摘要:氨挥发是农田活性氮损失的重要途径, 准确、有效地测定农田氨排放量是环境评估和政策制定的基础。由于氨挥发监测方法多样, 且方法间缺少系统的对比分析, 在一定程度上限制了相关研究数据的进一步利用。我国应用最广泛的氨挥发监测方法是通气式海绵吸收法和密闭室间歇抽气法, 目前, 两种监测方法仍缺少大田条件下的实测对比。本研究在不同施氮量处理下, 于水稻-小麦轮作系统作物生长期同时采用这两种方法对土壤氨挥发排放进行连续监测。结果表明, 在3个施氮水平下, 通气式海绵吸收法测得的氨挥发累积量低于密闭室间歇抽气法25%~35%, 稻麦两季结果一致, 两方法测试值的变化趋势也一致。通气式海绵吸收法在稻季测得累积氨挥发量为17.36~43.90 kg?hm?2, 麦季为5.90~20.43 kg?hm?2, 排放系数为2.56%~10.39%; 密闭室间歇抽气法在稻季测得累积氨挥发量为23.28~61.05 kg?hm?2, 麦季为14.63~27.73 kg?hm?2, 排放系数为7.09%~15.01%。相同研究区域的文献调研表明, 当施氮量为101~300 k?hm?2时, 通气式海绵吸收法比密闭室间歇抽气法低5%~25%, 与实测数据趋势相同。基于本研究和文献调研结果, 推荐通过这两种监测方法获取的氨挥发量在施氮量低于100 kg?hm?2时可不转换, 施氮量高于100 kg?hm?2时可按照密闭室间歇抽气法的75%转换为通气式海绵吸收法。
关键词:氨挥发/
氮肥用量/
密闭室间歇抽气法/
通气式海绵吸收法/
稻麦轮作
Abstract:Ammonia volatilization is an important pathway of active nitrogen (N) loss from farmlands. The accurate and effective measurement of farmland ammonia emissions is the basis for environmental assessments and policymaking. Soil ammonia volatilization is controlled by fertilizer application rates, fertilizer application methods, soil properties, and meteorological conditions, so there is a wide variability in the cumulative ammonia emissions and emission factors in different studies. There are also different methods for ammonia volatilization measurements, which further reduce the comparability of data across studies. The most widely used methods for soil ammonia volatilization measurements in China are the ventilated sponge absorption method and the intermittent airflow enclosure method. However, consistency between measurements is unclear because of substantial differences in the ventilation rates between methods, and only a few studies have compared the two methods. Based on a typical rice-wheat rotation system in the Lower Reaches of the Yangtze River, this study set up treatments with different N fertilizer application rates (N0: no N fertilizer; N1: 200 kg(N)·hm?2 for rice and 180 kg(N)·hm?2 for wheat; N2: 300 kg(N)·hm?2 for rice and 270 kg(N)·hm?2 for wheat; and N3: 400 kg(N)·hm?2 for rice and 360 kg(N)·hm?2 for wheat). Soil ammonia volatilization was measured continuously after fertilization during rice and wheat growth using the ventilated sponge absorption and intermittent airflow enclosure methods, and the ammonia emission factors in the study area were analyzed using literature analysis. The results showed that the cumulative ammonia emission measured by the ventilated sponge absorption method was 25%–35% lower than that measured by the intermittent airflow enclosure method under the three N application treatments (except for the N0 treatment), and the results were consistent for both rice and wheat seasons. Under fertilization treatments (N1, N2 and N3), the cumulative ammonia emissions measured by the ventilated sponge absorption method ranged from 17.36 to 43.90 kg·hm?2 in the rice season and from 5.90 to 20.43 kg·hm?2 in the wheat season, with emission factors ranging from 2.56% to 10.39%. The cumulative ammonia emissions measured by the intermittent airflow enclosure method ranged from 23.28 to 61.05 kg·hm?2 in the rice season and from 14.63 to 27.73 kg·hm?2 in the wheat season, with emission factors ranging from 7.09% to 15.01%. The cumulative ammonia emissions under the N0 treatment were higher for the ventilated sponge absorption method than for the intermittent airflow enclosure method, and the measurements of the two methods were significantly different in the rice season but not in the wheat season. The results of the literatures analysis in the study area were consistent with the monitoring results. The cumulative ammonia emissions measured by the ventilated sponge absorption method were higher than those measured by the intermittent airflow enclosure method when the N application rate was between 0 and 100 kg·hm?2, with average emission factors of 6.18% and 12.31%, respectively. When the N application rate was between 101 and 200 kg·hm?2, the ventilation sponge absorption method led to 25% lower emissions than the intermittent airflow enclosure method, with average emission factors of 9.46% and 12.61%, respectively. When the N application rate was between 201 and 300 kg·hm?2, the ventilation sponge absorption method led to 5% lower emissions than the intermittent airflow enclosure method, and the average emission factors were 12.71% and 13.43%, respectively. In general, the cumulative ammonia emissions measured by the two methods were consistent; the ventilated sponge absorption method led to higher measured values than the intermittent airflow enclosure method in fields without N application or with low ammonia volatilization rates, and the ventilated sponge absorption method led to lower measurements than the intermittent airflow enclosure method in fields with N application. The measurements of the two methods can be converted using a ratio. The results of this study provide support for the estimation of regional ammonia emissions using the ventilated sponge absorption and intermittent airflow enclosure methods.
Key words:Ammonia volatilization/
Nitrogen fertilizer amount/
Intermittent airflow enclosure method/
Ventilated sponge absorption method/
Rice-wheat rotation
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