N2O emission characteristics and its affecting factors in rain-fed potato fields in Wuchuan County, China.

Representing an important greenhouse gas, nitrous oxide (N2O) emission from cultivated land is a hot topic in current climate change research. This study examined the influences of nitrogen fertilisation, temperature and soil moisture on the ammonia monooxygenase subunit A (amoA) gene copy numbers and N2O emission characteristics. The experimental observation of N2O fluxes was based on the static chamber-gas chromatographic method. The ammonia-oxidising bacteria (AOB) and ammonia-oxidising archaea (AOA) gene copy numbers in different periods were measured by real-time polymerase chain reaction (PCR). The results indicated that rain-fed potato field was a N2O source, and the average annual N2O emission was approximately 0.46 ± 0.06 kgN2O-N/ha/year. N2O emissions increased significantly with increase in fertilisation, temperatures below 19.6 °C and soil volumetric water content under 15%. Crop rotation appreciably decreases N2O emissions by 34.4 to 52.4% compared to continuous cropping in rain-fed potato fields. The significant correlation between N2O fluxes and AOB copy numbers implied that N2O emissions were primarily controlled by AOB in rain-fed potato fields. The research has important theoretical and practical value for understanding N2O emissions from rain-fed dry farmland fields.