Effects of nitrogen rate, irrigation rate, and plant population on corn yield and water use efficiency

Improper N and irrigation management are major factors contributing to water quality and shortage problems in the Great Plains. This study was conducted on the Irrigation Research Farm in Yuma, CO, from 1,998 through 2000 to establish an accurate irrigation and N management system for corn (Zea mays L.) production in the Great Plains aimed at high yield and water use efficiency (WUE) simultaneously. A field experiment was conducted on a center-pivot-irrigated, well-drained Haxtun sandy loam soil (fine-loamy, mixed, superactive, mesic Pachic Argiustolls) by using a randomized complete block split-split plot design, with irrigation rates [0.60, 0.80, and 1.00 of the estimated evapotranspiration (ET)], N fertility rates (30, 140, 250, and 360 kg ha(-1), including N from soil, fertilizer, and irrigation water), and plant populations (57 000, 69 000, and 81000 plants ha(-1)) as the main-plot, split-plot, and split-split plot treatments, respectively. A combination of 0.80ET to 1.00ET, 140 to 250 kg N ha(-1), and 57 000 to 69 000 plants ha(-1) population provided optimum corn yield. Irrigation treatment 0.80ET, accompanied by 140 to 250 kg N ha(-1), and 57 000 to 69 000 plants ha(-1) population was the best management system for optimum WUE. No significant differences in water extraction from the soil profile for the entire season and soil moisture content at harvest between the 0.80ET and 1.00ET irrigation treatments were additional indications that 0.80ET is superior to 1.00ET. To preserve the Ogallala Aquifer, the best management system aimed at optimum WUE should be used for corn production in the Great Plains region.