论文标题:地膜覆盖对冬小麦田土壤中N_2O排放的影响
Effects of Clear Plastic Film Mulch on the Changes of Soil Nitrous Oxide Discharge in the Winter Wheat Field
论文作者 韩建刚
论文导师 曲东；白红英,论文学位 硕士,论文专业 土壤学
论文单位 西北农林科技大学,点击次数 157,论文页数 49页File Size2493k
2002-05-01论文网 http://www.lw23.com/lunwen_34559182/ 地膜覆盖;土壤性质变化;土壤N_2O排放通量
clear plastic film mulch,change of soil properties and flux of N_2O in soil
温室效应气体N_2O是氮素循环中的痕量气体之一，其温室效应强度是CO_2的200倍左右，它在大气中的停留时间长达120年，而且，其消耗或转化是以破坏O_3为代价的。土壤是N_2O主要的发生源，土壤中N_2O排放通量的强度和大气中N_2O总量的变化与土壤性质的改变密切相关。因此，研究N_2O排放与土壤性质之间的关系已成为当前土壤环境化学领域的热点问题。在西北干旱半干旱地区，为了克服水热资源对农业生产的限制，地膜覆盖的农作措施以其显著的增温保墒作用在冬小麦农田得到了大面积的推广和应用；与此同时，该农作措施下的土壤性质也发生了深刻的变化。在此前提下，本丈通过田间和室内模拟试验，研究了陕西关中地膜覆盖的农作措施对冬小麦田土壤中N_2O排放通量的影响，旨在为大气中N_2O源汇的探索研究和土壤中N_2O的农业减排措施的研究提供科学的依据。本项研究取得如下主要结论： 1 田间条件下，地膜覆盖可导致土壤水分、温度、硝态氮含量及土壤NR活性发生显著变化。由通径分析的路径系数比较，土壤含水量(0.3604)＞土壤温度(0.3091)＞硝态氮含量(0.1212)，并共同作用于土壤硝酸还原酶活性。 2 冬小麦的不同生育期地膜覆盖的农作措施显著的增加了土壤中N_2O排放通量。种小麦处理与不种小麦处理相比，土壤中N_2O排放通量明显较高。 3 地膜覆盖使5，10，20cm土层处N_2O的排放通量较未覆膜处理显著增加，且随着土层的加深，排放量依次增大，增加幅度也表现为下层大于上层。 4 在冬小麦生育期内，影响不同处理土壤中N_2O排放通量的主要土壤因子为：无种植情况下，覆膜所导致的膜下(0-5cm)土壤水分积累是引起土壤中N_2O排放通量增加的关键；无膜时较浅层土壤(5-10cm)中NO_3~--N浓度对土壤中N_2O的排放至关重要。对覆膜种小麦处理，10-20cm土层土壤的硝态氮含量对土壤中N_2O排放通量的影响最大；对无膜种小麦处理，5-10cm土层土壤的NH_4~+-N及0-5cm土层土壤中的有机质含量决定了土壤中N_2O的排放通量。 5 水分含量低时(8～58％WFPS)，土壤中N20释放速率与土壤湿度呈正相关，并且随着温度升高释放速率增大；土壤湿度接近田间持水量(58％WFPS)时，释放速率最大；超过田间持水量(106％WFPS)时，N_2O释放速率显著降低，且30℃时的释放速率小于10℃时的速率。 6 风干土存在吸收N_2O的现象，但吸收的强度较小，变异性较大。
Nitrous oxide (N2O), a naturally occurring greenhouse gas, was one of the trace gases of nitrogen cycle. Its lifetime was about 120 years in the troposphere. It has caused considerable concern since N2O not only contributed to the destruction of stratospheric ozone, but also its greenhouse effect strength was about 200 times higher than carbon dioxide (CO2). Soil was the most source of atmospheric N2O. The strength of soil N2O discharge flux and changes of the total N2O amount present in the atmosphere correlated well with the changes of soil properties. Therefore, recent study on relationship of N2O emission and soil properties has became the focus in the study of soil environment chemistry branch field in the global warming research. To overcome the restriction of water and heat on agricultural production in northwestern arid and semiarid region, the farming practice of clear plastic film mulch was spread due to its capacity of retaining water and temperature in the winter wheat field in many areas, however soil properties had also were affected significantly in the meantime. To offer the scientific bases for tracking the N2O sources and sinks processes well and reducing soil N2O discharge flux, effects of the farming practice of clear plastic film mulch on the changes of soil NaO discharge flux in the winter wheat field in shannxi guanzhong area were studied by field and incubation experiments.The conclusions were as follows:1. The farming practice of clear plastic film mulch produced significantly the effects on soil physical, chemical and biological properties. The changes of the three aspects have the cause-and-effect relationships: changes of soil moisture and temperature were affected directly by the farming practice, subsequently, the content of soil nitrate nitrogen was affected by the former changes, ultimately, the soil nitrate reductase (NR) and nitrite reductase (NiR) activities were affected by the formers.2. Soil N2O discharge flux became higher than the checks due to mulch and planting wheat in the winter wheat growing stages.3. Soil N2O discharge flux of mulch was higher than that of no mulch treatment, and with the depth of 5, 10, 20cm the soil N2O discharge flux and the net adding flux increased in the order of depth in the upper soil layers.4. Soil N2O discharge flux responsible for the different treatments were affected by the different soil factors in the winter wheat growing stages. Under no planting conditions, the moisture regime in the 0 to 5cm soil layer mostly made the soil N2O discharge flux adding in the mulch treatment, and the content of nitrate nitrogen in 5 to 10cm soil layer in the no mulch treatment. However, under planting conditions, the content of nitrate nitrogen in 10 to 20cm soil layer and the ammonium nitrogen content in 5 to 10cm soil layer, the organic carbon content in 0 to 5cm soil layer were the most critical factors in mulch and no mulch treatment, respectively.5. The correlation coefficients between soil moisture regime and soil N2O emission rate were positive in the lower soil moisture regime (8 to 58 percent WFPS), and soil N2O emission rate turned weaker and weaker when above the field moisture capacity (106 percent WFPS). The highest N2O emission rate occurred in the field moisture capacity. Soil N2O emission rate was higher in 30 than in 10 in the lower soil moisture regime(8 to 58 percent WFPS), however, the trend was reverse when above the field moisture capacity(106 percent WFPS).6. The wind drying soil could absorb N2O weakly in the incubation experiments.
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