COMPUTER-BASED IRRIGATION SCHEDULING FOR LESQUERELLA FENDLERI

Authors: Hunsaker, Douglas - Doug; Alexander, William

Submitted to: International Evapotranspiration Irrigation Scheduling Conference
Publication Type: Proceedings
Publication Acceptance Date: 4/1/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Effective irrigation management to achieve optimum yield is essential to the commercialization of Lesquerella fendleri, a plant native to the southwestern U.S., that contains high amounts of a unique oil for making lubricants, resins, waxes, nylons, plastics, cosmetics and other products. In Arizona, a computer-based irrigation scheduling system is used with traditional crops to assist growers in determining proper irrigation times and amounts. This research is developing a seasonal crop water use requirement curve for lesquerella that is needed in the irrigation scheduling system and is determining an effective irrigation schedule for the crop. Applying this scheduling system in lesquerella irrigation management will be a major step towards the commercialization of the crop and can be expected to benefit both growers and industry.

Technical Abstract: Crop water management information is lacking for Lesquerella fendleri, a promising new industrial oilseed crop. Research efforts toward commercialization of this crop in the arid southwestern U.S. include improved procedures to aid growers in irrigation scheduling. In Arizona, a computer-based irrigation scheduling program (AZSCHED) is presently used to assist growers of traditional crops. Data collected in prior studies were used to develop a growing-degree-day-based crop coefficient curve for lesquerella, which was incorporated with the AZSCHED program. A field study was conducted during the 1994-95 lesquerella season in central Arizona to evaluate irrigation scheduling with AZSCHED. A second objective was to determine the effect of 40, 50, and 60% allowable soil water depletion on the seed yield of lesquerella. Comparison of lesquerella evapotranspiration estimated by AZSCHED with measurements showed that AZSCHED overestimated evapotranspiration by 10 to 36% during peak periods of water use, suggesting that further work is needed to refine the lesquerella crop coefficient curve. Scheduling irrigations with AZSCHED at 50% soil water depletion (irrigations every 13 to 17 days) resulted in the highest seed yield. That result was consistent with prior studies, which indicated that the highest seed yields were obtained with irrigations about once every two weeks.