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

Abstract

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.