Contribution of nitrification and denitrification to N2O production in peat, clay and loamy sand soils under different soil moisture conditions

Agricultural soils are a significant source of nitrous oxide (N2O). Since mitigation of greenhouse gas emissions is needed in all sectors of society, it is important to identify the processes producing N2O and the factors affecting the production rates in agricultural soils. This study aimed to elucidate the N2O production in peat, clay and loamy sand at four different soil moisture conditions (40, 60, 80 and 100% Water Filled Pore Space). The acetylene inhibition technique was used to evaluate the contribution of nitrification to N2O production. Nitrous oxide production responded markedly to soil moisture in all three soils. The highest N2O production, measured at the wettest soils (100% WFPS), was up to four orders of magnitude higher than that at the dry soils (40% WFPS). In dry conditions N2O production decreased in the order of peat>clay>loamy sand, while in wet conditions the highest N2O production was measured in loamy sand, then in peat, and the lowest in clay soils. Nitrification was the dominant N2O producing process in all the soils at 60% WFPS. In the sandy soil 70% of the total N2O production originated from nitrification, while in the peat soil most of the total N2O production originated from denitrification. Data on processes producing N2O in agricultural soils are needed to develop process-based models that could reduce the uncertainty of the emission estimates in greenhouse gas inventories.