Cover Crop Water Use and Subsequent Effects on Wheat Yield in a Semi-Arid Environment.

The advantages of cover crops for protecting and improving the soil are well established. However, in semiarid environments, cover crop water use may result in significant yield losses in following crops such as winter wheat. Recently, there have been reports that a cover crop mixture consisting of at least 8 different plant species used much less water than a single-species cover crop. The objectives of this study were to determine if cover crops grown in mixtures use water differently than cover crops grown in single-species plantings and to determine effects on following wheat yields. The study was conducted at Akron CO and Sidney NE during 2012-2014. Cover crops were no-till seeded in April into proso millet residue. Treatments were cover crop plantings of flax, peas, oats, and rapeseed as single species and a 10-species mixture. An additional no-till fallow treatment was also included. Soil water content was measured periodically with a neutron probe. Cover crop biomass was measured at termination (mid-June). Winter wheat was planted in late September and harvested for yield in early July. At each location the experiment was conducted under both rainfed and irrigated conditions. The cover crop mixture used water similarly to the single-species plantings. The cover crop water use reduced the available soil water at wheat planting and subsequent wheat yield. The expenses associated with cover crop establishment and the subsequent reduction in wheat yield do not justify the use of cover crops in this semi-arid environment unless soil erosion protection is necessary. Practicing good no-till residue management may be a better option than planting cover crops for this semi-arid environment.