Keywords: earthworm casts, organic waste, compost, heavy metal.
Composting of paper mill sludge and some another organic waste by the earthworms is becoming on acceptable practice for converting these materials into useful soil amendments, while eliminating negative environmental impacts. Earthworm casts were collected from organic waste processing plant nearby agricultural land areas. A major food source for the earthworms was the paper mill sludge, food processing by-products and livestock solid wastes in Korea. These wastes have a high fertilizer value, but they have some problems such as high heavy metal content. The differences in cast quality of earthworms are related to their food organic substances. We compared some chemical properties in the earthworm casts. The properties of casts were significantly difference by the EC(dS m-1) of 11.7 ~ 18.0, by a salinity of 0.03 ~ 0.21%, by CEC(cmol kg-1) 27 ~ 63, by a C : N ratio of 41 ~ 59 and by an available phosphate 1.3 ~ 3.3%, in contrast by total nitrogen content of about 1%. We have been also investigated the content of the humic and fulvic substances in the earthworm casts, because these substances play a vital role in soil fertility and crop nutrition. The fulvic acids content was higher than humic acids. The humus content characterized by 4 ~ 10% in all casts of earthworms analyzed. Otherwise, high population of bacteria and actinomyces was found in the earthworm casts created from food processing sludge.