| Due to it is significant greenhouse effect, the greenhouse gas nitrous oxide (N2O) is considered as the greatest impact factors that destroy the ozone layer in the21century (Ravishankara et al,2009). Presently many experts and scholars both local and international are concerned about it.A growing number of studies indicate that agricultural activities are an important source of emissions of N2O, and is worsens by an increase application of nitrogen fertilizers. A lot of study on N2O emissions in the process of crop production in the farmland system in recent years, but the study of vegetable soil N2O emissions less, especially in the central region and even more rarely. A combined undisturbed soil column and field trials, with a typical vegetable soil (yellow-brown) from Peri-urban areas of Wuhan City were used in this study. Eleven different kinds of Wuhan common vegetables studied in this trial are eggplant, amaranth, celery, pepper, radish, spinach, mater convolvulus, cabbage, lettuce, pumpkin and bean, depth study the effects of the process of vegetable planting vegetable soil N2O emissions of the vegetable soil N2O emissions law and nitrification inhibitor dicyandiamide (DCD) under the Wuhan vegetable plot5rotation system. In order to provide a scientific base for the sustainable production of vegetables and vegetable soil N2O control and emission reduction under optimize the sound of the crop rotation system, reasonable choice of vegetable varieties, and DCD cost-effective application. The main findings were as follow:1. Study the diurnal, seasonal variation of Wuhan suburban vegetable soils N2O emissions under the soil column test. The results showed that the first increased and then decreased on the overall of the vegetable plot in autumn day emission rate of N2O, the amount of emissions were1723.20μg·m-2in24hours, the average emission rate were71.80μg·m-2·h-1, the best sampling time were7:00-8:00. The total amount of emissions in vegetables plot in summer were2286.72μg·m-2in24hours, the average emission rate were95.28μg·m-2-h"’, the best sampling time were between4:00-5:00am. Overall the N2O emission rate was high in summer than in autumn, and dramatic changes of temperature effects on N2O emission rate were more obvious than the temperature itself. The N2O emission rate has dramatic changed due to a sudden jump or a sudden drop, and temperature changed in a certain lag. After imposed DCD, the N2O emission rate also overall high in summer than in autumn, and the best sampling time changed to7:00-8:00am in autumn and4:00-5:00am in summer.2. It had been studied that soil column test of vegetable field N2O emissions in the five kings of crop rotation system. The results showed that:The total annual average N2O emissions of the five kinds of rotation system in Wuhan common grown vegetables were6.58kg·ha-1·y-1. Under the same fertilization circumstances, different crop rotation system significantly affected N2O annual emissions and emission factors. The optimal for crop rotation system3(mater convolvulus-amaranth-cabbage-lettuce-Cabbage), and then following were crop rotation system5(eggplant set in amaranth-radish-cabbage-cabbage), crop rotation system2(pepper-radish-spinach), crop rotation system4(pumpkin-bean-radish-spinach), crop rotation system1(eggplant-amaranth-celery). Application of nitrification inhibitor DCD on the role of emission reduction of greenhouse gas N2O under different crop rotation systems shows that the higher the annual emissions N2O, the greater the reductions of emission after imposed by DCD. The study also showed that N2O emissions were also enormous in the vegetable plots fallow period, it could not be ignored.3. Effects of vegetables cultivation on N2O emissions under different crop rotation systems, results showed that:the vegetable soils in which spinach and celery were planted had no significant differences between the daily emissions and other vegetables, on the other hand total emissions or emissions of N2O with fresh material weight ratio, when compared to the weight of vegetable were significantly higher than other vegetables, and occupied a high proportion of the total emissions of the respective crop rotation system. On a contrary, the total emissions, daily emissions of N2O, the ratio of total emissions, fresh materials weight and dry matter weight ratio were all significantly lower than the spinach and lettuce. The eggplant-amaranth interpolated in the vegetable plot, the ratio of the total emissions, daily emissions of N2O and the weight of fresh material, as well as the ratio of emissions and dry weight were lower than the value of these two vegetables that were planted separately, and significantly lower than their value. The total emissions of N2O of different varieties of vegetables order were recorded and are as follow, eggplant, radish, bean, cabbage, pepper, pumpkin, amaranth, mater convolvulus, lettuce whereas the daily emissions of N2O order were amaranth, eggplant, spinach, celery, radish, cabbage, bean, pumpkin, pepper, lettuce, mater convolvulus.4. Investigation on the effects of the nitrification inhibitor of the N2O emissions in vegetable field using combination of soil column tests and field trials. The results therefore showed that:applying nitrogen fertilizer on vegetables during planting time imposed the nitrification inhibitor DCD which significantly slowed down the speed of convertion of urea to NH4+-N. On the maintenance of soil NH4+-N content and slowed down it sudden drop, and reduced nitrate leaching in the soil and greenhouse gas N2O emissions had a significant role. For vegetables in different crop rotation systems, the imposition of the nitrification inhibitor DCD indeed reduced most of the vegetables in the planting process vegetable field N2O emissions of greenhouse gases, either from the total emissions, average daily emissions of N2O, or from the ratio of the N2O emissions and fresh material, N2O emissions and vegetables dry weight, emissions reduction effects were more pronounced. Moreover, the N2O emissions and total N2O emissions of vegetable field emission of vegetables their own planting cycle to be a certain degree of positive correlation. |
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