Denitrification from a Yolo loam field profile was studied in relation to the influence of soil-water content, organic carbon source, and temperature. Field plots were intensely instrumented with soil atmosphere samplers, soil solution samplers, and tensiometers. The two soil-water pressure treatments were -0.01 and -0.05 bars in the topsoil. Three levels of soil carbon were studied by evaluating plots cropped with ryegrass, uncropped plots, and plots amended with manure. Experiments were conducted at soil temperatures of 8 and 23C. Fertilizer was applied as KNO3 enriched with 15N. The flux of volatile gases at the soil surface was measured from the accumulation of N2O and 15N2 beneath an air-tight cover placed over the soil surface for 1 or 2 hours per day. Denitrification at 23C ranged from 73% of the fertilizer N for the manure treatment at -0.01 bar to 1% for the uncropped treatment at -0.05 bar. At 8C, denitrification ranged from 11% for the manure treatment at -0.01 bar to zero for the uncropped plots. The N2O flux at the soil surface varied between 5 and 26% of total denitrification.

"November 1977." "Prepared under Grant No. R804259." Includes bibliographical references (pages 72-73).