Submitted to: Journal of Soil and Water Conservation Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/13/2005
Publication Date: 11/7/2005
Citation: Terra, J.A., Reeves, D.W., Shaw, J.N., Raper, R.L. 2005. Impacts of landscape attributes on c sequestration during the transition from conventional to conservation management practices on a coastal plain field. Journal of Soil and Water Conservation Society. 60(6):437-446. Interpretive Summary: Researchers measured the effects of different agricultural management practices on soil organic carbon in Alabama using conservation tillage systems and conventional tillage systems with and without dairy manure fertilizer. Many of the soils in Alabama are depleted of carbon and nutrients due to long term conventional tillage management practices. Conservation tillage systems may improve soil quality by leaving more nutrients and organic matter or carbon from residues in the soil. More carbon or organic matter can improve soil properties such as water storage and retention capacity, balance the soil pH, and improve the texture and other physical properties of the soil. Storing carbon in the soil also means less CO2 will be released to the atmosphere and therefore will not contribute to the greenhouse effect or warming of the earth's atmosphere. Scientists at the USDA ARS J. Phil Campbell Sr. Natural Resource Conservation Center in Watkinsville, GA and the Soil Dynamics Research Unit in Auburn, AL, cooperated with Auburn University scientists to measure the soil carbon in conventional versus conservation tillage systems with and without dairy manure over a period of 30 months. The researchers found that conservation or no tillage systems and conventional tillage systems with dairy manure fertilizer increased soil organic carbon by approximatly 50% compared to conventional tillage systems without dairy manure. However, no tillage systems with dairy manure increased soil organic carbon by 157%. They also found that the carbon from the residues helped explain the large increase in soil carbon in the no tillage systems only, and not the conventional tillage systems. The information can be used by researchers, action agencies like USDA-NRCS, and policy-makers to better evaluate the effect of soil management practices on carbon storage, and to better estimate carbon storage in agricultural systems for potential monitoring of carbon storage in carbon trading programs.
Technical Abstract: Field-scale experiments on degraded soils comparing management systems would facilitate a better understanding of the SOC landscape dynamics associated with transition to conservation systems. We assessed soil management practices and terrain attributes effects on soil organic C (SOC) in a 9-ha Alabama field (Typic and Aquic Paleudults). Treatments were established in strips across the landscape in a corn (Zea mays L.)-cotton (Gossypium hirsutum L.) rotation. Treatments included a conventional system (chisel plowing/disking without cover crops) with or without dairy manure (CT+M or CT), and a conservation system (no-till and cover crops) with and without manure (NT+M or NT). A soil survey, topography, soil electrical conductivity (EC), initial SOC and soil texture were used to delineate management zones or clusters. After one rotation cycle (30 months), averaged across 240 positions distributed over the entire field, NT or CT+M increased SOC (0-5-cm depth) by ~50% compared to CT (7.34 and 7.62 vs. 5.02 Mg ha-1, respectively); but NT+M increased SOC by 157%. Initial SOC content was the most common correlated variable with SOC across the landscape for all treatments, and conservation systems had greater SOC increases relative to conventional systems at low soil quality landscape positions. Our results show that the potential to sequester C using high-residue producing conservation systems and manure is scale dependent, and may be higher than previously expected for degraded soils in the southeastern USA.