| China has long faced with land shortage due to the large population size.The tidal mudflats grown along the coastal areas can be reclaimed as potential agricultural land.However,the newly reclaimed tidal mudflats are generally characterized with poor physical structure,high pH,high salt content and low fertility(especially N and P supply),and can not be directly used as farmland for crop production.On the basis of salt reduction by engineering approaches,input of exogenous organic carbon is the leading strategy for the remediation and rapid fertility developemnt of mudflat soil.On the other hand,global greenhouse gas emission reduction has always been the focus of environmental protection,and farmland is the main source of greenhouse gas emission.However,information on greenhouse gas emission in the mudflat soil remediated with massive input of exogenous organic carbon has been in scares yet.In this study,exogenous organic carbon(sewage sludge and sludge-based vermicompost,with the rates of 0,25,50,100,200 t ha-1,respectively)was used to study the major greenhouse gas emission characteristics of improved mudflat soil.The effects of soil physicochemical properties including water content,salt and pH)on greenhouse gas emissions were also studied by incubation experiment under the condition of equal carbon input with field experiment.Then,the correlation between emission fluxes of the greenhouse gases and environmental factors affecting the soil carbon budget was analyzed and discussed.The results showed that:(1)In the field experiment,the soil CH4,CO2 and N2O emissions were significantly enhanced by the application of exogenous organic carbon(sewage sludge and vermicompost),compared with the non-fertilization treatment,and emissions of three gases increased with the increase of applied organic carbon rate.Under the same application rate,the CH4 and CO2 emissions in treatments of sludge-based vermicompost were all higher than those in sewage sludge treatments,while the N2O emissions showed the opposite trend.Under the experimental conditions,the exogenous organic carbon(domestic sludge,vermicompost)increased the amount of soil C solid,and was beneficial to the plant photosynthetic C solid.The mudflat soil under each treatment in this study showed the characteristic of "net carbon sink".(2)Laboratory incubation experiment indicated that CH4 emission increased with the increase of soil water content,while the emission of CO2 and N2O increased first and then decreased with the increase of soil moisture content and reached their peak values when the moisture content was 80%.With the increase of soil salt concentration,CH4 and CO2 emissions gradually decreased.CH4 and CO2 emissions at 2‰ salt concentration were 1.89 and 2.37 times of those at 13‰ salt concentration,respectively.When the salt concentration was lower than 4‰,the emission of N2O increased with the increase of the soil salt concentration,and when the salt concentration was higher than 4‰,the emission of N2O decreased with the increase of the soil salt concentration.The emissions of greenhouse gases in mudflat soil were affected by soil pH.The emissions of CH4,CO2 and N2O showed an upward trend when the pH of tidal flat soil was between 7.5 and 8.5,while the emissions of CH4,CO2 and N2O showed a downward trend when the pH was between 8.5 and 9.5.(3)In the field experiment,CH4 emission flux showed a significant positive correlation with soil temperature(p<0.05),and a significant negative correlation with soil pH and organic carbon content(P<0.05);The CO2 flux was significantly positively correlated with soil temperature(p<0.01),and negatively correlated with soil pH(P<0.05);N2O emission flux was positively correlated with soil temperature(P<0.05). |
PDF Full Text Request