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FARMER'S NOTEBOOK

Water hyacinth: potential source for vermicompost

M.J. PRABU

The weed enhances the growth and weight of the earthworms



YIELD RATIO: About 180 tonnes of water hyacinth can produce up to 60 tonnes of dry organic matter in a year. — Photo: D. Radhakrishnan

WATER HYACINTH (Eichhornia crassipes), also known as blue devil, grows rapidly as a dense green mat over stagnant water bodies such as lakes, streams, ponds, waterways, ditches and backwaters.

The plant is believed to have originated in the Amazon basin and was introduced as an ornamental plant in garden ponds. It is found to grow well in tropical and subtropical climates.

The weed is known as Jal khumbe in Hindi, Pisachitha tamara in Telugu, Akasa or Vengaya tamarai in Tamil and as Kola vazha in Malayalam.

Weed propagation

The weed is propagated by vegetative and sexual methods and adapts to the changing environment and water quality. It is a serious pest that can completely wipe out the native aquatic species.

It alters the ecosystem of the water body , causing oxygen fluctuation and raising the water temperature, according to Prof. N. Selvaraj, Head, Horticultural Research Station (HRS), Udhagamandalam.

The seeds of the plant will sprout even after 20 years of dormancy due to drought conditions. Under favourable conditions the weeds can infest as much as an acre within eight months, explained Prof. Selvaraj.

"It has been estimated that an area of one acre can be packed with 180 tonnes of water hyacinth that can produce up to 60 tonnes of dry organic matter in a year," he said.

Composting material

"The weed is a good absorber of nitrogen, phosphorus and potassium from water and can be used as a good source of compost material," he said.

Experiments were conducted by researchers at the institute to study the composting nature of the weed biomass in comparison with general agricultural wastes, according to him.

Water hyacinth biomass collected from Udhagai (Ooty), lake was mixed with cowdung in the ratio 1:3 and left to decompose for about 50 days.

The partially decomposed material was then transferred into vermicompost blocks and African earthworm strains (Eudrilus eugeniae) were introduced at the rate of 1,500 worms for every tonne of the weed biomass.

A similar experiment was simultaneously carried out with general agricultural wastes, according to Selvaraj.

"Composting of water hyacinth biomass was completed in 55 days, whereas the composting of agricultural wastes was completed only in 70 days," he said.

"Water hyacinth was also found to enhance the rate of multiplication of earthworms.

Increase in number

"At the end of the composting period, the number of adult worms was found to be 4,590 (more than three times increase over the initial number of worms introduced) in the water hyacinth compost and 2,610 (less than two times increase over initial population) in the agricultural waste compost," he said.

The weight of the worms was also found to have increased. "Each worm weighed about 1.70gms in the water hyacinth compost and about 1.21gms in the agricultural waste compost," he said.

The yield of horticultural crops can be increased by about 10-25 per cent by applying 2.5 tonnes of water hyacinth vermicompost as a fertilizer, according to him.

For more information readers may contact the Head, Horticultural Research Station (HRS), Tamil Nadu Agricultural University (TNAU), Udhagamandalam - 643 001, Phone: 0423-2442170, email: selvanan@yahoo.co.in

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