Effects Of Clear Plastic Film Mulch On The Changes Of Soil Nitrous Oxide Discharge In The Winter Wheat Field

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.