Effects of nitrate and organic carbon additions on denitrification in two artificially flooded soils

The effect of nitrate and organic carbon additions on denitrification was studied in one peaty and one sandy soil artificially flooded by stream water. The study was conducted during 3 years with regular sampling occasions from October to May. NO3- amendment enhanced the denitrification activity five times out of seven in the peaty soil, all occurring in spring. In the sandy soil, denitrification was enhanced six times out of thirteen, five of these occurring in spring. Organic carbon added as acetate and glucose resulted in increased denitrification once out of eight times in the peaty soil and twice out of fifteen times in the sandy soil, Of these three occasions, one occurred during a period of high NO3- concentration in the stream water, which may have caused a temporary lack of an electron donor. The results show that NO3- is a stronger regulator of denitrification than organic carbon in both soil types. Even in the sandy soil the pool of organic carbon was sufficient to fuel denitrification at natural NO3- concentrations.