Biological soil health indicators respond to tillage intensity: A US meta-analysis

Authors: NUNES, MARCIO - Orise Fellow; KARLEN, DOUGLAS - Retired ARS Employee; Veum, Kristen; Moorman, Thomas; CAMBARDELLA, CYNTHIA - Retired ARS Employee

Submitted to: Geoderma
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/11/2020
Publication Date: 3/18/2020
Citation: Nunes, M.R., Karlen, D.L., Veum, K.S., Moorman, T.B., Cambardella, C. 2020. Biological soil health indicators respond to tillage intensity: A US meta-analysis. Geoderma. 369:114335. https://doi.org/10.1016/j.geoderma.2020.114335.
DOI: https://doi.org/10.1016/j.geoderma.2020.114335

Interpretive Summary: Biological processes are important to nutrient cycling, regulation of gas fluxes, and suppression of root pathogens in soil. This study examined the responsiveness of seven biological indicators of soil health to tillage and cropping system. This meta-analysis extracted data from 302 published scientific articles that allowed comparison of three tillage practices: moldboard plowing (MP), chisel plow (CP), no-tillage in annual crops (NT) and no-tillage in perennial crops (PER). The seven soil health indicators were soil organic C (SOC), microbial biomass C (MBC), microbial biomass N (MBN), soil respiration (Resp), active-C (AC), beta-glucosidase activity (BG) and soil protein (Prot). Adoption of NT or PER resulted in increases in the soil health indicators compared to levels in the MP soils, with indicator levels in CP management being intermediate. The magnitude of these effects were greatest at lower latitudes. Based on this meta-analysis, reducing tillage intensity, planting cover crop and/or minimizing crop residue removal within annual cropping systems can significantly improve soil biological health in the U.S. Finally, we demonstrate that SOC and many other biological indicators are sensitive to management practices, confirming their utility in soil health assessment. The research informs NRCS, state and local agencies, crop consultants and farmers that are interested in soil health.

Technical Abstract: Tillage intensity affects soil microbiological activity in many ways, often driven by changes in soil organic C (SOC) content. The magnitude and direction of those changes, however, depends on inherent (e.g., soil type and texture), experimental (e.g., study duration and sampling depth) and agronomic factors (e.g., cropping system and crop residue management). This nationwide meta-analysis examines published effects of chisel plowing (CP), no-tillage (NT), and perennial cropping systems (PER) relative to moldboard plow (MP) on seven soil health indicators: SOC, microbial biomass C (MBC), microbial biomass N (MBN), soil respiration (Resp), active-C (AC), beta-glucosidase activity (BG) and soil protein (Prot) within four soil depth increments in 302 studies from throughout the United States (U.S.). Overall, converting from MP to CP primarily affected topsoil (0 to =15 cm) SOC, MBC, and Resp, whereas converting from MP to NT significantly increased all seven soil health indicators in the topsoil. Below the topsoil, NT had greater MBC, MBN, Resp, and BG relative to MP (i.e., 15 to 25-cm). The impact of NT was affected by latitude, soil order, time under NT, and cropping system. Among soil orders, management practices had the largest positive effects in Ultisols, Inceptisols, Alfisols, and Mollisols. Those effects were most noticeable at lower latitudes, in systems that included cover crops or residue retention, and in experiments conducted for at least three years. Perennial systems had a positive effect on all soil health indicators at all soil depths (0 to >40-cm). The positive response of PER systems compared to MP was enhanced at lower latitudes and in Alfisols, Inceptisols, Entisols, and Mollisols. Based on this meta-analysis, reducing tillage intensity, planting cover crop and/or minimizing crop residue removal within annual cropping systems can significantly improve soil biological health in the U.S. Finally, we demonstrate that SOC and many other biological indicators are sensitive to management practices, confirming their utility in soil health assessment.