Lesquerella seed production: water requirement and management

Lesquerella synthesizes unique hydroxy fatty acids (HFA) with potential industrial and consumer applications. However, information about its water use requirement and yield response to irrigation is limited. Detailed irrigation studies were conducted with Lesquerella fendleri (Gray) Wats. on a sandy loam in Arizona during the 1991-1992 and 1992-1993, fall-spring seasons to determine its water requirement and yield. In 1991-1992, dry matter yield was linearly related to the total evapotranspiration (ET). The highest dry matter yield was obtained for a control irrigation treatment with seven post-emergence irrigations. Four limited water treatments were given either three or four irrigations, and yielded 26-36% less dry matter than the control. Total ET for the control was 634 mm, whereas ET for the limited water treatments varied from 460 to 500 mm. Total seed yield in 1991-1992, was not determined. However, seed oil content was significantly higher for the control than for the limited water treatments. In 1992-1993, Lesquerella was grown under eight irrigation treatments: weekly (W; 12 post-emergence irrigations), biweekly (B; 7), weekly with two supplemental irrigations in early winter (WS; 14), biweekly with two supplemental irrigations in early winter (BS; 9), and four treatments that were irrigated like treatment B, except that irrigation was withheld during early flowering (B1; 5), withheld during mid-flowering (B2; 6), withheld at full bloom (B3; 6), and withheld during seed formation and ripening (B4; 5). Irrigation treatments affected both the dry matter and seed yield, but not the seed oil content and lesquerolic acid content of the oil. Withholding irrigation on the biweekly application during mid-flower and during seed formation and ripening resulted in the lowest seed yields. The BS treatment had the highest dry matter (7020 kg/ha) and seed yield (888 kg/ha), suggesting a possible yield benefit from the early winter irrigations. Total ET for treatments varied from 535 to 767 mm, and both dry matter and seed yield were related to total ET (although not by linear relationships). Total ET corresponding to the maximum yield was 668 mm. A water management that allows approximately equal to 50% depletion of the available soil water from the onset of flowering through seed ripening can result in maximum growth and yield. Providing irrigation every 14 days during this period may be optimum for Lesquerella grown on sandy loam soils.