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Effects of urea and adult palm fertilizer mixture on the survival and body wall tissues of the earthworm, Pheratima hawayana
By lakmali | March 4, 2010
O.K.C. De Silva and W.U. Chandrasekera
We carried out a laboratory experiment to find out the effects of urea and urea containing Adult Palm Mixture (APM) fertilizer on the percentage of survival and body wall tissues of one of the commonest earthworms, Pheretima hawayana.
In this experiment, twenty plastic dishes with the dimensions of 510 cm2 area and 10cm height were filled with a soil mixture prepared by mixing dried cow dung into wet soil. The containers were grouped into five batches and urea solutions were added evenly into each batch at a rate of 0, 0.1, 1.5, 3.0 and 16.2g per container. Later, a batch of 15 healthy earthworms was introduced into each container in each treatment and, their % survival was determined weekly for a period of four weeks. The pH, organic matter content, temperature and the moisture content of the test soil were also measured using standard methods. The experiment was repeated for APM fertilizer at a rate of 0, 1, 2.2, 5 and 21.6g per container in each replicate treatment.
Results revealed that the % survival of earthworms was significantly low at the highest concentration of urea or APM fertilizer. Further, the % survival of earthworms decreased significantly in both fertilizer treatments by the third week of exposure. A significant drop of pH was also noted in these containers. Histological sections of earthworms in the control revealed normal intact architecture of the body wall. However, it showed lesions and epithelial detachment from the underneath muscle layer upon exposing to high concentrations of urea or APM fertilizer mixture causing mortality among them.
Although the use of artificial fertilizers is imperative to meet the current demand of the crop yield, it is evident that the correct use of their recommended concentrations is of vital importance to the survival of earthworms whose presence is indeed helpful to increase the soil fertility.
O.K.C. De Silva and W.U. Chandrasekera
Department of Zoology, University of Kelaniya, Sri Lanka.
Topics: Biodiversity, sympoisum 2009 | No Comments »