基于15N的‘库尔勒香梨’园土壤N2O排放特征

N2O emission characteristics from the soil in a ’Kuerlexiangli’ pear orchard based on 15N tracing

【目的】N2O作为重要的温室气体,其潜在增温作用约为CO2的190~270倍,为准确掌握源自肥料的N2O损失状况。【方法】以6年生‘库尔勒香梨’园土壤为研究对象,采用15N示踪技术,密闭式静态箱-气相色谱法对梨园土壤N2O排放通量、累积量和Ndff值(15N尿素对土壤氮素气态损失的贡献率)进行监测与分析。【结果】施肥、灌溉及温度均会影响梨园土壤N2O排放通量、累积量及Ndff值。施肥后N2O排通量、累积量和Ndff值,在施基肥和追施肥处理的4d后均达到峰值;土壤N2O排放量在灌水时期明显增加,且土壤N2O排放通量表现为下午(16:00—20:00)>中午(12:00—16:00)>上午(8:00—12:00)>夜间(20:00—8:00),土壤N2O累积量表现为夜间(20:00—8:00)>下午(16:00—20:00)>中午(12:00—16:00)>上午(8:00—12:00);土壤N2O排放与土壤温度、土壤含水量之间均呈显著正相关(p<0.001)。15N尿素贡献的15N2O的Ndff值变化表现为下午(16:00—20:00)>中午(12:00—16:00)>上午(8:00—12:00)>夜间(20:00—8:00)。源于土壤原有氮素的N2O排放量为0.8933g·plant-1,占N2O总损失量的87.43%;而源自肥料的N2O损失量为0.1284g·plant-1,仅占总损失量的12.57%。【结论】‘库尔勒香梨’果园N2O排放主要源于土壤原有氮素的N2O排放。

【Objective】In Xinjiang, the cultivation of characteristic fruit trees has become an important means for farmers to increase their income.‘Kuerlexiangli’pear is the dominant tree species of Xinjiang’s characteristic fruit industry, and has become the dominant industry of characteristic fruit in southern Xinjiang. However, the problems in the production of‘Kuerlexiangli’pear is becoming more and more obvious, and the unreasonable fertilization and extensive management are becoming more and more serious, leading directly to waste of resources and environmental degradation. Nitrogen is a necessary nutrient for the growth and development of fruit trees. In some cases, increasing nitrogen application can effectively increase fruit yield and improve fruit quality. In‘Kuerlexiangli’pear orchards, unreasonable fertilization and excessive application of nitrogen fertilizer will not only reduce the nitrogen use efficiency, but also increase the nitrogen content in the soil, thus accelerating the Nitrous Oxide (N2O) emission from the orchard soil. As an important greenhouse gas, N2O has a potential warming effect, about 190 to 270 times higher than that of CO2.【Methods】Although the 15N tracer technique is widely used in the study on nitrogen cycling, the research on the use of 15N technology to distinguish N2O sources is rare. Therefore, the six-year-old‘Kuerlexiangli’pear orchard was studied by applying 15N tracer technique, and the closed static chamber gas chromatography method was used to monitor the soil N2O discharge flux, incense accumulation amount and Ndff value (Contribution Rate of 15N Urea to Soil Nitrogen Gas Loss).【Results】Fertilization, irrigation and soil temperature all affected N2O flux, accumulation and Ndff value in the orchard soil. In the afternoon of the 4th day after the application of the base fertilizer (April 5th, 16:00-20:00), the maximum flux of soil N2O flux was 0.25 g·hm^-2·h^-1. The cumulative value of N2O peaked at the night of April 5th (20:00-8:00), which was 1.560 g·hm^-2. On the 4th day (June 5th) after application of the dressing fertilizer, the N2O emission flux in the afternoon (16:00-20:00) and the N2O accumulation at the night (20:00-8:00) showed the second peak, which were 0.19 g·hm^-2 ·h^-1 and 1.440 g·hm^-2, respectively. On the 4th day (April 5th) after the application of the base fertilizer, the Ndff value of 15N2O increased significantly in each time period. Among them, the maximum peak value of Ndff of 15N2O (1.12%) appeared in the afternoon (16:00-20:00). On the 4th day (June 5th) after application of the dressing fertilizer, the Ndff value of 15N2O in each time period peaked again. Among them, the Ndff value of the 15N2O peak (1.09%) appeared in the afternoon (16:00-20:00). The amount of soil N2O emissions increased significantly during the irrigation period, and the soil N2O fluxes were expressed as follows: afternoon (16:00-20:00)> noon (12:00-16:00)> morning (8:00-12:00)> night (20:00-8:00). The accumulation of soil N2O was expressed as nighttime (20:00-8:00)> afternoon (16:00-20:00)> noon (12:00-16:00)> morning (8:00-12:00). Regression analysis of soil water content and N2O flux showed that soil water content explained 76.29% soil N2O flux, and there was a significant positive correlation with soil N2O flux (p < 0.001). However, after 10 days of watering every month, the Ndff value of 15N2O in the soil did not change significantly due to changes in soil water content. The soil temperature change in one day was in the ascending order: afternoon (16:00-20:00)> noon (12:00-16:00)> morning (8:00-12:00)> nighttime (20:00-8:00), and the N2O flux in soil was relatively consistent within one day. Regression analysis between soil temperature and N2O fluxe indicated that soil temperature contributed 82.16% of soil N2O flux, and showed a significant positive correlation with soil N2O flux (p < 0.001). The Ndff value of 15N2Ochanges in one day was in the ascending order: afternoon (16:00-20:00)> noon (12:00-16:00)> morning (8:00-12:00)> night (20:00-8: 00), which was consistent with the trend of soil N2O flux. The Ndff value of 15N2O contributed by 15N urea changed like this: afternoon (16:00-20:00)> noon (12:00- 16:00)> morning (8:00-12:00)> night (20:00-8:00). N2O emission from soil nitrogen was 0.8933 g · plant^-1, accounting for 87.43% of the total loss. The loss of fertilizer was 0.128 4 g · plant^-1, accounting for only 12.57% of the total loss.【Conclusion】There was a significant positive correlation between soil N2O emission and soil temperature and soil water content (p < 0.001). Moreover, N2O emission was mainly due to N2O emission of soil nitrogen. Nitrogen dioxide emission from soil was affected by many factors. There may be some coupling between these factors and the mechanism needs further studies.