Temporal Patterns of Soil Denitrification: Their Stability and Causes

Abstract

AbstractThe temporal stability of denitrification activity was assessed by monitoring N2O production in 30 rings installed in an acid sandy loam soil in which N2O was the only gaseous product of denitrification. When soil water was kept at field capacity or above, in the absence of NO3 limitation, some locations showed high denitrification compared with the average activity. These high‐activity locations persisted for up to several weeks. The ranking of locations with respect to denitrification rates was more stable over time than would have been expected due to chance alone. Additions of particulate organic matter (POM) that stimulated denitrification within 2 h in anaerobic soil slurries did not increase denitrification until 5 d after addition to soil cores. The increase in denitrification was preceded by an increase in respiration. The denitrification activity within the “hot spots” created by addition of POM was not limited by diffusion of NO3 in the soil. The addition of glucose 9 d before the injection of POM into field rings reduced the lag time preceding increased denitrification. Therefore, the delayed response of denitrification following POM addition in aerobic soil probably reflects the time required to establish an anaerobic soil volume.