Wednesday, November 15, 2006

Contribution of irrigation and storm water to total C and N budgets of a furrow-irrigated California agricultural field.

Amy King, Jeannie Evatt, and Jan Hopmans. "University of California, Davis", One Shields Ave., Davis, CA 95616, United States of America

The study area is a 30-ha, laser-leveled, furrow-irrigated field site in California’s Sacramento Valley, with a diverse suite of measurements conducted to assess the effects of standard tillage versus minimum tillage on soil C sequestration and greenhouse gas emissions. Incoming irrigation water and outgoing run-off water from irrigation and storm events were sampled for total suspended solids (TSS), dissolved organic carbon (DOC), dissolved organic nitrogen (DON), nitrate-N, ammonium-N, total C and total N in the sediment. Tillage treatment had no significant effect on water or sediment composition. TSS in incoming vs. outgoing irrigation water were variable, being higher in the outgoing water in some events and lower in others, but DOC concentration was consistently higher in the runoff water. NO3-N levels exceeded drinking water quality standards only in the irrigation event after sidedressing with nitrate fertilizer of the sunflower crop. NH4-N levels remained very low throughout the period of study. Storm run-off also contained very little dissolved N and DOC levels. We pose that the role of irrigation water in C budgets of agricultural systems is a significant factor in determining total C sequestration potential.

Handout (.pdf format, 1113.0 kb)