Soil organic carbon fractions influenced by organic input diversity and tillage frequency after 25 years in Mid-Atlantic US grain cropping systems

Authors: BONIFACE, HELEN - Soil Health Institute; Cavigelli, Michel; White, Kathryn; THAPA, RESHAM - Tennessee State University; SMITH, SOPHIE - University Of Maryland; Mirsky, Steven; TULLY, KATHERINE - University Of Maryland

Submitted to: Agriculture, Ecosystems & Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/15/2025
Publication Date: 8/1/2025
Citation: Boniface, H.S., Cavigelli, M.A., White, K.E., Thapa, R., Smith, S., Mirsky, S.B., Tully, K.L. 2025. Soil organic carbon fractions influenced by organic input diversity and tillage frequency after 25 years in Mid-Atlantic US grain cropping systems. Agriculture, Ecosystems & Environment. 394. Article e109869. https://doi.org/10.1016/j.agee.2025.109869.
DOI: https://doi.org/10.1016/j.agee.2025.109869

Interpretive Summary: Soil organic matter provides multiple benefits to agricultural systems including improved nutrient availability, water infiltration, and root growth, which are crucial to crop yield. However, the impact of management on soil organic matter stocks and pools remains uncertain. USDA-ARS researchers collaborated with university colleagues to investigate changes in soil organic matter stocks between 1996 and 2021 (25 years) in the five cropping systems that comprise the long-term Farming Systems Project at the USDA-ARS Beltsville Agricultural Research Center in Maryland. They found decreases in soil organic matter at depths of 0-20 inches in all systems except a 6-year organic rotation that included a perennial forage crop. In the surface soil (0-8 inches), soil organic matter decreased in all but 3-year and 6-year organic rotations. This work identified factors that support larger quantities of organic matter protected within soil aggregates and greater stability of soil organic matter stocks: 1) higher quality organic matter inputs (meaning amendments that increase microbial-use efficiency such as poultry litter, legume cover crops, and perennial crops) and/or 2) reduced soil disturbance. USDA-NRCS technical service providers, university Extension personnel, and other crop consultants can use these results to make management recommendations to farmers needing to increase soil organic matter to support and improve cash crop yields.

Technical Abstract: Due to multiple benefits, there is a need to identify management strategies that maintain and increase soil organic carbon (SOC) in agroecosystems. In the U.S. Mid-Atlantic region, cultivation has caused greater SOC loss than in other regions due to high rainfall and mild temperatures facilitating SOC mineralization. Changes in SOC stocks between 1996 and 2021 (25 years) were examined in the Farming Systems Project (FSP) in central Maryland, U.S. The FSP includes five grain cropping systems that vary by: conventional vs. organic management, tillage frequency, crop rotation complexity, legume cover crop use, and fertility inputs. Carbon stabilization (via permanganate oxidizable carbon (POX-C) and in soil aggregates) and SOC stocks were compared across systems in 2021. We found SOC loss (0-50 cm) in all systems except for a 6-yr organic rotation that included a perennial forage crop. In the surface soil (0-20 cm), SOC decreased in all but 3-yr and 6-yr organic rotations; the 3-yr rotation received greater poultry litter inputs than all other systems. Systems receiving higher quality C inputs (e.g., poultry litter, legume cover crops) and/or reduced soil disturbance had larger quantities of SOC protected within micro- or macroaggregates. Overall, trends suggest greater stability of SOC stocks in systems with reduced tillage, increased cropping system complexity, and poultry litter inputs compared to other systems after 25 years. This research also highlights the importance of collecting baseline SOC levels at the start of experiments to determine the trajectory of soil C storage in agricultural soils.