Single- versus double-species cover crop effects on soil health and yield in Mississippi soybean fields

Authors: Tyler, Heather

Submitted to: Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/14/2021
Publication Date: 11/18/2021
Citation: Tyler, H.L. 2021. Single- versus double-species cover crop effects on soil health and yield in Mississippi soybean fields. Agronomy. 11:2334. https://doi.org/10.3390/agronomy11112334.
DOI: https://doi.org/10.3390/agronomy11112334

Interpretive Summary: Winter cover crops are a conservation practice that can be employed in row crop systems, such as corn, cotton, and soybean, to reduce erosion, preserve soil moisture and nutrients, and promote the growth of the soil microorganisms involved in nutrient cycling. However, farmers are reluctant to use cover crops due to their added costs and potential to decrease yield of the main crop. A variety of different approaches have been investigated to determine how to maximize the benefits of cover cropping while minimizing yield inhibition. Scientists from the USDA-ARS Crop Productions Systems Research Unit in Stoneville, MS conducted a two-year field study examining the effects of single-species (rye only) and two-species (rye + clover) winter cover crop treatments on soil health and soybean yield under till and no-till field management. Compared to no cover plots, both single and two-species treatments increased the size of the microbial community in the soil, along with the activities of enzymes involved organic matter processing, nitrogen and phosphate mineralization, and general microbial activity. Soybean yield was inhibited by both cover crop treatments in tilled, but not no-till plots. This study demonstrates how tillage exacerbates the negative effects that cover crops can have on yield, and that two-species cover crop mixes are more consistent in their ability to produce ground cover in the winter and enhance soil microbial activities during the summer. These results provide insight for future mixed species cover crop studies to determine the best management practices to maximize yields for farmers who wish to employ cover crops in their fields.

Technical Abstract: Conservation management practices serve to maintain soil health resources and minimize deleterious effects of agriculture on the environment. However, adoption of these practices, particularly cover crops, is not widespread, as the benefits often do not outweigh the costs of implementation, particularly when crop yields are reduced compared to fields under traditional management practices. The purpose of the current study was to assess if a two-species cover crop mix of rye (Secale cereale L.) and crimson clover (Trifolium incarnatum L.) could increase soil health parameters such as microbial biomass and enzyme activities greater than single species rye only treatment, and if improvements in these soil health parameters aided in maximizing soybean (Glycine max L.) yield in tilled and no-till Mississippi field soils. Enhanced microbial biomass and organic matter input from degrading cover residues increased the activities of beta-glucosidase, cellobiohydrolase, fluorescein diacetate hydrolysis, N-acetylglucosaminidase, and phosphatase in surface soils. There were slight differences in how cover crop treatments performed between tillage treatments, with rye plus clover tending to elicit higher activities than rye only in no-till plots. Despite higher microbial activities and biomass, soybean yield was inhibited in both cover crop treatments, mainly in tilled plots, possibly due to allelopathic compounds in decomposing cover crop residues. These results indicate that tillage exacerbates negative effects of cover cropping on soybean yield and that future cover crop studies should focus on no-till systems. While double cover crop treatments were more consistent in increasing the activities of enzymes linked to nutrient cycling in Mississippi field soils, further study examining different combinations of crops in no-till systems is necessary to gain a better understanding of how conservation management practices can be implemented to enhance the benefits of soil health while maximizing crop yield.