Assessment of using solid residues of fish for treating soil by the biosolarization technique as an alternative to soil fumigation

Organic food-waste is an ever growing environmental, economic, and social problem. One way to address this problem is to find new ways to valorise food waste in a circular economical manner. In this study, the concept of separating food from waste at its source in eateries was applied to obtain separated fish waste residues from the general waste of our university's canteen. This study is the first known attempt to use separated fish residues as soil amendments for soil biosolarization (SBS), a soil treatment method which is an environment-friendly alternative to chemical fumigation of soil. In this study a unique laboratory simulation system was used which mimics the conditions of field temperature, monitors the soil respiration and the follows the temporal profile of emitted volatile organic compounds. The fish waste residues were used as soil amendment in 2% wt. and the results showed elevated levels of aerobic soil respiration without unwanted CH4 emission. A different profile of volatile organic compounds (VOCs) was also identified in the soils treated with fish residues. The profile of volatiles found in the soil with fish residues included changes in the amounts of compounds such as: Dimethylsulfide, Methanethiol and C9-aldehydes that have been found to supress soilborne plant pathogens. This is the first indication that VOCs can be used as indicators for the SBS process. Greenhouse studies and analyses of soils treated by fish residues showed no soil residual phytotoxicity affecting later growth of lettuce seedlings while not hindering the herbicidal effect of SBS on unwanted Bidens (Bidens pilosa) weeds. These results indicate that fish waste residues can be used as a soil amendment in the SBS process. © 2022