Production of the greenhouse gas (GHG) nitrous oxide (N2O) results from the activity of soil microorganisms. Nitrogen (N) inputs, soil moisture, and carbon (C) availability stimulate the production of N2O which contributes about one third of the total GHG emissions from California’s agriculture sector. Crop yields and cumulative N2O emissions were measured for two years in tomato, wheat, lettuce, and rice cropping systems fertilized at various N rates. Alfalfa was also monitored. The N2O emissions were observed to occur mainly during the growing season from soils with high moisture content after N fertilizer applications. In most cases, N2O emissions increased with increasing N rates. The levels of N application rates that resulted in the lowest N2O emissions while not reducing yields were identified. In alfalfa, a recently established one-year old stand released half as much N2O compared to a 5-year old stand. This study generated a database of field-level N2O emission measurements and accompanying soil moisture and temperature, and mineral N values that can be used to calculate the percentage of applied N released as N2O to estimate emissions on a larger scale, calibrate and validate N2O emission biogeochemical models, and develop recommended best management practices.
For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753
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