Effects of Land Use On Soil Organic Carbon and Hydraulic Properties in Upland Landscapes of Eastern Kansas.

An estimated 60% of the soil organic carbon (SOC) pool has been depleted in temperate regions via the conversion of natural to agricultural ecosystems.  It has been suggested that soils have the potential to regain more than half of this depleted stock through the use of appropriately chosen management practices.  However, management decisions of land use also affect soil hydraulic properties that govern the rate of accumulation and distribution of SOC and the potential for erosion.  Our objectives were to (1) examine the effects of land use on soil moisture retention, hydraulic conductivity, and the distribution of SOC and (2) evaluate potential effects of land use on erosion.  Four long-term management treatments were investigated (springtime burning, grazing, mowing, and untreated) on plots that were previously cultivated.  These plots were compared to an adjacent native prairie, which had not previously been plowed.  Undisturbed samples were taken from each plot in triplicates using a trailer-mounted hydraulic corer.  These samples were analyzed for morphological properties (horizonation and structure), physical properties (i.e., particle-size distribution, bulk density, and porosity), hydraulic properties (i.e., water retention), and SOC.  Additionally, infiltration was measured in the field using a mini-disk infiltrometer.  Results show that historically cultivated and native prairie field plots vary widely with respect to their surface and near-surface soil physical properties.  Using physical properties and detailed soil morphological descriptions, it was estimated that between 20 and 45 cm of soil has been eroded from cultivated plots suggesting that the redistribution of soil organic carbon is an important process in upland landscapes of eastern Kansas.  Evaluating the potential for C sequestration and erosion in different land use scenarios depends on the accurate assessment and integration of soil morphological, physical, and hydraulic properties.