Effect of amendments with different phenolic acids on soil microbial biomass, activity, and community diversity

We have used polymerase chain reaction (PCR) based on 16/18S rRNA sequences, followed by denaturing gradient gel electrophoresis (DGGE) to describe the effect of different types of phenolic acid on soil microbial populations. Further, we suggest a potential mechanism by which these acids selectively enhance specific microbial populations in soil, leading to the development of shifted communities with differing qualitative and quantitative compositions. Microbial biomass carbon (MBC) and basal soil respiration (BSR) were also measured to assess changes in quantitative estimation and the activity of the total microbial biomass. In this study, two types of phenolic acids, - phenol 2,4-di-tert-butylphenol (PEDT) and vanillic acid (VA) - were used. The results revealed that a significant effect on the microbial biomass and activity. The addition of PEDT and VA resulted in stimulation of microbial biomass at low concentrations and inhibition at high concentrations. In addition, DGGE analysis revealed that the two phenolic acid applications, VA in particular, could have a considerable impact on microbial communities. These results suggest that PEDT and VA play important roles in soybean allelopathy; this may be important for understanding the relationship between allelopathy and barriers in soybean monocropping. (c) 2008 Elsevier B.V. All rights reserved.