Interseeded pennycress and camelina yield and influence on row crops

Field pennycress (Thlaspi arvense L.) (PC) and winter camelina [Camelina sativa (L.) Crantz] (WC) have the potential to provide ecosystem services and economic incentives when adopted as an oilseed cover crops in corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotations. However, PC and WC establishment and yield in the northern Corn Belt and their subsequent impact on row crops are not well known. This study was conducted to determine the effects of interseeding dates (R4, R5, and R6; and R6, R7, and R8 development stages for corn and soybean, respectively) and cover crop species (PC, WC, and winter rye [Secale cereale L.]) on seed yield and oil content of interseeded oilseeds (PC and WC) and relay soybean, and 3rd‐year corn grain yield and quality. Study sites were initiated near Ames, IA; Morris and Rosemount, MN; and Prosper, ND. Late interseeding of PC and WC resulted in greater oilseed yield. Overall yields of PC (218–880 kg ha–1) and WC (15–770 kg ha–1), averaged across interseeding dates, were low when interseeded in corn and soybean. The PC and WC reduced relay‐soybean grain yield by 13–32% and 13–42%, respectively. Corn grain yield and quality following relay soybean were not affected by the residual effects of oilseed cover crops. Based on the results of our study, we do not recommend relay cropping soybean with PC and WC in the upper Midwest. Core Ideas Late interseeding of oilseed cover crops produced greater seed yield than early interseeding. Oilseeds yield of pennycress (218–880 kg ha−1) and winter camelina (15–770 kg ha−1) were low. Soybean yield relayed into pennycress and winter camelina was reduced by 13–42%. No residual effect of oilseed cover crops on grain yield or quality of subsequent season corn.