel tillage location, soybean in 0.19 m rows at the recommended 420,000 seeds ha^-1 yielded 4% more (4.27 Mg ha^-1) than in 0.76 m rows at the recommended 321,000 seeds ha^-1 (4.11 Mg ha^-1). Partial budget analyses indicated that soybean in 0.19 m rows at 420,000 seeds ha^-1 had ~$30 ha^-1 greater profit compared with 0.76 m rows at 321,000 seeds ha^-1. Partial budget analyses indicated that at present prices the 4% yield advantage offset purchasing and owning costs of a new drill and added seed costs, if planting 250 and 500 ha of soybean.