Novak, Jeff (USDA-ARS-CPRC, Florence, SC USDA-ARS-CPRC, 2611, West Lucas Street, Florence, SC, 29501; Phone: 843-669-5203; Fax: 843-669-6970; Email: novak@florence.ars.usda.gov)

Utilization of Conservation Tillage Practices to Rebuild Organic Carbon Levels in a Sandy, Coastal Plain Soil

J. M. Novak *, P. J. Bauer, P. G. Hunt

The pedogenic process in well-drained sandy, Coastal Plain soils has resulted in relatively low soil organic carbon (SOC) levels. In these soils, the predominance of sand-size particles, rapid internal drainage, and high residue oxidation rates causes rapid residue losses and a low build-up of SOC. Cultivation of soils using conventional tillage practices, whereby the residue is mixed into the soils, has increased the decline in SOC levels. Recent research, however, indicates that conservation tillage practices, which minimize residue incorporation, can increase SOC levels, but the increase is limited to the top few cm of soil. Long-term conservation and conventional tillage plots have been managed for 24 years in a sandy, well-drained Coastal Plain soil (Norfolk loamy sand). Crop rotation management in these plots consisted of corn, soybeans, winter wheat, and cotton. After 24 years of tillage management, annual deep coring (0 to 90-cm) within these plots has revealed that the surface SOC levels (0 to 5-cm depth) in soils under conservation tillage were significantly higher (1.33 % SOC, P less than 0.001) compared to soil under conventional tillage (0.84%). Mean SOC levels in lower profile depths were not significantly different (P greater than 0.05) between tillage systems. Efforts currently in progress are to enhance SOC sequestration in lower soil profile depths (below 5-cm) with a cover crop that has a high below ground root biomass (Secale cereale).