Water hyacinth scientifically known as Pontederia/Eicchornia crassipes is the worst weed spread out in water bodies for about 80 countries. The fibrous rooted free floating plant with its vibrant violet flower, had been brought to the Botanical Garden in West Bengal in 1896, by Lady Hastings for its aesthetic value. Over the years the plant known as "Bengal terror" dominates water bodies everywhere in India, including Kerala causing serious concern on the ecological sustainability of aquatic flora and fauna. Especially in flood prone Kuttanad region, water hyacinth adversely affects the paddy production area. Manual or physical modes of eradication every year involving Mahatma Gandhi National Rural Employment Guarantee Act scheme by panchayats, costs high and chemical treatment is not eco friendly.

In 2007, Gunnarsson's research team, reported that 10 water hyacinths will generate 6,55,360 plants within a period of about 8 months, that cover half a hectare area. This perennial plant had its origin in South America. It can reproduce both by seeds and as stolons or runners asexually. Quick invasion of these species lead to depletion of oxygen level below the surface of lakes and rivers hampering other plants and fish populations. It blocks navigation in irrigation channels as well as casting fishnets. There is a decline in the potability of drinking water. Besides, the water hyacinth mats act as breeding spots for disease vectors like mosquitoes that spread chikungunya or lymphatic filariasis. If eradication is impossible, how could we make use of the situation beneficial?

The South Central part of Bangladesh, an agricultural belt often affected by severe floods, follows floating gardens for vegetable cultivation using water hyacinth beds. A layer of the weed along with marshy mud or other weeds were developed as the base. Two or more layers of water hyacinth stacked on the top of the base layer were beaten up using poles and converted as compost. Every layer will be added after 8-10 days of interval. The base layer maintains the buoyancy, stability and thickness of the bed. A rectangular shaped floating bed is preferable for the ease of operations with a breadth of upto 1.25-4 m and a length of 60 m- 100 m. The beds should be made compact in order to sustain the prolonged water logging conditions. Hence it will take around 30-35 days to prepare beds suitable for vegetable cultivation.

With the basic knowledge from YouTube videos, on floating vegetable gardens in Bangladesh, Mr. Sujith, a young enthusiastic farmer in Cherthala of Alappuzha district, decided to experiment the same with available resources. He used bamboo poles as base and coir geotextile on top of the 4th layer to keep the stack intact. On one bed he is raising 200 seedlings of marigold plants meant for Onam season, in Vembanad lake. Another bed he set apart for mixed vegetable cultivation of ladies finger, chillies, tomato and brinjal. The sea water intrusion in the region during January- February may have an adverse effect on cultivation and scientific research is appropriate in containing the situation.

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Considering the demands of burgeoning population and the scarcity of available land area for agricultural production, floating vegetable gardens have much scope in flood prone areas. Water hyacinth as a bed is an option to convert the weed menace into a benefit. Cellulase, bioethanol, handicrafts, mushroom beds, plastic alternatives of disposable plates are some of the value added products that can be synthesised from water hyacinth. Dr. G. Nagendra Prabhu,Principal Investigator of Centre for Research on Aquatic Resources (CRAR) from SD college Alappuzha, is a doyen in the field and elucidated that the lack of data about the quantity of weed available per year negatively affects projects meant for industrial utilisation of the plant. Dr. Prabhu expressed optimism in the initial work and outcome of his team's international project, for quantifying the extent of water hyacinth coverage in Vembanad lake using satellite imagery, drone photography and ground based sensors.

Government intervention is quintessential in expanding this innovative, yet frugal technology in suitable locations all over Kerala. Pilot scientific studies on the scope of the method followed by standardization of technology should be the priority. Promotion of value addition by offering technical and financial support through optimal integration of diverse public departments may be analysed. Ensuring wide publicity with mass awareness can make Kerala a forerunner in eco-friendly management of an invasive weed, besides increasing agricultural production.

(Dr. Yamuna S, is Assistant Editor - Kerala karshakan, Farm Information Bureau

Thiruvananthapuram.)

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