Net Positive Soil Water Content Following Cover Crops With No Tillage In Irrigated Semi-Arid Cotton Production

Conservation management practices such as no-tillage and cover cropping can reduce soil erosion, enhance soil biological activity, increase water capture and storage, and sequester C. Cover crops, however, utilize stored soil water during the winter months, and the water depletion is thought to have negative impacts on the subsequent cotton (Gossypium hirsutum L.) crop in semi-arid ecoregions where water resources are limited. The objective of this research was to quantify the long-term impacts of conservation tillage and cover crop use on volumetric water content of soil in an irrigated cotton production system. Soil water was measured in a long-term (established 1998) conservation system in Lamesa, TX and water dynamics during the 2015-2017 growing seasons are presented here. Volumetric water content was reduced by cover crops prior to their termination but was replenished by spring precipitation and deficit irrigation prior to planting cotton. A stepwise regression analysis was used to determine changes in soil water at depth. In each of the study years, soil water increased more with no-tillage following cover crop termination and decreased less during cotton growth than the conventionally tilled system. Cotton water use efficiency was not significantly different between treatments in any year. Results from this study challenge the concept that winter cover crops result in reduced in-season soil water in irrigated systems, a supposition that has limited adoption of conservation tillage and cover crop use on the Texas High Plains.