Response Of Microbial Characteristics To Biochar Addition In Farmland Soil

It is well known that biochar has already brought significant ecological, economic and environmental benefit for soil carbon sequestration potential, crop yield and resources sustainable development, however, it is not chear how biochar affect the soil microbial ecosystem stability. Field micro-plot trials was conducted to investigate the impacts of different amount biochar addition(CK(0 t hm-2), C1(22.5 t hm-2), C3 (67.5 t hm-2) and C5(112.5 t hm-2)) and adding way(C1-3:biochar of 22.5 t hm-2 added year by year, this year is the third year) on soil microbiological characteristics including microbial biomass carbon (MBC), phospholipid fatty acid(PLFA) and amino sugar. The results were:1. The MBC content of whole growing stage was increased significantly by 80.63% to 107.24%(p< 0.05)with biochar amended to soil and the result MBC increased with biochar increased was related to the changed soil physical and chemical properties such as soil moisture content and density. Biochar addition also influenced the seasonal fluctuations of MBC:soil MBC content has different growth while added with different biochar content in every growing season and the growth fluctuated with the seasons. The result that soil MBC of C1-3 treatment significantly increased by 26.06% than C3 treatment indicated that biochar added year after year is better than added once. 2. Biochar addition increased microorganism’s activities, changed the amount of microorganismcomponent of community structure and stability of microbial ecosystem stability. Soil total microbial PLFA decreased with the increased biochar addition during early growth stage(seedling stage) and increased with biochar addition due to the improvement of soil nutrients and hydrothermal conditions. However, soil total PLFA has no significant seasonal variation for the results of the interaction of microbe, biochar, soil and plant. Biochar added in successive method is better than disposable method in enhancing soil total PLFA for the effect of biochar addition on soil structure. Soil fungal PLFA(Fun-PLFA) and bacterial PLFA(Bac-PLFA) have well correlation with soil totalPLFA. Soil Fun-PLFA and Bac-PLFA greatly influenced by seasonal fluctuations.The ratio of fungal to bacterial PLFA has little seasonal variation. The promotion of fungal growth affected by different amounts of biochar in every growing season was higher than that of bacteria.As well as, the ratio of fungal to bacterial PLFA increased with the increased biochar content indicated that the effect of biochar on soil PLFA is related to strains. Biochar addition enhanced the soil actinomycete PLFA (Act-PLFA) and arbuscular mycorrhiza fungal PLFA(AMF-PLFA). AMF-PLFA has great seasonal variation for that AMF activities is related to crop growth. The ratio of Gram-positive to Gram-negative PLFA decreased greatly with the increased biochar addition in seedling season and reached a certain value with the crop growth. It indicated that the ratio of Gram-positive to Gram-negative PLFA has no significant seasonal variation and Gram-positive and Gram-negative bacterial community structure tend to be stable.3. Soil amino sugar has no significant seasonal variation with biochar addition among growing seasons. Soil amino sugar has significant seasonal variation among different biochar concentrations and the range differ from the biochar content. Biochar amended to soil increased the accumulation of amino sugar by 10.92% maximally in the whole growing season while the CK treatment is 15.72%.The responses of glucosamine (GluN) derived from fungi to biochar addition vary significantly in growing seasons. The accumulation of GluN increased during early growth stage and booming stage and decreased at late growth stage. It indicated that the effect of biochar on soil fungi varies from growing seasons and biochar concentrations. The changes of muramic acid(MurA) derived from bacteria are similar to that of GluN. It indicated that response of fungi and bacteria to biochar addition is synchronized. Probably there is a threshold for biochar increasing fungi and bacteria quantities higher or lower than which the growth of fungi and bacteria will be restrained.The response of fungi and bacteria to biochar addition is of synchronized and the effect of biochar addition on bacteria is more significant than that on fungi. It showed that the relative contribution of bacteria to soil organic matter(SOM) exceed fungi and biochar affect the turnover of SOM through regulating effect process. Though the relative contribution of bacteria residues to SOM exceed fungi, the absolute content of fungi is far more than bacteria, so fungi will still be of great significance in maintaining the stability of SOM in the long term.4. The results that the ratio of fungal to bacterial PLFA increased and the ratio of GluN to MurA decreased from the study of fungal cell membrane PLFA and bacterial cell wall amino sugar indicated that biochar addition increase the growth of fungi but protect the bacteria from decomposing reativelily.