Keywords: nitrous oxide, N2O emissions, agricultural soil, fertilisers, oxygen availability, denitrification, global warming
Nitrous oxide emission from agricultural soils
Anthropogenic nitrogen loading, particularly fertiliser usage in agricultural soils is thought to be a potentially important source of nitrous oxide (N2O) emission, which can be controlled by properly managed fertiliser usage. In this research, laboratory scale experiments were conducted to evaluate N2O production and emission from agricultural soils under variable oxygen availability conditions. N2O was observed to be released from the reactors in the absence of oxygen as well as at low concentrations of oxygen. With the increase of oxygen concentration, N2O production decreased. In addition, N2O emission was found to coincide with corresponding nitrate (NO3−) depletion, indicating that denitrification was the dominating process that was responsible for N2O production. The depletion of NO3− was described by the sum of two exponential functions, i.e., NO3− reduction for N2O and NO3− reduction for N2. The simulation of the experimental results using above model demonstrated that N2 production dominated over N2O production in the absence of oxygen. Both N2O production rate and N2 production rate decreased with the increase of oxygen concentration. However, the decrease of N2 production rate was more pronounced than that of N2O production rate.