Study On CO₂, N₂O Emissions Under Different Water-fertilizer Treatment In Facility Vegetable Soil

In recent years, the greenhouse gas emissions causes the extreme global climate warming the loss of stratosphere ozone and this has become the significant environment question which the world faces. The primary reason of climate warming's is the concentrations of greenhouse gas in the atmosphere (mainly refers to CO2, CH4 and N2O) unceasingly. Because the greenhouse gases emissions's from the farmland ecosystem plays the vital role in the global climate warming, and the facility vegetable is the part of farmland ecosystem, and in recent years with the area of facility vegetable unceasing increase, the study of CO2, N2O emissions characteristic and produces'mechanism from the facility vegetable under the different fertilizer measure and the water management, the quantitative evaluation facility vegetable greenhouse gas emissions to the change of atmosphere greenhouse gas contribution, in order to provide the scientific basis that can reduce the greenhouse gas emissions from the facility vegetable.This paper through the laboratory soil incubation experiment to observation the soil CO2, N2O flux emission in Daxing District, Beijing. The treatments are following:Different water treatment for dry, normal water, flooding(30,60,90%WFPS); Different fertilizer treatment as the control, low-fertilizer, medium-fertilizer and high-fertilizer(0,170.94,341.88,512.82μg N·g-1dry soil); Different nitrogen treatments were divided into two groups, the one group are controlCK, calcium nitrateCN, ammonium bicarbonateAB, ammonium sulfateAS, ureaU, the other group add the straw with above the first group. We observed the CO2, N2O emissions. The main results are as follows:1,Measures for the same amount of water under the different fertilizer to observation soil CO2 emissions, the results show that in dry and normal water conditions, low-fertilizer and medium-fertilizer have the higher CO2 emissions. Only in flooding conditions, high-fertilizer have the high CO2 emissions. This is due to n flooding conditions, organic matter humification process is obviously, the soil anaerobic conditions, so the reducing gases are more. Dry, normal water, flooding conditions, the average cumulative emissions of CO2 which treatment with nitrogen was higher 74%,63% and 28% compared with the control. The soil emissions of N2O are increased with the increase of nitrogen regardless of soil moisture in any case, and the flooding conditions emit more N2O.2,The same fertilizer under the different water to the soil, the influence of CO2 peak emissions of three fertilizer treatment were higher than control, and remarkable difference. In simulating conditions, the CO2 emissions of control is increased with moisture content, the other three fertilizer treatments emissions are highest in normal moisture conditions. The control treatments N2O emissions in the whole training, almost without N2O in each moisture conditions but appear absorbing phenomena. The other three fertilizer treatments can discharge more N2O in the flooded conditions which is about other treatments 10-20 times. Under the condition that anaerobic conditions denitrification process strengthen, so it can generate higher N2O. Through the test of NH4+-N, NO3-N content that the N2O is closely related with them.3,The same fertilizer under the different water of soil CO2, N2O emissions compared with the water content, soil respiration and the water treatment showed extremely linear relationship (P<0.01, R2=0.8013), and the other fertilizer treatment no significant relationship with the soil respiration. Except the CK, other treatments N2O emissions and soil moisture relationship showed extremely significant (P<0.01). Moisture is the important limit factor of N2O emissions.4,Incubation experiments, the cumulative emissions between CO2 and N2O (except CK) are significantly (P＜0.001) which is index or a quadratic function relation. Thereinto, dry low-fertilizer and high-fertilizer normal water treatment exponentially with equations; The other treatment said a quadratic function relation.5,Incubation different nitrogen sources and straw added CO2 emissions, except CN, various treatments were significantly higher than CK, ammonium nitrogen can more stimulate the soil organic matter decomposition. Adding straw, CO2 emissions are about 2-4 times, comparing with no straw treatment.The reason for straw added that increasing soil C source, improve the soil C/N. The CN CO2 emissions is lower than control with straw or not. The N2O emissions, nitrate nitrogen (CN) is easy to achieve N2O rate discharge peak, and ammonium nitrogen (AB,AS) and amide state nitrogen (U) later. The N2O cumulative emissions order AB>U>AS>CN>CK. Ammonium and amide of nitrogen N2O emit more than nitrate nitrogen. When did not add exogenous carbon, the N2O emission coefficient are 1.01,0.77,0.62,0.42. After each treatment with straw N2O emission coefficient, respectively,1.96,1.58,1.34,0.20. Adding straw, the N2O emissions(except CN) are increased.6,Incubation experiments, different nitrogen source and straw adding, CO2 emissions without straw (y) and time (x) have the cumulative relationship:y=aLn(x)+b. CO2 emissions with straw (y) and time (x) have the cumulative relationship:y=ax+b. N2O emissions with strawor not (y) and time (x) have the cumulative relationship:y=aLn(x)+b (except CK). They have reached a significant related (P<0.001). Comparing with CK,soil pH that after using the ammonium nitrogen was significantly lower. After adding straw can slow this phenomenon.