Cover crop grazing length impacts on soil health and crop productivity

Authors: REITER, WADE - Auburn University; GAMBLE, AUDREY - Auburn University; CROWELL, HAYLEY - Auburn University; Balkcom, Kipling; FENG, YUCHENG - Auburn University; DILLARD, LEANNE - Auburn University; MULLENIX, KIM - Auburn University; PRASAD, RISHI - Auburn University

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/4/2024
Publication Date: 9/9/2024
Citation: Reiter, W.S., Gamble, A.V., Crowell, H., Balkcom, K.S., Feng, Y., Dillard, L., Mullenix, K., Prasad, R. 2024. Cover crop grazing length impacts on soil health and crop productivity. Agronomy Journal. 116:2885-2900. https://doi.org/10.1002/agj2.21679.
DOI: https://doi.org/10.1002/agj2.21679

Interpretive Summary: Integrated crop-livestock systems promote income diversification through cover crop grazing on degraded soils of the southeastern United States, but effects of these practices on crop yields and soil health in Coastal Plain soils are not well established. Cooperators from Auburn Univ. and an ARS scientist in Auburn, AL investigated effects of grazing intensity (mid-February, mid-March, and mid-April cattle removal dates) on soil health and crop productivity. Chemical, physical, and biological soil health indicators, crop yield, and cover crop biomass were evaluated. Cover crop biomass at termination decreased by 3,660, 5250, and 5610 kg ha-1 for the mid-February, mid-March, and mid-April treatments compared to no grazing. Grazing did not affect arbuscular mycorrhizal fungi, microbial biomass carbon, and permanganate oxidizable carbon, but soil organic carbon was greater for no grazing compared to the mid-April grazing treatment across 0-30 cm depths. Penetration resistance across 0-50 cm depths and water stable aggregates at the 0-30 cm depth were both negatively impacted by increased grazing lengths. Results suggest longer grazing periods have little effect on biological and chemical soil health indicators in the short term but can negatively impact some physical soil health indicators.

Technical Abstract: Introducing integrated crop-livestock systems into row crop production promotes income diversification and potential soil health benefits through cover crop grazing on degraded soils of the southeastern United States, but effects of these practices on crop yields and soil health in Coastal Plain soils are not well established. A four-year study was performed in the Coastal Plain region of Alabama to test effects of grazing intensity on soil health and crop productivity. Three cattle grazing regimes (mid-February, mid-March, and mid-April cattle removal dates) and a non-grazed control were included in a randomized complete block design with three replications. Chemical soil health indicators (soil organic carbon, permanganate oxidizable carbon), physical soil health indicators (water stable aggregates, penetration resistance), biological soil health indicators (microbial biomass carbon, soil respiration, arbuscular mycorrhizal fungi colonization), crop yield, and cover crop biomass were evaluated. Cover crop biomass at termination was reduced by 3,660, 5250, and 5610 kg ha-1 for the mid-February, mid-March, and mid-April treatments compared to the non-grazed control. Shorter grazing periods allowed for regrowth of cover crop biomass, leaving more residues to improve soil properties. No grazing treatment effects were observed for arbuscular mycorrhizal fungi, microbial biomass carbon, and permanganate oxidizable carbon. Soil organic carbon was higher in the non-grazed treatment than the mid-April grazing treatment across 0-30 cm depths. Penetration resistance across 0-50 cm depths and water stable aggregates at the 0-30 cm depth were both negatively impacted by increased grazing period lengths. Results from this study suggest that longer cover crop grazing periods have little effect on biological and chemical soil health indicators in the short term but can negatively impact some physical soil health indicators.