The Effect Of Biochar Application On Soil Microbial Biomass And Soil Enzymes

Biochar is the product of thermal degradation of organic materials in the absence of air （pyrolysis）and at relatively low temperatures （<700℃）. This solid has high stability and adsorbability. Thedegradation of biochar is extremely slow, and the mean retention time could be several hundred to a fewthousand years.Biochar can fix carbon in soil. Scienists appealed thatthe agriculture residue shouldbeprocessed to biochar and be returned to field, to increase carbon sequestration and mitigate globalclimate change. However, the influence of biochar on the soil environment is not clear. Biochar，as amost active component in soil, how soil microbe responsed to it is still not very clear.This study was conducted in the ecological and sustainable experimental station，Hunatai county,Shandong province, to investigate the effects of biochar application on the dynamic of soil microbialbiomass and soil enzymes activities. There were five treatments: CK （NPK fertilizer）, C1(NPKfertilizer+2250kg·hm^-2biochar), C2(NPK fertilizer+4500kg·hm^-2biochar)、CN(750kg·hm^-2biochar-based slow release fertilizer) and SR （NPK fertilizer+straw returning）, Each treatment hasthree replications，every treatment plot was6×6m2. The soil samples were collected from the fourlayers of0-5cm/5-10cm/10-20cm/20-30cm in depth in five growth periods in the winter wheat season.Soil moisture, soil microbial biomass carbon （MBC）, soil microbial biomass nitrogen （MBN） and soilenzymes including invertase, catalase, urease, alkaline phophetase were measured. The main results areas follows:Compared with the control, MBC in the treatment of biochar were increased significantly （by61.3%⁷62.6%, p <0.05）, and the rate of increment of it was positively correlated with the rate ofbiochar application. MBN were also increased in a certain degree.When the rate of biochar applicationwas high, MBN decreased significantly （by66.8%, P <0.05）. MBC and MBN under all treatmentsobviously fluctuate with seasons. The seasonal fluctuation of MBC under biochar application has adifferent trend compared to soil moisture, the temporal coefficient of variation under which weresignificantly less than others treatments. Biochar application will enhance the stability of soil microbeand mitigate the impact of environmental factors. The ratio of MBC to MBN （MNC/MBN） almostremained constant under different treatments among the winter wheat season except treatment C2,which improved MBC/MBN significantly and shown a most acute seasonal change. The temporalcoefficient of variation of MBC/MBN under C2was higher than other treatments siganificantly （by33.0%, P <0.05）.Biochar has an important impact on soil moisture,r while has no impact on soil temperature. Thereis a significant correlation between MBC and soil moisture, but there is no correlation between soiltemperature and MBC. It shown that biochar can regulate soil moisture but not soil temperature.Biochar application increased soil enzyme activities significantly. While the promotion undertreatment C2and SR is obvious，the changes under treatment C1and CN are more slightly. As tocatalase straw returning is more effective than biochar application. Change of soil enzyme activitiesmainly is shown as first increasing and then decreasing in season, and decrease with soil depth. Oppositely, the impact of biochar application on soil enzyme activities increases with soil depth, toreduce the changes in soil depth. MBC correlate poorly with catalase activities, and significantly withinvertase, urease and alkaline phophetase.Biochar application influenced the kinetic parameters of soil enzymes. V_max values increased in allthe four kinds of soil enzymes and K_m values had different effects in different soil enzymes, invertase,urease and alkaline phophetase increased while catalase decreased. It showed that biochar applicationincreased the capacity of enzymes catalyst, but the affinity of soil enzymes to substrate appeared morecomplex.Biochar had no significant effects on the yields of wheat and corn, and could improve the soilenvironment while maintain the field.