Effects Of Biochar Application On Greenhouse Gas Emission,crop Growth And Soil Fertility In A Rapeseed-rice Rotation System

Biochar,a material with large specific surface area,high chemical stability,and microbial inertness,shows great potential in controlling greenhouse gas emissions from agricultural sources and provides a new way for the recycling of agricultural waste.In this study,the static dark box-gas chromatography was used to investigate the continued effects of the different types of straw resource utilization（straw comminution and straw biochar returning）on farmland greenhouse gas emissions,soil physical and chemical properties,and crop yields in the rapeseed-rice rotation system in southern China based on a long-term experiment.Moreover,different fertilization levels（conventional fertilization and 30%reduction fertilization）were established to study whether the application of biochar still reduces fertilization after five years.The main results are as follows:1 The application of biochar slowed down the fluctuation of farmland greenhouse gas emissions during the entire cultivation cycle under the rapeseed-rice rotation system,and stabilizes greenhouse gas emissions in a relatively flat state,thereby reduced greenhouse gas emission;Compared with the conventional fertilization treatment,the application of biochar reduced CH₄ and N₂O emissions by 45.54%and 38.59%respectively;and the application of straw increased CO₂ and CH₄ emissions by 20.47%and 24.72%respectively.Compared with the straw treatment,the application of biochar reduced the CO₂,CH₄ and N₂O emissions by14.22%,56.32%,and 29.69%respectively;2 After 5 years of biochar application into soil,the soil organic carbon content,the total nitrogen content and available phosphorus content was significantly increased,soil available potassium content was not influenced,and the effects of biochar application on soil pH,EC and moisture content disappeared;3 After biochar was applied to soil for 5 years,rice yield between the biochar treatment and the conventional fertilization treatment was not significantly different;Biochar application significantly increased the yield of rapeseed by 58.42%and the 1000-grain weight by 11.49%;After biochar was applied to soil for 5 years,nitrogen fertilizer,phosphate fertilizer and potash fertilizer can still be 30%reduced without yield decreasing.The above results preliminarily showed that the application of biochar in the rice-rapeseed rotation system can reduce greenhouse gas emissions from farmland for a long time,and can reduce the application of nitrogen fertilizer,phosphate fertilizer and potash fertilizer without yield decreasing.