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Progress has been made towards the commercialization of Lesquerella fendleri (Gray) Wats. as a fall-planted oilseed crop for the southwestern United States. Research to develop suitable cultural practices for commercial production of lesquerella has been underway since the late 1980s; however, information is limited on the plant’s nitrogen (N) requirement. Field experiments were conducted during two growing seasons to determine the optimum amount and timing of N applications for lesquerella production. Yield results indicate that lesquerella grown on desert soils is strongly influenced by N fertilization. Nitrogen rates as high as 180 kg N ha(-1) increased seed yield. Seed oil content decreased as the N rate was increased. The increase in seed yield at the higher N rates generally offsets the decrease in oil content, but oil yields appeared to be near maximum at 180 kg N ha(-1). Split-applications of N in the Spring increased seed and oil yields in one of two seasons. Nitrogen had no influence on 1000-seed weight or lesquerolic acid content of the oil. No Spring leaf blade total N level was identified as being related to maximum seed yield. A suggested N management program for lesquerella production is to apply a small portion of N at planting time and the major portion of N in several applications during the period from onset of bloom through full bloom (February-April). (C) 1999 Elsevier Science B.V. All rights reserved.