Influence of exchangeable ammonium on the survival of earthworms during the vermicomposting of fish offal mixed with peat

摘要

Sphagnum peat mixed with cod (Gadus morhua) offal was vermicomposted for eight weeks with earthworms (Eisenia fetidd) following a two-week pre-composting period. Vermicomposting samples were compared with the same mixtures in the absence of earthworms. Results showed that the maximum amount offish offal that can be used during vermicomposting to get a 100 percent survival rate was 13 percent fish offal (dry wt). Fish offal of 15 percent or more (dry wt) was fatally toxic to the earthworms. This wastrue even when the pre-composting period was extended more than two weeks. Peat, the bulking agent, adsorbs much of the ammonia (NH_3) produced from the decomposition offish offal as ammonium ion (NH_4~+). Results indicate that when earthworms are initially added to a compost mixture, the level of ammonium ion should not exceed 1.0 mg/kg to allow for an earthworm survival rate of 100 percent.