Effects of γ-polyglutamic acid combined with chemical fertilizer on soil microbial community structure and function in Xinjiang cotton fields

Abstract:

[Objective] Long-term and excessive application of chemical fertilizers leads to soil degradation and an imbalanced microbial community structure in soil.The combination of organic active substances with chemical fertilizers is considered an important approach for controlling soil degradation and maintaining microbial community stability.[Methods] Metagenomics was employed to study the effects of combining the bioactive substance γ-polyglutamic acid (γ-PGA) with chemical fertilizer on soil microbial community and function in cotton fields.Four fertilization groups were designed:chemical fertilizer (NK),chemical fertilizer combined with γ-PGA aqueous solution (YT),chemical fertilizer combined with γ-PGA granules (GT),and no fertilizer (CK).[Results] GT and YT groups outperformed NK and CK groups in terms of cotton growth and soil nutrient content.The combination of γ-PGA with chemical fertilizer significantly increased the microbial abundance and diversity in soil,while chemical fertilizer alone did not improve soil microbial diversity.In addition,the application of γ-PGA changed soil microbial community composition.Compared with the NK group,YT and GT groups showed a 9.70%–12.72% decrease in the relative abundance of Proteobacteria and 13.33%–20.90% and 8.09%–13.01% increases in the relative abundance of Bacteroidetes and Actinobacteria,respectively.In addition,the relative abundance of Rhizophagus(a genus of mycorrhiza fungi) increased by 19.71% in the YT group.The functional gene analysis showed that GT and YT significantly increased the abundance of functional genes related to amino acid biosynthesis,secondary metabolite biosynthesis,and ABC transporters.[Conclusion] The application of γ-PGA has the potential of improving soil microbial diversity and ecosystem stability in Xinjiang cotton fields.