Determining Ideal Winter Wheat Cover Crop Termination Dates in Cotton Production Systems of the Texas Rolling Plains

An interest to grow cover crops has been increasing in the traditional monoculture cropping systems of the Texas Rolling Plains (TRP), mainly to build soil health. However, there are concerns that growing cover crops could potentially reduce soil water, and thereby affect subsequent cash crop yield. Previous field studies from this region demonstrated mixed results with some showing a reduction in cash crop yields due to growing of cover crops and others indicating no significant impact of cover crops on subsequent cotton lint yields. Cover crop termination date plays a major role in soil water availability for the subsequent summer crop and its yield. The objective of this study was to determine the ideal termination dates of winter wheat cover crop in cotton production systems of the TRP using the CROPGRO-Cotton and CERES-Wheat modules within the Cropping System Model (CSM) of the Decision Support System for Agrotechnology Transfer (DSSAT). These two modules were calibrated using the measured data on soil moisture and crop yields from two treatments of cover crop field experiments (cotton with wheat cover crop and cotton without a cover crop) at the Texas A&M AgriLife Research Center at Vernon during 2011 and 2015. Long-term simulations have been run with the calibrated model and the water balances under both systems (cotton with a terminated winter wheat cover crop and cotton without a cover crop) were assessed for different cover crop termination dates. Based on the preliminary analysis of average (2001-2015) annual water balances under various cover crop termination dates, the first week of April appears to be ideal for terminating cover crops in the TRP region. The effects of winter wheat cover crop termination dates on cotton yields are currently being studied.