Abstract: 【Objective】 High nutrient concentration may have a significant impact on soil carbon and nitrogen transformation and microbial characters. Soil carbon and nitrogen transformation and microbial characters of glucose addition at high nutrient concentration of the fertilizer were determined for understanding of the transformation process of the special characteristics of nutrient conditions and for proposing scientific measures to improve nitrogen use efficiency.【Method】Paddy soils were selected in subtropical region of China. Changes of NH4+-N, NO3--N, inorganic N, microbial biomass, microbial functional diversity were measured by an incubation experiment through setting different amount of ammoniums sulfate and glucose treatments.【Result】 Compared with using ammonium sulfate treatments, adding glucose at high concentration of ammonium sulfate treatments, NH4+-N, NO3--N and inorganic N contents ranged -4.3%-10.2%, -8.0%-41.8% and -3.9%-10.4% respectively. Microbial biomass carbon was increased significantly by 89.6%-126.7%, while microbial biomass nitrogen was increased by 11.5%-109.0%. NH4+-N, NO3--N and inorganic N contents of adding glucose at moderate concentration of ammonium sulfate ranged -7.5%-5.8%, 6.1%-58.3% and -7.2%-49.4% respectively. Microbial biomass carbon and nitrogen also showed an increasing trend. BIOLOG analysis showed that AWCD value, Shannon, Simpson and McIntosh indices were at a low level at high and moderate concentrations of ammonium sulfate. Glucose addition alone and glucose addition with conventional concentration of ammonium sulfate, NH4+-N, NO3--N and inorganic N contents were decreased by 17.3%-29.0%, 21.4%-92.9% and 18.8%-45.9%, respectively. Microbial biomass carbon and nitrogen were not significantly increased. AWCD value, Shannon, Simpson and McIntosh indices were higher. There were interactive effects on microbial biomass carbon and AWCD values of adding glucose and ammonium sulfate.【Conclusion】 Adding glucose at higher concentration of ammonium sulfate increased nitrogen immobilization efficiency and reduced soil inorganic nitrogen content as the increasing soil microbial activity. Under the conditions of using inorganic nitrogen, in particular, attention should be paid especially to the joint application of organic and inorganic fertilizers so that the nitrogen transformation can be regulated, and consequently the risk of loss of nitrogen can be reduced.

Key words: BIOLOG, C/N ratio, paddy soil, glucose, microbial biomass