Effect Of Biochar On Carbon Dioxide Emissions And Methane-releasing Potentials From Flooded Soil By Simulation

Climate warming and mitigation of Greenhouse Gases (GHGs) has been thefocus of the global attention at present. Biochar attracts many attentions in recentyears due to its potential application in improving soil properties, increasingcarbon sink and controlling GHGs emissions, especially for carbon abatement bythe increasing of carbon sink in soils.A waterlogged paddy soil environment was simulated by means of pillarexperiment in this research. Biochar with application rates of2%(C2, w/w),5%(C5, w/w) and8%(C8, w/w) were amended to the simulated paddy soils toinvestigate the effects of biochar admendments on soil CO2emissions and CH4releasing potentials, while C0(without biochar) was set for a contrast.Meanwhile, the changes of soil physicochemical properties, enzymatic activitiesand microbial community structures due to biochar addition were discussed hereto elaborate mechanism of biochar’s effect on soil CO2emissions and CH4releasing potentials. The results showed that:(1) Soil pH was significantly enhanced due to biochar application, andpromoted with increasing of biochar addition. The value of pH from C2, C5andC8treatment was increased by0.2,0.3and0.5unit approximately whencompared with control (C0). Additionally, the permeability of soil could beimproved as well as soil anerobic condition by biochar amendment. However, itwas showed that no regular changes of soil Eh was found in responde to biocharamendments.(2) Soil organic carbon content was obviously increased by biocharadditions and it would increased by7mg·g-1roughly for every1%(w/w) ofbiochar amendment. Furthermore, a significant inhibition of biochar on soilorganic carbon mineralization and water-soluble organic carbon（WSOC） wasobserved. (3) Microbial biomass carbon (MBC) from soils was evidently improvedwith biochar amendment, and that it was increased by75%,84%and50%for C2,C5and C8respectively, when compared with control. It might be benefit fromimprovement of soil properties so as to provide a preferable habitat for microbes’growth. However, no consistent variation of MBC was found with amount ofbiochar application.(4) Soil dehydrogenase (DHA) and coenzyme F420were both inhibited bybiochar addition, while as very similar as enzymatic activities followed:C0>C5>C2>C8. It seemed to be more effective in inhibiting enzymatic activitieswhen high applicated rate of biochar was amended.(5) Compared with control, soil cumulative CO2emissions were reducedby5.1%,2.4%and26.5%respectively. Obviously, CO2emissions weresignificantly decreased due to biochar addition. Moreover, high applicated rate ofbiochar (C8) might be better in reducing CO2emissions from waterlogged soilbecause of its functioning on soil organic carbon’s oxidation stability.(6) The BMP (biochemical methane potential) test results showed thatBMP of each treatment was decreased with waterlogging time. Biochar seemsprofitable to accelerate soil organic matter’s anerobic degradation as well asmethane-producing in a short term. While, a long-term experiment showed thesequence of BMP in all treatments was: C5>C0>C2>C8. Apparently, the BMPresults of C2, C8were surely less than control and it was suggested that moresignificant to inhibit soil methane production for high applicated rate of biochar.(7) The results on community structure of soil bacteria and methanogensby PCR-DGGE analysis demonstrated that: biochar’s addition wasunconspicuous on affecting community structure of soil bacteria, but obviouslyin growth of certain sort of methanogens instead. The specific archaeon of strip28,31from soil samples might be a crucial reason for higher BMP in C5treatment. What’s more, the abundance or activity of crenarchaeote of strip25from C5and C8treatment was quite poor, which could resulted in preferableinhibition of CH4-releasing potential by higher biochar amendment.In inclusion, soil properties such as pH, MBC, WSOC, organic carbonmineralization, soil enzymatic activities and microbial community structureswere dramaticlly affected by biochar amendment. Generally, higher amendment was more pregnant in controlling CO2emission. On the one hand, Oxidativestability of organic carbon from soil was improved so that CO2emission andCH4-releasing potentials was decreased by reducing soil organic carbonmineralization due to biochar amendment; on the other hand, weakening of soilorganic matter’s anerobic degradation due to soil microbial and enzymaticactivity inhibiting by biochar amendment was also an important reason fordecrease of CO2and CH4emissions. However, the comprehensive warmingeffect of biochar on agricultural GHGs emissions, quantification research andfunctioning micromechanism are still rarely reported, which would also be animportant task to be addressed for future.