Constraints on mineral-associated and particulate organic carbon response to regenerative management: carbon inputs and saturation deficit

Authors: KING, ALISON - Colorad0 State University; AMSILI, JOSEPH - Iowa State University; CÓRDOVA, S. CAROLINA - University Of Nebraska; CULMAN, STEVE - The Ohio State University; FONTE, STEVEN - Colorado State University; KOTCON, JAMES - West Virginia University; MASTERS, MICHAEL - University Of Illinois; MCVAY, KENT - Montana State University; Olk, Daniel - Dan; PRAIRIE, AARON - Colorado State University; SCHIPANSKI, MEAGAN - Colorado State University; Schneider, Sharon; Stewart, Catherine; COTRUFO, M. FRANCESCA - Colorado State University

Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/13/2024
Publication Date: 5/1/2024
Citation: King, A.E., Amsili, J.P., Córdova, S.C., Culman, S., Fonte, S.J., Kotcon, J., Masters, M.D., McVay, K., Olk, D.C., Prairie, A.M., Schipanski, M., Schneider, S.K., Stewart, C.E., Cotrufo, M. 2024. Constraints on mineral-associated and particulate organic carbon response to regenerative management: carbon inputs and saturation deficit. Soil & Tillage Research. 238. https://doi.org/10.1016/j.still.2024.106008.
DOI: https://doi.org/10.1016/j.still.2024.106008

Interpretive Summary: Soil organic matter plays important roles in several functions in agricultural soils, yet its formation and accumulation are only partially understood. Here we studied the factors that affected the amount and type of soil organic matter that accumulated in long-term field experiments having cover crops and other organic inputs. We gained a better understanding of soil organic matter accumulation by dividing it into two fractions. These fractions differed in their responses to the amounts of organic inputs and separately to soil properties. We found that long-term accumulation of soil organic matter in the larger and more stable fraction was associated with the long-term amounts of crop root growth. These results help identify important factors for increasing long-term carbon storage in soil. They will be of value to land managers who seek to optimize soil properties and to researchers of soil organic matter.

Technical Abstract: Regenerative management needs to increase soil organic carbon (SOC) to mitigate climate change and enhance food security. Yet, SOC exhibits an unexplained variability in responsiveness to regenerative management. We posited that particulate organic carbon (POC) and its faster turnover responds differently and to different moderators than does mineral-associated organic carbon (MAOC) and its slower turnover. In a global synthesis, increases in POC with regenerative management were smaller but more consistent than increases in MAOC (0.45±0.15 vs. 0.81±0.25 g C kg soil-1). MAOC increases were not constrained by MAOC saturation deficit, so we quantified the effects of carbon (C) inputs on MAOC at 15 United States sites. Long-term root C increases with regenerative management increased MAOC, whereas short-term root C input increased POC, highlighting these fractions’ distinct turnovers. Further study may identify additional SOC moderators, but we emphasize that increasing C inputs, particularly long-term root C, is key to the SOC accrual efficacy of regenerative management.