Soil Organic Matter Dynamics Under Dryland Winter-Wheat-Based Cropping Systems in Two Wyoming Production Areas.

Our objectives for this study were to evaluate and compare soil organic matter parameters under conventional wheat-fallow (CWF), organic wheat-fallow (OWF), no-till (NT) and minimum-till (MT) systems in use for at least 10 years by farmers in southeastern Wyoming. We selected two fields under each of the four management types for at least 10 years, and one field under the conservation reserve program (CRP) for at least 15 years to analyze for total organic carbon (TOC) and nitrogen (TN), labile C, microbial biomass C, dissolved organic C, mineral N, and potentially mineralizable N. Results show that amounts of TOC, TN, and other soil organic matter (SOM) components in the soil are closely related to the frequency and intensity of tillage. Results suggest that reduced- or no-till systems conserve and restore SOM while enabling more frequent cropping than CWF systems in Wyoming. Results also point to a need for development of soil-building practices compatible with organic dryland wheat production.