Water Use of Cover Crop Species and Mixes.

Water is the primary factor limiting cropping systems in many regions of the world. Cover crop mixes have been marketed to better foster water conservation following winter wheat (Triticum aestivum) compared to fallow and single species cover crops. The primary objective of this study is to determine the water use of individual cover crop species, mixtures, and fallow to find the least water consumptive. Ten cover crop treatments were tested, including: six single species (two grass, two legume, and two brassicas); two-three component mixes comprised of one of each of the grasses, brassicas, and legumes; a six component mix comprised of all the individual species; and one complex mix of nine (three grasses, two legumes, and four brassicas). The cover crops were planted using a Great Plains drill immediately following wheat harvest. Volumetric soil water content was measured with a neutron probe, with readings taken approximately weekly during the growing season and monthly until corn (Zea mays) planting. The cover crops were terminated with herbicide at flowering of most species, and aboveground biomass was harvested shortly thereafter. With 16.8 centimeters of rainfall, all cover crops were found to use more water than fallow. Water use of mixtures was found to be similar to the single species. The least water conserving treatment used 3.7 cm in addition to the precipitation, while the fallow gained 3.4 cm to the profile.