Nitrogen and Irrigation Effects on Seed Yield, Oil Content and Nitrogen Use Efficiency of Camelina.

Camelina (Camelina sativa) has been suggested as an especially drought tolerant and low-N requiring biofuel feedstock suitable for dryland systems. Efficient targeting of promising crops requires a precise assessment of crop response to water and N. We conducted a two-year study in Maricopa, AZ under a linear-move overhead sprinkler system with 10 water levels (irrigation fraction 0.5 to 1.1) and five N fertilizer rates (38 to 150 kg N ha^-1). Camelina cultivar ‘Robinson’ was planted on the 16^th and 4^th of December, in 2012 and 2013, respectively. Nitrogen fertilizer was applied in three split applications as 320 g N kg^-1 urea ammonium nitrate with a high clearance tractor and variable rate fertilizer nozzles. Irrigation amounts were 125 to 380 mm, and in-season rain was only 70 and 50 mm in the two seasons, 2012-2013, and 2013-2014, respectively. Seed yields of camelina were maximum at water level 8 (Irrigation fraction 1.0) in 2013 at 1850 kg ha^-1. Maximum seed yields were 1600 kg ha^-1 at water level 10 (irrigation fraction 1.1) in 2014, which was a warmer winter than 2012-2013. Nitrogen fertilizer response did not plateau in 2013 above water level 3 (irrigation fraction 0.6). In 2014, the optimal N rate was 113 kg N ha^-1. Oil concentration was maximum at 40 %, declined with N rate, but was not affected by irrigation level. This study suggests that high camelina seed yields can be obtained with modest N and water inputs the Western US.