Nitrogen Use in Two-Year Durum Rotations With Crucifer Oilseeds and Fallow.

Crucifer oilseeds as renewable biofuels feedstock could offset demand for petroleum-based alternatives.  Current knowledge is limited regarding crop yield potential and N management in semi-arid cropping systems.  In NE Montana, a 5-yr study considered no-till production of durum (Triticum durum Desf.) in rotation with oilseed crucifers camelina [Camelina sativa  (L.) Crantz], crambe (Crambe abyssinica Hochst. ex R.E. Fries), and Brassica juncea L. canola, with durum-chemical fallow as the control.  The N use efficiency was significantly related to seed yield in the three crucifer oilseeds and that juncea canola typically utilized N more efficiently than crambe and camelina. Similarly, N use efficiency was significantly related to grain yield in durum following oilseeds.  Yield of durum following juncea canola was as great as that for durum following fallow and greater than that for durum following camelina or crambe. Durum following camelina, juncea canola, or fallow used N more efficiently than durum following crambe.  Yield and N use of oilseeds and durum varied significantly among years, however, underlying the need to further develop durum-oilseed cropping systems in semi-arid environments.