Warmer weather over the last week has helped to warm and dry the soil making it optimum for planting warm season crops. Many farmers wait to plant soybeans after corn and first cut, as there is concern that soybean seed will not germinate at soil temperatures below 60º F. Your planting dates should be based on weather conditions, not necessarily a specific date.
Soybeans can germinate in soil around 50º F, but the ideal temperature is 70º F or higher, but those conditions may not occur in Vermont until mid to late June. Soybeans shouldn’t be planted in extremely damp conditions, because oxygen-deprived saturated soils and soil crusting can hinder emergence. Wet conditions can also reduce germination and increase the prevalence of diseases caused by pathogens like Pythium. When your soil temperature is around 50º F, germination may be slow and emergence can take up to 3 weeks.
Organic and untreated soybeans shouldn’t be planted until the soil temperature reaches at least 60º F. In northern New England and Eastern Canada, you often cannot plant soybeans until late May. However, if warm spring conditions occur, planting should begin to maximize yield.
Three years of research trials in Alburgh, Vermont have shown that optimum soybean yields are achieved when planting between late May and early June.
Remember to select varieties that can easily mature in Vermont when planted by mid-June. Generally, soybeans in the maturity groups 0 to 1.5 perform the best in Vermont. If planting in May a full-season variety should be planted, but as planting dates move into June a short maturity variety should be selected.
Lastly, soybeans also need a pH level of 6.0-7.5. Ideal soils are medium-textured loam with high levels of P and K, but low to medium levels of nitrogen. If nitrogen levels are high in soybean fields, nitrogen fixation will be diminished and weed pressure will increase. While saturated soils are poor for planting, moisture must be available in the upper layers of the seedbed, especially during germination, flowering, and podfilling.
For more research results on soybean planting dates and varieties, see our research reports at: https://www.uvm.edu/extension/nwcrops/research