Project at a Glance

Title: Calibrating, validating, and implementing process models for California agriculture greenhouse gas emissions

Principal Investigator / Author(s): Li, Changsheng

Contractor: University of New Hampshire

Contract Number: 10-309

Research Program Area: Climate Change, Atmospheric Processes

Topic Areas: Greenhouse Gas Emissions, Modeling


The goal of the project is to build up a modeling tool to quantify soil greenhouse gases (GHG) emitted from agricultural production in California (CA) under current climate, soil and management conditions. We conducted (1) field data collection and analysis, (2) model calibration, validation and comparison tests, (3) regional simulation, and (4) tool development to help ARB with greenhouse gas inventory and mitigation studies. As nitrous oxide (N2O) is the major greenhouse gas for CA agricultural production, we focused our analyses on N2O emissions.

Daily flux data of N2O were collected from a number of crops in 2003-2011. The Denitrification-Decomposition (DNDC) model was tested against observations with encouraging results (R=0.80, slope=0.97 and p=0.001). The modeled results indicated that (1) N2O is the leading GHG from the California croplands; (2) the California croplands seem sequestering C at -9.97 Tg CO₂ equivalent yr⁻ with a uncertain of 5.17 Tg CO₂ equivalent yr⁻; and (3) the CA agriculture seems an overall GHG sink regarding its contribution to global warming (-4.60 Tg CO₂ equivalent yr⁻) although the uncertainty is large (10.33 Tg CO₂ equivalent yr⁻). For 2011, the major N2O emitter crops are corn (28%), lettuce (11%), grape (11%), cotton (8%), and rice (6%); rice is the sole CH₄ emitter; the major CO₂ emitters are cotton (37%) and tomato (27%); and the major CO₂ sequestering crops are alfalfa (35%), corn (36%) and grape (16%). Manure amendment and crop residue incorporation are the major sources for soil C sequestration.

For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753

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