Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/29/2008
Publication Date: 3/9/2009
Citation: Novak, J.M., Frederick, J.R., Bauer, P.J., Watts, D.W. 2009. Rebuilding organic carbon contents in Coastal Plain soils using conservation tillage systems. Soil Science Society of America Journal 73:622-629.
Interpretive Summary: The concentration of carbon dioxide in the earth’s atmosphere has been increasing and scientists have been assessing methods to lower its concentration. Soils hold more carbon than the atmosphere, so it is an important storehouse. Soil scientists have studied tillage and crop management methods that can reduce crop residue decomposition rates thereby increasing soil carbon concentrations. More carbon stored in soils means that the pool of atmospheric carbon dioxide will be lower. Our research has been focused on examining different tillage management practices (disked vs. conservation) and incorporating a row crop (corn) into a cotton rotation that produces more residue. The studied was conducted over 6 years in sandy soils of the South Carolina Coastal Plain region. Soil and crop residue samples were collected over the 6 years from fields under the disked and conservation tillage system. We found that soil carbon levels under conservation tillage, where the plant residue is left mainly on the soil surface, had higher levels compared to disked soils. Soil organic carbon levels after 6 years under disked tillage stayed about the same. Using corn in the rotation added more residue to the fields compared to cotton, and the additional residue assisted in soil organic carbon accumulation under conservation tillage. Our results showed the importance of using conservation tillage as a counter measure to reduce carbon dioxide by sequestering more soil carbon.
Technical Abstract: Long-term disk tillage (DT) for cotton (Gossypium hirsutum L.) production in the Southeastern USA Coastal Plain has resulted in soil organic carbon (SOC) contents reductions. Conservation tillage (CT) management that returns more plant residues to soils can rebuild SOC levels. A field study, with two adjacent 3.5-ha fields both containing soil series formed in upland and depressional areas, was conducted using a six year rotation of corn (Zea Mays L.) and cotton to determine the CT and DT effects on SOC contents and residue characteristics returned to soil. Annual soil samples were collected from 50 locations per field at 0 to 3 cm and 3 to 15 cm. After six years under CT, residue accumulation promoted a significant SOC increase in the 0 to 3-cm depth in the upland soil series (about 0.7 Mg SOC/ha). The lack of residue mixing at 3- to 15-cm depth in upland soils under CT, however, resulted in a significant SOC content decline at this depth (1.25 to 2.51 Mg SOC/ha). There was no significant SOC content change in soils under CT formed in depressional areas or in all soils under DT. Over 6 yrs, 14.8 Mg/ha of organic carbon (OC) from both corn and cotton residues was returned to soils under CT; but less than 4% was incorporated into the SOC pool. Levels of SOC in sandy upland soils can be increased at the surface after six years of CT under a corn and cotton rotation, with the increase coming at the expense of a SOC decline at a deeper topsoil depth.