Feather-Based Compost Drastically Regulates Soil Microbial Community and Lettuce Growth in a Subtropical Soil: the Possible Role of Amino Acids

The role of soil organic nitrogen (e.g., amino acids) in regulating soil microbial community has not been well documented, which is much different from that of soil organic carbon. Feather-based compost (FBC) is rich in amino acids that can enhance soil life and microbial activity. Therefore, this study was designed to evaluate the possible role of amino acids in FBC in regulating soil microbial community. In pot experiment, FBC was applied to lettuce (Lactuca sativa) grown in an infertile subtropical soil. Soil chemical property, enzyme activity, and hydrolysable amino acids were analyzed, and microbial community was characterized with polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis. FBC significantly increased plant biomass, soil available nutrient contents, and enzyme activity. Thirteen kinds of amino acids were detected in soil, and FBC significantly increased the contents of 12 kinds of amino acids, with 5 absent in soils without FBC application. Both amino acids and soil chemical property were significantly correlated with microbial community and soil enzyme activity, and their contributions to the changes in microbial community and soil enzyme activity were comparable. Phenylalanine, leucine, and glutamate were the top 3 kinds of amino acids structuring microbial community. Our results suggest that FBC greatly promoted plant growth probably via the regulatory effects of amino acids on soil microbial community, which sheds light on the application of amino acid-rich compost in agricultural production.