Cover Crops and Compost Carryover Effects on Phosphorus Cycling in Calcareous Soils.

Producers in the High Plains Region of the western US need alternative management options for dryland wheat (Triticum aestivum L.) to help reduce soil erosion and increase yields. High costs of nutrient inputs, low precipitation, and alkaline soils constrain production and limit efficacy of practices such as crop rotation and cover crops. The excess of calcium carbonate (CaCO₃) present in calcareous soils leads to precipitation of phosphorus (P) in forms not available to plants, thereby restricting productivity of cropping systems. To evaluate alternatives for improving sustainable productivity of dryland, winter-wheat-based cropping systems, I am conducting greenhouse and incubation studies using calcareous soil from wheat fields near Lingle, WY, simulating rotation of winter wheat with cover crops. This controlled environment experiment allows for the evaluation of one-time compost applications, selected cover crops, and the interactions of both in regards to P availability and cycling. Greenhouse soil is being analyzed for carbon (C) and nitrogen (N), Olsen P, ammonium-acetate-extractable P, organic P and total P. Microbial parameters include enzyme testing for phosphatase and dehydrogenase as well as microbial biomass. Plant biomass is being measured and analyzed for wheat yield, above- and below-ground biomass, and P concentration. Expected results include increased P availability in calcareous soils with cover crop treatments and compost application, microbial activity differences among single species cover crop treatments and mixtures, and increased wheat yields with one-time compost application.