BACKGROUND: This paper details the results of solubilization of phosphates in spent mushroom substrate (SMS). As a substrate for the process, bones as a source of phosphates and SMS as medium were used. RESULTS: The process was conducted for 9 months and at the end of the process the substrate obtained was characterized as having a two times higher amount of available phosphorus (express as P2O5), which was confirmed by FTIR and SEM-EDX analysis. A decrease in pH was observed. Strong correlation was found between temperature and the effectiveness of the process (P= 0.000, r= 0.772). Solubilization combined with the degradation process lowered the C/N ratio from 13.6: 1 to 11.7: 1. The utilitarian properties of the substrate obtained were evaluated in germination tests. CONCLUSION: The substrate obtained was characterized as having two times more available phosphorus and can serve as a biofertilizer for the cultivation of plants. (C) 2016 Society of Chemical Industry