Labile Pool Soil Organic Matter Response to Transition to Organic and Reduced Input Management in Irrigated Crop and Forage Production.

A four-year study was conducted to evaluate the soil organic matter dynamics under organic, reduced-input, and conventional management in cash-crop and beef-calf forage production at the James C. Hageman Sustainable Agriculture Research & Extension Center near Lingle, Wyoming. Long-term goal of the project is to evaluate economic and environmental sustainability of crop-range-livestock production systems in Wyoming. Six treatments (3 approaches x 2 systems) on four replicated plots were established in 2009. Soil samples were collected in spring, early and late summer, and fall seasons of 2009-2012, and were analyzed for soil organic carbon, total nitrogen, inorganic nitrogen, microbial biomass carbon and nitrogen, and potentially mineralizable carbon and nitrogen. Greenhouse gas emissions (carbon dioxide, methane, and nitrous oxide) were measured in the same plots in 2011 and 2012. Results indicate that carbon and nitrogen parameters have started responding to the changes in management approaches. Labile and microbial biomass carbon and nitrogen and greenhouse gases are affected significantly by management approaches. Long-term investigation will lead to better understanding of differences among these management approaches in high dry condition of Wyoming crop-range-livestock farming.