Monday, November 5, 2007 - 2:20 PM
110-5

Dissolved Organic Carbon and Sediment Losses from Flooded Rice Fields in Northern California.

Matthew D. Ruark1, Bruce Linquist2, James Hill3, Chris A. Greer4, Randall G. Mutters4, Johan Six5, and Chris Van Kessel6. (1) Plant Sciences, University of California-Davis, One Shields Ave., Davis, CA 95616, (2) UC Davis, One Shields Ave, Davis, CA 95616, (3) One Shields Avenue - 249 Hunt Hall, University of California-Davis, University of California-Davis, Department of Plant Science, Mail top 1, Davis, CA 95616, (4) University of California Cooperative Extension, PO Box 180, Colusa, CA 95932, (5) University of California-Davis, Davis, CA 95616, (6) 1210A PES Building, University of California-Davis, University of California-Davis, Dept. of Plant Sciences, Davis, CA 95616-8515

In California’s Sacramento Valley, approximately 200,000 hectares of land is used for rice production.  The regulated reduction of rice straw burning has increased the amount of land flooded during the winter which may increase dissolved organic carbon (DOC) and sediment losses to surface waters.  High concentrations of DOC in surface waters have been linked to the formation of trihalomethanes during drinking water disinfection.  The overall objective of this study was to determine the effects of straw management on seasonal and yearly DOC and sediment loading from rice production fields into the Sacramento Valley surface waters.  Between April 2006 and April 2007, paired fields (straw-incorporated vs. burned) at four locations throughout the Sacramento Valley were studied.  Outflows were measured with pressure sensors and rectangle weirs.  Each grower managed their water differently causing a wide range of water losses (10,000 to 450,000 m3 yr-1).  At the onset of drainage early in the growing season, incorporated fields had greater (>14 mg L-1) DOC concentrations than burned fields in two of four field sites.  However, the flow-weighted (FW) DOC concentrations over the entire growing season were similar among all fields.  During winter flooding, incorporated fields had much greater DOC concentrations (24 to 75 mg L-1) than burned fields (7 to 18 mg L-1) at the onset of drainage and maintained higher concentrations through the winter.  Yearly losses of sediment ranged from 2 to 1100 kg ha-1.  Yearly losses of DOC and sediment were strongly correlated with yearly water loss.  The results suggest that yearly losses in DOC and sediment may be more affected by water management compared to straw management.  However, straw-incorporated fields had larger seasonal spikes in DOC concentration compared to burned fields, which may contribute to seasonal spikes of DOC concentrations in the Sacramento River.

Back to Management Effects on Water Quality
Back to S06 Soil & Water Management & Conservation

Back to The ASA-CSSA-SSSA International Annual Meetings (November 4-8, 2007)