Impacts of Winter Grazing on Soil Health in Southeastern Cropping Systems

Abstract

Coastal Plain soils are often characterized by low soil organic carbon as a result of historically intense row cropping practices, highly weathered soils, and the humid climate of the region which often breaks down organic matter faster than it can accumulate. A rotation of cotton (Gossypium hirsutum L.) and peanut (Arachis hypogaea L.) under conventional tillage is typical in this region, but an opportunity to encourage diversification of rotations that improve soil quality exists. If managed properly, combining annual winter grazing of cover crops in a cotton-peanut rotation under conservation tillage may provide additional soil organic matter to improve soil health and fertility. Studies are needed to establish guidelines for integrated crop-livestock (ICL) systems that maximize soil health benefits while maintaining yield and providing quality forage for livestock. A study was established at the Wiregrass Research and Extension Center in Headland, AL to determine the effects of an ICL system in which winter grazing livestock were incorporated into a cotton-peanut rotation with a winter cover crop mixture of ‘Cosaque’ oats, ‘FL401’ rye, ‘Sunrise’ crimson clover, and ‘T-raptor’ brassica. Three cattle removal dates (i.e., mid- February, mid-March, mid-April) and an ungrazed control were compared to assess the effect of grazing period length on soil organic carbon (SOC), permanganate oxidizable carbon (POXC), water stable aggregates (WSA), penetration resistance (PR), microbial biomass-carbon (MBC), and arbuscular mycorrhizal fungi (AMF) colonization rates. After the first two years of integrating winter grazing, selected soil health indicators did not change based upon length of grazing. The ungrazed control and treatments with shorter grazing periods resulted in increased biomass on the soil surface at the time of cover crop termination. Microbial biomass C was the only soil health indicator to exhibit a treatment effect having greater MBC in the ungrazed control treatments, likely due to greater cover crop biomass present on the soil surface at termination. Water stable aggregates and PR were unaffected by the presence of livestock and length of grazing showing that negative physical impacts of winter grazing are not detectable in the early years of this study. Higher biomass may have increased cotton lint yield in 2019, possibly through conserving soil moisture during the cash crop growing season. However, peanut yield in 2020 was unaffected by presence of livestock or grazing time. The lack of consistent results may indicate that integrating winter grazing livestock does not negatively nor positively impact soil health in southeastern row crop production systems. However, more time under this management will be needed to thoroughly evaluate how winter grazing livestock impact soil health and yield.