Soil Carbon Sequestration and Mineral Interaction In Tennessee Valley (Alabama) Rhodic Paleudults.

Agronomic management affects soil organic matter (SOM) pools that impact chemical and physical properties, soil quality, and ultimately, soil function. Pools of SOM and management-dependent soil chemical and physical properties were measured on Decatur (Fine, kaolinitic, thermic Rhodic Paleudult) soils, a benchmark soil in the Tennessee Valley region of Alabama. This region is intensively utilized for agronomic production, and issues related to sustainable productivity, soil quality, and soil organic carbon (SOC) sequestration are critical. These soil systems provide unique near-surface pedological environments for investigating the interaction of SOM with relatively high near-surface quantities of sesquioxides and phyllosilicate clays in highly weathered soil systems of the Southeastern U.S. Management practices investigated include long-term (>10 years) pasture, conservation (reduced tillage) and conventional cotton (Gossypium hirsutum) and grain row-cropping systems. Significant (α=0.05) differences in C pools and fractions (SOC, active organic C, and particulate organic matter) , bulk density, nutrient content, and  water dispersible clay, were found at shallow depths among the different management systems; results were mixed at lower depths. Total SOC was found to significantly differ among systems (73, 56, and 38 Mg ha⁻¹ for pasture, conservation, and conventional cotton, respectively). At shallow depths, higher SOM resulted in greater liquid and plastic limits. Significant correlation existed among SOC pools, dynamic chemical and physical soil properties, and inherent pedological properties.  The effect of differences in SOM as a function of management on phosphorus retention, anion exchange, and water stable aggregates in these sesquioxide-rich soil environments will also be presented.