Soil organic carbon dynamics in a sod-based rotation on coastal plain soils

Authors: GAMBLE, A - Auburn University; HOWE, J - Auburn University; WOOD, C - Southwest Florida Research And Education Center; Watts, Dexter; VAN SANTEN, EDZARD - Auburn University

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/13/2014
Publication Date: 11/11/2014
Publication URL: http://handle.nal.usda.gov/10113/5491324
Citation: Gamble, A.V., Howe, J.A., Wood, C.W., Watts, D.B., Van Santen, E. 2014. Soil organic carbon dynamics in a sod-based rotation on coastal plain soils. Soil Science Society of America Journal. 78:1997-2008.

Interpretive Summary: Peanuts are commonly rotated with cotton under conventional tillage in the Southeastern Coastal Plains Region. This rotational practice has resulted in erosion and loss of soil organic carbon. Incorporating perennial grasses into the peanut-cotton crop rotation as well as the use of conservation tillage practices could improve soil organic carbon (SOC). Thus, a long-term study (>10 years) was conducted to determine effects of including bahiagrass in a peanut-cotton rotation on soil improvements. Also strip tillage (reduced tillage practice) was evaluated to determine if this practice could conserve or increase soil organic C. Including perennial grasses into the crop rotations and utilizing strip tillage increased soil organic C within the surface 10 cm of soil. However, grazing the bahiagrass slightly decreased soil organic C in the 5 to 10 cm depth. Including perennial grasses into the rotation alone did not improve soil organic C. However, SOC was increased when perennial grasses were rotated in the peanuts-cotton system and managed under conservation tillage.

Technical Abstract: A frequently used cropping system in the southeastern Coastal Plain is an annual rotation of cotton (Gossypium hirsutum L.) and peanut (Arachis hypogaea L.) under conventional tillage (CT). The traditional peanut-cotton rotation (TR) often results in erosion and loss of soil organic carbon (SOC). Incorporation of perennial grasses such as bahiagrass (Paspalum notatum Fluegge) into the peanut-cotton rotation for 2 yr (also called a sod-based rotation or SBR) has been suggested for improving SOC, particularly in conjunction with conservation tillage practices. To determine the effect of the SBR on carbon sequestration, SOC and its isotopic composition were evaluated on established (>10 yr) crop rotation systems. Mineralization studies assessed the recalcitrance of bahiagrass-derived SOC. Cropping systems evaluated in this study included 1) TR under CT, 2) TR under strip tillage (ST), 3) SBR under CT, 4) SBR under ST and 5) SBR under ST with cattle grazing. Total SOC, bahiagrass-derived SOC, and potential C mineralization increased in the top 10 cm of soil and were stratified with depth under ST in the SBR, indicating the potential for ST to improve soil fertility in SBR cropping systems. Grazing bahiagrass decreased SOC in the 5- to 10-cm depth, but this effect was not observed for the subsequent peanut crop and did not appear to have a long-term negative effect on SOC storage. The SBR did not show consistent improvements in total SOC compared to the TR. A 3-yr comparison of SOC concentration revealed C increases in the SBR and TR systems over time, indicating that other conservation practices (e.g., winter cover cropping) are the primary contributors to SOC storage for Coastal Plain soils evaluated in this study. Isotopic analysis of mineralized CO2 indicated SOC with a higher 13C/1221 C ratio (e.g., bahiagrass-derived SOC) may be preferred over SOC with a lower ratio (e.g., C3 crop-derived SOC) for degradation.