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 (1 910), 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.