Contrasting soil management systems had limited effects on soil health and crop yields in a North Central US Mollisol

Authors: CRESPO, CECILIA - Orise Fellow; O'Brien, Peter; NUNES, MARCIO - University Of Florida; Ruis, Sabrina; Emmett, Bryan; Rogovska, Natalia; Malone, Robert - Rob; CAMBARDELLA, CINDY - Retired ARS Employee; Kovar, John

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/15/2024
Publication Date: 6/18/2024
Citation: Crespo, C., O'Brien, P.L., Nunes, M.R., Ruis, S.J., Emmett, B.D., Rogovska, N.P., Malone, R.W., Cambardella, C., Kovar, J.L. 2024. Contrasting soil management systems had limited effects on soil health and crop yields in a North Central U.S. Mollisol. Soil Science Society of America Journal. https://doi.org/10.1002/saj2.20716.
DOI: https://doi.org/10.1002/saj2.20716

Interpretive Summary: Growing corn and soybean in the central United States can produce very high yields, but continuously producing these crops has the potential to harm soil health. Soil health, which refers to how well soil can perform all its functions now and into the future, can be affected by the many field-related operations that go along with producing growing corn and soybean, such as tillage, high nitrogen fertilization, and long periods of time where plants are not growing. Soil health can be assessed using individual measurements of soil properties, called indicators, or it can be assessed with a tool using lots of different soil properties to create a soil health index. In this study, researchers measured soil health in Iowa soils growing corn and soybean with typical farming practices compared to soils using managing practices such as cover crops, reduced tillage, and different fertilizer applications. Soil health was assessed using both individual indicators and an index from the Soil Management Assessment Framework (SMAF). In most instances, soil health was not affected by any of these management practices. However, one soil physical property, aggregate stability, which is the ability of soil particles to bind together, did change due to the different management systems practiced. These findings suggest that soil health indicators or indices may not always be a good way to determine the effect of farming management practices in this region because they did not change in this study. In contrast, this study identified that aggregate stability is an important indicator of soil health that does change due to management practices in relatively short, less than 5 years, time periods. These results are important to land managers, producers, and crop advisors because they show that soil health was not greatly affected by management in this region. Additionally, the results are important to researchers because they highlight a critical soil property, aggregate stability, that may need to be reevaluated to be more important in soil health indices like SMAF.

Technical Abstract: Management practices such as relay cropping, cover crops, and no-tillage may promote soil health in the North Central US. However, soil health indicators in corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] production systems involving multiple management aspects are not well documented. The objective of this study was to determine the sensitivity of soil health metrics and the Soil Management Assessment Framework (SMAF) to contrasting management practices in a high soil organic carbon (SOC) soil in a North Central U.S. Different management systems, including conservation tillage and nitrogen (N) fertilization strategies, cover cropping, and camelina [Camelina sativa L. Crantz] relay intercropping were compared to a conventional corn-soybean system. The management practices had been implemented for varying lengths of time, between 5 and 20 years, but this study found that the different management systems did not improve soil health indicators as compared to the conventional corn-soybean rotation. Aggregate stability was the only soil health indicator to change due to management, where no-till with cover crops increased aggregate stability by 38% compared with camelina relay crop. The SMAF scores for all the soil quality indices were unaffected by treatments. Nevertheless, the SMAF scores indicated that the evaluated soils are functioning at over 90% of their potential. Overall, crop yields were more closely related to weather conditions and management systems than to soil health indicators. Soybean yields were only decreased in the camelina relay cropping system, ranging between 1-2 Mg ha-1 lower than the other systems. Alternatively, corn yields were only lower (up to 70%) in the treatment that received no N fertilization. Ultimately, these findings suggest that soil health indicators are resilient to change in these highly productive Mollisols and may not be closely correlated with crop yields.