HR: 1340h
AN: B43A-0253    [Abstracts]
TI: Evaluating Changes in Organic C and Emission of Greenhouse Gases in a California Agricultural Landscape.
AU: Rolston, D E
EM: derolston@ucdavis.edu
AF: University of California, Davis Department of Land, Air and Water Resources, One Shields Ave., Davis, CA 95616 United States
AU: Hopmans, J W
EM: jwhopmans@ucdavis.edu
AF: University of California, Davis Department of Land, Air and Water Resources, One Shields Ave., Davis, CA 95616 United States
AU: Van Kessel, C
EM: cvankessel@ucdavis.edu
AF: University of California, Davis Department of Plant Sciences, One Shields Ave., Davis, CA 95616 United States
AU: Six, J
EM: jwsix@ucdavis.edu
AF: University of California, Davis Department of Plant Sciences, One Shields Ave., Davis, CA 95616 United States
AU: Paw U, K
EM: ktpawu@ucdavis.edu
AF: University of California, Davis Department of Land, Air and Water Resources, One Shields Ave., Davis, CA 95616 United States
AU: Plant, R E
EM: replant@ucdavis.edu
AF: University of California, Davis Department of Plant Sciences, One Shields Ave., Davis, CA 95616 United States
AU: Hsiao, T C
EM: tchsiao@ucdavis.edu
AF: University of California, Davis Department of Land, Air and Water Resources, One Shields Ave., Davis, CA 95616 United States
AU: Poch, R M
EM: rosa.poch@macs.udl.es
AF: University of California, Davis Department of Land, Air and Water Resources, One Shields Ave., Davis, CA 95616 United States
AU: Shaver, G
EM: gshaver@ucdavis.edu
AF: University of California, Davis Department of Land, Air and Water Resources, One Shields Ave., Davis, CA 95616 United States
AU: Ideris, A J
EM: ajideris@ucdavis.edu
AF: University of California, Davis Department of Land, Air and Water Resources, One Shields Ave., Davis, CA 95616 United States
AU: Lee, J
EM: ecolee@ucdavis.edu
AF: University of California, Davis Department of Plant Sciences, One Shields Ave., Davis, CA 95616 United States
AU: Louie, D T
EM: dtlouie@ucdavis.edu
AF: University of California, Davis Department of Land, Air and Water Resources, One Shields Ave., Davis, CA 95616 United States
AU: MacIntyre, J L
EM: jlmacintyre@ucdavis.edu
AF: University of California, Davis Department of Land, Air and Water Resources, One Shields Ave., Davis, CA 95616 United States
AU: Matista, T A
EM: aamatista@ucdavis.edu
AF: University of California, Davis Department of Land, Air and Water Resources, One Shields Ave., Davis, CA 95616 United States
AU: Evatt, K J
EM: kjevatt@ucdavis.edu
AF: University of California, Davis Department of Land, Air and Water Resources, One Shields Ave., Davis, CA 95616 United States
AU: * King, A P
EM: apking@ucdavis.edu
AF: University of California, Davis Department of Land, Air and Water Resources, One Shields Ave., Davis, CA 95616 United States
AB: A major question in CA agriculture is how much C may be sequestered in soil of irrigated, minimum tillage systems. Our main research goals are to identify and quantify the underlying mechanisms and processes controlling the rate of CO2 and other greenhouse gas emissions versus soil C stabilization as affected by tillage operations. A landscape research approach is used to increase our mechanistic understanding of the biotic and abiotic processes that govern C dynamics under standard and minimum tillage practices. We have selected an irrigated, laser leveled agricultural site in the CA Central Valley for this study. The 70-acre site, located approximately 10 miles northwest of Davis, has been split into two fields. Beginning in the fall of 2003, one field has been managed under standard tillage (ST) and the other under minimum tillage (MT). Each field is instrumented with 1) an eddy-covariance mast to measure field-scale CO2 fluxes, 2) with a 0.62-m2 automated chamber to assess the temporal pattern of CO2 and N2O fluxes, 3) with 36 506-cm2 portable PVC chambers to evaluate the spatial characteristics of CO2, N2O and NO fluxes, 4) with 4 subsurface soil gas probes to measure CO2 and N2O concentrations with depth and 5) with multiple piezometers and tensiometers to monitor the movement of soil water throughout the growing season. Round-up Ready corn was planted in both fields in April 2004. Results from this growing season indicate that the various methods of CO2 measurement compare well with one another. There was no notable difference in soil CO2 flux between tillage treatments, but the eddy-covariance towers measured differences in net CO2 flux between treatments based on differential crop growth patterns. The MT treatment had slightly higher N2O emissions than ST, but N2O and NO emissions were primarily restricted to areas and time periods of fertilizer application. Preliminary results from the 2005 growing season (sunflower crop) indicate similar results. MT corn yield was 73% of that in the ST treatment. Patterns of soil texture, ground water movement, and treatment effects are being explored to help explain the yield gap and other spatial patterns in the data. Upcoming years of the project include continued monitoring of greenhouse gases and soil C dynamics in the two tillage systems, comparison of field data with DNDC and Daycent models, and economic evaluation of the two systems. These results will help provide a realistic assessment of the role CA agriculture can play in C sequestration when land is converted from standard to minimum tillage.
DE: 0402 Agricultural systems
DE: 0428 Carbon cycling (4806)
DE: 0469 Nitrogen cycling
DE: 0485 Science policy (6620)
DE: 0496 Water quality
SC: Biogeosciences [B]
MN: Fall Meeting 2005