Saturday, 15 July 2006

Soil Borne Saprophytic Nematodes on Nutrient Mobilization in the Western Ghats Region of Tamil Nadu, India.

Selvi Duraisamy1, Deepa Subramanian2, Subramanian Shanmugam3, Jayakumar Jayaraman3, Senthamizh Kasinathan4, Thiyageshwari Subramanian4, and Rajkannan Bellie5. (1) Dept of Soil Science,Tamil Nadu Agricultral Univ, Lawley Road, Coimbatore, 641 003, India, (2) Dept of Soil Science,TNAU, Lawley Road, Coimbatore, 641 003, India, (3) Dept Agricultural Nematology, TNAU, Lawley Road, Coimbatore, 641 003, India, (4) Dept of Soil Science, TNAU, Lawley Road, Coimbatore, India, (5) Dept. of Soil Science, TNAU, Lawley Road, Coimbatore, 641 003, India

Bacterial feeding and omnivorous species of nematodes often dominate soil–nematode communities comprising as much as 90 % of the total nematode fauna. These nematodes have a high metabolic activity but low productivity coupled with high bacterial intake rates. This would result in a rapid turnover of nitrogen and trace elements and increased substrate utilization through stimulation of bacterial population. As very little specific information on quantifying the effect of bacterial and fungal grazing by nematodes is available under natural conditions and hence an attempt has been made to assess the role of bacterial and fungal feeding nematodes on nutrient mobilization under natural conditions in the Western Ghats region of Tamil Nadu, India. A systematic survey was conducted at four months interval in the Western Ghats region of Tamil Nadu at an altitude of 300 – 3000m MSL in fifteen locations. The bacterial feeding nematodes encountered in the survey were viz., Rhabditis, Plectus, Butlerius, Acrobeloides and Acrobeles. Fungal feeders were viz., Ditylenchus, Tylenchus, Aphelenchoides and Tylencholaimus. Omni feeders were (both bacterial and fungal feeders) viz., Eudorylaimus and Dorylaimus. The results showed that all the locations have higher density of saprophytic nematode fauna compared to first sampling showing increased activity of organic matter decomposition, nitrogen content, availability of phosphorus, potassium and micronutrient contents. Out of 15 locations surveyed, in four locations viz., Palani, Coonoor, Sengottai and Aliyar there was an increase in the abundance of saprophytic nematode fauna as well as increase in the available N, P, K and organic carbon content. The transformation of micronutrients to soil at different intervals differs not following a definite trend. The study clearly established the hypothesis that soil borne nematodes might play a major role in the nutrient mobilization in the Western Ghats region of Tamil Nadu, India. Key words: Soil borne nematodes, nutrient mobilization,positive effects.

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