Sources of nitrous oxide production following wetting of dry soil

Abstract

Production of N2O was detected within 30 min of adding water to very dry soil (matric water potential < -9 MPa) sampled at the end of the dry season from an annual grassland of California, U.S.A. Using C2H2 to inhibit nitrification, we demonstrate that nitrification was a modest source of N2O in sieved soil wetted to a water content below field capacity, but that denitrification was the major source of N2O in sieved soils wetted to a water content above field capacity and in intact cores wetted either below or above field capacity. Significant abiological sources of N2O were not detected. De novo enzyme synthesis began within 4-8 h of wetting, and denitrifying enzyme activity doubled within 26 h, indicating that denitrifying bacteria can quickly transform their metabolic state from adaptation to severe drought stress to rapid exploitation of changing resources. © 1991.