Poly-γ-glutamic acid differentially alters the abundances and communities of N functional genes involved in urea hydrolysis, nitrification and denitrification when applied with different nitrogen fertilizers

Poly-γ-glutamic acid (γ-PGA), a fertilizer synergist, has a significant promotional effect on nitrogen (N) fertilizer efficiency and crop production by regulating N transformation in soil. However, the underlying mechanism of its effect on soil N cycling is not well understood. The effects of γ-PGA on the soil properties, extracellular enzyme activities (EEA), abundances and community structures of N functional genes (NFGs) involved in urea (UF) hydrolysis (ureC), nitrification (ammonia oxidation archaea amoA (Arch-amoA) and bacterial amoA (Bacterial-amoA)), denitrification (narG, nirK, qnorB, nosZ) and dissimilatory N reduction (nrfA) were investigated in this study by applying γ-PGA with different N fertilizers (UF; ammonium sulfate, ASF), so as to reveal the microbial mechanism of γ-PGA on soil N transformation.