Skip to main content
ARS Home » Southeast Area » Florence, South Carolina » Coastal Plain Soil, Water and Plant Conservation Research » Research » Publications at this Location » Publication #369313
Research Project: Improvement of Soil Management Practices and Manure Treatment/Handling Systems of the Southern Coastal Plain

Location: Coastal Plain Soil, Water and Plant Conservation Research

Title: Loamy sand soil approaches organic carbon saturation after 37 years of conservation tillage

Author
item Novak, Jeffrey
item Watts, Donald - Don
item BAUER, PHILIP - Retired ARS Employee
item KARLEN, DOUG - Retired ARS Employee
item HUNT, PATRICK - Retired ARS Employee
item MISHRA, UMAKANT - Department Of Energy

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/7/2020
Publication Date: 3/12/2020
Citation: Novak, J.M., Watts, D.W., Bauer, P.J., Karlen, D.L., Hunt, P.G., Mishra, U. 2020. Loamy sand soil approaches organic carbon saturation after 37 years of conservation tillage. Agronomy Journal. 112:3152-6162. https://doi.org/10.1002/agj2.20184.
DOI: https://doi.org/10.1002/agj2.20184

Interpretive Summary: Sandy soils in the Southeastern United States Coastal Plain region have been cultivated for centuries using conventional tillage (CvT) practices. Coupled with a warm, humid climate, tillage plus crops producing little residue have resulted in low soil organic carbon (SOC) and total nitrogen (TN) concentrations due to increased plant residue decomposition. Decreased SOC contents has been shown to degrade soil quality. However, conservation tillage (CnT) practices have been identified as a management method to rebuild SOC and TN contents. Conservation tillage results in less soil incorporation of plant residue resulting in SOC and TN accumulation, although, few long term (> 35 years) tillage studies are available that quantity of SOC and TN changes. We conducted a field study using soils that were under CnT and CvT for 37 years and confirm that long-term CnT can significantly raise SOC and TN content in the surface 5 centimeter compared to CvT. We also showed that CnT resulted in significant vertical stratification of SOC and TN which did not occur under CvT. These results demonstrate that conservation tillage is one management practice to increase SOC and TN contents.

Technical Abstract: Conservation tillage is reported to increase soil organic carbon (SOC) and total nitrogen (TN) contents, but; long-term (> 30 years) field results quantifying the responses in Coastal Plain Ultisols are sparse. The distribution, accumulation, and topsoil storage of SOC and TN after 37 years of crop production using conventional (CvT) or conservation tillage (CnT) on a Norfolk loamy sand (fine-loamy, kaolinitic, thermic, Typic Kandiudult) were quantified. Soil samples were collected annually from the 0 to 5-, 5 to 10-, and 10 to 15- centimeter (cm) depth increments beneath corn (Zea mays), soybean (Glycine max), and cotton (Gossypium hirsutum) crops. Overall, SOC and TN accumulation in the 0 to 5-cm depth were highest for both CnT and CvT. Focusing on total long-term changes for the 0 to 15-cm sampling depth beneath various corn crops shows that CnT and CvT sequestered 24.7 Megragrams carbon per hectare and 21.4 Megragrams carbon per hectare, respectively. Between 1978 and 2016, there was a highly significant exponential increase in SOC within the top 5 cm soil depth. However, the exponential curves began to plateau suggesting the Norfolk topsoil was approaching its organic carbon (OC) storage capacity. These field measurements strongly indicate that additional topsoil SOC increases with current tillage and crop management practices are limited.