Risk-based environmental management of Auricularia spent mushroom substrate: a review-based conceptual framework for safe soil application.

The rapid expansion of Auricularia cultivation has generated a growing lignocellulosic waste stream, yet soil recycling of Auricularia spent mushroom substrate (SMS) remains constrained because its woody origin, incomplete decomposition, variable formulations, mineral additives, and post-harvest handling make it a heterogeneous residue rather than a ready-to-use organic fertilizer. This review synthesizes the attributes governing its environmental suitability for soil application and evaluates the main soil-oriented management pathways. Across the available evidence, the principal recurrent constraints are elevated salinity, insufficient maturity or residual phytotoxicity, and C/N-related nitrogen immobilization. Restricted direct field use is generally limited to screened materials with adequate maturity, low salinity, a narrowed C/N ratio, and no evident contaminant or biosafety concern. Indicative decision criteria should therefore be treated as method- and use-dependent screening aids rather than universal thresholds. GI values should be interpreted with the reported test species, extract ratio, moisture condition, and assay protocol; EC should be interpreted only with a defined extraction method and intended use; and C/N ratio should be assessed together with maturity, salinity, contaminant status, mineral N status, and crop-soil compatibility. For stabilized materials, application rates should be calculated on a dry-weight basis and constrained by the most limiting agronomic or environmental factor rather than assigned from a fixed universal t ha-1 yr-1 range. Future work should strengthen harmonized thresholds, long-term field evidence, and integrated environmental and techno-economic assessment.