DIFFUSION ANALYSIS OF N2O CYCLING IN A FERTILIZED SOIL

The behavior of nitrous oxide (N2O) in fertilized soil was studied in terms of soil fluxes, the production rates at various depths and the t urnover in soil. The diffusive losses of N2O to the atmosphere calcula ted from soil N2O profile compared favorably with the flux directly de termined with a closed chamber technique. The estimate of N2O producti on rates at several depths demonstrated that the sites of N2O producti on was only near the soil surface. The calculated residence time of N2 O in the entire soil column studied was only 1.4 hour during active em ission period and less than 1 day even in the later period having trac e N2O emission. The prolonged N2O emission observed after the active p hase was due likely to a lasting N2O production rather than a supply f rom the soil N2O reservoir. The results suggested that most N2O in soi l was emitted quite promptly to the atmosphere after its production. A minor role of soil as an N2O reservoir is emphasized from the viewpoi nt of the origin of groundwater N2O.