Nitrogen Use in Durum and Selected Brassicaceae Oilseeds in Two‐Year Rotations

Brassicaceae oilseeds can serve as potential feedstocks for renewable biofuels to offset demand for petroleum‐based alternatives. However, little is known about oilseed crop yield potential and N use in semiarid, wheat (Triticum spp.)‐based cropping systems that dominate the northern Great Plains (NGP). A 5‐yr study was conducted in northeast Montana to investigate the yield potential of a direct seeded system of durum (T. durum Desf.) in rotation with either chemical fallow or three Brassicaceae oilseeds: camelina [Camelina sativa (L.) Crantz], crambe (Crambe abyssinica Hochst. ex R.E. Fries), and canola‐quality Brassica juncea L. Overall, results from the study indicated that seed yield in the three Brassicaceae oilseeds tested in rotation with durum was related (P < 0.001; r2 = 0.68) to a nitrogen recovery index (NRI), indicating the importance of nitrogen use (NU) efficiency in dryland oilseed production, and that B. juncea generally used N more efficiently than crambe and camelina. Similarly, NRI was related (P < 0.001; r2 = 0.72) to grain yield in durum following oilseeds. Grain yield of durum following B. juncea was similar to durum following fallow and greater than durum following camelina or crambe. Durum following crambe tended to use N more inefficiently than durum following camelina, B. juncea, or fallow. Differences in yield and N use of durum and oilseeds varied among years, which underscores the need to further develop management tools to optimize durum‐oilseed cropping systems in highly variable rainfall environments typical of the NGP.