Cover crop monocultures and mixtures impact soil health indicators in the Southeast U.S.

Authors: DECKER, HANNAH - Auburn University; GAMBLE, AUDREY - Auburn University; Balkcom, Kipling; JOHNSON, ANNA - Auburn University; HULL, NOAH - Auburn University

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/20/2022
Publication Date: 8/26/2022
Citation: Decker, H., Gamble, A.V., Balkcom, K.S., Johnson, A., Hull, N. 2022. Cover crop monocultures and mixtures impact soil health indicators in the southeast United States. Soil Science Society of America Journal. 86:1312-1326. https://doi.org/10.1002/saj2.20454.
DOI: https://doi.org/10.1002/saj2.20454

Interpretive Summary: The southeastern United States contains degraded soils caused by intensive agriculture and detrimental climatic factors. An ARS scientist in Auburn, AL and scientists from Auburn Univ. studied cover crop performance and short-term effects on soil health indicators for a north and south Alabama soil. Treatments included winter fallow, monocultures, and two- and three-way mixtures of cereal rye, crimson clover and forage radish. Rye and clover aboveground biomass were greater than radish. All cover crops, except the radish monoculture, increased soil organic carbon 19-30% in the surface at north Alabama compared to winter fallow. Similarly, some cover crop treatments increased permanganate oxidizable carbon (POXC) compared to the fallow control. However, this effect was not observed in south Alabama. Treatments containing rye or clover decreased soil strength by 14-22% in north Alabama after four years of cover crop use. Growers can expect improved soil health and reduced soil degradation depending on soil type and cover crop selection with short-term use.

Technical Abstract: The southeastern United States has a long history of soil degradation due to intensive agriculture and detrimental climatic factors. Conservation management practices such as cover cropping aim to improve soil productivity and restore soil health. Our objectives were to evaluate the performance of cover crops and short-term effects on soil health indicators for two southeastern soil types. Cover crop experiments were conducted at the Wiregrass (WREC) and Tennessee Valley (TVREC) Research and Extension Centers in Alabama from 2017 to 2021. Cover crop treatments included winter fallow, monocultures, and two- and three-way mixtures of cereal rye (Secale cereale L.), crimson clover (Trifolium incarnatum L.) and forage radish (Raphanus sativus L.) preceding a cotton (Gossypium hirsutum L.)- legume cash crop rotation. At TVREC, aboveground biomass for both rye and clover were greater than radish. All cover crops, except the radish monoculture, increased soil organic carbon (SOC) 19-30% in the top 5 cm at TVREC compared to winter fallow. Similarly, some cover crop treatments increased permanganate oxidizable carbon (POXC) compared to the fallow control. However, this effect was not observed at WREC. Cover crops did not produce many meaningful aggregate stability differences at either location. Treatments containing rye or clover decreased soil strength by 14-22% at TVREC after four years of cover crop incorporation. Short-term cover crop use can improve soil health and reverse soil degradation depending on soil type and cover crops selection.