Poly-γ-glutamic acid bioproduct improves the coastal saline soil mainly by assisting nitrogen conservation during salt-leaching process

Salt-leaching is considered to be a major method for soil desalting in agriculture. Therefore, conservation of soil nutrition is significant to soil fertility and environment protection during the salt-leaching process. The effect of poly-γ-glutamic acid bioproduct (PGAB), which was manufactured by solid-state fermentation with the bacteria producing glutamic acid (GA) and poly-γ-glutamic acid (γ-PGA) and organic waste, on keeping nitrogen (N) during salt-leaching was investigated in this study. The isolated bacteria producing GA and γ-PGA were identified as Brevibacterium flavum and Bacillus amyloliquefaciens , respectively. After the saline soil was leached for 90 days, compared to the control, soil salinity (0–30 cm) in the PGAB treatment was decreased by 39.9%, while soil total N was significantly ( P