Soil Water Use and Economics of Cover Crops in Semi-Arid Cotton Cropping Systems.

Soil water use by cover crops is a chief concern in semi-arid regions, especially in areas with high ET demands.    In addition, net returns are typically marginal in such environments and costs of management practices such as cover cropping must be carefully weighed. The objective of this research is to quantify the impact of cool-season cover crops in cotton cropping systems on soil moisture, lint yields, and net returns.  The dryland system consists of seven treatments: 1) conventional tillage without a cover crop; 2) no-till without a cover crop; and no-till with cover crops consisting of 3) crimson clover; 4) Austrian winter field pea; 5) hairy vetch; 6) wheat, and 7) legume/grass cover crop mixture. The irrigated system consists of four treatments: 1) conventional tillage without a cover crop; 2) no-till without a cover crop; 3) no-till with a wheat cover crop; and 4) no-till with a legume/grass cover crop mixture. These cover crop treatments have been in place since fall 2012. Neutron probes are used to record soil moisture bi-weekly throughout the year.  Cover crops result in lower stored soil moisture at termination timing. However, infiltration has appeared to improve over time and no significant differences in soil moisture are observed among treatments entering the cotton growing season. Within the dryland system, 2-yr average net returns have been higher for cropping systems without cover crops. Net returns are similar among treatments within the irrigated system.