Use of Invasive Water Hyacinth for Composting of Ordinary Leaf Litter

Abstract

Many lakes, canals and wetlands in Sri Lanka are infested by water hyacinth (Eichhornia crassipes (Mart.) Solms), which is a non-indigenous invasive aquatic weed species. It causes a complete blockage of water resources that makes irrigation and fishing very difficult. Among various eradication methods of water hyacinth, composting has been extensively used in many countries. However, the degree of toxicity and the quality of compost are important for field applications. Therefore, the present study was aimed at transforming ordinary leaf litter into quality compost using water hyacinth and various other amendments, and comparing the compost quality in terms of heavy metals, pH, electrical conductivity (EC) and C: N ratio. The weeds were collected from the Moragoda canal, Galle, Sri Lanka. The compost trials were prepared using water hyacinth and different other raw materials and one compost trial was prepared using water hyacinth alone. The mixtures were decomposed aerobically for 12 weeks by windrow method and prepared composts were analysed for pH, EC, organic C %, total N %, Cu, Cd, Pb, Zn, Ni, and As. Finally, the obtained results were compared with the indices given for compost by the Sri Lankan standards. Considering the C: N ratio, pH, EC which obtained 17.84, 7.5, 1.95 dSm-1, respectively and heavy metal content less than permissible limit, it revealed that compost mixture with a composition of water hyacinth and dry leaf litter was the most suitable mixture to recommend for field application.