ACRE - Agricultural Conservation for Resilient Environments

Soil Carbon Amendment  (NRCS #336)

Applicable Systems

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About

Soil carbon amendment1 is any organic material, derived from plants or animal byproducts, that is applied to the soil to enhance physical, chemical, and/or biological characteristics in croplands, pastures, or rangelands. Soil carbon amendments include animal residue, manure, compost, biochar, mulch, biosolids, and sawdust. The NRCS also recognizes biostimulants as soil amendments when they are applied to soil, improve soil properties, and contribute to soil organic matter and carbon inputs2.

Key aspects and considerations:

  • Complete soil and carbon amendment analysis prior to application.
  • Use compost produced in controlled aerobic and biological decompositions, and tested for several parameters and quality assurance.
  • Adjust nutrient and pest management for the specific amendment type and purpose.
  • Test soil at least three years after application to monitor long-term impacts.
  • Ensure products comply with federal, state, and local laws and regulations.
  • Preferably use mature composts to avoid GHG emissions.
  • Consider challenges associated with hauling bulky materials and spreading large volumes.
  • Adjust for evolving knowledge on optimal rates, material types, and long-term impacts.

Benefits and Limitations

ACRE CategoryBenefitsLimitations
Soil Health

  • Improves aggregate stability and soil structure.

  • Facilitates penetration of plant roots.

  • Can improve long-term soil resilience.

  • N/A
Water Management

  • Improves water infiltration and soil water-holding capacity.

  • Reduces runoff.

  • Reduces irrigation requirements and water usage.

  • N/A
Nutrient Management

  • Increases nutrient cycling and soil cation exchange capacity.

  • Promotes slow-release nutrition.

  • Helps retain nutrients due to reduced runoff.

  • Can reduce fertilizer requirements.

  • Variable nutrient content, salts, contaminants, and stability.

  • Requires careful nutrient management to avoid over application.

Agricultural Production
  • Increases yield in the long term.

  • Field-level results can be inconsistent and variable among soil types.

  • Hard to predict outcomes due to composition inconsistency.

  • Benefits may not be immediate.

Biodiversity and Wildlife

  • Supports and stimulates microbial growth3.

  • Enhances soil biota population and diversity.

  • N/A
GHG Emission
  • Enhances carbon sequestration and adds stable carbon to soil3.
  • Can increase N2O if amendments contain high nitrogen, such as manure-based composts, or in wet and poorly aerated soils.
Economics

  • Decreases costs related to reduction of external inputs, such as fertilizers, pesticides, and irrigation water.

  • Increases economical return related to higher yield in the long term.

  • NRCS Environmental Quality Incentive Program (EQIP) provides partial cost-share payments.

  • High upfront costs associated with material purchase/production, transportation, and application.

Impact on Agricultural Resilience

  • Promotes resilience to drought, heat waves, or heavy rains.
  • Reduces external water and fertilizer needs.
  • Promotes plant growth and aboveground biomass, thus enhancing carbon assimilation via photosynthesis3.

Regional Applicability

  • A research team at University of Nebraska--Lincoln, in collaboration with the City of Lincoln and Oregon Biochar Solutions, conducted a 16-acre field trial using biochar and biosolids to support the biochar industry in the Midwest.
  • University of Minnesota Extension provides some guidelines for manure management while reducing air and water quality issues.
  • Natural mulches are widely applied as soil amendment to a range of cropping systems, including those that are cultivated in the Midwest, small farms and gardens.

Case Studies

  • Meet Janaki and his wife Annie Dugan, who operate a certified organic farm in Wrenshall, MN. They manage a winter rye cut-and-carry mulch system for several crops. "The better we can treat the soil, the healthier it is, the better crops do, the more resilient they are," Janaki said.
  • Nick Cuchetti is a family farmer in Luebbering, MO. He pours the biochar into soil beds where he plants vegetables to sell at a farmer's market. "You put it in soil, it's just there. You can just forget about it. It's gone," he said.

Resources

References

  1. USDA-NRCS (2022). Soil Carbon Amendment Standard Document, Code 336. https://www.nrcs.usda.gov/sites/default/files/2022-11/336-NHCP-CPS-Soil-Carbon-Amendment-2022.pdf
  2. Rubin, R., Oldfield, E., Lavallee, J., Griffin, T., Mayers, B., & Sanderman, J. (2023). Climate mitigation through soil amendments: quantification, evidence and uncertainty. Carbon Management, 14(1), 2217785. https://doi.org/10.1080/17583004.2023.2217785
  3. Enebe, M. C., Ray, R. L., & Griffin, R. W. (2025). Carbon sequestration and soil responses to soil amendments - A review. Journal of Hazardous Materials Advances, 18, 100714. https://doi.org/10.1016/j.hazadv.2025.100714
  4. USDA-NRCS (2022). Soil Carbon Amendment Conservation Practice Overview (Code 336). https://www.nrcs.usda.gov/sites/default/files/2022-11/336-NHCP-PO-Soil-Carbon-Amendment-2022.pdf
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Soil Carbon Amendment photo 1

Photo 1: Biochar is applied to lettuce in a Minnesota field.

Courtesy of USDA-ARS, Photo by Amanda Bidwell.

Soil Carbon Amendment photo 2

Photo 2: In Oregon, a landowner creates biochar from tree debris and applies it to the landscape.

Oregon NRCS photo by Tracy Robillard. Attribution: "biochar pile in forest" by NRCS Oregon, CC BY-ND 2.0.

  • Purdue University
  • University of Illinois Urbana-Champaign
  • University of Nebraska-Lincoln
  • Iowa State University
  • Midwest Regional Climate Center
  • U.S. Department of Agriculture

This research is supported by Agriculture and Food Research Initiative Competitive Grant 2023-67023-39246 from the USDA National Institute of Food & Agriculture.

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