Carbon Storage and Greenhouse Gas Emissions for an Integrated Crop-Livestock System in Coastal Plain Soils.

A frequently used cropping system in the Southeast is an annual rotation of cotton (Gossypium hirsutum L.) and peanut (Arachis hypogaea L.) under conventional tillage.  This traditional peanut-cotton rotation (TR) often results in erosion and loss of soil organic carbon (SOC).  Incorporation of 2 yr of perennial grasses such as bahiagrass (Paspalum notatum Fluegge) into the peanut-cotton crop rotation (also called a sod-based rotation or SBR) has been shown to improve soil quality, relieve environmental stress, and increase resistance to disease and pests.  Incorporation of cattle grazing on bahiagrass and winter cover crops further increases the efficiency of the SBR.  To determine the environmental effect of perennial grasses and grazing in the peanut-cotton rotation, SOC storage and soil greenhouse gas (GHG) emissions were assessed on established (>10 years) crop rotation systems.  Yields were measured to assess productivity of the SBR.  Results indicated that the SBR has potential to increase SOC storage compared to the TR in the top 5 cm of soil.  Although grazing of bahiagrass reduced SOC in the 5‑ to 10‑cm depth, this effect was not observed in the subsequent peanut crop and did not have a long-term negative effect on SOC storage.  Dependent upon season and crop, a moderate stocking rate of 2.5 cattle ha^-1 appeared to result in fewer emissions of CO₂ and N₂O and greater uptake of CH₄ compared to ungrazed management.  For the moderate cattle stocking rates used in this study, grazing did not have a negative effect on SOC storage or soil GHG emissions in SBR systems.  In addition, improvements in peanut yield for the SBR compared to the TR indicate the potential of bahiagrass to improve the productivity of the peanut-cotton rotation.