Release Of Loess Soil N₂O And Cropper's Influence Of Different Use In Shaanxi Province

As one of the most important greenhouse gases, N₂O has been paid great attention due to its substantial contribution to global warming and ozone depletion. Different land use can cause corresponding changes in soil N₂O emission flux, density and vertical distribution. There is obvious difference in land use type and farmland management since 1980s, so the study on N₂O flux of different soil types, flux regulation and affecting factors plays an important role in evaluating of farmland N₂O flux, making flux lists and improving land use structure.In order to study the different soil N₂O flux characters and their affecting factors in Shaanxi Province, we committed a raise experiment and analyzed four factors-soil depth, moisture , temperature and crop which can affect the N₂O flux mechanism. The results indicated:1. The amount of N₂O flux among three soil types can be ranked from farmland, grassplot, to forest lot. Different depths of N₂O flux accord to Elovich equation, the optimal N₂O emission are: farmland, 17.59cm; grassplot, 10.12cm; forest lot: 2.4cm.2. The increase in soil moisture and the soil temperature in N₂O emissions has positive effect, and maximum flux of average emissions appears in the water for 22 % of the processing. Lower water content(7.86%) was found in the absorption phenomenon, And, when 7.86% and 14.50% moisture contents, take temperature as 35℃which N₂O emissions is biggest, when 18.70% and 22% moisture contents, 30℃which N₂O emissions is highest, and all the biggest N₂O emissions appears after the raise 1d.3. N₂O emission flux between of the wheat field and the fallow plot's has the extremely remarkable difference (P <0.01). N₂O emission decreased in the order: film mulching treatment>routine treatment>single phosphorus fertilization treatment. The results showed that winter wheat increases soil N₂O emission in Loess regions, regardless of fertilizer or mulch treatment. 4. In conventionally tilled and film mulched treatments, the water content of the wheat field was less than that of the fallow treatment except a seeding and after harvest, while the NH₄⁺-N content of the wheat field was more than that of the fallow field. But other physical and chemical properties of soil have not displayed the regularity. Multiple regression analysis indicated that differences in N₂O flux between wheat fields and fallow fields were negatively correlated to the increasing amount of organic matters in the soil, the extent of exuberance of energy material is a key factor which determines the changes of N₂O in our experiment.5. N₂O emission in the main root-zone and the inter-row was different. The largest differences occurred at the booting stage, when the flux of N₂O between plants was 5.64 times more than in the main root-zone. During the latter two stages, temperature effects due to wheat roots had a significant effect on N₂O emission. Moisture effects due to roots were significant in the 15～20cm layer. The results also indicated that N₂O increased due to the activity of wheat roots in the soil.