Abstract: A field experiment including 4 treatments， CK （neither urea nor vermicompost was applied）， CF （100% of nitrogen was provided by urea）， VC （100% of nitrogen was provided by vermicompost）， and VC+CF （50% and 50% of nitrogen was provided by vermicompost and urea， respectively） was performed， to determine the effects of different treatments on microbial population， microbial biomass carbon content， root system construction， root exudates content， microbial respiration and metabolic quotient in the rhizosphere soil of cowpea. It was shown that in comparison with CF treatment， VC+CF treatment significantly increased microorganism population and microbial biomass carbon content. Bacteria population under VC+CF treatment was increased by 12413%， 7048% and 1783% compared to that under CK， CF and VC treatment， respectively. Vermicompost application obviously promoted the root growth and construction of cowpea， especially fine root weight and the ratio of fine root. Meanwhile， VC+CF treatment evidently increased the root exudates content and significantly increased microbial respiration， but the metabolic quotient was decreased. Microbial respiration under VC+CF treatment was increased by 64.91%， 36.23% and 16.05% compared to that under CK， CF and VC treatment， respectively， while the metabolic quotient was reduced by 10.85%， 9.06% and 5.32%， respectively. However， the effect of VC treatment on micro\|domain environment characteristics was minor. In conclusion， vermicompost application could significantly improve micro\|ecological environment and enhance the microbial activity of cowpea rhrizosphere soil compared with CF treatment， especially when vermicompost was co\|applied with inorganic fertilizer.

Key words: cowpea, vermicompost, root construction, soil microbial respiration, metabolic quotient