Abstract:

【Objective】 Microbiological aspects of soil quality under different fertilizer amendments were investigated to clarify the effect of over-use fertilizer, especially, chemical fertilizer on the agro-ecosystem sustainability. 【Method】 Soil microbial biomass, respiration intensity and functional diversity in Hapli-Stagnic Anthrosols were investigated by an incubation experiment with different fertilizer applications. 【Result】 During the incubation, the content of microbial biomass carbon was different under different fertilization: chemical fertilizer incorporated with 2% straw or 2% manure＞CK (no fertilization) and chemical fertilizer incorporated with 0.5% straw or 0.5% manure＞chemical input alone; Case in microbial biomass nitrogen was similar: chemical incorporated with 2% straw＞CK, chemical incorporated with 2% manure or 0.5% straw＞chemical alone. Respiration intensity and metabolic quotient declined with different fertilizer rates along the incubation. Soil respiration under chemical incorporated with 2% straw or 2% manure amendments were higher during the incubation and the patterns of metabolic quotient was: chemical plus 2% straw or manure and maximum level of chemical input alone＞chemical plus 0.5% straw or 0.5% manure and minimum chemical input＞CK and normal level chemical input. BIOLOG analysis indicated that over-use of fertilizer, especially chemical fertilizer decreased the potential of carbon utilization and functional diversity of soil microorganism. 【Conclusion】 As sensitive indicators, soil microbial biomass, respiration intensity and functional diversity corresponded to the changes in soil quality. Over-use of chemical fertilizer attenuated biological aspects of soil quality and interrupted the sustainability of agro-ecosystem.

Key words: fertilization, paddy soil, microbial biomass, respiration intensity, microbial functional diversity