Methods for Cropland and Grazing Land Systems
Effective beginning 5/20/2025: Please note this site is under review and content may change.
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Ogle, S.M., P.R. Adler, G. Bentrup, J. Derner, G. Domke, S. Del Grosso, J. Lehmann, M. Reba, D. Woolf. 2024. Chapter 3: Quantifying greenhouse gas sources and sinks in cropland and grazing land systems. In Hanson, W.L., C. Itle, K. Edquist. (eds.). Quantifying greenhouse gas fluxes in agriculture and forestry: Methods for entity-scale inventory. Technical Bulletin Number 1939, 2nd edition. Washington, DC: U.S. Department of Agriculture, Office of the Chief Economist.
Chapter 3: Quantifying Greenhouse Gas Sources and Sinks in Cropland and Grazing Land Systems
This chapter provides methodologies and guidance for reporting greenhouse gas (GHG) emissions and sinks at the entity scale for cropland and grazing land systems. The guidance focuses on methods for estimating the influence of land use and management practices on GHG emissions (and sinks) in crop and grazing land systems.
Croplands include:
- Those producing cultivated crops such as row or close-grown crops including corn, soybeans, wheat, and vegetables.
- Those producing non-cultivated crops including hay, perennial crops, and horticultural crops.
- Rice grown on natural or constructed wetlands.
- Wetlands drained for crop production.
- Agroforestry systems such as alley cropping, shelterbelts, and riparian buffers.
- Reserve cropland.
Grazing lands include:
- Rangeland, a land cover or use composed of grasses, grass-like plants, forbs, shrubs, and trees. Includes:
- Natural lands that have not been cultivated and consist of a historical complement of adapted plant species.
- Natural (go-back lands, old-field) or converted revegetated lands that are managed like native vegetation.
- Pastureland, a land use in which introduced or domesticated (tame) and/or native forage species mixtures are established that can be grazed and/or occasionally hayed or deferred for environmental purposes.
As these systems are managed in a variety of ways, resulting in varying degrees of GHG emissions or sinks, a single method is provided for each of the GHG emission sources (and sinks). Chapter 3 provides methods for quantifying the following emissions:
- Emissions from biomass and litter carbon stock changes
- Emissions from soil organic carbon (SOC) stock changes for mineral soils
- Emissions from SOC stock changes for organic soils
- Direct and indirect nitrous oxide (N2O) emissions from mineral soils
- Direct N2O emissions from drainage of organic soils
- Methane (CH4) flux for non-flooded soils
- CH4 emissions from rice cultivation
- CO2 emissions from liming
- Non-CO2 emissions from biomass burning
- CO2 emissions from urea fertilizer application
These emissions can be influenced by the select practices used, as the influence of one practice can depend on another practice. These emissions can also be reduced through mitigation efforts. Recognizing the complexities associated with management, the net impact of management changes on emissions can be estimated and the amount of mitigation quantified using the methods in this chapter.
