Water Productivity of Three Oilseeds in Rotation with Durum.

Oilseeds have shown potential as alternative crops to diversify wheat-fallow systems in the northern Great Plains. However, little is known about water use and water productivity of oilseeds in semi-arid environments. From 2007 to 2009 camelina (Camelina sativa L.), crambe (Crambe abyssinica  H.), and juncea canola (Brassica juncea var. juncea canola) were grown in rotation with durum (Triticum turgidum L. var. durum) to determine growing season water use (WU) and productivity (WP) to a 120-cm depth. The WU did not differ among oilseeds for any year, but due to drought conditions in 2008 (165 mm Apr-Aug precipitation), oilseed WU was 53% of the 291 mm average for other years (average 283 mm Apr-Aug precipitation). Water use for durum and oilseeds measured during 2008 and 2009 was similar and averaged 218 and 215 mm, respectively, suggesting oilseeds use as much water as durum. Water productivity differed among oilseeds only in 2008, where WP for juncea was four times greater than the average 1.1 kg ha^-1 for camelina and crambe. Preliminary results from this 5-yr study suggest juncea could have a competitive advantage over camelina and crambe in a drought-prone environment such as the NGP.