Nitrogen Use of Three Oilseeds in Rotation with Durum.

Oilseeds as potential feedstock for renewable biofuels could offset demand for petroleum-based alternatives.  Information is currently lacking regarding crucifer oilseed crop yield potential and N management in semi-arid cropping systems.  A 5-yr study in NE Montana investigated the production of direct seeded durum (Triticum durum Desf.) in rotation with chemical fallow and three oilseed crucifers, camelina [Camelina sativa  (L.) Crantz], crambe (Crambe abyssinica Hochst. ex R.E. Fries), and Brassica juncea L.  Results indicated that N use efficiency was significantly related to seed yield in the three crucifer oilseeds and that juncea generally used N more efficiently than crambe and camelina. Similarly, indicators of N use efficiency were significantly related to grain yield in durum following oilseeds.  Yield of durum following juncea was as great as that for durum following fallow and greater than that for durum following camelina or crambe. Durum following camelina, juncea, or fallow used N more efficiently than durum following crambe.  Yield and N use of oilseeds and durum varied significantly among years, however, indicating the need for further development of durum-oilseed cropping systems in highly variable rainfall environments such as the northern Great Plains.