Lesquerella Yield and Oil Quality Response to N Fertilizer Rate and Irrigation

Water and nitrogen are the first and second limiting factors for crop production in the arid and semiarid Southwestern United States. We studied the response of lesquerella (Lesquerella Fendleri L.) to six nitrogen rates (0, 56, 1112, 168, 224, and 336 kg·ha^-1) and two irrigation levels (well-watered and water-stressed) at University of Arizona's Maricopa Agricultural Center in the 2011–12 and 2012–13 growing seasons. Lesquerella is a member of the mustard family and the oil in lesquerella seeds, as a component of engine oil at concentrations as low as 0.25%, has superior performance compared to many other vegetable oils in reducing wear and damage in fuel injected diesel engines. The hydroxylated oil in lesquerella is similar to castor oil but does not contain the deadly poison ricin. Therefore, lesquerella is a safer alternative to castor in the United States and can be handled both at the farm level and the oilseed processing level with industry standard equipment and technology. Nitrogen fertilizer and irrigation response was significant in both growing seasons. The optimal N rate for seed yield was 224 kg·ha^-1 of urea-N at both water levels. The highest lesquerella seed yield of about 2200 kg·ha^-1 despite very short plants (i.e. < 25 cm). Recovery efficiency of N fertilizer ranged from 31% to 47% and was not affected by irrigation level.  Recovery efficiency reached maximum at 168 kg·ha^-1 of urea-N . This study provides guidelines for lesquerella N and irrigation management for maximum yield and oil quality.