Skip to main content
ARS Home » Midwest Area » Ames, Iowa » National Laboratory for Agriculture and The Environment » Agroecosystems Management Research » Research » Publications at this Location » Publication #417180

Research Project: Managing Nutrient, Carbon, and Water Fluxes to Provide Sustainable and Resilient Cropping Systems for Midwestern Landscapes

Location: Agroecosystems Management Research

Title: Organic cropping systems enhance soil health indicators in a Mollisol of the US Corn Belt

Author
item Ruis, Sabrina
item Kovar, John
item Wacha, Kenneth
item Carney, Derek
item O'Brien, Peter
item DELATE, KATHLEEN - Iowa State University
item CAMBARDELLA, CYNTHIA - Retired ARS Employee

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/5/2024
Publication Date: 12/23/2024
Citation: Ruis, S.J., Kovar, J.L., Wacha, K.M., Carney, D., O'Brien, P.L., Delate, K., Cambardella, C.A. 2024. Organic cropping systems enhance soil health indicators in a Mollisol of the U.S. Corn Belt. Soil Science Society of America Journal. 89(1). https://doi.org/10.1002/saj2.20795.
DOI: https://doi.org/10.1002/saj2.20795

Interpretive Summary: Organic farming is an increasingly popular practice due to soil, human, and environmental health benefits. Organic farming may sustain soil health compared with conventional farming due to the practices embedded within the system itself. Studies comparing organic farming with conventional row-crop farming in the long term are few. We compared the impacts of conventional and organic cropping systems on soil health indicators. The experiment was managed under these cropping systems for 9 years and took place on a highly fertile central Iowa soil. The conventional system was a corn and soybean rotation. The organic rotation was a corn, soybean, oat/alfalfa, and alfalfa rotation. The conventional and organic rotations were also compared with an organic perennial pasture. The organic systems improved soil microbial biomass, activity, and food sources compared with the conventional system. They also improved soil structure, but not soil carbon content or most fertility indicators. They had varying effects on soil fertility indicators. The use of perennial crops, animal manure, reduced tillage frequency, and increased plant inputs in the organic systems contributed to improvement in these soil health indicators. In this highly fertile soil, organic systems can improve soil biology and soil structure, but not most fertility indicators. The study findings support organic farmer observations regarding soil health. It facilitates scientist, policymaker, and farmer understanding of organic farming impacts on soil health in fertile soils.

Technical Abstract: The use of organic cropping systems may potentially improve soil and environmental health relative to simplified conventional systems due to the use of extended crop rotations, perennial crops, and animal manure. However, studies evaluating the impacts of organic row crop systems on a suite of soil health indicators relative to conventional systems across time are few. Thus, our objective was to assess how cropping system [conventional corn (Zea mays L.)-soybean (Glycine max L.) vs organic corn-soybean-oat (Avena sativa L.)/alfalfa (Medicago sativa L.)-alfalfa vs organic perennial pasture)] and duration of management affect surface soil health indicators (soil biological, chemical, and physical properties) after 1-9 yr of management in a central Iowa Mollisol. Overall, the organic rotation improved 6 of 14 soil health indicators compared with the conventional system and the organic pasture 8. The improved indicators included soil biological indicators, labile C and N pools, and wet-aggregate stability, but not organic C or total N concentrations. Organic systems had fewer effects on most soil chemical properties. The conventional system reduced soil C by 0.35 g kg-1 yr-1 (r= -0.84, n= 9, p= 0.005), unlike the organic systems in which soil C levels were generally maintained. The changes in soil health indicators were attributed to reductions in tillage frequency, use of perennials and manure, and differing plant residue amounts among the three systems. In conclusion, organic cropping systems can enhance soil biological and related indicators in the medium-term, but have fewer effects on soil fertility indicators under the conditions of this study.