Effects of Combined Application of Mushroom Residue and Chemical Fertilizer on Greenhouse Soil Quality and Microbial Community Structure and Function

To explore the effects of different fertilization regimes on physicochemical properties and microbial ecology of greenhouse soil, we set five treatments with original soil (BS) as the control: chemical fertilizer alone (GF), high/low-rate mushroom residue combined with chemical fertilizer (MH, ML), and high/low-rate organic fertilizer combined with chemical fertilizer (OH, OL). Metagenomic sequencing and bioinformatic analyses were adopted to characterize soil nutrients, microbial communities, and C-N-P-S metabolic functions. All treatments increased soil nutrients. MH had the highest organic matter, total nitrogen, nitrate nitrogen, and available phosphorus, while GF contained the most available potassium and ammonium nitrogen. Bacteria dominated the soil microbiota, with Pseudomonadota and Pseudomonas as keystone taxa. Mushroom residue amendments improved microbial richness and diversity. By improving soil physicochemical properties, the combined application of organic fertilizer with chemical fertilizer and mushroom residue with chemical fertilizer both enriched some beneficial microorganisms. Chemical fertilizer alone enhanced anaerobic metabolism, which was reversed by high-rate mushroom residue. Available phosphorus, available potassium, and ammonium nitrogen were key environmental factors driving the differentiation of microbial communities and their functions. Overall, mushroom residue combined with chemical fertilizer is effective for greenhouse soil improvement, with proper dosage and tillage recommended.