Effects of Seafood Mushroom Spent Substrate Solid-State Fermentation Combined with PGPR as a Microbial Fertilizer on the Soil Environment and Growth Promotion of Cenchrus fungigraminus

Abstract

Purpose Careless burning, discarding, or overfertilization of spent mushroom substrate (SMS) is environmentally harmful. The reuse of SMS resources is a matter of concern. Methods Spent seafood mushroom substrate solid-state fermentation combined with Rhizobium pusense solution was added to soil to evaluate its environmental and Cenchrus fungigraminus seedling growth effects in pot trial experiments. Results The 40% fermented seafood mushroom SMS (fresh weight) with R. pusense treatment had significantly higher total nitrogen (TN), ammonium nitrogen (AMN), organic matter, etc., and decreased soil electrical conductivity (EC) and increased pH compared with other treatment. Soil catalase (CAT), dehydrogenase (DHA), and urease (UE) activities were significantly improved; there were no differences in CAT and UE activities between 40% (T4) and 50% (T5) SMS additions. C. fungigraminus seedling height and leaf length increased gradually and were significantly different from those of the positive control. The 30–50% seafood mushroom SMS treatment increased plant TN by 5.76–10.00% and total phosphorus by 15.44–16.55%. Plant root length and root activity peaked in T4; however, plant split root number and root activity in T5 decreased by 43.96% and 26.97% compared with those in T4. According to Pearson correlation and one-dimensional regression analyses, the seafood mushroom SMS content affected fertility > enzyme activity > plant growth. Principal component analysis and redundancy analysis showed that the effect of the seafood mushroom SMS concentration on the soil environment was mainly reflected in plant aboveground and root activity. Conclusions Under an SMS addition amount of 40%, plant growth-promoting rhizobacteria promoted the growth of C. fungigraminus seedlings to a greater extent.