Heat pre-treatment as an initial step in vermicomposting significantly influences worm population and cocoon production

Abstract

Heat treatment of vermicompost and cow manure is mandated before their use as fertilizers to address the risk of pathogenicity in vermicompost derived from cow manure. While vermicomposting under mesophilic conditions does not significantly reduce microorganisms or degrade enzymes and proteins, organic matter passing through the earthworm's digestive system is effectively composted and sterilized. This study focused on cow manure and subjected it to three heat treatments: 25 °C (HT1), 70 °C for 1 hour (HT2), and 121 °C at 1.5 atm for 15 minutes (HT3). We assessed these treatments over five incubation periods (0, 7, 15, 30, and 45 days) on earthworm (Eisenia fetida L.) biomass, juvenile counts, and cocoon production. The results showed that all earthworms in HT3 died at the second incubation, while the HT1 and HT2 groups survived. Cocoon counts in HT1 and HT2 increased with each period (P<0.01). Remarkably, the number of cocoons in the control group exceeded that of the HT2 group throughout the study (P<0.01), highlighting the significant impact of heat treatment on vermicompost quality and earthworm productivity. Earthworm productivity was significantly affected by the carbon-to-nitrogen ratio (C/N), organic carbon (%), total nitrogen (%), NH4⁺-N, and NO3⁻-N. Elevated NH4⁺-N from heat treatments had a negative effect on earthworm activity.