Résumé
Coupled nitrification-denitrification and potential denitrification were measured as ^sup 15^N^sub 2^O and ^sup 15^N^sub 2^ evolution rates in ammonium sulphate-treated rice soils with or without Terrazole [5-ethoxy-3 (trichloromethyl) 1,2,3 Thiadizole] under laboratory and field conditions. The greatest coupled nitrification-denitrification activity was found after drying and rewetting the soil, with maximum values of 322 ng N cm^sup -2^ h^sup -1^in the laboratory and 90.8 ng N cm^sup -2^ h^sup -1^ in the field. These ^sup 15^N^sub 2^O + ^sup 15^N^sub 2^ evolution rates were about 10 times lower than potential denitrification in these soils. These results and the observed decrease in ^sup 15^N^sub 2^O + ^sup 15^N^sub 2^ evolution rate in soils treated with Terrazole (60% under laboratory conditions and 52% under field conditions) indicate that denitrification was limited by coupled nitrification-denitrification activity. Oxygen and previous addition of ammonium sulphate appear to control the rate of ^sup 15^N^sub 2^O + ^sup 15^N^sub 2^ evolution in ammonium sulphate-fertilised soils.[PUBLICATION ABSTRACT]