|ANAPALLI, SASEENDRAN - COLORADO STATE UNIVERSITY
Submitted to: Water Resources Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/12/2008
Publication Date: 7/25/2008
Citation: Anapalli, S.S., Ahuja, L.R., Nielsen, D.C., Trout, T.J., Ma, L. 2008. Use of Crop Simulation Models to Evaluate Limited Irrigation Management Options for Corn in Semi-Arid Environment. Water Resources Research. Water Resources Research, 44,W00E02, doi10.1029/2007WR006181.
Interpretive Summary: The CERES-Maize v4.0 model was calibrated and validated for simulations of corn growth and yield with various levels of irrigation over a 3-yr period (1984-1986) in the semiarid climate of northeastern Colorado. The model was successfully tested for simulation of dryland (rainfed) corn production at the location during 1993-1997. Maximizing returns while practicing limited irrigation in the Great Plains region is a challenge facing farmers of the region today. The model was used to develop limited irrigation management strategies. Long-term weather data recorded at the Akron location from 1912 to 2005 were used to represent the potential effects of weather variability on corn water use and grain yield. When available water for irrigation was 100 mm or less, maximum yields and WUE were obtained when 40% of the irrigation was applied during the vegetative stage and 60% applied during the reproductive stage, or when the irrigation was uniformly split between the two growth stages. When more than 100 mm of irrigation water was available, yield was maximized when 20% of the water was applied in the vegetative stage and 80% in the reproductive stage. Maximum grain yield and WUE were obtained with 400 mm of irrigation, which also maximized N uptake with only small N losses to leaching. Under the extreme conditions of a total absence of rain after planting the crop, at least 500 mm of irrigation water would be needed to attain the average grain yield that was achieved at 400 mm irrigation with rain; and maximum yields and WUE were obtained when 40% of the irrigation was applied during the vegetative stage and 60% applied during the reproductive stage for all irrigation levels. Irrigating 50% of the area with 200 mm of water and leaving the remaining area in dryland corn management yielded greater than irrigating 100% of the area with 100 mm water. When more than 100 mm of irrigation water was available, corn yields were maximized when the irrigation was spread across 100% of the crop area. Simulations confirmed that under rainfed conditions, corn yields increased with increases in soil water content at planting up to 90% of plant available water capacity. Under irrigated corn management, simulations showed little grain yield response with late initiations of irrigation when plant available soil water was above 20% (80% depletion).
Technical Abstract: Increasing competition for land and water resources due to increasing demands from rapid population growth calls for increasing water use efficiency of irrigated crops. It is important to develop location-specific agronomic practices to maximize water use efficiency (WUE). Adequately calibrated and validated agricultural systems models provide a systems approach and a fast alternative method for developing and evaluating agronomic practices that can utilize technological advances in limited irrigation agriculture. The objectives of this study were to 1) calibrate and validate the CERES-maize model under both dryland and irrigated corn (Zea mays L.) production in northeastern Colorado; and 2) use the model with a long-term weather record to determine a) optimum allocation of limited irrigation between vegetative and reproductive growth stages, b) effect of soil water content at planting on corn yield, and c) optimum soil water depletion level for initiating limited irrigation. The soil series was a Rago Silt Loam, and the initial water content on January 1 of each year was equal to field capacity in the upper 300 mm and half of the field capacity below this depth. Optimum production and WUE with minimum nitrogen (N) losses were found when: 1) a water allocation ratio of 40:60 or 50:50 (uniform) between vegetative and reproductive stages for irrigations up to 100 mm, and a ratio of 20:80 for irrigations above 100 mm was used; 2) planting occurred with a soil water profile of up to 90% of the plant available water (PAW); and 3) irrigation was initiated at 20% PAW (80% depletion). When available water for irrigation is limited to 100 mm, irrigating 50% of the area with 200 mm of water at 20:80 split irrigations between the vegetative and reproductive stages produced greater yield than irrigating 100% of the area with 100 mm water. Concepts developed in the study can potentially be adapted to other locations, climates, and crops where similar limited irrigation strategies need to be developed.