氮肥用量和脲酶抑制剂对滴灌马铃薯田氧化亚氮排放和氨挥发的影响

【目的】 氨挥发和氧化亚氮排放是氮素损失的重要途径。内蒙古阴山北麓滴灌马铃薯田种植面积大，普遍存在过量施肥的问题。研究适宜的氮肥用量，利用脲酶抑制剂来抑制氨挥发和氧化亚氮排放，对提高当地氮肥利用率和减缓环境压力具有重要意义。 【方法】 田间试验分两年在内蒙古武川县两个村庄进行，供试地块种植马铃薯，采用滴灌技术。2015年设置4个处理，分别为:不施氮 (CK)；优化施氮模式，施N 180 kg/hm2 (Opt)；优化施氮减半模式，施N 90 kg/hm2 (OptR)；农民传统施肥量，施N 270 kg/hm2 (Con)。2016年试验处理根据2015年的结果进行调整，设置4个处理:不施氮 (CK)；优化施氮添加脲酶抑制剂模式，施N 162.6 kg/hm2 (OptI)；优化施氮模式， 施N 162.6 kg/hm2 (Opt)；农民传统施肥量，施N 320 kg/hm2 (Con)。分别采用静态暗箱法和通气法采集氧化亚氮和氨气，每次施肥后，两天采集一次气体样品，氧化亚氮连续取样三次，氨气持续取样直至气体含量低于仪器检测值下限。 【结果】 氨挥发速率在施入尿素后第1～5 d出现峰值。Con处理2015和2016年氨挥发的最大峰值分别是13.2 mg/(m2·d) 和5.3 mg/(m2·d)，氨挥发累积量分别为N 3.61和3.96 kg/hm2；Opt处理的最大峰值分别为8.69 mg/(m2·d) 和3.19 mg/(m2·d)，累积挥发量分别为N 3.11和2.72 kg/hm2；OptR处理氨挥发速率最大峰值为5.63 mg/(m2·d)，氨挥发累积量为2.66 kg/hm2，OptI处理氨挥发速率最大峰值为3.67 mg/(m2·d)，氨挥发累积量为2.50 kg/hm2。氨挥发累积量随着氮肥用量的增加而增多，Con处理的氨挥发量显著高于其他处理；氧化亚氮排放量在施入尿素后第3 d达到峰值，Con处理2015和2016年的氧化亚氮排放峰值分别达到0.3 mg/(m2·d) 和0.2 mg/(m2·d)，氧化亚氮累积排放量分别为N 1.96和1.18 kg/hm2，显著高于其他处理；Opt处理两年的排放最大峰值均为0.11 mg/(m2·d)，氧化亚氮累积排放量为N 0.95、0.69 kg/hm2；OptR的氧化亚氮排放量最大峰值为0.09 mg/(m2·d)，累积量为0.90 kg/hm2。OptI的氧化亚氮排放量最大峰值为0.12 mg/(m2·d)，氧化亚氮累积量为0.66 kg/hm2。相比Opt，OptI处理的氨挥发和氧化亚氮累积排放量分别降低了11.8%和16.7%，但未达到显著水平。氨挥发速率与土壤温度呈显著正相关，土壤温度的升高会显著增加氨挥发速率，土壤湿度的增加会抑制氨挥发速率，影响不显著。氧化亚氮的排放与土壤湿度呈显著正相关，土壤中水分增加会显著增加氧化亚氮的排放量，土壤温度与氧化亚氮排放成负相关，影响未达到显著水平。 【结论】 与农民传统施肥模式相比，优化施氮模式可显著降低氨挥发和氧化亚氮排放量，添加脲酶抑制剂未达到显著降低尿素氨挥发量和氧化亚氮排放的效果。土壤湿度和土壤温度在一定程度上影响着氨挥发速率和氧化亚氮的排放通量。在供试地区马铃薯田的施肥管理中，推荐可有效地降低氨挥发和氧化亚氮排放量的优化施氮模式。

Effects of nitrogen rate and urease inhibitor on N2O emission and NH3 volatilization in drip irrigated potato fields

【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.