Evaluation of irrigation scheduling program and spring wheat yield response in southwestern Colorado

Effective irrigation scheduling to manage water fur spring wheat (Triticum aestivum L.) in southwestern Colorado was investigated under variable water applications. This study was conducted (1) to determine the effects of varying rates of water replacement (GET, 0.33ET, 0.67ET, 1.0ET, and 1.33ET) on spring wheat grain yield, dry matter yield, root water uptake, and water use efficiency, (2) to develop local crop coefficients, and (3) to I:valuate the irrigation scheduling program called 'SCHED' that had been used in the area, Daily weather data was used to calculate reference ET using the Penman equation. Crop ET was predicted by using the irrigation scheduling program, 'SCHED'. Both grain yield and dry matter increased significantly with the increase in water application rates, up to 1.0ET application rate. Crop coefficients estimated at various water application rates were greater than the values used in the irrigation scheduling program. Total water use efficiency (TWUE) and irrigation water use efficiency (IWUE) for grain yield were considerably greater at 0.33ET than for other rates, whereas TWUE and IWUE for dry matter yield followed the order 0.33ET > 1.0ET > 0.67ET > 1.33ET > GET. (C) 1997 Elsevier Science B.V.