Root crops (NRI, 1987, 308 p.)[edit | edit source]
Kudzu (Pueraria lobata)[edit | edit source]
Pueraria lobata (Willd.) Ohwi syn. P. thunbergiana (Siab. and Zuva) Bouth., P. hirsuta Schneid. non Kurz., P. triloba (Lour.) Makino. P. tuberosa (Roxb.) DC.
Arrowroot vine; Baite, Bala (N. Cal.); Denai (Yap. Is.); Fen-ko (China); Gmadhi hulu (Ind.); Japanese arrowroot; Ko, Ko hemp, Ko hue, Ko t'eng (China); Kudazinila teigi (Ind.); Magnagna (N. Cal.); Rheru (Marï¿½ Is.); Va yaka, Yaka (Fiji).
Pueraria is a small genus of perennial twining herbs or shrubs with tuberous roots. P. lobata is a vigorous vine, which climbs or trails over the ground with stolons rooting at the nodes. The leaves are trifoliate with entire or slightly 3-lobed leaflets, pubescent, 5-12 cm long and 4-10 cm broad. The flowers are borne in dense, pubescent racemes 20-50 cm long, are mauve to violet and fragrant. The pods are flat, oblong-linear, 5-10 cm long, hairy with 8-20 seeds. P. tuberosa is generally similar but the leaf margins are entire, the racemes slightly longer, and the flowers are blue to purplish-blue; the pods are constricted between the 3-5 seeds, and somewhat shorter. In both species the roots are elongated and often tuberous, and may reach to as much as I m in length and 40 cm in diameter and weigh up to 40 kg, though such sizes are relatively uncommon. They may be tapering, cylindrical or a variety of irregular shapes.
Origin and distribution
P. lobata is believed to have originated in the China/Japan region of eastern Asia, where it is still cultivated for the edible roots, especially in China. It was at one time a staple food in South-East Asia and Oceania. It was introduced into the USA as a food plant, but became popular as a crop for erosion control, and quickly spread out of control and has assumed pest proportions in some areas. It was introduced into India in the
1920s, but was not as successful as P. tuberosa which has long been cultivated there. These two species, along with one or two other species of Pueraria are now widely cultivated in the tropics and subtropics, mainly as as cover crop in regions liable to soil erosion.
P. lobata does best in moderately humid subtropical and warm temperate regions; P. tuberosa thrives in a wider range of conditions from sea level in the tropics to 1 200 m (in India), except in very humid or arid areas. A wide variety of soils may be used, though sandy loam is preferred. Both acid and alkaline soils are tolerated, with pH between 5 and 8. It can be grown on poor acidic soils deficient in calcium and phosphorus, but responds well to fertilisers, either organic or chemical. Soil preparation can be minimal. For establishment the land should be ploughed but ridging or furrowing is not essential; in India planting is often in small hills.
Material - seeds or cuttings. P. lobata does not set seed freely but P. tuberosa produces seeds abundantly.
Method - vegetative propagation (more commonly used, especially for P. lobato) employs rooted cuttings (crowns), 1-2 years old, planted in holes large enough to hold the roots comfortably. Watering should be carried out until the crowns are established. Regular cultivation is required in the first one or two years for the plant to produce the numerous intertwining stolons which root and produce tubers at the nodes.
Field spacing - seeds are sown at about 100 x 100 cm. For crowns, 30 x 30 x 30 cm is commonly used.
Seed rate - about 400 crowns/ha (a single plant will normally cover 5-6 m2 of ground per year, and this planting rate should ensure a full cover).
Pests and diseases
Kudzu appears to be relatively free from serious pests and diseases and when well established forms a heavy enough ground cover to suppress weed growth, though a yellow leaf mould (caused by Mycovellosiella puerariae sp. nov.) has been reported.
Harvesting and handling
The roots are dug by hand: the depth to which they penetrate and the irregular pattern in which they grow (from rooting stolons) does not lend itself to mechanisation. A considerable amount of searching among the tangled vines may be necessary to locate suitable roots.
Root tubers - which are starchy, and in both P. lobata and P. tuberosa may be 30-60 cm long, 25-30 cm in diameter and weigh 35 kg (or larger on older plants), sometimes connected to the main roots and each other by thin, stringy roots.
Yields of 5-7 t/ha have been reported.
The main use of kudzu tubers is as a source of edible starch, especially in Japan. This starch, 'kudzu powder', is highly regarded and is used instead of arrowroot starch, corn starch, potato starch, etc or gelatine in many Oriental recipes. It is stated to have a subtle flavour and unique aroma, and to produce excellent gels of exceptional clarity. It is used as a basis for soups, sauces, jellied salads and desserts, noodles, etc.
The tubers may be cooked and eaten in a manner similar to other root crops, but are excessively fibrous, especially in P. tuberosa. The starch can be used as a substrate for the lysine-enriched baker's yeast and ethanol-fermentation process. In China and Japan decoctions of the root are used for colds, fever, dysentery and other complaints; in India dried slices of the root, and in Japan a cream made from kudzu powder, are taken internally for the same purposes.
Kudzu is regarded primarily as a perennial multipurpose crop, being especially valuable in soil conservation because of its deep and strong root system and heavy ground cover, but it is also grown as protein-rich forage or as green manure; the tubers are an added bonus. Its exceptional ability to cover ground and vegetation - even trees - quickly, and the difficulty of eradicating it, has led to its being regarded in parts of the southern USA as an extremely troublesome weed. However, its highly prolific quality has enabled it to perform well in a process being developed for producing methane involving systems of treating waste water with higher plants.
Secondary and waste products
Fibre - the stalks yield about 46 per cent of crude fibre which has been used for centuries in Japan, Korea and China to make a cloth ('grass cloth') that is valued both for its texture and its durability. Fishing nets are still occasionally made from the fibre.
Tobacco substitute - it has been proposed that the leaves could be used as a tobacco substitute or that an essential oil obtained from the plant might be used as a tobacco additive (see Special features).
Biomass - the extremely high rate of growth of kudzu has led to interest in its possible use in a biomass programme.
A typical analysis of the edible portion of P. lobata tubers is: moisture 68.6 per cent; protein 2.1 per cent; fat 0.1 per cent; carbohydrate 27.1 per cent; fibre 0.7 per cent; ash 1.4 per cent; calcium 15 mg/100 g; iron 0.6 mg/100 g; phosphorus 18 mg/100 g.
A glycoside daidzin, an aglycone daidzein and an isoflavone puerarin are among compounds identified in the roots. An essential oil has been obtained from the leaves, in which have been identified 2-methoxy-4vinylphenol, 2-methoxy-5-vinylphenol, damascenone, phytol, megastigmatrienones, 3-hydroxy-13-ionone, and 3-hydroxy-13-damascone. The last three compounds have previously been reported only from tobacco leaves.
The dried roots contain about 40 per cent starch; the easily digested grains are round, kettle-drum shaped, or polygonal, 16-35 microns in diameter.
The extract of the vine is stated to contain traces of a gibberellic acid-like substance.
No comparable analysis of P. tuberosa is available, but it has been reported to contain as much as 28 per cent crude fibre on a dry weight basis. It is stated that, in addition to starch, sucrose, glucose and fructose occur in the carbohydrates, and 13-sitosterol is present. It is also reported that an extract of the tuber is active against Helminthosporium sativum.
Starch (kudzu powder) - the preparation of kudzu powder in Japan is a cottage industry or even done in the home. However, there are a few small commercial plants which produce the starch for export.
The process involves pulverisation of suitable roots and an elaborate succession of settling and filtration stages, and is extremely time consuming and labour intensive: full details are given in Shurtleff and Aoyagi, 1972 (see Bibliography).
Fibre - vines of suitable length are boiled to loosen the soft layers and after thorough washing are fermented and teased out into fibres. As with starch, the process is complex and labour intensive and is also described in detail in Shurtleff and Aoyagi, 1972.
Production and trade
No information is available about the extent of production of kudzu. In the USA it grows wild over considerable areas of the south-east USA and is occasionally cultivated as a forage or cover crop, but the roots are relatively little used. It also grows wild in parts of south and east Asia, and occasionally is cultivated for its roots as well as for forage or cover. It appears, however, that much of the material used in processing comes from harvesting the roots or vines from the wild material.
There is a small export trade from eastern Asia to the USA of kudzu powder (starch), mainly to 'health food' outlets.
The fibrous nature of the root tubers makes them unattractive as human food, and difficulty of harvesting militates against commercial production. However, the high quality of the starch seems to ensure a continuing popularity in gourmet foods in eastern Asia, and efforts are being made to develop the use of this product in the USA. Recent work in the USA has also suggested that the root could provide a vitamin-enriched source of starch for ethanol and yeast production. The vine, which does not present the harvesting problems of the root, has also been proposed in the USA as a source of high tensile strength fibre for textiles, clothing and wallpaper. The rapid growth of the vine makes it a possibility for the production of biomass in an energy programme.
EDWARDS, M. B. 1982. Kudzu, ecological friend or foe. Proceedings of the 35th Annual Meeting of the Southern Weed Science Society, pp. 232-236. Champaign, Illinois, USA: Southern Weed Science Society.
HERKLOTS, G. A. C. 1972. Kudzu. Vegetables of South East Asia, pp. 468-470. London: George Allen and Unwin Ltd, 525 pp.
KRISHNAMURTHI, A. (ed.) 1969. Pueraria. The wealth of India: Raw materials, Vol. 8 (Ph-Re), pp. 313-317. New Delhi, India: Council for Scientific and Industrial Research, 394 pp.
KUMAR, R. 1977. Kudzu, a perennial fodder legume vine. Indian Farming, 27 (8), 17-19.
LOOSLI, J. K., VILLEGAS, V. and YNALVEZ, L. A. 1954. The digestibility of tropical kudzu (Pueraria javanica) and pongapong (Amorphophallus campanulatus) by swine. Philippine Agriculturist, 38, 491-493.
SHAW, D. E. and DEIGHTON, F. C. 1970. Yellow leaf mould of Pueraria lobata caused by Mycovellosiella puerariae sp. nov. Transactions of the British Mycological Society, 54, 326-330.
SHIBATA, S., KATSUYAMA, A. and NOGUCHI, M. 1978. On the constituents of an essential oil of kudzu (Pueraria lobata). Agricultural and Biological Chemistry, 42 (1), 195-197.
SHURTLEFF, W. and AOYAGl, A. 1977. The book of kudzu. A culinary and healing guide. Brookline, Massachusetts: Autumn Press, 102 pp.
TANNER, R. D. and SHAHID HUSSAIN, S. 1979. Kudzu (Pueraria lobata) root starch as a substrate for the lysine-enriched bakers' yeast and ethanol fermentation process. Journal of Agricultural and Food Chemistry, 27, 22-27.
TANNER, R. D., SHAHID HUSSAIN, S., HAMILTON, L. A. and WOLF, F. T. 1979. Kudzu (Pueraria lobata): Potential agricultural and industrial resource. Economic Botany, 33, 400-412.
WEEKES, B. 1982. Kudos for Kudzu (Pueraria lobata). American Forests, 88 (8), 36-39; 55-56.
WOLVERTON, B. C. and MCDONALD, R. C. 1981. Energy from vascular plant wastewater treatment systems. Economic Botany, 35, 224-232.