|Root Crops (NRI, 1987, 308 p.)|
SWAMP TARO, Gallan, Giant swamp tarot
Cyrtosperma chamissonis (Schott) Merr.
Ape de veo (Tah.); Baba, Babai (Kiri.); BihPhilipp.); Brak (Polyn.); Galiang (Philipp.); lj (Mar. Is.); Kakake, Karake (Sol. Is.); Lok (Polyn.); Maota (Tah.); Muiang, Mwong (Ponape); Palanau, Palauan (Philipp.); Paluku (Cook Is.); Puna, Pura, Puraka, Pwolok, Simindou (Polyn.); Tao kape (Fiji); Tepuraka (Mortlock Is.); Ula (Polyn.); Via kana (Fiji); Wasrmar (Polyn.).
The swamp taro is a giant herbaceous perennial with typically 6-8 huge leaves arising from a short subterranean stem. The leaf blades are arrow shaped, 1-2 m in length, and are borne on stout petioles, 1-2 m long and tapering from about 10 cm in diameter; in some cultivars the lower parts are covered with spines. A mature plant may reach 3-4 m in height. The inflorescence has a long, thick yellowish spathe and a purplish spadix, though the seeds are often not fertile. The stem thickens rapidly at the base becoming a large corm, varying in shape from cylindrical to conical or almost spherical. The size varies with cultivar and age; 15-25 kg is common, but it can weigh up to 90 kg or more in a 10 year old plant. (The giant swamp taro is believed to be the largest plant in the world which produces edible corms.) Cormels which send up leaves and develop into suckers are produced as side shoots on the parent corm after about three years.
Origin and distribution
The swamp taro is thought to have originated in Indonesia and to have been introduced into the Philippines, Papua New Guinea and the Pacific Islands in pre-European times.
A more or less continuous supply of water is essential, though the plant cannot be grown in streams where the water is running swiftly, nor in a fresh marine soil, nor on a slope where the soil is frequently washed away by heavy rains. The plant is tolerant of a wide range of soil types and acidity, and can be grown in areas of moderate rainfall if the soil is deep and swampy, and it is at least partially shaded and sheltered from wind. Ideal growing conditions are natural swamp land rich in humus, covered with 0.2-0.7 m of slow running (or irrigation) water: it is often grown in coastal swamps just inland of mangrove swamps.
Cyrtosperma is often the staple starchy food of islanders on coral atolls. The only sure supply of fresh water is the hydrostatic 'lens' which floats at variable depth on the salt water that permeates the lower levels of the coral, sometimes several feet below the surface of the land, and planting procedures have been developed to suit these particular circumstances.
Material - suckers (sprouting cormels) are the commonest planting material although sometimes the top of the corm of the harvested plant is used (setts). In each case one or two of the youngest leaves in the shoot are retained.
Method - in atolls where there are subterranean fresh water lenses, pits are dug deep enough to reach the fresh water layer, which may be 0.5-3 m below the surface. The pits may extend to 10 x 20 m across, and once the fresh water is reached individual holes are dug for each plant and filled with organic material (eg chopped leaves), covered with sand, and the sucker or sett planted in the sand so that its upper roots are at the water level. Additional leaf mulch may be added as the plants grow, or each single plant may be surrounded by a bottomless basket woven in situ from Pandanus or coconut leaves, and the enclosed area filled with a mixture of chopped leaves and soil; as this compost rots and settles more is added. This type of basket cultivation gives the largest corms, but a slow growth rate.
In other areas methods similar to those employed for wet land cultivation of taro (Colocasia) are used, but great attention is paid to mulching, and shading (if possible natural shade, such as overhanging trees, bushes, etc) is provided until the plants are 1-2 m high. For non-puddled or firmer soils deep planting holes or furrows are prepared (15-100 cm deep) and after the setts or suckers are placed in position, the furrows are partially filled with soil and, if possible, compost, to 10-15 cm above the base of the sucker or sets.
Field spacing - in pit planting 40-100 cm between plants of the larger types: the smaller cultivars may be as close as 30 x 30 cm or 50 x 50 cm. In wet land cultivation swamp taro is often interplanted with Colocasia: the Colocasia is planted at 1-1.5 m, and Cyrtosperma is interplanted between the Colocasia. The latter may be replanted for three annual crops but subsequently the Cyrtosperma is allowed to grow alone for a year longer.
Pests and diseases
The most serious pest is reported to be the taro beetle (Papuana huebneri), which tunnels into the corm. Minor pests include Aphis gossypii, which has been reported to transmit virus diseases, but the importance appears to be small. Rats cause serious losses on some islands.
In many areas it is generally considered that the giant taro requires 2-3 years to produce a reasonably-sized tuber, younger than this the tubers of some cultivars are reported to have an unpleasant taste, although on the Pingelap Attoll, Caroline Islands, some early-maturing types are harvested after about one year. Some authorities, however, consider that for optimum results as regards flavour and yield, the crop should be harvested when the plants are 5-6 years old.
Harvesting and handling
The tubers are dug by hand as required, and normally eaten as soon as harvested. As the crop is for subsistence, rather than for sale, continuous harvesting and replanting is the normal procedure in any one family patch. Storage is not usually practiced, but tubers are sometimes buried in a damp place where they may be kept for up to 6 months.
Corms - usually conical to spherical in shape. The size at harvest depends upon cultivar and age. Although corms of 10 years old or more may be very large and weigh 100 kg or more, requiring two or three men to carry them, they are fibrous and not suitable for eating, though in certain circumstances such corms have a considerable prestige value.
7 - 10 t/ha for a crop between 18 months and 2 years of age.
The tubers are the staple carbohydrate foodstuff in many Pacific Islands, where they are eaten boiled, steamed or roasted, sometimes with the addition of coconut milk, or they may be sliced and fried and eaten with sugar.
It has been reported that a number of food products are prepared from the tubers in the Philippines.
Secondary and waste products
The leaves and inflorescence are sometimes eaten as a vegetable.
Analyses of tubers grown in the South Pacific have been given as: energy 598 kJ/100 g; water 60-70 per cent; protein 0.5-1.4 per cent; fat 0.1-0.5 per cent; carbohydrate 28-36 per cent; fibre 1-1.6 per cent; ash 1-1.9 per cent; calcium 301-598 mg/100 g; iron 0.9-1.4 mg/100 g; phosphorus 28-79 mg/100 g; thiamine 0.03-0.06 mg/100 g; riboflavin 0.08-0.11 mg/100 g; niacin 0.6-1.1 mg/100 g; ascorbic acid trace- 1 mg/100 g.
Workers in the Philippines have reported a starch content ranging from as low as 7.5 up to 22.6 per cent. The starch granules are of medium size, from 4 to 18 microns, and rounded or angular.
In some islands the tubers may be peeled, sliced and scalded, and then dried in the sun; preserved in this way they can be stored for several months.
Production and trade
No production figures are available. There is some evidence that, following the introduction of polished rice into the Polynesian diet many years ago, swamp taro is not eaten to the extent that it was in the distant past. In the drier islands there is evidence of abandoned cultivation pits. Until recently the plant was grown solely for home consumption, but in one or two islands is now sold on the local market. There is no international trade in this commodity.
Despite the long growing period necessary, swamp taro remains an important staple and source of prestige in many of the Pacific islands, especially as it can yield well on coral atolls which are notoriously difficult agriculturally. It appears to be receiving more attention recently from trained agriculturists, and improvement in practices leading to higher yields may be expected; the crop may therefore become more attractive and play a greater part in reducing the economic burden of imports.
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