Intersowing Cover Crops into Standing Soybean in the US Upper Midwest

Nutrient losses and soil erosion after soybean (Glycine max (L.) Merr.) harvest are common in the US Upper Midwest. Cover crops need to provide adequate growth and cover to prevent soil degradation throughout the winter and early spring months. The objective of this study was to determine the establishment of intersown cover crops and their impacts on a soybean-wheat rotation. Four cover crops—winter camelina (Camelina sativa (L.) Crantz), winter pea (Pisum sativum ssp. arvense (L.) Poir), winter rye (Secale cereale L.), and radish (Raphanus sativus L.)—were directly sown at the R4 and R6 stages of soybean at two locations, Prosper and Fargo, ND in 2016–2017. Cover crops above ground biomass in the fall ranged from 0.4 to 3.0 Mg ha−1 and N accumulation ranged from 28.7 to 73.2 kg ha−1. Winter camelina and winter rye reduced subsequent spring wheat yield compared with the no cover crop treatment. Fall soil residual NO3-N levels were lowest where cover crops were sown compared with the check. Spring NO3-N levels were lowest in winter camelina and winter rye compared with all the other cover crops and the check. Results indicated intersowing cover crops have no impact on soybean yield, and show potential to mitigate soil nitrate losses in areas that grow soybean as a cash crop.