Abstract:Soil microbial biomass as an important active component in global carbon and nitrogen cycle, and its relative parameters can function as sensitive indicators of changes in soil quality. Our objective was to investigate effects of different fertilization practices on soil microbial biomass Carbon (SMBC), Nitrogen (SMBN), the microbial quotient (MQ) and the ratio of SMBC to dissolved organic carbon (DOC), and to analyze the correlations of these biological indices with other soil parameters, the physicochemical properties in tea leaves, respectively, through the long-term fertilizer experiment of the tea garden in east Fujian(119°23'-119°51'E, 26°41'-27°24'N). Six fertilization treatments were designed in this study: chemical fertilizers (C), half-organic manure plus half-chemical fertilizers ((CO)1/2), organic manure fertilizers (O), leguminous green manure plus chemical fertilizers (CL), half-organic manure, leguminous green manure plus half-chemical fertilizers ((CO)1/2L), and without fertilizers (CK). Results indicated that in comparison with CK, SMBC concentrations in (CO)1/2L, CL and O treatments increased by 1.87, 1.26, 1.49 times, SMBN increased by 2.18, 1.32 and 1.70 times, respectively, whereas SMBC and SMBN concentrations in the C treatment decreased by 46%, 59%, individually. In terms of the ratio of SMBC to DOC, different fertilization treatments followed the orders of O>(CO)1/2L>CL>(CO)1/2>CK>C. Thus the fertilizing effect on soil fertility improvement in the O and (CO)1/2L treatments was better than those in other treaments. A correlation analysis revealed that the concentration of SMBC and the ratio of SMBC to DOC were significantly and positively correlated with soil urease activity, the contents of soil organic matter, total N and P, hydrolysable N, available P and K, soil water, CEC(P<0.05), respectively, further suggesting the concentration of SMBC and the ratio of SMBC to DOC are closely related with soil fertility, and can be used as the sensitive indices of soil fertility in the tea garden with long-term fertilizer application.