Stover Removal Effects on Seasonal Soil Water Availability Under Full and Deficit Irrigation.

Removing corn (Zea mays L.) stover for livestock feed or bioenergy feedstock may impact water availability in the soil profile to support crop growth.  The role of stover in affecting soil water availability will depend on annual rainfall inputs as well as irrigation level. To assess how residue management affects soil profile water availability during the crop growing season, soil moisture was measured continuously at 30, 60, 90, and 120 cm soil depths during a severe drought year (2012) and in an above average rainfall year (2014) in an irrigated, no-till continuous corn system in south central Nebraska, USA.  Residue management included no stover removal (0% of non-grain aboveground biomass removed) or maximum removal (60% of non-grain aboveground biomass removed) under full irrigation or deficit irrigation (60% of full).  Soil water availability decreased at all soil depths with stover removal throughout both growing seasons.  During the drought year, grain yields were highest under full irrigation when stover was retained, and stover removal under full irrigation reduced both total available soil water and yields to levels measured under deficit irrigation.  In contrast, during the high rainfall year, grain yields under full irrigation were lower when stover was retained compared to removed, despite greater total soil water availability with stover retention.  Although stover removal may exacerbate yield losses during drought years even under full irrigation, small but significant yield increases with stover removal during more abundant rainfall years may stabilize long-term grain yields in irrigated continuous corn systems incorporating stover harvesting practices.