Conservation Practice Effects On Soil Quality Indicators: The Fort Cobb Reservoir Case Study.

While there has been controversy amongst researchers about the concepts and terminology of soil quality, there is agreement that management practices affect soils and that indicators can be used to determine how soils deviate  from conditions favorable for a defined use of that soil. Within watersheds, soil condition, along with storm characteristics, controls the basic hydrologic process of infiltration, retention, and runoff of precipitation. Soil condition also controls the ability of soils to retain, bind, and transmit solutes and contaminants that flow with waters. Many conservation practices (CPs), by explicit design or otherwise, impact soil condition. Therefore, to understand hydrologic and water quality processes at a watershed scale, it is essential to quantify responses across a range that address field, edge-of-field, landscape, stream and channel processes and interactions. Four contrasting management systems were evaluated in the Fort Cobb Reservoir watershed in southwestern Oklahoma:  conventionally tilled wheat, no-till wheat, perennial grass converted from cropland (e.g., peanut conversion to bermudagrass), and native grass land.  Each of the four management systems were monitored on contrasting soil types, with 10 replications (fields) for each management/soil combination.  Soil quality indicators measured included field water content, microbial biomass carbon, water stable aggregation, potential mineralizable N, electrical conductivity, pH, soil test P and K, and total organic C and N, bulk density, porosity, soil volume, and water filled pore space. Changes in soil indicators will be used as metrics to classify soil quality as improved, stable, or degraded by applying factor analysis. The soil management assessment framework (SMAF) will be used to assess the capacity of the soils to function (i.e nutrient cycling, water relations, filtering and buffering, etc.) for selected combinations of soil and land management practices within the watershed.