Abstract: Improving soil structure and fertility can increase crop yield and quality. To provide empirical evidence for the reuse of spent mushroom substrate, we investigated the effects of spent mushroom substrate fermented by biochemical fulvic acid (BFA) agent and vermicompost produced by spent mushroom substrate fermented by BFA agent on soil physicochemical properties, soil enzymes, rhizosphere soil microbial diversity, as well as the tuber yield and quality of potato. The results showed that T1 treatment (150 kg·hm^-2 (20%) NPK fertilizer + 7.5 t·hm^-2 of vermicompost) performed better than T2 treatment (20% NPK fertilizer + 7.5 t·hm^-2 of spent mushroom substrate composting). Compared with chemical fertilizer application alone (750 kg·hm^-2 NPK fertilizer, CK treatment), the T1 treatment significantly increased the contents of available phosphorus, available potassium, organic matter, soil pH, the activities of acid phosphatase, neutral phosphatase, alkaline phosphatase, sucrase, catalase and urease, the number and weight of large potatoes, the number and weight of whole potatoes, and the contents of dry matter, starch, vitamin C and potassium of potato tubers. T1 treatment increased the relative abundances of norank_f_norank_o_Gaiellales, Mycobacterium, Mortierella, Paraphaeosphaeria, Naganishia, Trichocladium, and Pseudaleuria, which promoted the release of soil hydrolytic nitrogen, available phosphorus, and available potassium in rhizosphere. In conclusion, T1 treatment improved soil physical and chemical properties, enhanced soil enzyme activities, changed the composition of soil microbial communities, promoted nutrient release, and increased potato yield and quality.

Key words: spent mushroom substrate compost, microbial diversity, soil enzyme, BFA fermentation agent