The Effect Of Fertilization On Greenhouse Gas And Nitrogen Gas Emissions From The Field In North China Plain

The exchange fluxes of greenhouse gases (N2O, CO2and CH4) from a summer maize-winter wheat crop rotation field during the whole growing seasons in the North China Plain were investigated by static chamber method. And the exchange fluxes of NOx(NO+NO2) and NH3were investigated by dynamic chamber method during this research. Greenhouese gases fluxes were measured from control plot, normal fertilization plot, nitrate fertilization plot and wheat straw returning plot during the whole seasons, and the fluxes of NOx and NH3were investigated from control plot, normal fertilization plot and nitrate fertilization plot only.The results of this study showed that the cumulative N2O emissions during the fertilization periods (about lOd after fertilization) accounted for more than61%of the cumulative emissions from each crop growing period, and the emission factors were ranged from0。1%-3.3%, indicating that fertilization greatly promoted the N2O emission. Compared with the normal fertilization plot, the application of nitrate fertilizer could effectively reduce the N2O emissions in each period. Straw returned had a positive effect of N2O emission during the maize growing season in2010, but it appeared a negative effect during the wheat-maize rotation period from2010to2011.There was an obviously seasonal varation of the emission fluxes of CO2, and related with the crop growth situation. Higher CO2emissions appeared from stempushing to silking stage during the maize growing season and from green up stage to postulation period in wheat growing season. No significant difference was appeared in different fertilization treatments. The straw returning increased the accumulated emission of CO2to some extent.The accumulated emission of CH4was negative during maize and wheat growing season from2010to2011, indicating that the investigated field was a sink of atomosphere CH4. It was positive in CF, NF-L and SN plot in maize season in2011, indicated that the investigated field was a source of atomosphere CH4. That could arrtibuted to the large precipitation in2011, and lead to higher soil moisture and improved the activity of methanogens, increased the emissions of CH4.NO emissions increased after fertilization in a short time, after precipitation or irrigation events NO exchange flux shows a tendency of first decreases then increase. In addition to normal fertilization plot in2010maize season, the cumulative emission fluxes of NO were all negative, indating that the investigated field was a sink of atomosphere NO. Compared to normal fertilization plot, application of nitrate fertilizer could effectively decrease NO emissions. The cumulative emission fluxes of NO2were all negative in each treatment, indating that the investigated field was a sink of atomosphere NO2. NH3 emission were just found lower values in4days after fertilization.In a cycle of wheat-maize rotation field from2010-10to2011-05, the net GWP were positive in control, normal fertilization and straw returned treatments, but negative in nitrate fertilizer plot. Thus it can be seen that the current farming practice would be a source of atmosphere greenhouse gases in wheat-maize rotation field and nitrate fertilizer application could reduced the contribution of greenhouse gases emission from field to the atmosphere.