Monday, November 13, 2006 - 10:00 AM

Crop Simulation and Crop Evapo-Transpiration for Irrigation Management of Corn and Spinach.

Giovanni Piccinni1, Jonghan Ko2, Daniel Leskovar2, Thomas Gerik3, Evelyn Steglich3, Wyatte Harman3, Armen Kemanian3, and Thomas Marek2. (1) Texas A&M University Research & Extention Center, Texas A&M Univ. Res. & Ext. Ctr., 1619 Garner Field Rd., Uvalde, TX 78801-6205, (2) Texas A&M Univ. Res. & Ext. Ctr., 1619 Garner Field Rd., Uvalde, TX 78801-6205, United States of America, (3) Blackland Research Ctr, 720 E. Blackland Rd., Temple, TX 76502-9622

Improving irrigation water management for crop production is becoming increasingly important in South Texas as the water supplies shrink and competition with urban centers in the region grows. Crop simulators and crop evapo-transpiration (ET) are appealing methods for estimating crop water use and irrigation requirements because of the low investment in time and dollars required by on-site (in-field) measurement of soil and/or crop water status. We compared the effectiveness of the CroPMan/EPIC crop simulator and Crop-ET approaches in estimating the crop water use for irrigation scheduling of corn and spinach.  In-ground weighing lysimeters were used to measure real time corn and spinach water use during the growing season. We related the water use of the corn and spinach crops to a well-watered reference grass crop to determine crop coefficients (Kc) to assist in predicting accurate crop needs using available meteorological data.  In addition we run several simulations of CropMan to evaluate the best management for growing corn and spinach under limited water availability.  Results show the possibility of saving approximately 61 to 74 million m3 of water per year in the 36,500 ha of irrigated farms of the Edwards aquifer region if proper irrigation management techniques are implemented in conjunction with the newly developed decision support systems.  We discuss the implications of the use of these technologies for improving the effectiveness of irrigation and for reducing irrigation water requirements in South Texas.