DENITRIFICATION IN ORTHIC LUVISOL

Denitrification in orthic Luvisols (Praha-Ruzyne) was observed in labo ratory soil experiments of three water saturation levels (100, 200, an d 300% water-filled pore space - WFPS). The 10-day preincubation at 20 to 22 degrees C stabilized the soil system in N-cycle. After that KNO 3 (5 mg NO3-N in 100 g soil) and glucose (5 mg C in 100 g soil) were a dded and the 5-day incubation prolonged the experiment. The reduction of nitrates and the production of N2O showed the direct relationship w ith WFPS and the content of extractable C-ox. One set of every variant was inhibited by acetylene to depress the N2O-reductase activity. The nitrate reduction and N2O production slowed down (18 and 5%) in the v ariant A of 100% WFPS. The values of Eh reached 400 to 300 mV at pH 6 to 8. The amount of extractable C-ox was consumed in 80 to 90%. The re duction of nitrates (50 to 60%) and N2O emissions (10 to 12%) increase d with increasing WFPS (200 to 300%). The content of extractable C-ox decreased to zero and the exogenic carbon source was necessary. The re dox potential was 200 to 180 mV. The CO2 production was adequate. The acetylene inhibition was convenient.