Nitrogen transformations in a flooded soil in the presence and absence of rice plants: 2. Denitrification

Abstract

Denitrification rates (d) in a flooded alkaline clay were measured following addition of either 15NO3/- 15NH4/+ to the floodwater, by collecting evolved N2 + N2O in an enclosure in the absence or presence of rice plants. Similar estimates of d were obtained in the 15NO3/- treatment when the isotopic composition of the enclosed atmosphere was determined using arc redistribution or direct mass spectrometric analysis. Approximately 90% of the gaseous products of denitrification were physically trapped in the soil five days after 15NO3/- addition. Mechanical shaking of the soil-water system was an effective method for releasing entrapped gas. Denitrification showed a marked diurnal variation in ..