Assessment of spent mushroom substrate recycling via soil biosolarization

Biosolarization is an alternative to pesticides for soil pest management that can utilize food industry organic matter byproducts as soil amendments to create conditions conducive to pest suppression. Spent mushroom substrate (SMS) is the main byproduct of mushroom cultivation. New uses are needed for this waste stream as its production continues to increase. This study evaluated two types of SMS as sole amendments and as co-amendments with cover crop biomass for biosolarization. SMS consisted of rice bran with hardwood sawdust (BS SMS) and soybean hulls with oak sawdust (SO SMS). Cover crop biomass was a mix of Secale cereale and Trifolium incarnatum. Gas evolution, pH, biocidal organic acid (BOA) production, phytotoxicity, and soil nitrogen were tracked during and/or after simulated biosolarization. SMS and cover crop treatments were compared to rice bran-amended soil and unamended, solarized soil. Results indicate that SO SMS treatments can produce BOA concentrations and phytotoxic conditions comparable to rice bran-amended soil, with BOA content correlating to radish seed germination indices with a coefficient of determination of 0.683. The pH of treatments including cover crop biomass, whether as a sole or co-amendment, significantly decreased during biosolarization, but were higher than pH of rice bran controls. SO SMS and cover crop biomass as sole amendments significantly increased total nitrogen content compared to solarized soil (P < 0.05), likely due to the addition of nitrogen-containing organic matter, but not mineral nitrogen. These findings suggest that certain SMS compositions may be valuable amendments for agricultural pest control via biosolarization.