Stover Removal and Cover Crop Effects on Corn Production and Water Use Under Full and Limited Irrigation.

Corn (Zea mays L.) residue removal in irrigated cropping systems for livestock forage or cellulosic ethanol is of great interest in south-central Nebraska. Irrigation water restrictions in the region have also resulted in adoption of limited-irrigation strategies. Little is known regarding the interaction between residue removal and irrigation level in the central Great Plains. An on-going no-till continuous corn study was established in 2010 to evaluate the effects of irrigation level [full (100% ET; FI) and limited (60% ET; LI)], corn residue management (0 and ~65% removal), and cover crop inclusion (with and without) on grain production and crop water use efficiency (WUE). In 2012, when in-season precipitation (1 April – 31 September) and air temperature were 14% less and 8% greater than the 30-year normal, respectively, corn residue removal with LI reduced grain yield by ≥18% than all other residue management × irrigation treatments. Crop WUE was greatest with FI, regardless of residue management treatment. Residue removal reduced crop WUE by 12% with LI. In 2014, when in-season precipitation and air temperature were 21% greater than and within 0.5% of the 30-year normal, respectively, residue removal with FI resulted in ≥7% more grain yield than all other treatments, and grain yield when residue was retained and FI was similar to the LI treatments. Crop WUE was ≥9% less with residue retention under FI compared to all other treatments. These results indicate that residue removal effects on corn production can be sensitive to weather conditions, even under full and limited irrigation.