Wednesday, December 2, 2009

POTENSI BESAR 3 jenis tumbuhan air di rawapening

These plants are often called water weeds. This is unfortunate as it has tended to conceal their real value as a useful resource. Too much effort has been dedicated in many countries to getting rid of the water plants rather than assessing their potential value. The water plants which are relevant in this case are -
- Water hyacinth - or enceng gondok - Eichornia crassipes.
- Hydrilla sp.
- Typha sp.

gambar; Typha banyak terdapat di pinggir rawapening, khususnya di sekitar muara kali galeh, muara kali jalen/bejalen, muara kali torong dan muara kali muncul, tingginya rumput typa ini bisa mencapai 2 meter lebih.

Water plants as a resource

There is an abundant literature which shows that water plants cannot be effectively controlled by chemical means. They may be eliminated at one time in a limited area such as a lake, but the seeds of Eichornia can remain dormant in mud for at least 7 years. Chemical control is effective in the short term but expensive. It is not economically viable in the long term, particularly in an environment such as Rawa Pening where there is no substantial direct economic value resulting from the control of the weeds.

Biological control of Eichornia crassipes has been successful in some environments. Fungal infections affect the leaves and some insects will eat the leaves. Some fish will eat the roots of water hyacinth, but it is not necessarily their preferred food.

It would be much preferable if the water plants could be regarded as a resource, as they represent one of the main outputs from a very productive ecosystem.

Eichornia crassipes or water hyacinth is known to be able to take into its tissues large quantities of nutrients such as phosphates. It is therefore likely that much of the mobile phosphate in the Rawa Pening ecosystem is held at any one time in the Eichornia mats. Sporadic efforts are made and have been made in the past to remove some proportion of the Eichornia mat from the rawa. No sound and profitable use has so far been found for Eichornia in Java.

Hydrilla has been used as feed for pigs in the past, and has proved quite successful. Nevertheless the use of the plants for this purpose has not continued. They are not used for anything at present.

Typha has been shown, in other countries, to be a valuable asset in providing a cheap and effective method of water purification. The plant has the advantage that it has a strong rhizome which helps to stabilise river banks and limit erosion. The plants of Typha have a "luxury uptake" of phosphate. That is to say, the plants absorb more phosphate than they actually need for growth and store it in their tissues. Thus they act as sponges, mopping up phosphate from the environment. A species of Typha is reported to live in Rawa Pening.

The presence of these three species suggests that it should be possible to establish an industry based on the use of this resource.

The water in the rawa, though probably having very high values of phosphate does not appear to suffer from algal blooms, though small blooms of Cyanophyceae can be seen on some of the small creeks and land drains entering the lake. One reason may be that much of the mobile phosphate is incorporated in the tissues of the water plants at any one time. The water plants, and particularly Eichornia, therefore offer a cheap and effective means of extraction of phosphate from the rawa. It would be very desirable to continue to extract water plants from the rawa on a planned and controlled basis to establish some control over phosphate levels with the aim of ultimately reducing the phosphate levels in the water.


There have been numerous attempts in the past to find an effective and economically viable use for these and similar water plants. Some uses have been found for the water plants in the lake, but none have proved to be economically attractive, or at least, none have attracted any substantial economic investment either by Government or by private industry. In a number of papers Soerjani has reported the use of water hyacinth leaves in the manufacture of specialty paper and thin cardboard. The technology for introduction of a cottage industry manufacturing these products has been demonstrated.

Plants of water hyacinth could be sold to industries elsewhere in Java as a cheap and effective means of removing certain pollutants from industrial waste waters. It is unlikely that this would be economic for large quantities of water hyacinth in view of the transport costs, but could well be economic in terms of supply at intervals of new plants for an ongoing extraction process.

Plants of Hydrilla have been used successfully as food for pigs, and though water hyacinth is not a preferred food for pigs they will eat it if mixed with Hydrilla. Water hyacinth is known to have been used successfully as a stock feed for cattle in Queensland when mixed with molasses from sugar processing plants, and urea. Again, the costs of transport would seem to limit this possibility to use of leaves as cattle fodder in the immediate area round the edge of the lake.

Eichornia is used as green fertiliser for growing rice. During the dry season, the exposed area of mud on the lake shore is available for the cultivation of rice. Goeltenboth (1979) reports that in the period prior to his report about 1,100ha of exposed mud was converted to padi fields every year. This exposed mud was tilled and divided into fields by creation of mud walls, using water hyacinth plants as supports and as green fertiliser. He calculates that over 60ha of water hyacinth plants were used this way each year and notes that this makes a major contribution to restriction of the growth of water hyacinth on the body of the lake. The other major contribution to this limitation is the number of plants of water hyacinth which die during exposure to the sun on the mud during the dry season.

Water hyacinth has been shown to be an effective mulch which is necessary at times in the dry season in this area. Investigation has shown that increases of up to 10% in production of some crops can be achieved by use of this material as a mulch. Again the costs of transport limit the area through which this use of water hyacinth would be commercially viable.

The use of water hyacinth leaves to generate gas in a small scale bio-gas generator has been demonstrated at Universitas Kristen Satya Wacana. The use of such generators is only economic if the leaves can be transported or carried cheaply to the generator. Households in the immediate vicinity of the lake might benefit from such generators. The cost of manufacture is unknown.

One of the most profitable potential uses for water hyacinth is in the growing of mushrooms. This has the great advantage that mushrooms are seen as a luxury crop and command a relatively high value in the market. The demand in Central Java may be met at the present time by the present level of production. The question is whether an export industry of dried or tinned mushrooms would be economically viable using the leaves of water hyacinth as a growth medium.

No investigation of the economics of the mushroom industry has been undertaken. This was considered to be outside the parameters of the investigation. Already one commercial grower uses leaves of water hyacinth in mushroom production from a small factory in the Dieng Plateau. Leaves are collected periodically from Rawa Pening for this purpose. It is believed that these mushrooms are sold locally and in Jakarta.

If a viable export industry were to be developed it would call for a large scale operation using similar principles. The requirements would start with a system of regular collection of good quality leaves of water hyacinth. These would be collected using boats and presumably bought from local boat owners on the lake shore at agreed points on the shore. Trucks would be necessary to transport the leaves to a processing plant. The processing facility would probably be situated on the upper slopes of one of the adjacent volcanoes. It is noteworthy that most tropical mushroom production facilities are situated on mountains or at high altitude as in the Dieng Plateau, and the Genting Highlands in Malaysia. Transport costs would therefore be substantial. There would be considerable capital cost in construction of the production factory for the mushrooms, of the growing rooms which would be kept dark and cool, of the cleaning and of the preparation facility. If the mushrooms were dried or canned for export this would require further substantial capital investment. The entire enterprise would call for a considerable work force for maintenance of the process. It would be necessary to investigate the nature of a potential market for the end product and perhaps to engage a marketing group. A guaranteed market is essential before such an enterprise is started.

The level of capital investment involved would call for Government support initially or for investment by a large private corporation. This is a level of investment which is quite beyond the individual small business man. Any initiative to develop effectively an industry using water plants as a source of raw material calls for investigation by a Government which is prepared to invest in the selected enterprise. So far no Government initiative has been detected in developing any industry using the water plant resources of the lake or the human resources provided by the people living on the lake shore.

Rawa Pening is one area where it would be feasible to establish large scale economic production of Eichornia crassipes, and where it would be possible to manage the plants efficiently.

The capacity of these plants to take up phosphate is equalled by their release of the same phosphate when the plants or particular leaves die. So to be effective in removing phosphate from the rawa, the water hyacinth plants need to be taken from the rawa regularly (harvested) and taken some distance from the shore. They can then be burned to produce ash, incorporated in the soil as green fertiliser, fed to cattle, or fed to appropriate species of fish in fish ponds.

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