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.