Integrated Analysis Of The Effects Of Biochar Addition And Organic Fertilizer Replacement On Soil Greenhouse Gas Emissions

Global warming caused by greenhouse effect is one of the major ecological and environmental problems facing mankind.The main reason for the intensified greenhouse effect is the rapid increase in atmospheric concentrations of carbon dioxide(CO2),methane(CH4),nitrous oxide(N2O)and other greenhouse gases.Soil is one of the important sources of greenhouse gas emissions,soreducing soil greenhouse gas emissions is of great significance to global climate change.In this study,Chinese and English literatures related to the effects of biochar addition(158 studies,985 measurements)and organic fertilizer replacement(95 studies,773 measurements)on soil greenhouse gas emissions were collected.The combined effects of biochar addition and organic fertilizer replacement on soil CO2,CH4,N2O emission and global warming potential(GWP)were studied by data integration analysis,and the potential regulatory factors were discussed.The main conclusions of this study are as follows:(1)In dryland soils,the addition of biochar reduced CO2 emissions by 5.13%,N2O emissions by 7.43%and GWP by 3.31%,and increased CH4 emissions by 12.47%.In paddy soils,the application of biochar reduced CO2,CH4,N2O emissions and GWP by 19.64%,9.75%,36.82%and 24.76%,respectively.(2)The effects of biochar application on soil greenhouse gas emissions and global warming potential are influenced by the type,amount,characteristics of biochar and soil properties.In dryland soils,the application of non-straw biochar,biochar amount>30 t hm-2,pH≤9,C/N>100 and pyrolysis temperature>500℃ had the best effect on reducing GWP.When soil pH≤6.5,organic carbon content>20 g kg-1,bulk density≤1.3 g cm-3 and total nitrogen content>2 g kg-1,application of biochar has a better inhibition effect on GWP.In paddy soils,the application of straw biochar,biochar amount>30 t hm-2,pH>10,C/N in the range of 50-100 and the pyrolysis temperature in the range of 400-500℃had the best effect on reducing GWP.When soil pH≤6.5,organic carbon content>20 g kg-1,bulk density>1.3 g cm-3,and total nitrogen content>2 g kg-1,application of biochar has a better inhibition effect on GWP.The application of biochar changed soil physical and chemical properties,reduced soil bulk density,soil pH and total nitrogen content by 6.98%,0.13%and 0.72%,respectively,and increased soil organic carbon content by 51.20%in dryland soils.In paddy soils,biochar addition decreased soil bulk density by 16.80%,while increased soil pH,organic carbon content and total nitrogen by 2.82%,16.59%and 13.53%,respectively.(3)Compared with single application of chemical fertilizer,the substitution of organic fertilizer for chemical fertilizer generally increased CO2,CH4,N2O emissions and GWP in dryland soils by 25.45%,25.08%,70.20%and 48.41%,respectively.In paddy soils,organic fertilizer replacement increased CH4,N2O and GWP by 25.08%,59.78%and 28.08%,respectively,and decreased CO2 emission by 3.80%.(4)In dryland soils,the global warming potential decreased when applied straw fertilizer,organic fertilizer application rate≤100 kg N hm-2 and organic fertilizer replacement ratio:≤30%.When soil pH ≤ 6.5,organic carbon content in the range of 10-20 g kg-1 and total nitrogen content in the range of 1-2 g kg-1,organic fertilizer replacement had the least promotion effect on GWP.In paddy soils,when applied other types of organic fertilizer,organic fertilizer application rate ≤100 kg N hm-2 and organic fertilizer replacement ratioin the range of 30-70%,the promotion effect on global warming potential is the least.When soil pH ≤6.5 and total nitrogen content ≤1 g kg-1,organic fertilizer instead of chemical fertilizer had the least promotion effect on GWP.