The improved N2O microelectrode calibration method significantly improves the sensitivity of the sensor

Micro sensors have large potential to measure soil nitrous oxide (N2O) emissions. However, because of its low sensitivity to get the electrical signals on soil with low moisture content, little research has been conducted in semi-arid agro-ecosystem. Moreover, the use of N2O microelectrode studies were largely focused on the marshy fields, paddy fields and waste waters with high soil moisture content. In order to characterize the boundary of the sensor signal (upper and lower), purified water without N2O is usually used as the calibration medium to calibrate the electrode. However, the physical and chemical properties of purified water and soil leaching solutions are very different. In this study, we improved and verified a microelectrode calibration method based on selecting appropriate media and optimal electrolyte concentration. In addition, we applied the improved microelectrode calibration method to continuously observe N2O flux from the soil column in a 30-day-long incubation experiment. The results pointed to noteworthy improvement of the microelectrode calibration compared to the current method, with soil solution validated as a calibration medium at optimal electrolytic concentration of 7:1-8:1, expressed as water/soil ratio. The emission of N2O from soil with different soil fertility were also significantly different. Our research is beneficial to establish the microelectrode calibration method of N2O emission under low moisture conditions from soil microenvironment, and also points on management practices of agro-ecosystem for N2O mitigation strategies.