Crop Residue Cover Effects on Evaporation, Soil Water Content, and Yield of Deficit-Irrigated Corn in West-Central Nebraska

Competition for water is becoming more intense in many parts of the U.S., including west-central Nebraska. It is believed that reduced tillage, with more crop residue on the soil surface, conserves water, but the magnitude of water conservation is not clear. A study was initiated on the effect of residue on soil water content and corn yield at North Platte, Nebraska. The experiment was conducted in 2007 and 2008 on plots planted to field corn ( Zea mays L.). In 2005 and 2006, soybean was grown on these plots. There were two treatments: residue-covered soil and bare soil. Bare-soil plots were created in April 2007. The residue plots were left untreated. In April 2008, bare-soil plots were recreated on the same plots as in 2007. The experiment consisted of eight plots (two treatments with four replications each). Each plot was 12.2 m x 12.2 m. During the growing season, soil water content was measured several times in each of the plots at six depths, down to a depth of 1.68 m, using a neutron probe. The corn crop was sprinkler-irrigated but purposely water-stressed, so that any water conservation in the residue-covered plots might translate into higher yields. In 2007, mean corn yield was 12.4 Mg ha-1 in the residue-covered plots, which was significantly (p = 0.0036) greater than the 10.8 Mg ha-1 in the bare-soil plots. Other research has shown that it takes 65 to 100 mm of irrigation water to grow this extra 1.6 Mg ha-1 , which may be considered water conservation due to the residue. In 2008, the residue-covered soil held approximately 60 mm more water in the top 1.83 m compared to the bare soil toward the end of the growing season. In addition, mean corn yield was 11.7 Mg ha-1 in the residue-covered plots, which was significantly (p = 0.0165) greater than the 10.6 Mg ha-1 in the bare-soil plots. It would take 30 to 65 mm of irrigation water to produce this additional 1.1 Mg ha-1 of grain yield. Thus, the total amount of water conservation due to the residue was 90 to 125 mm in 2008. Water conservation of such a magnitude will help irrigators to reduce pumping cost. With deficit irrigation, water saved by evaporation is used for transpiration and greater yield, which may have even greater economic benefits. In addition, with these kinds of water conservation, more water would be available for competing needs.