| Climate warming caused by greenhouse gases such as carbon dioxide（CO2）,nitrous oxide（N2O）and methane（CH4）has become one of the most concerned environmental problems.Cropland has great potential for greenhouse gas emission reduction.The application of organic amendments（animal manure and crop straw）can not only maintain soil productivity and improve soil fertility,but also increase soil organic carbon（SOC）content,and fix CO2 in soil in the form of SOC to mitigate the greenhouse effect.At present,the application of organic amendments has become an important agricultural measure to mitigate climate warming.Due to the different climatic conditions,management measures,soil properties and other factors in different regions,the "carbon sequestration" and "emission reduction" effects of adding organic amendments are very different.Therefore,this study intends to determine the main driving factors of soil carbon sequestration,CH4 and N2O emission reduction by using meta-analysis,and quantitatively evaluate the comprehensive impact of organic amendments on soil carbon sequestration rate,annual CH4 and N2O emissions and global warming potential（GWP）.It is helpful to scientifically evaluate the contribution of rational application of organic amendments in mitigating climate warming and help achieve the goal of carbon peak and carbon neutrality in agriculture as soon as possible.Keywords such as “nitrous oxide”,“methane”,“greenhouse gas”,“global warming potential”,“organic amendments”,“nitrous oxide”,“methane”,“GWP” and “organic amendments” were selected.Related references on cropland SOC content,N2O and CH4 emissions were searched in CNKI and Web of Science databases,and a total of 207 references and 1344 valid data were screened out.A large number of data were scientifically sorted out and meta-analysis was conducted to quantitatively evaluate the comprehensive effects of organic amendments addition on soil carbon sequestration rate,annual CH4 and N2O emissions and GWP under different influencing factors.The results of meta-analysis showed that:（1）There was a significant negative correlation between annual SOC sequestration rate and experiment duration（r2=0.45,p<0.05）;There was also a significant negative correlation between annual SOC sequestration rate and experiment duration（r2=0.43,p<0.05）.When the annual average temperature is ≤10℃ and annual average precipitation is ≤600mm,the increase of SOC content and storage is the largest.The increase of SOC content and storage of organic amendments under one year cropping system is better than that of two years cropping system.The increase of SOC content and storage in tillage was better than that in no-tillage and rotary tillage.Among different land use types,upland had the highest SOC content and storage increase compared with paddy field and drought-flood rotation.After adding organic amendments,SOC storage increased the most in 10 20 years.（2）N2O cumulative emission,N2O emission factors,yield-scaled N2O emissions,and yield-scaled GWP did not relate to the nitrogen application rate.The N2O emission factors and crop yield increased significantly and yield-scaled N2O emissions decreased significantly with the addition of organic amendments in subtropical region.Under the climatic conditions of annual precipitation > 1000 mm and annual temperature > 15℃,adding organic amendments could significantly increase the N2O emission factors and crop yield,and significantly reduce yield-scaled N2O emissions.When organic amendments were added to acidic soil（p H≤6.5）,yield-scaled N2O emissions significantly decreased,and N2O emission factors and crop yield significantly increased.Adding organic amendments to soil with total nitrogen ≤0.6 g·kg-1 and SOC≤8 g·kg-1 could significantly reduce yield-scaled N2O emissions.Applying manure fertilizers can significantly reduce yield-scaled N2O emissions and increase crop yield.When nitrogen application rate was 100 200 kg·hm-2,high yield of wheat and maize could be achieved,and yield-scaled GWP could be decreased to the maximum.N2O emission,GWP and crop yield were significantly increased by manure fertilizers application.（3）The CH4 emissions related negatively to the nitrogen application rate（r2=0.2,p<0.05）.N2O emission factors,yield-scaled N2O emissions did not relate to the nitrogen application rate;while the yield-scaled GWP related negatively to the nitrogen application rate（r2=0.24,p<0.05）.The CH4 emissions,N2O emission factors and crop yield were significantly increased by adding organic amendments under the climatic conditions of annual precipitation > 1400 mm and annual temperature 15 17 ℃.The CH4 emission,N2O emission factors and crop yield were significantly increased when organic amendments were added to soil with total nitrogen > 2 g·kg-1 and SOC > 20 g·kg-1.In acidic soil（p H≤6.5）,CH4 emission and N2O emission factors increased significantly.The addition of organic amendments and fertilization methods（one-time fertilization,basic fertilizer and topdressing）could significantly increase CH4 emissions in rice fields.The N2O emission factors and crop yield could be significantly increased under split fertilization regime（basic fertilizer and topdressing）,and N2O emission factors could also be significantly increased by applying manure fertilizer.When the nitrogen application rate was less than 200 kg·hm-2,the yield-scaled GWP could be kept low while the high yield could be guaranteed.In rice planting,straw instead of manure fertilizer can be used as organic amendments to reduce yield-scaled GWP without reducing rice yield.In summary,under different climatic conditions,soil properties,field management measures and other factors,adding organic amendments can significantly increase SOC content and storage.Cropland ecosystem is a sink of CO2 absorption and a source of N2O and CH4 emission.When the nitrogen application rate was 100 200 kg·hm-2,the yield-scaled GWP could be reduced to the maximum on the basis of high yield of wheat,maize and rice. |
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