Response to annual applications of de-inked papermill biosolids by field earthworms on three agricultural soils

Papermill biosolids (PB) have been used as soil conditioners on agricultural soils, to reclaim mining soils, and to rehabilitate old landfill sites. Earthworm population responses to a de-inked PB were measured on three agricultural soils in southern Ontario, Canada. Four rates of PB, 0, 50, 100, and 150 Mg ha−1, were applied annually for 3 years. In addition, plots receiving the PB treatments were planted to corn (Zea mays L.) and soybean (Glycine max L.). Earthworm populations prior to PB applications ranged from 9 to 22 individuals m−2 on the sandy loam and loam soils. Linear increases in earthworm populations were observed ranging from approximately 153 to 280 individuals m−2 after 3 years of PB amendments. On the clay loam soil, initial fall earthworm populations were about 124 individuals m−2 which increased to 482 individuals m−2 after 2 years of PB applications. Earthworm population increases to PB amendments were evident after 2–3 years at the sites measured.