Objectives Nitrous oxide emission and ammonia volatilization are important ways for nitrogen loss in calcareous soil. The planting area of potato in the northern Yinshan of Inner Mongolia is increasing year by year, and the problem of excessive fertilization is still common. The effects of nitrogen management and the addition of urease inhibitor were studied in this paper, so as to find a satisfactory way of inhibiting the ammonia volatilization and nitrous oxide emission in the area.

Methods Monitoring was carried out in the field where potato had been grown for two successive years in two villages using drip irrigation technique. In 2015, 4 different nitrogen fertilizer levels were set up respectively: No N application (CK); N 90 kg/hm² in reduced fertilization mode (OptR); N 180 kg/hm² in optimized fertilization mode (Opt); N 270 kg/hm² in conventional fertilization mode (Con). The treatments were regulated in 2016 according to the results of 2015, and the four treatments were: No N application (CK); N 162.6 kg/hm² in optimized fertilization mode and added urease inhibitors in urea (OptI); N 162.6 kg/hm² in optimized fertilization mode (Opt); N 320 kg/hm² in conventional fertilization mode (Con). The static camera obscura and ventilation methods were used to monitor the amounts of N₂O emission and ammonia volatilization. After each fertilization, the gas samples were collected for two days, and the N₂O was continuously sampled for three times, and the NH₃ was not stop sampling until the gas content was lower than the detection limit of the instrument.

Results The ammonia volatilization reached peak after 1–5 days of nitrogen application in potato fields. The maximum ammonia volatilization in 2015 and 2016 were 13.2 mg/(m²·d) and 5.3 mg/(m²·d), and the accumulative volatilization were N 3.61 and 3.96 kg/hm² under Con mode, respectively. The maximum peaks were 8.69 and 3.19 mg/(m²·d), and the accumulative volatilization were N 3.11 and 2.72 kg/hm² under the Opt mode, respectively. The maximum volatilization peak was N 5.63 mg/ (m²·d), and the cumulative amount was N 2.66 kg/hm² under OptR mode. The maximum peak was N 3.67 mg/(m²·d), and the cumulative volatilization was N 2.50 kg/hm² under OptI mode. The cumulative ammonia volatilization was increased with the increase of nitrogen application rate. The amount of ammonia volatilization in Con mode was significantly higher than in the others. The content of N₂O emission reached the peak after 3 days of N application. The cumulative N₂O emission under Con mode was N 1.96 and 1.18 kg/hm² respectively in 2015 and 2016 with the maximum peak of 0.3 mg/(m²·h) and 0.2 mg/(m²·h), respectively. The loss rate of N₂O in Con mode was the highest, which was significantly higher than those in the others; N₂O cumulative emissions in the Opt mode were 0.95 and 0.69 N kg/hm², respectively, with the maximum peak of 0.11mg/(m²·h). The cumulative N₂O emission was 0.90 kg/hm² with the maximum peak value of 0.09 mg/ (m²·h) in OptR mode. The maximum peak value of N₂O in the OptI was 0.12 mg/(m²·h), and the cumulative N₂O emission was 0.66 kg/hm². Compared with the Opt mode, the cumulative ammonia volatilization and N₂O emissions in OptI mode were respectively decreased by 11.8% and 16.7%, although they are not significant. The ammonia volatilization rate and soil temperature showed a significant positive correlation, while soil moisture did not. Nitrous oxide emission was significantly and positively correlated to soil moisture, but the soil temperature was not.

Conclusions The optimized nitrogen application treatment could significantly reduce the ammonia volatilization and nitrous oxide emission compared with the farmers' practice. The addition of urease inhibitor does not significantly reduce ammonia volatilization and nitrous oxide. Soil temperature increases ammonia volatilization rate and soil moisture increases nitrite oxide emission flux. Therefore, optimizing nitrogen fertilization mode should be considered firstly for the reduction of nitrogen fertilizer loss in the tested potato field.