Effects Of Biochar Application Modes On Rice Yield And Methane Emission In Medium-Low Yielded Paddy

Straw carbonization?biochar?returning is a promising technology for carbon sequestration,yield increase and greenhouse gas mitigation in paddy ecosystem.Currently,biochar returning are primarily based on two modes:one-time high dose application or year by year continuous low-dose application,it still lacks comparative study about the effects of the two application modes on rice yield and greenhouse gases emission in paddy ecosystem.Therefore,a 2-year experiment was conducted in a paddy field of medium-low soil fertility under a single cropping system in northern part of Zhejiang Province to investigate the effects of successive low-dose biochar application(RSDB1,2.8t ha^-1 yr^-1)and one-time high dose application(RSDB2,22.5 t ha^-1)on soil nutrient concentrations,rice yield,CH₄ emission and the relative potential mechanisms.The research could help to explore suitable biochar application mode for single cropping medium-low yielded paddy field,the main results are as follows:?1?Both biochar application modes could enhance soil nutrient concentrations.The increase rate by RSDB2 is significantly higher than RSDB1.Compared to RSDB1,RSDB2 could increase soil pH,CEC,TC,TN,available K,P,Mg,Ca contents and decrease available Al,Fe contents?p<0.05?.?2?Both biochar application modes could increase rice yield.The increasing rates in concessive two years are 8.0%and 4.3%in RSDB1 and 16.5%and 12.9%in RSDB2?p<0.05?.The increase of concentrations of the soil pH,TC,TN,available K and P contents and the decrease of available Fe contents in the biochar treatments might be the key factors contribute to increase of the rice yield.?3?Both biochar application modes could significantly decrease CH₄ emission from paddy field.RSDB1 could decrease 43.0%and 31.0%CH₄ emission,RSDB2 could decrease 52%and 22%CH₄ emission in the concessive two years.Compared to rice straw amendment,the effect of biochar application on the reduction of cumulative CH₄ emission from paddy field were even higher,it could decrease 71.3%?84.2%of total CH₄ emission.The possible mechanisms for CH₄ emission mitigation in paddy were due to that biochar application could decrease the ratio of methanogenic archaeal 16S rRNA gene to methanotrophic bacterial pmoA gene copy numbers and increase the rate of CH₄ oxidation to methanogenic activity?p<0.05?.