Planting Date and Seed Treatment Effects on Soybean in the Northeastern United States

Soybean [Glycine max (L.) Merr.] production is limited in the northeastern United States so research on optimum planting date is scarce. Soybean production in this region may increase because of biodiesel demand so we initiated a 2-yr study in New York that compared soybean planting dates with and without seed-applied fungicide/insecticide treatments. Soybean planted in mid-compared with late May had a longer emergence time (15 and 6 d) and lower plant densities (35.6 and 39.5 plants m(-2)), but produced more pods side branch(-1) (7.4 and 5-5), which contributed to more pods plant(-1) (30.9 and 25.7) and pods m(-2) (1079 and 958, respectively). The late compared with mid-May planting date, however, had more seeds pod(-1) (2.28 and 2.19), which contributed to similar seeds m(-2) (2180 and 2357) and seed yield (3.8 and 3.9 Mg ha(-1), respectively). Soybean planted in mid-June compared with mid-May had more plants m(-2) (38.0) but fewer pods side branch(-1) (3.4), pods plant(-1) (22.5), pods m(-2) (879), seeds m(-2) (1910), and lower seed yield (3.5 Mg ha(-1)). Seed treatments did not affect plant density, pod density, and seed yield, but had inconsistent effects on seeds pod(-1), seeds m(-2), and seed mass. The results of this study indicate that there is a fairly broad optimum planting date range and that insecticide/fungicide seed treatment is not required for soybean production in the northeastern United States, but more research is necessary to corroborate these findings.