碳氮交互对华北典型农田土壤团聚体及氧化亚氮产生的影响机制

The North China Plain is not only the main grain product area in our country, but also the main area of soil N2O emissions. To ensure the food security, the rate of nitrogen and organic fertilizer increased year by year on North China Plain. However, the long-term carbon and nitrogen input will influence on the soil aggregate structure and its carbon and nitrogen content, and then affect the soil N2O production. In this study, dry and wet sieving method was used to reveal the mechanism of the effects of carbon and nitrogen interactions on soil aggregate formation and stability on the basis of the long-term different carbon and nitrogen input field experiment in North China Plain. The influence of soil aggregate structure on N2O production was determined by the N2O emissions from different water contents and nitrogen fertilizer application rates by using undisturbed soil core in the laboratory. The mechanism of the effects of soil aggregate carbon and nitrogen content on N2O production was illustrated by the N2O emissions from the same fractions by using Robot and micro-site incubations. The results will provided the scientific basis for applying carbon and nitrogen reasonable, improving soil fertility and reducing N2O emissions.

华北平原既是我国粮食的主产区，也是土壤N2O排放的主要区域。为保证我国粮食安全，该地区的氮肥和有机肥施用量逐年增加，而长期不同的碳氮投入会改变华北典型农田土壤的团聚体结构及其碳氮含量并进而影响土壤N2O的产生。本项目以华北平原长期不同碳氮投入的田间定位试验为基础，应用团聚体干、湿筛分法揭示碳氮交互对团聚体形成及稳定性的机制；采用室内原状土柱培养法测定不同含水量和施氮量对N2O排放的影响，明确团聚体结构与N2O产生的关系；利用连续自动培养测定法(Robot)和室内微域培养法测定不同碳氮含量团聚体的N2O排放，阐明团聚体碳氮含量对N2O产生的影响机制。研究结果为在华北平原合理投入碳氮，提高土壤肥力，降低农田土壤N2O排放提供科学依据。

本项目以华北平原长期不同碳氮投入的田间定位试验为基础，应用团聚体干、湿筛分法揭示了碳氮交互对团聚体形成及稳定性的机制；采用室内原状土柱培养法测定不同含水量和施氮量对N2O排放的影响，明确了团聚体结构与N2O产生的关系；利用连续自动培养测定法(Robot)和室内微域培养法测定了不同碳氮含量团聚体的N2O排放，阐明了团聚体碳氮含量对N2O产生的影响机制。主要结果如下：1）长期不同的碳氮管理措施后，所有处理53-250和<53 μm的团聚体含量较高，分别占到了50.2-57.3和35.4-41.4%，而250-2000 μm的大团聚体含量最少，仅占到4.9-9.4%。2）经过长期不同的碳氮管理措施后，土壤有机碳大部分分布在微团聚体内颗粒有机质(iPOM_m)和微团聚体外的粘粉粒(s+c_f)组分之中，其含量分别为2.3-5.4和2.8-4.9 g C kg-1。其次为粗颗粒有机质(cPOM)，其含量为0.8-1.5 g C kg-1。3）不施肥处理，优化施肥处理和传统施肥处理的N2O排放量范围分别为22 - 77，21 - 665和29 - 1682μg N2O-N m-2 h-1。在玉米季，N2O排放量范围为27-103μg N2O-N m-2 h-1，在小麦季，N2O排放量范围为12-38μg N2O-N m-2 h-1。4）长期施用尿素和/或有机肥显著增加了土壤中氨氧化细菌(AOB)的数量，其每克干土拷贝数在1.4e+7至1.9e+7范围内。长期不同碳氮投入增加了Nopt、CNopt和CM的AOB数量；长期秸秆还田和施用有机肥增加了土壤中反硝化菌的数量，尤其是有机肥CM处理；研究结果为在华北平原合理投入碳氮，提高土壤肥力，降低农田土壤N2O排放提供科学依据。