Location, Variety, and Seeding Rate Interactions with Soybean Seed-Applied Insecticide/Fungicides

Cool conditions aft er soybean [Glycine max (L.) Merr.] planting may increase soil pest incidence and reduce emergence. Field-scale studies were conducted in 2009 and 2010 at three locations in New York on two varieties at four seeding rates (272,000, 346,000, 420,000, and 490,000 seeds ha(-1)) with and without seed-applied insecticide/fungicides to determine if treated seed enhances plant establishment, allowing for lower seeding rates for maximum yield and partial return. Plant density and yield had location x variety x seed treatment interactions. A treated vs. untreated Asgrow variety had 16 to 22% plant density increases and 4% yield increases at two locations, whereas a Pioneer variety had a 16% density increase at one location but no yield increases. At a third location, the treated vs. untreated Pioneer variety had 19 and 4% increases, respectively, whereas the Asgrow variety had no increases. Yield, which had no seeding rate x seed treatment interaction, had quadratic responses to seeding rate and early plant densities (maximum yield at 478,300 seeds and 295,300 plants ha(-1), respectively). Partial return, which had a seeding rate x seed treatment interaction, had quadratic responses to seeding rate with maximum values at 398,800 and 341,800 seeds ha(-1) for untreated and treated seed, respectively. Maximum partial returns at these seeding rates ($1241-1245 ha(-1), respectively) were similar because seed treatment cost off set lower seed cost. Maximum partial return occurred at early plant densities of 248,400 plants ha(-1), but the variety x location x seed treatment interaction complicates selecting seeding rates for this plant density.