Diurnal Variability in Rate of Emission of Nitrous Oxide from Soils

Abstract

AbstractDiurnal variability in the rate of emission of nitrous oxide (N2O) from Iowa soils was studied by using a chamber technique to measure the N2O emission rates at sites on fertilized and unfertilized soils at 1‐ or 2‐h intervals for periods of from 1 to 5 d. The coefficients of variation for the rates of N2O emission observed at these sites within 24‐h periods ranged from 12 to 66% and averaged 38%. As much as 90% of the diurnal variability observed could be attributed to diurnal N2O emission patterns related to changes in soil temperature. Observations reported suggest that these patterns were caused largely by changes in the solubility of N2O in soil water induced by diurnal changes in soil temperature, that the amplitudes of these patterns were determined largely by the amounts of water and N2O in the surface soil, that the times of minima and maxima in these patterns were determined by the depth at which temperature‐induced changes in the solubility of N2O in water were significant, and that neither the amplitudes nor the times of minima and maxima in these patterns can be predicted solely from soil temperature. Data reported show that there is no short time during a 24‐h period that is always satisfactory for assessing the amount of N2O evolved during that period.