Comprehensive impacts of diversified cropping on soil health and sustainability

Authors: BALDWIN-KORDICK, REBECCA - Iowa State University; DE, MRIGANKA - Minnesota State University; Lopez, Miriam; LIEBMAN, MATT - Iowa State University; Lauter, Nicholas; MARINO, JOHN - University Of Colorado; MCDANIEL, MARSHALL - Iowa State University

Submitted to: Agroecology and Sustainable Food Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/9/2021
Publication Date: 1/10/2022
Citation: Baldwin-Kordick, R., De, M., Lopez, M.D., Liebman, M., Lauter, N.C., Marino, J., McDaniel, M.D. 2022. Comprehensive impacts of diversified cropping on soil health and sustainability. Agroecology and Sustainable Food Systems. 46(3): 331-363. https://doi.org/10.1080/21683565.2021.2019167.
DOI: https://doi.org/10.1080/21683565.2021.2019167

Interpretive Summary: Agriculture has become less diverse with increased modernization and industrialization. For example, the U.S. Midwest specializes almost exclusively in corn and soybean production contributing to over one third of the world’s production for these crops. This narrow specialization results in high external inputs to maintain crop yields which contributes to soil and water quality degradation. Using multi-crop rotation systems and incorporating livestock production into these rotations offers promising solutions to problems linked to industrialized agriculture. To better understand how agricultural diversification affects soil health and function, we compared 20 soil features linked to critical ecosystem services in 1) a conventional 2-year maize-soybean rotation, and 2) a diverse 4-year corn-soybean-oat+alfalfa-alfalfa rotation that periodically received cattle manure. The features most improved by the diverse cropping system included: 1) an 8% reduction in soil resistance to root growth, 2) a 16% increase in the soil's ability to retain nutrients, 3) a 157% increase in a measure of beneficial organic matter, and 4) a 62% increase in soil microbes that help improve soil fertility. These improvements in soil function were associated with enhanced crop yields, reduced requirement for agricultural inputs, and decreased environmental impacts. An analysis of productivity, external inputs, and environmental impacts, demonstrated that the use of a diverse cropping system is profitable for producers. Despite declines in cropping system diversity, these results provide strong evidence for the benefits of cropping system diversification.

Technical Abstract: Conventional agriculture in the Midwestern US lacks diversity, relies heavily on external inputs to maintain crop yields, and contributes to soil and water quality degradation. Using diverse crop rotations and incorporating livestock are promising solutions to these and other problems linked to current cropping systems dominated by maize (Zea mays L.) and soybean (Glycine max (L.) Merr.). To better understand how agricultural diversification comprehensively affects soil health and function, we compared 20 parameters linked to critical soil ecosystem services in 1) a conventional 2-year maize-soybean rotation, and 2) a diverse 4-year maize-soybean-oat (Avena 9 sativa L.)+alfalfa (Medicago sativa L.)-alfalfa rotation that periodically received cattle manure. The strongest and most salient improvements included: 8% reduction in soil resistance to root growth (p=0.006), 16% increase in cation exchange capacity (p=0.001), 157% increase in salt extractable soil carbon (p=0.024), and 62% increase in soil microbial biomass (p=0.017). These comprehensive improvements in general soil functioning coincided with enhanced crop yields, reduced requirement for agricultural inputs, and decreased environmental impacts – all while maintaining profitability. Despite declines in cropping system diversity globally, but especially in the Midwestern US, these results provide strong evidence for benefits of diversification.