Nutrient Mineralization and Leaf Litter Preference by the Earthworm Pontoscolex corethrurus on Iron Ore Mine Wastes

摘要

The effects of the earthworm Pontoscolex corethrurus (Muller) on the rate of mineralization of cattle dung-amended iron (Fe~(2+)) ore mine wastes and its preference for partially decomposed leaf litter with contrasting chemical composition were studied in pot trials. The growth and survival rates of earthworms showed significant positive correlations with percent of organic matter. During 96 days of exposure, the earthworms significantly increased exchangeable Ca~(2+), Mg~(2+), PO_4~(3-) and NH_4-N. Iron ore mine wastes amended with 5-10% organic matter supported earthworm fauna better than mine wastes amended with 0-3% organic matter. The leaf litter preference shown by the earthworm was, in descending order, Phyllanthus rericulatus, Tamarindus indica, Anacardium occidentale, Casuarina equisetifolia, Acacia auriculiformis, and Eucalyptus camaldulensis. A significant positive correlation was observed between the survival and growth rates of earthworms and the nutrient contents of partially decomposed leaf litter. The first three plant species were significantly richer in nutrients, mainly organic carbon, calcium, phosphorus, and nitrogen, than the other two plant species. Acacia auriculiformis and E. camaldulensis litter were preferred less because of their high lignin and polyphenolic compounds, despite being rich in other macronutrients like nitrogen and phosphorus. It is concluded that the introduction of P. corethrurus to cattle dung-amended (5-10%) iron ore mine wastes or revegetation of the sites with P. reticulatus, T. indica, and A. occidentale plant species should be attempted before earthworm introduction. The litter from these species acts as a source of food for earthworms, thereby hastening the process of restoration of abandoned iron ore mines of Goa, India.