Conservation Practices to Enhance Soil Carbon Sequestration Across Southeastern Coastal Plain Soils.

Coastal Plain soils consist of highly weathered Ultisols with coarse textures, poor structure, and soil organic carbon (SOC) contents below 0.5 %, which decreases crop productivity across the region.  Two separate experiments were established in Central (Prattville) and Southeast (Wiregrass) Alabama on a Lucedale fine sandy loam (fine-loamy, siliceous, thermic Arenic Paleudult) and a Fuquay sand (loamy, kaolinitic, thermic Arenic Plinthic Kandiudults), respectively.  The Prattville experiment focused on how tillage and cover crop interactions affect SOC with a factorial treatment combination of conservation tillage systems (no-till, fall paratill, spring paratill, and spring strip-till) and winter cover crops [no cover, rye (Secale cereale L.), and wheat(Triticum aestivum L.)] from 2004-2009 in a corn (Zea mays L.)/cotton (Gossypium hirsutum L.) rotation.  The Wiregrass experiment focused on enhancing rye cover crop growth with nitrogen (N) fertilizer sources and rates to promote high residue levels that increase surface SOC contents in a continuous cotton rotation from 2006-2008.  At Prattville, a reduction in surface soil disturbance with no cover crop increased surface SOC levels 105% compared to initial levels.  Using a cover crop increased SOC levels an additional 15%.  At the sandier Wiregrass location, a cover crop with no fertilizer increased SOC levels 63% compared to initial levels, while supplemental N, regardless of N source, increased SOC levels an additional 10%.  The inherent poor physical and chemical nature of Coastal Plain soils can be improved by using conservation tillage combined with high residue cover crops to enhance soil productivity by primarily increasing SOC contents in the soil surface.