Effect of crop residue on soil water contenl and yield of sprinkler-irrigated corn

Competition for water is becoming more intense in many parts of the U&A, including west-central Nebraska. It is believed that reduced tillage with increased cropresidue conserves water, but the magnitude of water savings is not clear. In 2007, a study was initiated on the effect of residue on soil water content and crop yield at North Platte, Nebraska. The experiment was conducted on a set of plots planted to field corn (Zea mays). There were two treatments: residue-covered soil and bare soil. Bare-soil plots were created by using a dethatcher and subsequent hand-raking, removing most of the residue. The residue plots were left untreated. The residue was mostly from previous no-till soybean crops. Residue mass and cover were measured twice: at the beginning (June) and at the end (October) of the growing season. The experiment consisted of eight plots (two treatments times four replications). Each plot was 12.2 m (40 ft) by 12.2 m. During the growing season, soil water content was measured seven times in each of the plots at six depths using a neutron probe (CPN Hydroprobe). Winter and spring 2007 were very wet at North Platte and the corn was only irrigated three times with a total of 113 mm (4.5 inch) of water. The crop was purposely water-stressed, so that any water conservation in the residue-covered plots might translate into higher yields. Differences in soil water content between the residue-covered and the bare-soil plots were small. Corn yield was 12.4 Mg/ha (197 bu/ac) in the residue-covered plots and 10.8 Mg/ha (172 bu/ac) in the bare-soil plots, which was significantly (p <0.01) greater. This yield difference may be interpreted as an additional amount of water of 50-100 mm (2-4 inch) available to the crop in the residue-covered plots. Water conservation of such a magnitude will help irrigators to significantly reduce pumping cost and more water would be available for competing needs including those of wildlife, endangered species, municipalities, hydroelectricity plants, and compacts with other states.