Wednesday, November 15, 2006

Field scale greenhouse gas emissions in a furrow-irrigated field under standard and minimum tillage.

Amy King, Dennis Rolston, Jan Hopmans, Chris Van Kessel, Johan Six, Richard Plant, Kyaw Tha Paw U, Jeannie Evatt, Dianne Louie, and Tony Matista. "University of California, Davis", One Shields Ave., Davis, CA 95616, United States of America

This study aimed to quantify CO2 and N2O release from an irrigated field in California’s Sacramento Valley in an effort to determine greenhouse gas mitigation potentials through minimum tillage (MT) practices.  The 30 ha, laser-leveled field site was monitored with portable static chambers for CO2 and N2O flux from the soil surface in standard tillage (ST) and MT treatments from September 2003 through August 2006.  The field was also equipped with 2 eddy-covariance masts and 2 continuously sampling auto-chambers, to estimate total C budgets at the field scale and temporal changes in soil CO2 flux, respectively.  The crop grown on the field was different each year; the first year it was wheat, then corn, sunflower and chick peas.  Overall, there was very little difference in CO2 flux between the two tillage treatments.  Flux numbers were highly spatially variable, well-correlated with air and soil temperature, and dependent on soil moisture and the degree of soil disturbance in the 2 tillage systems.  Chambers placed over the crop roots showed higher CO2 flux during the growing season due to root respiration, but did not differ significantly between the 2 treatments.  N2O flux was negligible in both systems until a fertilization and irrigation event occurred in each growing season, at which point the MT treatment showed slightly higher fluxes.  CO2 and N2O data from this site is being used in several models that will enable us to predict greenhouse gas emissions from similar agricultural systems in the California landscape.  Results from this site indicate that short-term MT may not significantly decrease the contribution to global warming by irrigated agroecosystems and thus may not be a beneficial strategy for greenhouse gas mitigation.

Handout (.pdf format, 2306.0 kb)