Root Crops (NRI, 1987, 308 p.)

Daisy E. Kay revised by E. G. B. Gooding

Tropical Development and Research Institute
127 Clerkenwell Road, London EC1R 5DB
Overseas Development Administration

Acknowledgments

Daisy E. Kay revised by E. G. B. Gooding

Tropical Development and Research Institute
127 Clerkenwell Road, London EC1R 5DB
Overseas Development Administration

This report was produced by the Tropical Development and Research Institute (formed by the amalgamation of the Tropical Products Institute and the Centre for Overseas Pest Research) a British Government organization, funded by the Overseas Development Administration, which provides technical assistance to developing countries. The Institute specialises in post-harvest problems and pest and vector management.

Short extracts of material from this digest may be reproduced in any non-advertising, non-profit context provided that the source is acknowledged as follows:

Kay, D. E. (revised by Gooding, E. G. B.) (1987) Crop and Product Digest

No. 2-Root Crops, Second Edition. London: Tropical Development and Research Institute, xv & 380 pp.

Permission for commercial reproduction should, however, be sought from the Head, Publications, Publicity and Public Relations Section, Tropical Development and Research Institute, College House, Wrights Lane, London W8 5SJ, England.

First edition 1973
Price £13.50

No charge is made for single copies of this publication sent to governmental and educational establishments, research institutions and nonprofit making organizations working in countries eligible for British Aid. Free copies cannot normally be addressed to individuals by name but only under their official titles.

Tropical Development and Research Institute ISBN: 0 85954 200-9

Preface

This digest is a complete revision and updating of TPI Crop and Product Digest No. 2, which was published in 1973, and is an attempt to present in a concise form basic data relating to the production and utilisation of most of the root crops of economic importance to countries in the tropics. For quick reference the data are arranged under standard headings and include particulars of growth requirements, planting and harvesting procedures, yield, products and their uses, processing techniques, comments on production and trade, and a bibliography for each crop.

The digest does not claim to be exhaustive or comprehensive. The aim is to provide a ready reference tool, for use particularly by non-specialists, and especially by practical workers in the developing countries concerned with advancing the rural economy. However, it is hoped that in addition it will provide a starting point for specialists and researchers working on these crops or their products.

The reviser has received valuable assistance from many persons and organisations during the preparation of this digest. In particular, he wishes to thank the Librarian and Library staff of TDRI who made available a wide range of services, including a computer search of the main agricultural and food processing data bases, and many other members of the TDRI staff, in particular the late Mrs Daisy Kay and the late Mr D. G. Coursey. Special thanks are due to Drs J. C. Caygill, A. K. Thompson and June Rickard who 'vetted' the manuscript, and to many others who provided advice and assistance on specialist matters. Scientific and technical information was obtained from several organizations, including the Royal Botanic Gardens at Kew and at Edinburgh; the Botany Department of the British Museum (Natural History); the University of Hawaii; the University of Idaho, USA; the University of Puerto Rico; the Soybean Center, California, USA; several branches of the United States Department of Agriculture; the Directorate of Agricultural Research, Wageningen, the Netherlands; the Department of Primary Industries, Queensland, Australia; the Central Potato Research Institute, India; the Bangladesh Agricultural Research Institute; the International Potato Center, Lima, Peru; the Caribbean Agricultural Research and Development Institute, Barbados. In addition to production and trade statistics obtainable within TDRI, information was provided by ULG Consultants Ltd. Warwick, UK; Geest Produce Marketing, Spalding, UK; Montego Imports and Exports Ltd. Toronto, Canada; the Barbados Agricultural Society; the Central Marketing Agency,

Trinidad; and a number of individuals concerned in the marketing of tropical root crops. Without the help of these, and of many others, the task of updating this digest would not have been possible.

Reference to trade names of agricultural chemicals, etc. implies no endorsement of the efficacy of these products nor any criticism of competing products not mentioned.

Introduction

The term 'root crops' is applied to plants which produce subterranean structures that may be used for human or animal food. They are normally perennating organs, storing plant nutrients through a resting period (dry season or winter) which are used in the regrowth of the plant when growing conditions are again favourable. The word 'root' is often a misnomer, as in many cases the storage organ may be morphologically a modified stem, eg a swollen rhizome or corm, or a tuber such as a potato, rather than a swollen root as in carrot or sweet potato. All these swollen underground organs are commonly spoken of as 'tubers'.

Root crops are the second most important source of carbohydrates in the world's food: FAO figures for world production in 1981 showed 1,661 million tonnes of cereals and 561 million tonnes of root crops. The tropical world, however, where root crops are proportionally much more important, produced 82 million tonnes of root crops and only 42 million tonnes of cereals. In many tropical countries where rice is not grown they are the staple diet. In general, protein content is low, but some, for example Solanum tuberosum (potato) and Dioscorea spp. (yam), provide significant amounts of certain vitamins.

The following pages briefly describe 42 root crops, the most important of which are Manihot esculenta (cassava), Solanum tuberosum (potato), Ipomoea batatas (sweet potato), Colocasia esculenta (taro), Xanthosoma spp. (tannia) and Dioscorea spp. (yam). Many others are of only minor or local importance, but have been included to make this compilation as comprehensive as possible.

Each crop is listed alphabetically under its first common name, followed by local names. In the index of 'trivial' names (Appendix E) these local names are cross-referenced to the first common name. Selected literature references are given, but are not exhaustive; some crops, eg Manihot esculenta (cassava) have been the subject of so much study that lengthy bibliographies for them have been published, and such bibliographies are included in the relevant lists of references.

Data about each crop are arranged under the following headings:

Common names

Widely used English names are given, the first being printed in capitals and being used for the alphabetical arrangement of the entries and for cross-referencing.

Botanical name; Family

Nomenclature closely follows the Index Kewensis and its Supplements

Other names

Most plants have a wide range of local names, and many of these are listed, with the country or language to which they normally apply being appended in parentheses. Less common English names are given without the country being indicated.

Botany

A short description of the plant, its form and habit, varietal differences and systematics where appropriate is given.

Origin and distribution

Brief particulars of the origin and distribution of the crop are given.

Cultivation conditions

The main climatic regions in which it is possible to cultivate the plant are given in accordance with van Royen and Bengtson. The climates of the world are divisible into tropical, subtropical, intermediate or temperate and polar types.

Tropical climates have an average annual temperature of above 25°C, no month having an average temperature below 18°C. Subtropical climates have short, mild winters and long growing seasons. There is a period of 1-2 months when freezing temperatures may occur, though the average temperature of the coldest month is above 6°C. The summer temperatures may be as high as those of the tropical climate. Intermediate or temperate climates, ie those between subtropical and polar, have cold winters and warm to hot summers. They vary from areas where the winters are short to those where they are long and severe. All intermediate climates have a season of frost as well as a frost-free season.

The humid tropical climates are tropical rainforest, tropical monsoon, and tropical savanna. The tropical rainforest has no pronounced or prolonged dry season, an annual rainfall of 200-400 cm or more, a relative humidity of around 80 per cent and a high and uniform temperature with annual means ranging from 25 to 26.5°C with little seasonal variation. The tropical monsoon climate exhibits marked daily and seasonal temperature changes, has an annual rainfall of 100-200 cm with abundant rainfall during the wet season, alternating with a period of drought lasting 4-6 months or longer. The tropical savanna climate has a rainfall often exceeding 100 cm annually, well spread over 120-190 days, with a prolonged drought often lasting 6-7 months. The climate is hot with a moderate range of temperature. The dry tropical climates are subdivided into semi-arid or steppe type and arid or desert type. In the areas of tropical steppe climate the rainfall is occasional, though seasonal and commonly averages 20-50 cm or more annually; the temperature is variable but high at all seasons. The desert climate has a rainfall usually averaging less than 20 cm per annum, and a daytime relative humidity (RH) commonly less than 50 per cent.

The subtropical climate is subdivided into dry subtropical or Mediterranean and humid subtropical. The former has an average annual rainfall generally below 75 cm, in some places below 50 cm, with most of the rainfall occurring during the cool season. In some regions there is a moderate amount of summer rainfall, while others may be nearly rainless during this period. There are about 6-8 months with an average temperature below 18°C. In humid subtropical regions the rainfall averages above 75 cm per annum, with no pronounced dry season. There are generally 4-6 months with an average temperature below 18°C. In both types of subtropical climate frost may occur during the coldest period.

Humid intermediate climate has an annual rainfall which ranges from 50 cm in the drier parts to 200 cm in the more rainy sections. Dry intermediate climates have an annual rainfall which is commonly less than 50 cm. They may be subdivided into middle latitude steppe and middle latitude desert; the former having an annual rainfall of 15-50 cm and the latter less than 15 cm per annum.

Plant growth requirements are arranged under the main headings of temperature, rainfall and soil, with additional factors such as altitude and day-length noted where they are crucial. The possibility of growth under irrigation is mentioned when describing rainfall requirements and any positive evidence concerning the effects of fertilisers is included in the information on soil. The main climatic zones in which the root crops listed are generally grown are shown in Appendix A.

Planting procedures

Information concerning the type or types of planting material is given, with brief mention of their relative merits, and with special emphasis on the preferred type, where more than one type of planting material is available. The usual methods of planting are given, together with details of field spacing and, where applicable, seed rate.

Pests and diseases

The most serious pests and diseases attacking the crop in various growing regions are noted, along with methods of control. (A list of the pesticides referred to in the digest is given in Appendix C.)

Growth period

An approximate average or range of time lengths from planting to harvesting is quoted.

Harvesting and handling

The most common and best methods of harvesting, handling and storage are briefly indicated.

Primary product

The part of the plant for which the crop is primarily grown and the form in which it is commonly marketed are given. Normally one form only has been selected and this is shown at the beginning of the heading; this form will be used as the basis for quantitative data given in subsequent headings, unless otherwise stated. In some cases where there are other main products, eg seeds or pods, these are noted separately.

Yield

A good average yield of the primary product is given. Yields obtained in different regions or circumstances may be separately quoted.

Main use

The main use or uses of the primary product are given.

Subsidiary uses

Additional uses of the primary product are entered under this heading.

Secondary and waste products

Useful by-products resulting from the processing of the primary product or prepared from other parts of the plant are listed, together with their uses, etc. Major waste products which result from primary or secondary product processing are noted, with possible outlets where applicable.

Special features

Information is given on the chemical components of importance in the plant, and the main nutrients of the edible portion are listed wherever possible. The percentage composition often varies widely according to the variety, locality, conditions of growth, etc. so 'typical' figures are quoted, taken from the most reliable source available, eg FAO Food Composition Tables, recent papers, etc. Only a few publications quote ranges of high and low values; workers in the nutritional field are advised to seek local information for the food in question. Fibre and protein represent 'crude' fibre and 'crude' protein (N x6.25) respectively, unless otherwise stated.

In addition, the presence of constituents that may call for special treatments, eg toxins, are indicated, and also of those that may have value as drugs, antibiotics, etc.

Processing

The main processing operations through which the primary product may have to pass in order to produce a final marketable commodity, are listed. In certain circumstances, similar information may also be given for secondary products.

Production and trade

There is very little statistical information available regarding the production and trade of many of the individual root crops included in this digest, largely because most root crop production in the tropics is in smallholder units. Moreover, the major part of the production is consumed locally, since tropical root crops, owing to their high water content and perishability, have not assumed any great significance in international trade. Where information is available, details are provided of: (i) the estimated average world production of the crop; (ii) the output of the major producing countries; (iii) shipments from the major exporting countries; and (iv) shipments to the major importing countries. In some cases only very fragmentary information is available, in others none. In view of the extreme variations in exchange rates, commodity prices and general economic instability of recent years, prices have not been included as any such figures could be misleading.

Major influences

Any factors which might have a significant influence on the future supply of and demand for the commodity are mentioned under this heading.

Particular attention is paid to possible competition from synthetic materials and other substitutes.

Bibliography

Textbooks, technical bulletins, research reports, papers given at recent symposia, articles in technical periodicals and bibliographies are cited. For some root crops literature is scant, but for many it is extensive, and the bibliographies for each individual crop are selective and by no means exhaustive. Emphasis has been given to material published between 1972 and 1982.

Abbreviations

African yam bean (Sphenostylis stenocarpa)

Common names

AFRICAN YAM BEAN, Wild yam bean.

Botanical name

Sphenostylis stenocarpa (Hochst. Ex A. Rich.) Harms syn. Sphenostylis ornata A. Chev.

Family

Leguminosae, sub-family Papilionoideae.

Other names

Akitereku (W. Afr.); Diegemtenguere (Mali); Girigiri (W. Afr.); Haricot igname (Fr.); Kotonosu (W. Afr.): Kulege (W. Afr.); Norouko (Sud.); Okpu dudu (W. Afr.); Pempo (W. Afr.); Pomme deterre du Mossi (Fr.); Roya (Sud.); Sese (W. Afr.); Yam pea.

Botany

A vigorous, herbaceous, climbing vine, reaching 1.5-2 m in height, with trifoliate leaves, the leaflets being up to 14 cm in length and 5 cm broad. The conspicuous flowers are mauvish-pink, purple or greenish-white in colour, about 2.5 cm in length and borne on stout axilliary peduncles. The glabrous seed pods are linear, flat, with both margins raised, 25-30 cm long and 1-1.5 cm broad, containing 20-30 seeds which may be ellipsoid, rounded or truncated, and show considerable variation in size and colour; the largest are usually about I cm long and 0.7 cm wide. Seed colour may vary from creamy-white or brownish-yellow to dark brown, sometimes with black marbling, and there appear to be a number of 'types' according to seed colour. The plant produces small spindle-shaped tubers, about 5-7.5 cm long. There is some evidence that yields of seeds and tubers are inversely related.

Origin and distribution

The African yam bean originated in Ethiopia. Both wild and cultivated types now occur in tropical Africa as far south as Zimbabwe, throughout West Africa from Guinea to southern Nigeria, being especially common in the latter and in Togo and the Ivory Coast, and in East Africa from northern Ethiopia (Eritrea) to Mozambique, including Tanzania and Zanzibar.

Cultivation conditions

Small-scale cultivation is practiced throughout tropical Africa: the plant is especially suited to lowland conditions, though it can be grown up to 1800 m. Climates ranging from savannah to rainforest are tolerated provided there is a combination of adequate rainfall (100 cm or more during the growing season) and reasonably good drainage. It is often planted along with yams and beans, using the same stakes as the yam for support, though sometimes left to trail on the ground. It is sometimes stated that plants perform better when interplanted than when grown alone.

Planting procedure

Material-both seeds and tubers can be used for propagation; planting is usually at the start of the rainy season.

Method-planting is done by hand, often two seeds to a hole (or one tuber).
Field spacing-varies considerably, often according to the crop with which they have been interplanted. One spacing quoted is 45 cm apart alternated with yam in 120 cm rows.

Pests and diseases

Fungal diseases reported are powdery mildew (due to Oidium sp.), which is parasitised by Cincinnobolus cesati; leaf spot (caused by Phoma sp.) and stem rust (caused by Aecidium sp.). Virus mosaics have also been reported. Pests have not been defined in detail but include Orthopterous and Lepidopterous insects. Leaf rolling caterpillars and leaf miners have been described as causing serious damage to the foliage, and thrips damage the flowers. Nematodes may attack the root system leading to reduction in yield.

Growth period

The tubers are ready for harvesting 5-10 months after planting.

Harvesting and handling

The crop is dug by hand usually towards the end of the dry season.

Primary product

Tubers-these are small and spindle-shaped, externally rather similar to sweet potatoes, usually about 5-7.5 cm long and weighing on average 50-150 g, although under favourable conditions they can weigh up to 300 g. The flesh is white and watery.

Yield

On a basis of 24 200 plants/ha, yield has been calculated at 1 452-2 904 kg/ha, depending upon variety. (Seed yield on the same basis ranged from 3 461-3 872 kg/ha.)

Main use

The tubers are cooked and eaten in the same manner as potatoes, which they resemble in flavour.

Secondary and waste products

The seeds also are eaten, but must be soaked in water for about 12 hours before being cooked. They are said to cause giddiness if eaten in excess, but to cure drunkenness when mixed with water.

Special features

Tubers-the tubers are rich in starch and protein. Dry matter is approximately 35 per cent, of which starch is about 80 per cent and protein about 14 per cent, ranging from 12.5 to 19 per cent for six varieties; however, some analyses have indicated that the non-protein nitrogen can be 50 per cent of the crude protein nitrogen.

Seeds-analytical figures for the seeds showed dry matter about 90.5 per cent; the dry matter composition was: protein 24-28 per cent; fat 1.5-2 per cent; total carbohydrate 74.1 per cent; fibre 5.2-5.7 per cent; ash 2.8-3.2 per cent; calcium 61 mg/100 g; phosphorus 437 mg/100 g. The amino acid content of the protein was very similar to that of soya bean, though rather higher in histidine and iso-leucine. The energy content of the seeds per 100 g dry matter was 1,640 kJ.

The plants have beautiful flowers and are grown as ornamentals in European and other countries.

Major influences

The tubers of African yam bean are regarded as an important source of starch and protein in tropical Africa, and the plant is potentially important also as a food legume. It appears likely to remain a valuable constituent of African peasant agriculture.

Bibliography

BOIS, D. 1927. Les plantes alimentaires, chez tous les peuples et � travers les ages, pp. 163-164. Paris, France: P. Lechevalier, 596 pp.

BUSSON, F. 1967. Plantes alimentaires de l'ouest Africain, �tude botanique, biologique et chimique, pp. 245; 247-248; 252; 254-255. Marseille, France: Leconte, 568 pp.

DALZIEL, J. M. 1948. The useful plants of West tropical Africa, pp. 261- 262. London: The Crown Agents for the Colonies, 612 pp.

DUKE, J. A., OKIGBO, B. N. and REED, C. F. 1977. Sphenostylis stenocarpa (Hochst ex A. Rich) Harms. Tropical Grain Legume Bulletin, 10, 4-6.

EVANS, I M. and BOULTER, D. 1974. Amino acid composition of seed meals of yam bean (Sphenostylis stenocarpa) and Lima bean (Phaseolus lunatus). Journal of the Science of Food and Agriculture, 25, 919-922.

EVANS, I. M., BOULTER, D., EAGLESHAM, A. R. J. and DART, P. J. 1977. Protein content and protein quality of tuberous roots of some legumes determined by chemical methods. Qualitas Plantarum. Plant Foods for Human Nutrition, 27, 275-28S.

EZUEH, M. I. 1977. Cultivation and utilization of minor food legumes in Nigeria. Tropical Grain Legume Bulletin, 10, 28-32.
GREENWAY, P. J. 1944. Origins of some East African food plants. East African Agricultural Journal, 10, 38.

IRVINE, F. R. 1949. Indigenous food plants of West Africa. Economic Botany, 3, 442.

OKIGBO, B. N. 1973. Introducing the yam bean Sphenostylis stenocarpa (Hochst. ex. A. Rich) Harms. Proceedings of the 1st International Institute of Tropical Agriculture Grain Legume Improvement Workshop (Nigeria, 1973), pp. 224-238. Ibadan, Nigeria: IITA, 325 pp.

SCHNELL, R. 1957. Plantes alimentaires et vie agricole de l'Afrique Noire, p. 169. Paris, France: Larose, 223 pp.

A�u (Tropaeolum tuberosum)

Common name

A�U.

Botanical name

Tropaeolum tuberosum Ruiz and Pav.

Family

Tropaeolaceae.

Other names

Cubio (Col.); Isa�o, Isa�u (Bol., Peru, Arg.); Mashua (Peru, Bol.); Navi�s, Navo (Col.); Ysa�o (S. Am.).

Botany

A herbaceous climber, resembling the garden nasturtium to which it is closely related, although it is more compact and has smaller flowers. The stems are green or reddish-green and the leaves show a considerable variation in form, but are normally 5-20 cm long, peltate, with 3-5 lobes.
The flowers have long peduncles 10-19 cm long; the red calyx forms a spur, sometimes two, and there is considerable variation in the size and shape of the orange petals. The tubers are conical or ellipsoid in shape, generally deeply furrowed, each furrow containing a bud. Over 100 clones are recognised and some authorities consider that two separate species should be recognised: Colombian species, characterised by long deeply furrowed white tubers or white with pink extremes, and numerous rootless; and Peruvian/Bolivian species, with yellow tubers, often with dots and lines on them and without rootless. Chemical examination and cytological evidence have both suggested that there are two distinct types and subspecies status has been suggested, namely T. tuberosum ssp. tuberosum and T. tuberosum ssp. silvestre.

Origin and distribution

The a�u is native to the high Andes of South America and is confined to this area where it is cultivated in the Andean valleys of Peru and Bolivia.

Cultivation conditions

This crop requires cool and moist conditions and is tolerant of frost; it is normally grown at altitudes of 3 000 m or above, frequently in rotation with ullucu. It is considered to require approximately 12 hours day-length for successful growth.

Planting procedure

Material-a�u is propagated vegetatively from tubers. Method-a�u is usually cultivated in small plots on terraces on hillsides; for good yields it must be kept free from weeds and earthed up.
Field spacing-planting is usually in rows 70-100 cm apart with 40-70 cm between the plants.

Growth period

The tubers reach maturity in approximately 7 months.

Harvesting and handling

The tubers are dug by hand and are reported to keep better in the fresh state than the other Andean tuber crops, oca and ullucu, with a storage life at ambient temperatures of up to 6 months.

Primary product

Tubers-a�u produces small conical or ellipsoidal tubers approximately 5-15 cm long and 3-6 cm wide, with a wide range of colouring which can vary from dirty-white or yellow to red or purple. In the fresh state they have a disagreeable odour.

Yield

Yields are reported to lie between 20 and 30 t/ha.

Main use

A�u tubers are eaten boiled as a vegetable and are said to resemble turnips. In some communities at high altitudes in the Andes, where potatoes and other tubers cannot be grown, a�u is the staple foodstuff.

Subsidiary uses

It has been suggested that a�u could be grown for use as a feedingstuff for pigs. In some areas the tubers are valued for their medicinal properties and are used in the treatment of kidney and liver diseases, sores on the skin, and head lice. Traditionally, they are regarded as having anti-aphrodisiacal properties. Planting among other crops is reported to bring protection against nematodes.

Special features

Published figures give the composition of the edible portion of the tubers as: energy 218 kJ/100 g; water 86 per cent; protein 1.6 per cent; fat 0.6 per cent; carbohydrate 11 per cent; fibre 0.8 per cent; ash 7 per cent; calcium 7 mg/100 g; iron 1.2 mg/100 g; phosphorus 42 mg/100 g; vitamin A 0.015 mg/100 g; thiamine 0.06 mg/100 g; riboflavin 0.08 mg/100 g; niacin 0.6 mg/100 g; ascorbic acid 67 mg/100 g. The exceptionally high ascorbic acid content is noteworthy.

The plant contains isothiocyanates and thiourea; differences in composition correspond with the cultivated form and wild form and a division into two subspecies, Tropaeolum tuberosum ssp. tuberosum and T. tuberosum ssp. silvestre, has been proposed.

The traditional medicinal uses have been examined:

(i) Effect on reproduction: no effect was found on the male capability of impregnating females, though animals fed extracts of the plant showed a 45 per cent drop of testosterone/dihydrotestosterone in their blood; a similar effect in man would be expected to reduce libido.

(ii) Antibiotic activity: both subspecies contain p-methoxybenzyl glucosinolate, and both show strong antibiotic activity against Candida albicans, Escherichia cold and Staphylococcus albus.

(iii) Kidney diseases: isothiocyanates are diuretic.

(iv) Nematicidal effect: this has been demonstrated and is believed to be due to isothiocyanates.

(v) Head lice: similarly, it is believed that isothiocyanates are effective against head lice.

Production and trade

Little information has been recorded; Peru is stated to have approximately 4 000 ha under cultivation.

Major considerations A�u is reported to be grown rather less than formerly, but continues to be an important crop, especially for remote Indian communities where its medicinal value and food value both find favour. A germplasm collection is being made, to be maintained at Cusco and Puna in Peru.

Bibliography

BATEMAN, J. V. 1961. Una prueba exploratoria de la alimentaci�n usando
Tropaeolum tuberosum. Turrialba, 11, 98-100.

GIBBS, P. E., MARSHALL, D. and BRUNTON, D. 1978. Studies on the cytology of Oxalis tuberosa and Tropaeolum tuberosum. Notes from the Royal Botanic Gardens, Edinburgh, 37, 215-220.

HODGE, W. H. 1951. Three native tuber foods of the high Andes. Economic Botany, 5, 185-201.

JOHNS, T., KITTS, W. D., NEWSOME, F. and TOWERS, G. H. N. 1982. Anti-reproductive and other medicinal effects of Tropaeolum tuberosum. Journal of Ethnopharmacology, 5, 149- 161.

JOHNS, T. and TOWERS, G. H. N. 1981. Isothiocyanates and thioureas in enzyme hydrolysis of Tropaeolum tuberosum. Phytochemistry, 20, 2687-2689.

LEON, J. 1964. Plantas alimenticas andinas. Instituto Interamericano de Ciencias Agricolas, Zona Andina, Lima, Peru, Bolet�n T�cnico, No. 6, pp. 31 -36.

LEON, J. 1967. Andean tuber and root crops: origin and variability. Proceedings of the International Symposium on Tropical Root Crops (Trinidad, 1967) (Tai, E. A., Charles, W. B., Haynes, P. H., Iton, E. F. and Leslie, K. A., eds), Vol. 1, Section 1, pp. 118-123. St. Augustine, Trinidad: University of the West Indies (2 vole).

LEON, J. 1977. Origin, evolution and early dispersal of root and tuber crops. Proceedings of the 4th Symposium of the International Society for Tropical Root Crops (Colombia, 1976), IDRC-080e (Cock, J., MacIntyre, R. and Graham, M., eds), pp. 20-36. Ottawa, Canada: International Development Research Centre, 277 pp.

MONTALDO, A. 1972. Mashua. Cultivo de ra�ces y tub�rculos tropicales, pp. 235-236. Lima, Peru: Instituto Interamericano de Ciencias Agricolas de la OEA, 284 pp.

TAPIA, M. E. 1980. Collecting in the Andes. Plant Genetic Resources Newsletter No. 40, pp. 20-22. Rome, Italy: Food and Agriculture Organization of the United Nations, 39 pp.

TAYLOR, W. A. 1918. Inventory of seeds and plants imported by the Office of Foreign Seed and Plant Introduction during the period from July I to September 30, 1915. United States Department of Agriculture, Bureau of Plant Industry Inventory, No. 44, pp. 6-7; 49. Washington, DC: Government Printing Office, 71 pp.

TOWNSEND, J. 1964. Unexploited crops in Bolivia. World Crops, 16, 67-68.

Arracacha (Arracacia xanthorrhiza)

Common names

ARRACACHA, Peruvian carrot, Peruvian parsnip.

Botanical name

Arracacia xanthorrhiza Bancroft syn. A. esculenta DC.

Family

Umbelliferae.

Other names

Apio (criollo) (Venez., P. Rico); Arrecate (Lat. Am.); Batata baroa, Mandioquinha salsa (Braz.); Pomme de terre c�leri (Fr.); Racacha, Virrac� (Peru); Zanhoria blanca (Ecu.).

Botany

A stout semi-caulescent herb, somewhat resembling celery but one of the largest of the cultivated umbellifers. Its coarse stems and leaves usually attain a height of 0.6-1.2 m, and the leaves are dark green or purple. The flowers are small, typical of the family, and usually purplish or yellow, but seldom seen because the crop is harvested before flowering. The subterranean portion of the plant is a compound structure consisting of a large, more or less cylindrical rootstock, indistinctly marked with a number of horizontal nodose rings, and with a coarse central core: from this root stock 6-10 irregularly spindle-shaped secondary tubers arise as off-shoots.

These are smooth skinned and resemble parsnips in texture, colour and odour. The crown of the rootstock gives rise to a number of shoots which arise from enveloping sheaths to form the stems and leaves. Three main varieties are recognised depending upon the colour of the flesh of the roots-white, yellow or purple-but several cultivars have been developed.

Origin and distribution

Arracacha originated in the Andes in Peru, Ecuador and Colombia but cultivation has now spread to Venezuela, parts of Brazil, Puerto Rico, Mexico and to parts of Africa.

Cultivation conditions

Temperature-for optimum results an equable temperature of 15-20°C throughout the year is required. In Colombia, for example, high yields are obtained in the Andes, where the annual mean temperature is 16°C; in savanna areas where the mean temperature is slightly lower, about 14°C, the vegetative cycle is lengthened. Some varieties are sensitive to frost and are grown only at the lower altitudes but those adapted to the higher altitudes are resistant to occasional light frost.

Rainfall-arracacha requires a moderate, evenly-distributed rainfall of at least 60 cm but preferably 100 cm, and if the natural rainfall is insufficient it should be supplemented by irrigation.

Soil-deep, fertile, well-drained sandy soils with a pH of about 5-5.5 are ideal, and the application of a 12:24:12 or 10:30:10 complete (NPK) fertiliser at the rate of 500-600 kg/ha has been recommended. The application of phosphorus has been found to increase yields considerably, while heavy applications of nitrogen have an adverse effect.

Altitude-arracacha yields a crop at elevations above about 600 m in the northern Andes: in Colombia it grows best at elevations between 1 800 and 2 600 m; in Brazil it is successfully grown in the state of Sao Paulo at altitudes of 1 000-1 200 m.

Day-length-there is some evidence that arracacha requires short day-lengths in order to produce economic yields.

Planting procedure

Material-although it is possible to obtain fertile seed with a good rate of germination, arracacha is traditionally propagated vegetatively by the use of offsets or shoots produced on the crown of the main rootstock. Only the basal portion of the shoot actually possessing a bud with leaves is used; this is cut to a piece 2-3 cm in length and the leaves are cut off to 10-20 cm above their points of attachment to the stem. After the offset is detached from the rootstock, the basal end is cut several times to stimulate sprouting of the shoot, and to ensure that secondary roots begin to form and are well-distributed laterally on the primary rootstock. After the offsets are cut they are left to dry for 2-3 days before planting. It is important to use only material from virus-free stock.

Method-arracacha is cultivated in a manner similar to potatoes, with which it is often interplanted. Although it may be grown throughout the year, the main crop is usually planted at the beginning of the rains in April and September. The normal procedure is for the offsets to be put in holes along furrows, with fertiliser placed in each hole before planting. Often the offset is positioned in such a way that the basal portion is covered and the shoot is left slightly above the soil level, but in some parts of the Andes the traditional method is to cover the offsets completely to a depth of 2-3 times their own length. After planting, the rows are mulched with trash and kept earthed up and free from weeds. Subsequent hand-weeding is usually carried out 2 months after planting and again after 5 months, but in Colombia the use of the herbicide linuron at the rate of 0.75 kg/ha has been found to give excellent control over broad-leaved weeds if applied 40-50 days after planting.

Field spacing-the furrows are normally about I m apart with 50-60 cm between the plants.

Seed rate-approximately 16 700-20 000 offsets are required to plant one hectare.

Pests and diseases

Among the pests reported to attack arracacha are the flea beetles Epitrix spp. and Systena s-littera, the swallow-tail butterfly Papilio polyxenes and the moths Automeris spp., whose larvae feed on the foliage, the leafhopper Erythrogonia quadriguttata, the tree-hopper Amastris simillima, the mole cricket Tridaclylus minutus, the scarab beetle Ancognatha scarabeoides, spider mites Tetranychus spp., nematodes, in particular Pratylenchus penetrans which may cause necrosis of the whole plant, and slugs.

Diseases include those caused by Cercospora spp., Cercosporidium depressum, Septoria apii, and Gloeosporium sp. The last is the most serious, though control can be effected by copper-based fungicides or thiabendazole. A bacterial necrosis, first appearing as yellow leaves and stunted growth, is caused by Erwinia amylovora. The disease is transmitted by infected buds of diseased plants used in planting, or the organism may penetrate from the soil into the root system. Two viruses-arracacha virus A and arracacha virus B-have been identified as causing yellow mosaic symptoms and poor growth. Neither appears to be transmitted by vector and spread is apparently by infected planting material. A strain of virus B has been found in oca (Oxalis tuberosa). The only known control measure for the bacterial and virus infections is avoidance of infected planting material. The symptoms are easily recognised in the growing crop and therefore rogueing can greatly minimise this danger.

Growth period

The secondary tubers usually mature in about 10-14 months after planting; sometimes an early harvest of immature roots is taken after 4-8 months.

Harvesting and handling

The crop is judged to be mature when the leaves begin to yellow and production of new shoots ceases. Some growers accelerate the onset of maturity by breaking the petioles, often by twisting or doubling them over. Harvesting is usually accomplished by digging up the whole plant, detaching the offsets for the next crop, and collecting the tubers and main rootstocks. Harvesting cannot be delayed, because if the roots are left in the ground they become fibrous and tough, and develop a strong unpleasant flavour. After harvesting, the tubers have a very short storage life, and in Colombia were considered unmarketable after 3-4 days at 25°C and 40 per cent RH. However, after storage at 10°C and 90 per cent RH, or at 3°C and unspecified humidity for about I month, the roots maintained good condition. Irradiation with doses of 10-11 head has also been found to extend the storage life. Deterioration of the tubers is due mainly to fungal and bacterial rots and desiccation, and it has been shown that wrapping of individual tubers in plastic cling or shrink film of low moisture penetrability within 24 hours after harvest extended shelf-life to 7 days or more at 17-20°C and 68-70 per cent RH, and was economically advantageous for tubers that were to be marketed.

Primary product

Tubers-the edible secondary tubers are the primary product and under good cultural conditions each plant can produce 6-10 tubers, weighing 2-3 kg. These tubers have a delicate flavour and a crisp texture, and the flesh may be white, creamy-yellow or purple, depending upon the cultivar; in many areas the yellow tubers are preferred.

Yield

Yields range from about 3 to 18 t/ha, depending mainly upon growing conditions, and in Colombia the best yields are obtained at altitudes of over 2 000 m in the northern Andes.

Main use

The secondary tubers are used as a source of carbohydrate, boiled, fried or as a constituent of stews, eg along with cassava in the Colombian sancocho. They are regarded in Venezuela as especially important for children because of their easy digestibility.

Subsidiary uses

The tubers and main rootstock can be used as a source of an easily digestible starch, suitable for the preparation of invalid and baby foods.

Secondary and waste products

The coarse main rootstocks and mature leaves are used for livestock feeding; they have a higher protein content that alfalfa. In certain Andean communities the tubers are used in traditional medicine. The young blanched stems are utilised as a salad ingredient or as a vegetable.

Special features

Analyses of the edible portion of Colombian tubers (the lateral swollen roots) have been published as: water 71.9-73 per cent; protein 0.8-1.1 per cent; fat 0.1-0.2 per cent; carbohydrate 24.9 per cent; fibre 0.6-0.8 per cent; ash 1.6 per cent; calcium 24 mg/100 g; iron 0.7 mg/100 g; phosphorus 65 mg/100 g; vitamin A 20-60 IU/100 g (in yellow cultivars); thiamine 0.04-0.06 mg/100 g; riboflavin 0.03-0.04 mg/100 g; niacin 2.7-3.4 mg/100 g; ascorbic acid 15-28 mg/100 g.

The starch, which is similar in many respects to that of cassava, is easily digestible and is also suitable for laundry use. The grains are usually spherical or ovoid, ranging from 5 to 27 microns, averaging 14 microns.

Production and trade

Little statistical information is available although production was reported to be increasing in Colombia: average 1960-64, 111 000 t/a; average 1965-67, 123 000 t/a. For 1977 no figures of total production were available but 123 000 t was stated to have reached the markets.

Major influences

Arracacha has been an important staple carbohydrate foodstuff in parts of South America for at least 300 years and today forms an important and popular item of diet, particularly amongst children, but because of its short shelf-life it has been relatively high-priced. However, recent work appears to have demonstrated that the shelf-life can be extended. It is expected to prove a valuable root crop if introduced into other high altitude areas of the tropics, and a considerable amount of research is currently being undertaken, in particular on the development of new cultivars and in breeding: a germplasm bank has been established at Campinas in Argentina.

Bibliography

ABEELE, M. van den and VANDENPUT, R. 1956. La pomme de terre c�leri.

Les principales cultures du Congo beige, 3rd edn, p. 869. Bruxelles, Belgium: Direction de l'Agriculture, des For�ts et de l'�levage, 932 pp.

ANON. 1975. Arracacha. Underexploited tropical plants with promising economic value, pp. 29-32. Washington DC: National Academy of Sciences, 188 pp.

BRICE�O VERGARA, A. 1975. Resultados preliminares de la introduccion de material clonal de apio criollo (Arracacia xanthorrhiza Banc.) en los Andes venezolanos. Agronom�a Tropical, 25, 31 -37.

BRITO, O. and ARISMENDI, L. G. 1983. Agro-socio-economy of production and commerce of Arracacia xanthorrhiza in Sucre state, Venezuela. Abstracts of the 6th Symposium of the International Society for Tropical Root Crops (Peru, 1983), p. 6. Lima, Peru: International Potato Center, 113 pp.

CAMINO A., J. M. and D�AZ POLANCO, C. 1972. Identificaci�n de una bacteriosis en apio (Arracacia xanthorrhiza). Agronom�a Tropical, 22, 563-567.

CZYHRINCIW, N. 1969. Consideraciones sobre industrializacion du ra�ces y tub�rculos tropicales. Revista del Facultad de Agronomia, Universidad Central de Venezuela, 5, 108-117.

CZYHRINCIW, N. and JAFFE, W. 1951. Modificaciones qu�micas durante la conservaci�n de tub�rculos y ra�ces. Archivos Venezolanos de Nutricion, 2, 49-67.

D�AZ POLANCO, C. and CAMINO A., J. M. 1976. Una nueva forma de Fusarium solani, patogeno del apio (Arracacia xanthorrhiza) en Venezuela. Agronom�a Tropical, 26, 353-358.

GRUBBEN, G. J. H. 1977. Other warm weather vegetables. Tropical vegetables and their genetic resources, pp. 111-115. Rome, Italy: International Board for Plant Genetic Resources, 197 pp.

HIGUITIA MU�OZ, F. 1968. El cultivo de la arracacha en la sabana de Bogot�. Agricultura Tropical, 24, 139-146.

HIGUITIA MU�OZ, F. 1969. [Comparative yield of nine varieties of Arracacia xanthorrhiza.] Agricultura Tropical, 25, 566-570. (Field Crop Abstracts, 24, 1015).

HODGE, W. H. 1954. The edible arracacha, a little known root crop of the Andes. Economic Botany, 8, 195-221.

JONES, R. A. C. and KENTEN, R. H. 1978. Arracacha virus A, a newly recognised virus infecting arracacha (Arracacia xanthorrhiza; Umbelliferae) in the Peruvian Andes. Annals of Applied Biology, 90, 85-91.

JONES, R. A. C. and KENTEN, R. H. 1981. A strain of arracacha virus B infecting oca (Oxalis tuberosa: Oxalidaceae) in the Peruvian Andes. Phytopathologische Zeitschrift, 100 (1), 88-95.

KENTEN, R. H. and JONES, R. A. C. 1979. Arracacha virus B, a second isometric virus infecting arracacha (Arracacia xanthorrhiza; Umbelliferae) in the Peruvian Andes. Annals of Applied Biology, 93, 31-36.

KROLL, R. 1956. Pomme de terre c�leri. Les cultures potag�res au Congo be/ge. Tract 22, p. 114. Bruxelles, Belgium: Direction de ['Agriculture, des For�ts et de l'�levage, 131 pp.

L�ON, J. 1964. Plantas alimenticias andinas. Instituto Interamericano de Ciencias Agricolas, Zona Andina, Lima, Peru, Bolet�n T�cnico, No. 6, pp. 51 -56.

L�ON, J. 1967. Andean tuber and root crops: origin and variability. Proceedings of the International Symposium on Tropical Root Crops (Trinidad, 1967) (Tai, E. A., Charles, W. B., Haynes, P. H., Iton, E. F. and Leslie, K. A., eds), Vol. 1, Section 1, pp. 118-123. St. Augustine, Trinidad: University of the West Indies (2 vole).

L�ON, J. 1977. Origin, evolution and early dispersal of root and tuber crops. Proceedings of the 4th Symposium of the International Society for Tropical Root Crops (Colombia, 1976), IDRC-080e (Cock, J., MacIntyre, R. and Graham, M., eds), pp. 20-36. Ottawa, Canada: International Development Research Centre, 277 pp.

L'HEUREUX, L. and BASTIN, R. 1936. �tude de deux f�cules pr�par�es � la station exp�rimentale de Kisozi. Bulletin Agricole du Congo beige, 27, 270-281.

MONTALDO, A. 1972. Arracacha. Cultivo de ra�ces y tub�rculos tropicales, pp. 137-143. Lima, Peru: Instituto Interamericano de Ciencias Agricolas de la OEA, 284 pp.

MONTEIRO, A. R. 1980. Pratylenchus penetrans as a cause of necrosis in Arracacia xantizorrhiza in Brazil. Piracicaba, S.P. Brasil Sociedade Brasileira de Nematologia, pp. 59-63.

PEREZ-ARBELAEZ, E. 1956. Plantas utiles de Colombia, pp. 732-733. Madrid, Spain: Sucesores de Rivadeneyra (S.A.), 831 pp.

REVETTI, L. M. 1967. Gamma irradiation of Arracacia xanthorrhiza, a Venezuelan nutritious vegetable. Food Irradiation, 8, 41-43.

SILVA, J. R. da, GARCIA BLANCO, H., NORMANHA, E. S. and FRERE, E. S. 1966. Effeito de doses crescentes de nitrog�nio, f�sforo e pot�ssio s�bre a producao de ra�zes de mandioquinha-salsa. Bragantia, 25, 365-369.

SILVA, J. R. da and NORMANHA, E. S. 1963. Cultura da mandioquinhasalsa ou batata-baroa. Agron�mico, 15 (11-12), 11-19.

THOMPSON, A. K. 1980. Reduction of losses during the marketing of arracacha (Arracacia xanthorrhiza). Acta Horticulturae, 116, 55-60.

ZAPATA, G. M. A. and PARDO, C. V. M. 1974. Studies on bacterial wilt of arracacha caused by Erwinia sp. Revista de la Facultad Nacional de Agronomia, Medellin, 29 (1), 39-42.

Arrowhead (Sagittaria sagittifolia)

Common name

ARROWHEAD.

Botanical name

Sagittaria sagittifolia L.

Family

Aponogetonaceae.

Other names

Beea beea (Mal.); Chee-koo (China); Chotakut (Ind.); Duck potato, Echtes (Ger.); Fl�che d'eau, Fl�chi�re (Fr.); G�uai-g�uai (Philipp.); Kuwai (Japan); Muy�-muy� (Ind.); Pfeilkraut (Ger.); Pijkruid (Nether.); Sagittaire (Fr.); Swamp or Swan potato, T'zu ku (China).

Botany

A perennial robust, aquatic plant, from 0.6 to 1.2 m tall, with smooth, broad sagittate leaves, raised above the water level, as is the erect inflorescence, which is long-peduncled, glabrous, racemose, simple or branched. The flowers are whorled, usually white, sometimes with a purple spotted base. The carpers are flat and crowded into a globular head. Each plant produces 4-6 small subterranean tuberous rhizomes at the base of the erect stem.

Origin and distribution

The arrowhead is believed to be a native of the more temperate parts of China but has now spread to tropical and subtropical parts of Asia. A closely related species, S. latifolia Willd., is native to North America, and there may be some confusion between the species in the literature. Arrowhead is an aquatic plant and is found growing wild or in a semi-wild state in the marshes and lakes of China, Japan, India, Malaysia, the Philippines and certain islands in the Pacific.

Cultivation conditions

The plant will thrive in wet or marshy places in a range of climates from tropical to warm temperate. Where cultivation is undertaken it is often similar to that used for rice.

Planting procedure

Material-propagation is vegetative using pieces of corm with an axilliary bud.

Method-arrowhead is easily established. In some countries the field preparation is similar to that used for rice or lowland tarot This involves ploughing, discing and harrowing to level the surface and providing a well-puddled soil suitable for flooding, into which the pieces of corm are set by hand at a depth of about 20 cm.

Growth period

The corms mature in about 6-7 months.

Harvesting and handling

The corms are dug by hand.

Primary product

Corms-the starchy corms are hard, with a globular base and an acute apex, approximately 5 cm in diameter, covered with whitish or bluish-white scales, which quickly wither to expose creamy-white or buff flesh, which exudes a milky juice when cut. Each corm weighs about 15-30 g.

Main use

The corms are used as a starchy vegetable after boiling and are a constituent of several Japanese and Chinese meat dishes. In the USA they were formerly much used by Indians, but apparently are now seldom employed as human food in that country, except by some ethnic minorities.

Subsidiary uses

The tubers are sometimes employed as a source of starch in China, or for pig-feed. The plant has also been used medicinally for skin diseases and in childbirth.

Secondary and waste products

The young leaves are sometimes eaten as a green vegetable and are also used for medicinal purposes in China.

Special features

The composition of the edible portion of the corms has been published as: energy 448 kJ/100 g; water 70.6 per cent; protein 5 per cent; fat 0.3 per cent; carbohydrate 22.4 per cent; fibre 0.9 per cent; calcium 13 mg/100 g; iron 2.6 mg/100 g; phosphorus 165 mg/100 g; potassium 729 mg/100 g; thiamine 0.16 mg/100 g; riboflavin 0.04 mg/100 g; niacin 1.4 mg/100 g; ascorbic acid 5 mg/100 g.

The carbohydrate consists mainly of starch with about 2 per cent of sucrose. The starch grains are large, round, oval or rounded-angular, with a diameter of up to 30-36 microns. An anti-inflammatory principle, sagittariol, occurs in the plant.

Bibliography

CHUNG, H. L. and RIPPERTON, J. C. 1929. Utilization and composition of oriental vegetables in Hawaii. United States Department of Agriculture, Hawaii Agricultural Experiment Station Bulletin, No. 60, 45-46.

LERMAN, M. H. 1980. Arrowhead or duck potato. Minnesota Horticulturist, 108 (7), 207.

OCHSE, J. J. 1931. Sagittaria sagittifolia L. Vegetables of the Dutch East Indies, pp. 8-10. Buitenzorg-Java: Archipel Drukkerij, 1005 pp.

PORTERFIELD, W. M. 1940. The arrowhead as a food among the Chinese. Journal of the New York Botanic Garden, 41, 45-47.

PORTERFIELD, W. M. (Jr.) 1951. The principal Chinese vegetable foods and food plants of Chinatown markets. Economic Botany, 5, 16-18.

SHARMA, S. C., TANDON, J. S. and DHAR, M. M. 1975. Sagittariol; a new diterpene from Sagittaria sagittifolia. Phytochemistry, 14, 1055-1057.

SHERMAN, H. E. and WANG, C. T. 1929. Chemical analyses of thirty-seven oriental foods. Philippine Journal of Science, 38, 69-79.

Arrowroot (Maranta arundinacea)

Common names

ARROWROOT, Bermuda arrowroot, St. Vincent arrowroot, West Indian arrowroot.

Botanical name

Maranta arundinacea L.

Family

Marantaceae.

Other names

Aloro (Philipp.); Amaranta (P. Rico); Araru (Philipp.); Ararut (Beng.); Araruta (Braz.); Aroro (Philipp.); Arraroet (Cur.); Arruruz (Fr.); Aru-aru (Braz.); Car� maco (S. Am.); Envers blanco (Ant.); Guate (gallina) (Venez.); Hoangting (Viet.); Kuzuukon (Japan); Marantale (S. Am.); Mouchasse (St. Lucia); Pfeilwurz (Ger.); Pijlwortel (Nether.); Sag� (Cur.); Sag� belanda (Mal.); Sag� bribri (C. Rica); Sal� (S. Am.); Uraro (Philipp.); Yuquilla (S. Am.).

Botany

An erect, herbaceous, dichotomously branched perennial, 60-180 cm high, with large, fleshy, cylindrical, obovoid subterranean rhizomes, large lanceolate leaves and white flowers arranged in twin clusters, which very rarely produce red seeds. Two main cultivars are recognised in St. Vincent: 'Creole', which has long thin rhizomes, which spread more widely and penetrate more deeply into the soil and 'Banana', which has shorter, thicker, less fibrous rhizomes, produced near the soil surface. The latter is more easily adapted to mechanical harvesting. There are, however, many other cultivars, twenty-two of which were reported to be growing in a Philippine germplasm nursery.

Origin and distribution

Arrowroot is indigenous to tropical America and has long been cultivated in the West Indies, particularly St. Vincent, which produces about 95 per cent of the world's commercial supply. Cultivation has spread to many other tropical countries, including Brazil, India, Sri Lanka, Indonesia and the Philippines.

Cultivation conditions

Temperature-arrowroot is a tropical plant that grows best at temperatures of 20-30°C.

Rainfall-a minimum annual rainfall of 95-150 cm is required, but a sufficient water supply in the soil throughout the growing period of the plant is of primary importance, and optimum yields are only obtained where the rainfall is evenly distributed throughout the year or where the dry season is of short duration.

Soil-arrowroot requires deep, well-drained, slightly acid, loam soils for the best results. Badly-drained and heavy clay soils are unsuitable. When grown on light soils, a degree of shade has been found beneficial. The sandy loam soils of St. Vincent, containing minerals of volcanic origin, have proved admirably suitable for arrowroot cultivation. Fertilising is important. It is recommended that on the St. Vincent soils the crop should receive an 8:5:14 NPK mixture at the rate of 900 kg/ha, 14 weeks after planting.

Altitude-arrowroot normally grows from sea level up to about 900 m but does particularly well near the sea at elevations of 60-90 m.

Planting procedure

Material-arrowroot is normally propagated from 'bits' which are small pieces of rhizomes 4-7 cm in length, with buds on them. In parts of Asia the 'bits' are sometimes treated with smoke to aid germination. Suckers are also used occasionally for propagation.

Method-planting usually starts at the beginning of the rainy season, after the soil has been thoroughly ploughed and harrowed to obtain a fine filth (forking may be necessary on steep terrain where mechanisation is not possible). Holes about 8 - 15 cm deep are made and the pieces of rhizome are dropped in and covered with soil. The crop must be kept clean-weeded during the first 3 or 4 months and the flowers removed as they appear. Pre-emergence applications of 2,4-D, MCPA, monuron and diuron at the rate of 1.7 kg/ha have been recommended for weed control.

In St. Vincent, where cultivation usually follows a 5-7 year rotation, small pieces of the rhizomes are usually left in the ground at harvest to produce the root crop.

Field spacing-an average spacing of 75 x 37.5 cm is recommended.

Seed rate-approximately 3 000-3 500 kg of 'bits' are required to plant one hectare.

Pests and diseases

Arrowroot is not normally subject to serious attacks by pests or diseases. In St. Vincent the only pest of any importance is the leaf roller, Calopodes ethlius, which has proved resistant to many common insecticides but has been controlled by deltamethrin. In Brazil and Venezuela, the crop is attacked occasionally by Ascia monuste orseis, Neocurtilla hexedactyla and Scapteriscus vicinus. In parts of the Caribbean, particularly in wet districts, arrowroot sometimes suffers from a rot caused by Rosellinia bunodes. Two leaf blights, caused by Rhizoctonia solani and Pellicularia filamentosa, are reported to infect arrowroot in India. A condition known as 'cigar roots', in which the rhizomes become elongated and very fibrous, has also been reported from the Caribbean but is thought to be due to nutritional deficiencies.

Growth period

The rhizomes mature in 10-11 months.

Harvesting and handling

The rhizomes are ready for harvesting when the leaves begin to wilt and die down. At this stage the plants are usually dug up by hand and the rhizomes separated from the leafy stem. In St. Vincent a modified potato spinner has been used with limited success to harvest 'Banana' arrowroot. The rhizomes are normally left in the ground until required for processing. Once harvested, deterioration is rapid and the 'Banana' cultivar must be processed within 2 days and the 'Creole' within 7 days.

Primary product

Rhizomes - these are fleshy, cylindrical, covered with regular scales, and grow to approximately 2.5 cm thick and 20-45 cm long.

Yield

Yields of rhizomes normally average about 12.5 t/ha, although under favourable conditions yields as high as 31 t/ha have been recorded. In St. Vincent the normal commercial yield of starch at the factories is 8-16 per cent. Average production of starch per hectare is 2 500 kg, though farmers using improved methods recommended by the St. Vincent Ministry of Agriculture have reported average yields of 3 700 kg (up to 5 600 kg at the maximum).

Main use

The rhizomes are used for the production of a very fine, easily-digested starch, which appears on world markets as a dry white powder known as arrowroot starch. It is valued as a foodstuff, particularly for infants and invalids, and is used in biscuits, cakes and puddings.

Subsidiary uses

Arrowroot starch possesses demulcent properties and is sometimes used in the treatment of disorders of the intestine. It may also be employed in the preparation of barium meals and in the manufacture of tablets where rapid disintegration is desirable. The starch is also used as a base for face powders, in the preparation of certain specialised glues and, more recently, in the manufacture of carbonless paper for computers.

Secondary and waste products

(i) The rhizomes are sometimes eaten boiled or roasted.

(ii) In the West Indies the pounded rhizomes may be used for poulticing wounds and ulcers.

(iii) The plant leaves are occasionally used as local packing material.

(iv) The fibrous material, known as 'bittie', which remains after the extraction of the starch can be used as cattle feed or manure. Typical analyses of 'bittie' from 'Creole' rhizomes are: water 12.5 per cent; protein 3.7 per cent; fat 0.3 per cent; starch 64 per cent; fibre 14 per cent; ash 2.2 per cent. Analyses of 'bittie' from 'Banana' rhizomes give: water 11.9 per cent; protein 2.3 per cent; fat 0.3 per cent; starch 50.4 per cent; fibre 14.8 per cent; ash 2.6 per cent.

Special features

Arrowroot starch is one of the purest forms of natural carbohydrate and has a high maximum viscosity, although this is adversely affected by the salinity of the processing water.

Typical analyses of 'Creole' rhizomes are: water 69.1 per cent; protein I per cent; fat 0.1 per cent; starch 21.7 per cent; fibre 1.3 per cent; ash 1.4 per cent.

Typical analyses of 'Banana' rhizomes are: water 72 per cent; protein 2.2 per cent; fat 0.1 per cent; starch 19.4 per cent; fibre 0.6 per cent; ash 1.3 per cent.

Arrowroot starch is composed of simple oval grains 15-70 microns in length; the 'Banana' type has a slightly higher proportion of large grains than 'Creole'. Commercial good-quality arrowroot starch should be pure white, clean and free from specks, and have a moisture content of not more than 18.5 per cent, with low ash and fibre content, an initial pH of 4.5-7 and a maximum viscosity of between 512 and 640 Brabender units, according to the grade.

Processing

Small-scale

(i) The rhizomes are washed and the skin scales carefully peeled from the white fleshy core, otherwise they impart a bitter taste to the final product.

(ii) The peeled rhizomes are washed again and grated into a coarse pulp.

(iii) The pulp is mixed with a large quantity of clean water and the mixture passed over a series of sieves to separate the fibre.

(iv) The liquid is allowed to stand and the starch to settle out on long tables.

(v) The starch is removed from the tables, mixed with more water and resettled overnight.

(vi) The lumps of starch are placed on racks to air-dry, a process which can take from 4 to 14 days according to the weather; slow drying can result in the material becoming discoloured.

(vii) After drying, the lumps of starch are pulverised and prepared for marketing in different grades according to viscosity ratings. The pulverised starch is packed in moisture-proof bags.

Large-scale

Most of the St. Vincent factories operate on a combination of the small scale and large-scale techniques.

(i) On arrival at the factory the rhizomes are first thoroughly washed in special tanks.

(ii) They are then cut into small pieces, rasped and crushed into a pulp.

(iii) The pulp is passed in a continuous flow of water into a series of three vibratory sieves.

(iv) The starch milk then passes to the separator.

(v) The residues remaining on the sieves are crushed and sieved twice more to effect the maximum extraction of starch. The resultant starch milk is passed to the separator.

(vi) The separator divides the starch from the water within 4 minutes and it is next mixed with fresh water, passed through a fine sieve of 120 mesh wire cloth and re-centrifuged.

(vii) The starch is then mixed with fresh water, treated with sulphurous acid and fed into settling tanks.

(viii) After the starch has settled, the supernatant liquid is run off and the upper layers of sediment are washed away by vigorous hosing to remove as much as possible of the residual fibrous tissue.
(ix) The starch is then dried in low temperature driers at 55-60°C for 2-3 hours, to a moisture content of approximately 17 per cent or slightly less.

(x) When dry, the starch is pulverised as in the small-scale processing procedure.

Production and trade

Production - St. Vincent accounts for the major proportion of the world's output of arrowroot, but for several years it has been grown to a moderate extent in Brazil, mainly in the Otujai valley, Santa Catarina. Arrowroot starch facilities are known to exist in China. Following an exceptionally heavy crop resulting in 4 000 t of unsold stock, production in St. Vincent declined steadily and might have collapsed entirely, but in recent years there has been renewed interest, particularly from buyers in the USA where arrowroot starch is used in the manufacture of carbonless paper for computers.

Production in St. Vincent during the period 1960-80 was: 1960, 2 952 1964, 5 400 t; 1968, 1 272 t; 1972, 784 t; 1976, 740 t; 1980, 630 t.

Current production in each of St. Vincent and Brazil is less than I 000 t/a.

Trade - Exports - St. Vincent: 1961-65 average, 2 939 t/a; 1966-69, 2 097 t/a; 1972, 842 t; 1974, 930 t; 1976, 720 t; 1978, 810 t. Brazil: 1961-65 average, 159 t/a; 1966-69, 139 t/a The export market in 1983 was about I 000 t/a.

Imports - most countries do not show arrowroot separately. Imports of 'arrowroot' starch, which includes sago (ie cassava) starch and flour, into the USA, were reported as: 1961-65 average, 2 158 t/a; 1966-70, 1 492 t/a.

Major influences

The demand for arrowroot starch tends to be limited by its high price compared with other starches and the fact that its manufacture requires large quantities of very pure water. In St. Vincent, recent attempts to increase production to meet the increased demand from the USA for arrowroot starch for use in the manufacture of carbonless paper for computers have been handicapped by the shortage and cost of labour to harvest the crop, and there is an urgent need to mechanise field production. Even so, as arrowroot starch is sold entirely on the basis of its 'special properties', and recent developments in starch technology have produced cheaper substitutes, eg fractionated wheat starch, market competition is becoming more severe and a decline rather than an increase in demand seems likely.

Bibliography

ANON. 1972. Arrowroot computer demand. West Indies Chronicle, 87, 149.

ANON. 1973. West Indies Chronicle, Supplement 36.
BARTOLINI, P. U. 1979. The obscure arrowroot (Maranta arundinacea L.). A promising food crop in the Philippines. Visca Vista, 2 (7), 10-12.

BOLT, A. 1962. Monopoly island - arrowroot. World Crops, 14, 386-388.

BRIANT, A. K. 1933. Maladies affecting arrowroot in St. Vincent. Tropical Agriculture, Trinidad, 10, 183- 188.

BROWNE, G. and LEWIS, A. 1981. St. Vincent: Pest and pesticide management. Pest and Pesticide Management in the Caribbean: Seminar and Workshop on Pest and Pesticide Management in the Caribbean (Barbados, 1980) (Gooding, E. G. B., ed.), Vol. III Country Papers, pp. 170-177. Bridgetown, Barbados: Consortium for International Crop Protection, 204 pp.

HAARER, A. E. 1956. St. Vincent's arrowroot industry. Commonwealth Producer, 135- 136.

JONES, S. F. 1983. The world market for starch and starch products with particular reference to cassava (tapioca) starch. Report of the Tropical Development and Research Institute, G173. London: TDRI, viii+98 pp.

KASASIAN, L. 1971. Root crops: Maranta arundinacea (arrowroot). Weed control in the tropics, p. 159. London: Leonard Hill, 307 pp.

KEMPTON, J. H. 1955. Our arrowroot comes from the Windward Islands. Foreign Agriculture, 19, 167-168.

KERR, R. W. 1950. Manufacture of tapioca and arrowroot starches. Chemistry and industry of starch, 2nd edn, pp. 97-98. New York: Academic Press Inc., 719 pp.

LAMERS, Th. C. W. 1937. Note sur l'arrowroot et l'industrie de sa f�cule. Comptes-Rendus, 5th Congr�s international technique et chimique des industries agricoles (Sh�veningue, 1937), Vol. 2, pp. 268-274. Naarden, Netherlands: Commission Nationale des Industries Agricoles des Pays-gas, 964 pp.

LAWTON, O. 1956. New West Indian arrowroot factory. Food, 25 (10), 368-372.

LE FRANC, E. 1980. St. Vincent. Small Farming in the Less Developed Countries of the Commonwealth Caribbean, pp. 58-92. Weir's Agricultural Consulting Services, Jamaica: Caribbean Development Bank, Barbados.

L�ON, J. 1977. Origin, evolution and early dispersal of root and tuber crops. Proceedings of the 4th Symposium of the International Society for Tropical Root Crops (Colombia, 1976), IDRC-080e (Cock, J., Maclntyre, R. and Graham, M., eds), pp. 20-36. Ottawa, Canada: International Development Research Centre, 277 pp.

MAITI, S., CHANDRA, S. and SAHAMBI, H. S. 1980. A new leaf blight (identified as Rhizoctonia solani) of arrowroot (Maranta arundinacea) and turmeric (Curcuma longa) in Meghalaya. Indian Phytopathology, 33, 492-493.

MARTIN, C. I. 1967. The arrowroot industry in St. Vincent; a case study of a unique root crop industry. Proceedings of the International Symposium on Tropical Root Crops (Trinidad, 1967) (Tai, E. A., Charles, W. B., Haynes, P. H., Iton, E. F. and Leslie, K. A., eds), Vol. 2, Section V, pp. 125-139. St. Augustine, Trinidad: University of the West Indies (2 vole).

MONTALDO, A. 1972. Arrurruz. Cultivo de ra�ces y tub�rculos tropicales, pp. 204-209. Lima, Peru: Instituto Interamericano de Ciencias Agricolas de la OEA, 284 pp.

PANDARAKALAM, J. C. 1956. The plant that yields the arrowroot. Indian Farming, 6 (5), 43; 45.

PURSEGLOVE, J. W. 1972. Maranta arundinacea L. Arrowroot. Tropical crops: Monocotyledons 2, pp. 336-342. London: Longman Group Ltd, 607 pp. (2 vole).

RAYMOND, W. D. and SQUIRES, J. A. 1956. The effect of Antiguan well water on the quality of starch extracted from arrowroot rhizomes. Colonial Plant and Animal Products, 6, 42-52.

RAYMOND, W. D. and SQUARES, J. 1959. Sources of starch in colonial territories. II: Arrowroot (Maranta arundinacea Linn). Tropical Science, 1, 182-188.

ROCHIN, R. I. and NUCKTON, C. F. 1980. The arrowroot industry of St. Vincent: at a crossroads. Agribusiness Worldwide, Oct./Nov., 20-26.

SILVA, J. R. da and MONTEIRO, D. A. 1968. [Cultivation of industrial arrowroot. I Agronomico Campinas, 20, 11 -21. (Field Crop Abstracts, 24, 3930).

SPLITTSOESSER, W. E. 1977. Protein quality and quantity of tropical roots and tubers. Hortscience, 12, 294-297.

VIBAR, T. and MONTEMAYOR, Z. 1932. Arrowroot (Maranta arundinacea L.), its possibilities in the Philippines. Phi/ippine Journal of Agriculture, 3, 65-69.

Cassava (Manihot esculenta)

Common names

CASSAVA, Manihot, Manioc, Tapioca, Tapioka.

Botanical name

Manihot esculenta Crantz syn. M. utilissima Pohl.

Family

Euphorbiaceae.

Other names

Aipi, Aipim ubi (Braz.); Bafifanapaka (Madag.); Brazilian arrowroot, Cassadal� (Afr.); Cassave (Nether.); Caxcamot� (Guat.); Cu san tau (Viet.); Delhazo (Madag.); Guacamote (Mex.); Kamoteng kahoy (Philipp.); Kasp� (Indon.); Kelala (Ind.); Ketalla (Braz.); Khoaimi (Viet.); Kute (agbeli) (Togo); Macaxeira, Mandioca (Braz.); Mandioko (Gam.); Manoco (P. Rico); Mayaca (Zar.); Obikajoe (Indon.); Ramu (Lat. Am.); San (Viet.); Tentu neskok (Philipp.); Ubi kayu (Mal.); Ubi singkong (Indon.); Yautia, Yuca (S. Am.).

Botany

Cassava is a perennial shrub, with latex in all its parts, which produces enlarged tuberous roots. There are over 100 cultivars and there is great variation in the form of the plant. The height ranges from about 1 to 3 m or more. The stems are usually slender and glabrous, with leaves borne near the apex; the lower parts of the stems have nodes made conspicuous by prominent leaf scars. Branching is variable; some cultivars branch near the base and are spreading in form, others are erect and branch nearer the apex. Stems vary in colour, being grey or silvery, green, greenish-yellow, reddish-brown, or streaked with purple. The leaves, which are spirally arranged with phyllotaxis 2/5, have petioles 5-30 cm long, usually longer than the blades; the blades are deeply palmately divided with 5-7 (occasionally 3-9) lobes, each 4-20 cm long and 1-6 cm wide, obovatelanceolate, pointed and with entire margins. They vary in colour from green to reddish; the petiole and midrib may be deep red. Older leaves are shed leaving the prominent leaf scars mentioned above. The flowers are borne in axillary racemes near the ends of branches, and are monoecious, pale yellow or red, 1-1.5 cm in diameter. The fruit is a six-winged capsule with 3 ellipsoidal seeds each about 12 mm long. Root tubers develop by a process of secondary thickening as swellings on adventitious roots a short distance from the stem.

Great variation is shown in the number, shape and size of the tubers and the angle at which they penetrate the ground. There are usually 5-10 tubers per plant, cylindrical or tapering, 3-15 cm in diameter and 15-100 cm long, occasionally longer. Hydrocyanic glycoside is present in varying quantity. Cassava clones are often classified by taste as 'sweet' or 'bitter', but - contrary to the commonly stated notion - this does not always reflect a direct relationship with the cyanogenic glycoside content of the root. The two types have sometimes been regarded as different species, the former being called M. esculenta and the latter M. palmata or M. dulcis. This division is clearly not tenable. Further, the toxicity of a cultivar varies according to environmental growth conditions. However, in any one location it is possible to find some cultivars 'bitter' and some 'sweet', so that a local separation between bitter and sweet can often be made.

Origin and distribution

Manihot esculenta is not known in the wild state. Some 98 species of the genus Manihot have been found in the western hemisphere, and it appears that M. esculenta must have arisen by mutation or hybridisation, the probable centre being southern Mexico/Guatemala or north-eastern Brazil, or both. It was early domesticated and was cultivated in Peru 4 000 and in Mexico 2 000 years ago. It was subsequently spread throughout Central and tropical South America, and was taken by the Portuguese to Africa in the 16th century. Its spread in Africa was slow until the end of the 19th and first half of the 20th century, but Africa now produces almost 40 per cent of the world's total. The crop has become important throughout the tropics, under a wide range of conditions of climate and soil, with West Africa, Brazil, Indonesia and Thailand being major producers.

Cultivation conditions

Temperature - the optimum temperature range for cassava is 25-30°C, and the approximate boundaries for its culture are latitudes 30°N and 30°S. The minimum temperature for its growth is 18°C and yields are reduced above 30°C. It cannot withstand freezing and must have a minimum of 300 frost-free days.

Rainfall - a well-distributed annual rainfall of 100-150 cm is regarded as ideal, but the crop can be successfully grown in areas with rainfall ranging from 50 to 250 cm. Occasionally (eg in Kerala, India), with rainfall of less than 75 cm it is irrigated. Except at planting cassava can withstand prolonged periods of drought and is therefore a useful crop in areas of low or uncertain rainfall.

Soil - light sandy loams of medium fertility give the best results, but cultivars can be grown successfully on soils ranging from stiff marine clays with a pH of 8-9, to sands or loose laterites with a pH of 5-5.5. When grown on clay soils, the plant produces stem and leaf growth at the expense of the roots and many cultivars give poor yields. Saline and swampy soils are unsuitable. Cassava can tolerate soils of low fertility, especially if the feeder roots can penetrate to depths of 40-60 cm; deep cultivation before planting is therefore recommended.

Although it responds well to fertilisation, cassava will grow on relatively infertile soils which are unsuitable for other crops. However, it removes considerable quantities of nutrients from the soil; published figures indicate that for a crop of 25 t/ha of roots the following quantities of nutrients are absorbed: nitrogen 53.5 kg; phosphorus 26.3 kg; potassium 105 kg; calcium 17.2 kg and magnesium 9.75 kg. Thus continuous growing of cassava on improverished soils leads to even more severe soil deficiencies. Potassium is often the limiting factor. Proper fertilising practice will depend upon the soil in question (and on other limiting factors, such as rainfall) but a general basic recommendation is to use about 500 kg/ha of a 12:12:18 complete (NPK) fertiliser. FYM at 20-30 t/ha augmented with 500 kg/ha of rock phosphate and 300 kg/ha of muriate of potash has given good results in Madagascar with average yield of roots about 40 t/ha.

Altitude - cassava can be grown from sea level up to about 1 000 m in equatorial regions, though at the highest altitudes growth is slow and yields are reduced.

Day-length - cassava is a short-day plant and less productive of tuberous roots in day-lengths greater than 10-12 hours; it is, therefore, most productive when grown in areas between latitudes 15°N and 15°S, though some cultivars will tolerate longer days and extend the limits to 30°N and 30°S.

Planting procedure

Material - seed is difficult to germinate and is used only for breeding work. In any case it is necessary to use vegetative material to propagate cultivars and stem cuttings (sticks) are used. For hand planting, sticks about 20-30 cm long, 2.5-3.75 cm thick and with at least 5 buds, taken from stems 8-18 months old are recommended. It is essential that virus-free material be selected and treatment of the cuttings with a mixture of fungicides and insecticides (eg maneb + propineb + copper oxychloride + malathion) has been advised. The sticks can be stored for up to 8 weeks in cool, well-ventilated conditions except when harvested under rainy conditions, when storage is normally reduced to 7-10 days. For mechanical planting shorter sticks, 15-20 cm long, are used.

Method - most cassava is still planted by hand, though mechanisation is increasing. Planting is normally at the start of the rainy season, often in flat fields, though planting on ridges is desirable in wet regions. The sticks may be cut obliquely or at right angles to the axis, and planted vertically or at an angle, with half their length in the soil, or flat below the surface at a depth of about 10 cm. When sticks are planted vertically or inclined, tubers form only at the extreme end of the cut, forming a slanted cluster often of irregular size; when a stick is cut at right angles and planted vertically, the roots are evenly distributed around the circumference and are more uniform in size. Horizontally-planted sticks produce tubers at each node, but lodging of the aerial part is increased and yields reduced. With vertical or inclined planting the roots penetrate more deeply and tubers may be formed at intervals along the planted portion, but in areas of low rainfall desiccation of the cuttings may occur. After 8-12 weeks the plants are usually earthed up to encourage tuber formation.

In smallholdings cassava is frequently grown in mixed cultivations, eg among vegetables, bananas, yams or sweet potatoes, or intercropped with rubber and coconuts: it has been shown that financial gains can be made by certain mixed cultivation systems when compared with monoculture of cassava. When interplanted with coconuts a ground cover of the legume Stylosanthes sp. (stylo) has led to a substantial increase in yield.

Mechanisation of planting (and of the complete production system) is practiced on a large scale in Brazil, parts of Africa and elsewhere. Several types of machine have been developed or modified from vegetable planters: some plant the cuttings vertically or at an angle, others plant the cuttings horizontally in a trench which the machine then covers. The rate of planting can be up to 3-4 ha/day. Sprouting usually takes place in about a week with only about a 5 per cent failure rate: new cuttings are substituted within a month.

Weed control is extremely important, the timing and frequency depending upon local conditions, but, assuming planting was in a clean field, the first weeding should normally be 2-3 weeks after sprouting, followed by three or four weedings during the following 4-6 months. Chemical control gives excellent results: pre-emergence application of, for example, linuron or diuron with subsequent application of shielded sprays of paraquat, has proved successful.

Field spacing - the plant density preferred varies greatly from country to country and within countries, and is affected by cultivar, soil conditions, local customs, and the use to which the roots will be put: a range of between 3 000 and 20 000 plants/ha is quoted for cassava for direct eating (the closer spacing is used on the more infertile soils) but 7 000 to 10 000 plants/ha is the more usual range. If other factors remain constant, closer spacing gives higher yields but smaller roots, and is thus favoured for mechanical harvesting of tubers to be used for processing. In parts of Brazil, with certain cultivars, 30 000 plants/ha are used. High densities of planting, however, tend to encourage certain fungal diseases.

Seed rate - planting is usually at 90 cm intervals in rows 90-120 cm apart. With tows 120 cm apart and 90 cm spacing along the row, the plant density would be approximately 9,250/ha.

Pests and diseases

Pests - root knot nematodes (Meloidogyne spp.) are common but seldom of economic importance except when cassava is intercropped with good hosts for the nematode, eg egg plant (Solanum melongena) or Hibiscus sabdariffa. Pratylenchus sp., Helicotylenchus erythrinae, Rotylenchus reniformis and a few other species have been found in cassava but are considered of little importance.

A number of insects may cause defoliation. In Africa the grasshopper Zonocerus variegatus may be serious; control is by destruction of the egglaying sites or by fenitrothion. Cassava hornworm (Erinnyis ello) may attack the crop in the Americas and Caribbean; biological control is best, by Bacillus thuringiensis sprays, by the egg parasite Trichogromma fasciatum, or by the predatory wasp Polistes canadensis. Leaf cutting ants, Atta sp. and Acromyrmex sp., can cause severe defoliation; poisoned bait is the recommended control. In South America the cassava lacebug (Vatiga manihotae) may cause early defoliation; fenitrothion will control the pest, but will not be economic unless the attack is severe. Among borers in South America, the shootflies, Silba pendula and Carpolonchaea chalybea, burrow into the growing point at the start of the rainy season; resistant cultivars are recommended. Control of larvae may be with diazinon, dimethoate or other chemicals. Stems may be attacked by the weevil borers, Coelosternus spp.; cutting off the infected branches is recommended for control. Scale insects are reported to cause damage especially in areas subject to drought. These include the cassava stem mussel scale (Aonidomytilus albus), the white peach scale (Pseudaulacaspis pentagona), and the black scale (Parasaissetia nigra); oil emulsion plus malathion is recommended for control. Spider mites, Mononychellus tanajoa and Tetranychus cinnabarinus, sometimes affect the crop; mitetolerant cultivars have been developed and M. tanajoa is attacked by predaceous mites and staphylinid beetles, so that chemical control should not be necessary. However, control can be obtained by a number of acaricides. In some areas rodents, baboons, monkeys and wild pigs are reported to cause severe damage, and smallholders sometimes plant bitter cassava around their areas of sweet cassava to discourage such predators.

Diseases - cassava is subject to several virus diseases. In Africa, the most important is African mosaic or curly leaf disease (manihot virus), transmitted by a white fly (Bemisia sp.). No host plant is known for this virus. A virus producing similar effects, Asian mosaic, occurs in India; Cucumis sativus (cucumber) is reported to be a host. In northern South America another mosaic, also causing chlorosis and leaf curl, has several hosts, eg other species of Manihot, some Chenopodiaceae and some Malvaceae. Recommended control measures include the removal and destruction of diseased plants, the use of healthy planting material of resistant cultivars, and the control of vectors and host plants where these are known.

Of the fungal diseases the most important are leaf spots caused by Cercospora henningsii and C. caribaea. These may be controlled by copper fungicides, thiophanate or benomyl, but chemical methods are unlikely to be economic and the use of resistant cultivars is recommended, and measures to reduce the humidity in the stand, eg wider spacing. Phyllosticra sp. also causes leaf-spotting; no specific control has been reported except the possible use of resistant material. Uromyces spp. cause rusts of leaves and stems but do not appear to be of serious economic importance. Stem rots on stored planting material can cause loss of viability. Glomerella sp., Botryodiplodia theobromae and some Basidiomycetes and Ascomycetes are causative agents. Control involves careful selection and handling to avoid wounding, and storage under not excessively humid conditions. 'Seed treatment' fungicides, eg captan+carbendazim, mancozeb and chloroneb, are among those recommended. Root rots include those caused by Phytophthora spp., Rigidoporus lignosus (white rot, white thread), Rosellinia necatrix (black rot), Corticium rolfsii, and a number of others of lesser importance. Control is by cultural practices, including drainage, early harvest, crop rotation, the removal of crop debris, and planting of healthy material. The most important bacterial disease is cassava bacterial blight, caused by Xanthosoma manihotis, which appears as leaf spotting and blight, wilting, die-back, gum exudation and vascular necrosis throughout the plant; resistant cultivars are available. Other bacterial diseases, but of less importance, are bacterial stem rot (Erwinia cassavae) and Agrobacterium sp. (bacterial stem gall).

A package of integrated pest control has been advocated for cassava. The first objective is to ensure healthy and resistant plants by good soil preparation and good drainage, the use of robust sticks taken from well-lignified stems, free from disease and undamaged, dipped in fungicide (captan + benomyl) before planting, correct planting practices, including wide spacing between plants, good weed control and fertilising. Weed control is important not only to avoid all competition with the crop, but also to avoid the appearance of plants that may be hosts to cassava pests. Disease- and pest-resistant cultivars should be used where possible. As monoculture is the usual practice different cultivars should be planted together or in adjacent plots, to provide different degrees of susceptibility (or resistance) within the planted areas. Regular inspections should be made so that appropriate pest control may be applied at an early stage when necessary. Natural biological control is important and chemicals should be used only when absolutely necessary. After harvest all plant residues should be removed. Continuous planting of adjacent areas should be avoided as this gives the opportunity for pests to have uninterrupted access to plants at their most susceptible age.

Growth period

Generally cassava reaches maturity in 9-24 months, according to the cultivar, climate and soil conditions. A few quick-growing cultivars can be harvested in 6-7 months, but good yields are normally only obtained after 9-12 months. When used as a vegetable the tubers are normally harvested within 12 months, otherwise they become very fibrous.

Harvesting and handling

The exact time, in terms of months after planting, when the tubers are ready for harvesting depends very much on the cultivar and growth conditions. Delays in harvesting do not seriously affect tuber quality or yield. The plants are normally topped, ie the above ground parts removed by hand, using a machete, or by machine, eg pushed down by a heavy screen mounted on the front of a tractor. The roots may then be dug by hand, but machine harvesting is being increasingly employed. A number of devices are used, from simple 'ridge breakers' which expose the roots and leave them to be picked up by hand, to relatively sophisticated equipment somewhat resembling potato harvesters. Damage to tubers is still a problem with mechanical harvesting, but smaller tubers are more easily lifted and less liable to damage. For this reason mechanical harvesting is particularly suitable for tubers to be used for processing, where small tubers are satisfactory, and a greater degree of damage can be tolerated.

After harvesting, cassava tubers deteriorate rapidly. There are two distinct types of deterioration which occur during storage, one physiological and the other due to microorganisms. Physiological deterioration, which begins to appear within three days, is essentially a humidity-sensitive wound response with increases in enzyme activity leading to the production of phenols including catechins and leucoanthocyanidins which in the later stages of discoloration polymerise to form condensed tannins. Visible signs of discoloration are at first blue, becoming brown, and initially generally appear in the peripheral vascular bundles and spread to adjacent parenchyma. Physiological deterioration appears to be connected with enzyme activity and some measure of control has been obtained by holding the roots at low temperature, or storing in air with low oxygen levels or in carbon dioxide. Mechanical damage to the roots also permits the entry of microorganisms, causing rapidly-spreading internal rotting. Storage under conditions that favour wound healing, such as packing in moisture-absorbent material, has been reported to minimise physiological deterioration and invasion by pathogens to give a storage life of 4 or more weeks. Pre-pruning of aerial portions of the plant 2-3 weeks before harvesting has also been shown to minimise physiological deterioration in the tubers Coating with a fungicidal wax is stated to extend the storage life up to 1-2 months under ambient conditions in the tropics, while holding undamaged tubers at 0-2°C and 85-90 per cent RH is reported as satisfactory for periods of about 4 weeks.

Primary product

Tubers - these are dark coloured, fleshy and cylindrical, varying a great deal in size and form, with a starch content of 20-40 per cent. Each plant normally yields 5-10 tubers, usually 30-45 cm long, with a diameter of 5-15 cm and weighing 0.9-2.3 kg. The peel accounts for 10-20 per cent of the tuber and consists of an outer corky rind and an inner part which separates the peel from the flesh of the roots.

Yield

Yields vary greatly according to cultivar, soil, climate, age at harvesting, etc. Average yields in t/ha for 1984 were quoted as follows: world 9.1; Central America and the Caribbean 5.6; Africa 6.8; Oceania 10.7; South America 11.6; Asia 12. Of the major producers Thailand had the highest average yield, 15 t/ha, though a very minor producer, the Cook Islands, is reported to have averaged 32.5 t/ha. In fact average yields on a world basis changed little during the decade 1974-84; that for 1974-76 was 8.8 t/ha and for 1984 the figure was 9.1. Yields of smallholdings normally range from 5 to 15 t/ha under normal conditions but can drop to 3 t/ha on poor soils without fertilisation. On plantations yields of 30-40 t/ha are normal and with selected high-yielding cultivars can exceed 50 t/ha. Under poor soil conditions appropriate fertilising can triple or quadruple yields.

Main use

Cassava is the staple food of the poorer section of the population of many tropical countries, and has been estimated to provide 37, 12 and 7 per cent of the energy in the diet of the tropical areas of Africa, America and Asia respectively. The fresh peeled tubers are eaten as a vegetable after boiling or roasting. They are often boiled and pounded into a paste and added to soups and stews ('fufu' in Nigeria). As the fresh tubers deteriorate rapidly they are often preserved in the form of sun-dried chips ('kokonte' in West Africa) and consumed after cooking or being ground into a flour. The principal form in which cassava is eaten in West Africa is as a fermented meal known as 'gari', while in Central and South America a product, 'farinha de manioca' which is similar to 'gari' except that much less fermentation occurs during its preparation, is very popular. In the Philippines 'landang' or 'cassava rice' is prepared and retains much of the original small quantity of protein.

Subsidiary uses

Starch - a substantial industrial outlet for cassava is in the manufacture of starch for use in the foodstuff, textile and paper industries, the manufacture of plywood and veneer, adhesives, glucose and dextrin. Minor industrial applications include use in the manufacture of explosives, dyes, drugs, chemicals, carpets and linoleum, the production of alcohol and the coagulation of rubber latex.

Dried cassava roots - increasing quantities of dried cassava roots are being used for livestock feeding, particularly in the EC countries. Formerly, they entered international trade in the form of chips, made by slicing the roots and then sun drying, but these have almost completely been supplanted by pellets made by grinding the dried chips and compressing the powder into portions approximately 2 cm long and I cm in diameter. These pellets are used as a carbohydrate source in animal feed rations, particularly for pigs

Tapioca - made from cassava starch and used for the preparation of puddings and in infant and invalid foods. In Thailand tapioca is known as sago, which can lead to confusion with true sago starch obtained from the sago palm, Metroxylon sagu.

Cassava flour - the flour is used in the preparation of bread, biscuits and confectionery and in products such as macaroni, spaghetti and rice substitutes, also as an adulterant of cereal flour and in the production of adhesives.

Glucose - which is produced from cassava in Kerala (southern India).

Secondary and waste products

Cassava meal - about 10-20 per cent residue is left after the extraction of starch and tapioca, and this can be used as a livestock feed, or as a raw material for the production of adhesives. The approximate composition (dry matter) is: protein 5.3 per cent; fat 0.1 per cent; starch 56 per cent; fibre 35.9 per cent; ash 2.7 per cent.

Leaves - young leaves are eaten in some areas of Africa as a vegetable. Mature leaves, which have a protein content of 5-7 per cent, can be used for animal feeding and are sometimes dried and ground into a meal. They have a high lysine content.

Stems - the possibility of utilising cassava stems for the manufacture of particle board has recently been investigated.

Juice - the juice expressed from the tubers during starch production is sometimes concentrated and spices added to obtain a sauce, known as 'cassari po' or 'cassareep' in the West Indies and 'tucupi' in Brazil.
Miscellaneous - the tubers may be stored as silage and used for animal feeding. In some countries fermented beers are prepared on a small scale. In Brazil, alcohol has been produced directly from cassava roots, through malt saccharification and immediate fermentation, but cane sugar alcohol can now be produced more cheaply.

Special features

The typical range of composition for the edible portion of the tubers is: energy 607 kJ/100 g; water 62-65 per cent; protein 0.7-2.6 per cent; fat 0.2-0.5 per cent; total carbohydrate 32-35 per cent; fibre 0.8-1.3 per cent; ash 0.3-1.3 per cent; calcium 33 mg/100 g; iron 0.7 mg/100 g; thiamine 0.06 mg/100 g; riboflavin 0.03 mg/lOOg; niacin 0.6 mg/100 g; ascorbic acid 20-30 mg/100 g; vitamin B 10 IU/100 g.

The principal amino acids present in the protein are arginine, histidine, isoleucine, leucine and Iysine. Owing to the low protein content the disease Kwashiorkor is prevalent in areas where cassava is the main staple item of diet. A method of enriching the protein by innoculation of cassava flour paste with Rhizopus or other suitable fungi has recently been developed and the protein content can be increased to about 3.25 per cent.

Cassava roots contain the glycoside linamarin which is converted into HCN by the enzyme linamarase. HCN contents can vary from 10 to 490 mg/kg, being highest in roots grown on soils of low fertility, particularly if there is a potassium deficiency, and also in the first year's growth and in the dry season. It is usually highest in the rind and in the fibrous core at the centre, but considerable variation can occur between various parts of the same tuber. For edible purposes cultivars with a high starch and protein content and a low HCN content are preferred. For starch manufacture cultivars with a high starch content are favoured and HCN content is of less importance. As all cultivars contain some cyanogenic glycoside all are toxic in some degree and 'chronic cassava toxicity' is recognised in populations in which cassava is a major portion of the diet, particularly in Africa, as goitre and tropical ataxic neuropathy. In severe cases cassava can cause respiratory difficulties and occasionally death. Detoxification of bitter cassava is normally practiced. Peeling and cooking gives a partial detoxification, but soaking of roots for long periods, repeated boiling in changes of water, soaking after comminution, and fermentation or fermentation followed by heat treatment, are all used. However, there appears to be no evidence that animals develop toxicity symptoms from continuous intake of cassava or cassava forage.

Cassava starch granules are of various shapes, round, truncated, etc, and vary in size from 5 to 35 microns (average 15-17 microns). The amylose content is about 17 per cent compared with 22 per cent for potato starch and 27 per cent for maize starch. The approximate composition of commercial samples is: moisture 9-18 per cent; protein 0.31-1 per cent; fat 0.1-0.4 per cent; starch (and a little fibre, etc) 81-89 per cent; ash 0.1-0.8 per cent. Good quality starch should be absolutely free from specks and have a pure white colour, a pH of 4.7-5.3, a moisture content of 10-13.5 per cent, and an ash content of less than 0.2 per cent.

Processing

Starch production

(i) The mature roots are first washed to remove dirt and loose soil.

(ii) In small-scale operations the roots are then peeled by hand to remove the skin and cortex; on a factory scale only the outer skin is removed, since when processing large quantities of roots it becomes economic to recover the starch from the cortex although it only contains about 50 per cent of that in the core of the root.

(iii) The roots are next sliced and put through a rasping or grating machine to produce a slurry or pulp.

(iv) The slurry is then sieved to separate the fibrous tissue from the starch milk; considerable quantities of clean water are used at this stage in order to ensure efficient separation of the starch granules from the slurry.

(v) The starch milk is collected and left in settling tanks for at least 6 hours, when the starch sinks to the bottom and the liquid is drained away.

(vi) The surface layer of the starch mass is usually a yellowish-green colour and contains impurities and is therefore scraped off, leaving a creamy-white mass below, which is stirred vigorously with water and then left to settle. This washing and settling process is repeated once or twice more until the starch is judged to be sufficiently pure.

(vii) The starch cake is dried, either by spreading it out in trays in the sun or in factories in hot-air driers.

(viii) Finally, the hard lumps of starch are crushed into a powder and sieved.

It should be pointed out that, because the cells of cassava roots are relatively tough, the grinding process must be efficient in order to liberate all the starch granules and to obtain a commercial extraction rate of approximately 20-25 per cent of the raw material.

Tapioca - tapioca consists of pieces of partially-gelatinised cassava starch and can be prepared in the form of flakes, seeds and pearls. In the preparation of tapioca flakes, the moist starch, prepared as above, is rubbed through a sieve of about 8 mesh/cm to give a coarse ground moist flour, and partially gelatinised by cooking for about 2 minutes in iron pans previously smeared with oil. The flakes of tapioca are then dried at about 50°C to a moisture content of approximately 12 per cent. In the preparation of tapioca seeds or pearls, the sieved damp starch is made into globules by shaking in cloth bags or by the use of mechanically-operated granulators. The globules are then graded according to size and gelatinised by roasting them for about 15 minutes in hot pans smeared with coconut oil. They are finally dried in a hot-air drier at 40-50°C for about 1.5-2 hours; the yield of tapioca from fresh tubers is usually about 25 per cent.

Production and trade

Production - world output increased on average 2 per cent/a for the period 1974-84, reaching nearly 129 million tonnes of roots (corresponding to about 46 million tonnes of grain equivalent). The largest increases were in Laos, Thailand, the Philippines and Vietnam, but Brazil showed a decline. A slight fall in 1982 was mainly the result of lower production from Thailand. In Africa, supplies still fell short of the food requirements of the population. In the Far East consumption increased in China, Indonesia and the Philippines. World wide, about 65 per cent of the production is consumed direct as human food and about 30 per cent is consumed or processed as animal feed, of which about half is exported (see next section). About 4 per cent is converted into starch and other industrial products and rather less than I per cent into ethanol, mostly in Brazil.

For production data in the more important producing countries see Table 1.

Trade - because fresh cassava deteriorates rapidly only a very small quantity of fresh roots is traded internationally, mainly to immigrant populations. However, substantial quantities of processed roots (chips and pellets) and cassava starch are traded; world trade in 1981 is estimated to have exceeded 17 million tonnes in root equivalent, compared with 14.7 million tonnes in 1980. Tables 2 and 3 show gross imports and exports for the major cassava trading countries. Exports from China, Indonesia and Thailand rose substantially, with Thailand providing nearly all the 5.5 million tonnes to the EC permitted by a 'voluntary' agreement which reduces this quota to 5 million tonnes for 1983 and 1984, and 4.5 million tonnes for 1985 and 1986. With present EC policies, the market for cassava as animal feed seems unlikely to develop further, nor does there appear to be much likelihood of increased demand elsewhere: 1981 may represent a peak year for trade in this commodity, with relative stability or a slight decline in the forseeable future.

Only about 4 per cent of world starch production moves in trade and most of this is cassava starch: the major importers are Japan, the USA and Taiwan. However, in the USA home-produced maize starch is taking the place of cassava starch and in Japan the domestic starch industry is highly protected by quotas and tariffs, with the result that there has been a decline in imports of cassava starch in these countries. Only in Taiwan has there been an increase. Table 4 shows production of cassava starch and

Table 5 imports by by the importing countries It is believed that in developed countries the decline in demand will continue and that while, for a time, demand in developing countries may increase, locally-produced starches will eventually reduce imports.

Table 1: Cassava: Area and production in selected countries

Table 2: Cassava: Exports from selected countries ('000 t root equivalent)

Table 3: Cassava: Imports by selected countries ('000 t root equivalent)

North America and Japan take most of their cassava imports in the form of starch and tapioca; pellets for animal feed predominate in the European and Soviet Union imports. na not available.

Table 4: Cassava starch: Production in selected areas ('000 t)

Table 5: Cassava starch: Imports to major markets ('000 t)

Major influences

Cassava produces more starch per hectare under relatively dry conditions than any other known crop. Production is likely to increase in semi-arid areas of the tropics, especially where the land is level and machinery can be used, and it may replace to some extent yams, aroids and sweet potatoes in local diets. Increasing urbanisation in the tropics is likely to lead to an increase in plantation production particularly where there is a need to supply local processing units. This will result in the increasing mechanisation of crop production, although mechanical harvesting still poses problems.

The overall prospects for any significant increase in international trade in cassava products is limited at present price levels. Any future increase in cassava production will therefore need to be utilised primarily in the producing countries themselves.

Bibliography

ACENA, B. and PUNO, G. D. 1955. A study of the use of cassava in the beer industry. Philippine Journal of Agriculture, 20, 1-13.

ADRIAN, J. and PEYROT, F. 1971. Possible use of the cassava leaf (Manihot utilissima) in human nutrition. Qualitas Plantarum: Plant Foods for Human Nutrition, 2 (2), 61-65.

AKINRELE, I. A. 1967. Nutrient enrichment of gari. West African Journal of Biological and Applied Chemistry, 10 (1), 19-23.

ANON. 1972. The mechanised production of gari. Food Manufacture, 47, 62-63.

ARRAUDEAU, M. 1967. Cassava in the Malagasy Republic. Proceedings of the International Symposium on Tropical Root Crops (Trinidad, 1967) (Tai, E. A., Charles, W. B., Haynes, P. H., Iton, E. F. and Leslie, K. A., eds), Vol. 1, Section 111, pp. 180-184. St. Augustine, Trinidad: University of the West Indies (2 vole).

AYRES, J. C. 1972. Manioc. Food Technology, 26 (4), 128-132; 134; 136; 138.

BALAGOPAL, C., VIJAYAGOPAL, K. and HRISHI, N. 1982. Bioconversion of cassava - a potential source of energy in India. Proceedings of the 5th International Symposium on Tropical Root and Tuber Crops (Philippines, 1979), pp. 339-344. Los Ba�os, Laguna, Philippines: Philippine Council for Agriculture and Resources Research, 720 pp.

BEENY, J. M. 1969. Mechanisation for tapioca. Incorporated Society of Planters, Proceedings of Conference on Crop Diversification (Malaysia) (Blencowe, E. K. and Blencowe, J. W., eds), pp. 167-180. Kuala Lumpur, Malaysia: Yau Seng Press, 300 pp.

BELLOTTI, A. C., REYES, J. A., ARIAS, B. and VARGAS, O. 1982. Insectos y acaros de la yuca y su control. Yuca, Investigaci�n, Producci�n y Utilisaci�n (Dominguez, C. E., ed.), pp. 367-391. Cali, Colombia: Centro Internacional de Agricultura Tropical, 659 pp.

BELLOTTI, A. C., VARGAS, O., PE�A, J. E. and ARIAS, B. 1982. Perdidas en rendimiento en yuca causadas por insectos y acaros. Yuca, Investigaci�n, Producci�n y Utilisaci�n (Dominguez, C. E., ed.), pp. 393-408. Cali, Colombia: Centro Internacional de Agricultura Tropical, 659 pp.

BEST, R. and GOMEZ, G. 1982. Procesamiento de las raices de yuca pare alimentaci�n animal. Yuca, Investigaci�n, Producci�n y Utilisaci�n (Dominguez, C. E. ed.), pp. 513-538. Cali, Colombia: Centro Internacional de Agricultura Tropical, 659 pp.

BOLHUIS, G. G. 1966. influence of length of illumination period on root formation in cassava. Netherlands Journal of Agricultural Science, 14, 251-254.

BRAMBILLA, J., HELFGOTT, S. and RUIZ, V. 1983. Integrated weed control in cassava. Abstracts of the 6th Symposium of the International Society for Tropical Root Crops (Peru, 1983), p. 24. Lima, Peru: International Potato Center, 113 pp.

BROOK, E. J., STANTON, W. R. and WALLBRIDGE, A. 1969. Fermentation methods for protein enrichment of cassava. Biotechnology and Bioengineering, I I, 1271 - 1284.

BRUIJN, G. H. de. 1971. �tude de caract�re cyanog�n�tique du manioc (Manihot esculenta Crantz). [A study on the cyanogenetic character of cassava.] Thesis with English summary, pp. 124-128. Mendelingen Landbouwhogeschool, Wageningen, 71-13. Wageningen, Netherlands: H. Veenman and Zonen, N. V., 140 pp.
CARIBBEAN FOOD AND NUTRITION INSTITUTE. 1974. Food composition tables for use in the English-speaking Caribbean. Kingston, Jamaica: CFNI, 115 pp.

CEDILLO, V. G. 1952. Cassava rice or landang. Philippine Agriculturist, 35, 434-440.

CENTRE FOR OVERSEAS PEST RESEARCH. 1978. Pest control in tropical root crops. PANS Manual, No. 4. London: COPR, 235 pp.

CHADHA, Y. R. 1961. Sources of starch in Commonwealth territories. III: Cassava. Tropical Science, 3, 101-113.

CHAN SEAK KHEN. 1969. Notes on the growing of cassava at Serdang. Incorporated Society of Planters, Proceedings of Conference on Crop Diversification (Malaysia) (Blencowe, E. K. and Blencowe, J. W., eds), pp. 139-148. Kuala Lumpur, Malaysia: Yau Seng Press, 300 pp.

COCK, J. H., CASTRO, M. A. and CESAR TORO, J. 1978. Agronomic implications of mechanical harvesting. Cassava Harvesting and Processing: Proceedings of a workshop held at CIAT (Colombia, 1978), IDRC-114e (Weber, E. J., Cock, J. H. and Chouinard, A., eds), pp. 60-65. Ottawa, Canada: International Development Research Centre, 84 pp.

COOKE, R. D. and COURSEY, D. G. 1981. Cassava: a major cyanide-containing food crop. Cyanide in biology (Vennesland, B., Conn, E. E., Knowles, C. J., West, J. and Wissing, F., eds), pp. 93-114. New York: Academic Press, 548 pp.

COURSEY, D. G. and HAYNES, P. H. 1970. Root crops and their potential as food in the tropics. World Crops, 22, 261-265.

DINA, J. A. AND AKINRELE, I. A. 1970. An economic feasibility study for the establishment of a glucose industry in Nigeria. Federal Institute of Industrial Research, Nigeria, Technical Memorandum, No. 25, 28 pp.

DOKU, E. V. 1969. Cassava in Ghana. Accra, Ghana: Universities Press, 44 pp.

DOLL, J. D., PIEDRAHITA, C. and LEIHNER, D. E. 1982. Metodos de control de malezas en yuca (Manihot esculenta Crantz). Yuca, Investigaci�n, Producci�n y Utilisaci�n (Dominguez, C. E., ed.), pp. 241-249. Cali, Colombia: Centro Internacional de Agricultura Tropical, 659 pp.

FLAWS, L. J. and PALMER, E. R. 1968. The production of particle board from cassava stalks. Report of the Tropical Products Institute, G34. London: TPI, 3 pp.

FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS. 1982. Cassava. Commodity Review and Outlook 1982, pp. 52-55. Rome, Italy: FAO, 128 pp.

FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS. 1983. Cassava. Production Yearbook 1982, pp. 128-129. Rome: FAO, 320 pp.

FR�HLICH, G. and RODEWALD, W. 1970. Cassava. Pests and diseases of tropical crops and their control, pp. 173-176. Oxford: Pergamon Press, 371 pp.

GHOSH, B. N. 1967. Recent developments in the manufacture of starch from cassava roots in Uganda. Proceedings of the International Symposium on Tropical Root Crops (Trinidad, 1967) (Tai, E. A., Charles, W. B., Haynes, P. H., Iton, E. F. and Leslie, K. A., eds), Vol. 2, Section VI, pp. 37-47. St. Augustine, Trinidad: University of the West Indies (2 vole).

G�MEZ, G. G., CAMACHO, C. AND MANER, J. H. 1977. Utilization of cassava-based diets in swine feeding. Proceedings of the 4th Symposium of the International Society for Tropical Root Crops (Colombia, 1976), IDRC-080e (Cock, J., Maclntyre, R. and Graham, M., eds), pp. 262-266. Ottawa, Canada: International Development Research Centre, 277 pp.

GRACE, M. 1971. Processing of cassava. Food and Agriculture Organization of the United Nations Agricultural Services Bulletin, No. 8. Rome, Italy: FAO, 124 pp.

HAMID, K. and JALALUDIN, S. 1972. The utilisation of tapioca in rations for laying poultry. Malaysian Agricultural Research, I (1), 48-53.

HARRIS, N. V. and DOGGRELL, L. M. 1984. Developing cassava as an industrial crop in Australia. (Abstract). Proceedings of the 6th Symposium of the International Society for Tropical Root Crops (Peru, 1983), p. 431. Lima, Peru: International Potato Center, 672 pp.

HORTON, D., LYNAM, J. AND KNIPSCHEER, H. 1984. Root crops in developing countries - an economic appraisal. Proceedings of the 6th Symposium of the International Society for Tropical Root Crops (Peru, 1983), pp. 9-39. Lima, Peru: International Potato Center, 672 pp.

HOWELER, R. H. 1982. Nutrici�n mineral y fertilisaci�n de la yuca. Yuca, Investigaci�n, Producci�n y Utilisaci�n (Dominguez, C.E., ed.), pp. 317-357. Cali, Colombia: Centro Internacional de Agricultura Tropical, 659 pp.

INGRAM, J. S. 1970. Selected bibliography on cassava (Manihot esculenta Crantz). Report of the Tropical Products Institute, G51. London: TPI, 35 pp.

INGRAM, J. S. and HUMPHRIES, J. R. O. 1972. Cassava storage: a review. Tropical Science, 14, 131-148.

JACOB, A. and UEXKULL, H von. 1960. Cassava. Fertiliser use: Nutrition and manuring of tropical crops, pp. 151-157. Hannover, Germany: Verlagsgesellschaft f�r Acherbau mbH, 617 pp.

JARMAI, S. 1968. A new fast method for the production of kokonte. Ghana Journal of Agricultural Science, I (1), 59-63.

JENNINGS, D. L. 1970. Cassava in Africa. Field Crop Abstracts, 23, 271 -278.

JOHNSON, R. M. and RAYMOND, W. D. 1965. The chemical composition of some tropical food plants. IV: Manioc. Tropical Science, 7, 109-115.

JONES, S. F. 1983. The world market for starch and starch products with particular reference to cassava (tapioca) starch. Report of the Tropical Development and Research Institute, G173. London: TDRI, viii+98 pp.

JONES, W. O. 1959. Manioc in Africa. Stanford, California: Stanford University Press, 315 pp.

KASASIAN, L. 1971. Root crops: Manihot esculenta (cassava, manioc). Weed control in the tropics, p. 159. London: Leonard Hill, 307 pp.

KOENS, A. J. and BOLHUIS, G. G. 1948. Knolgewassen: cassava. De Landbouw in den Indische Archipel. [Agriculture in the Indonesian Archipelago.] (Hall, C. J. J. van and Koppel, C. van de, eds), Vol. 2a, pp. 166-200. The Hague, Netherlands: NVUW van Hoeve, 905 pp.

KROCHMAL, A. 1966. Labour input and mechanisation of cassava. World Crops, 18 (3), 28-30.

KROCHMAL, A. 1969. Propagation of cassava. World Crops, 21, 193-195.

LEE KOK CHOO, T. and HUTAGALUNG, R. I. 1972. Nutritional value of tapioca leaf (Manihot utilissima) for swine. Malaysian Agricultural Research, 1(1), 38-47.

LEIHNER, D. E., THUNG, H., COCK, J. H. and LYMAN, J. K. 1982. Cosecha mechanica de la yuca, dos equipos diferentes. Yuca, Investigaci�n, Producci�n y Utilisaci�n, (Dominguez, C. E., ed.), pp. 359-364. Cali, Colombia: Centro Internacional de Agricultura Tropical, 659 pp.

LEIHNER, D. E., THUNG, H., COCK, J. H. AND LYMAN, J. K. 1982. Producci�n de yuca in cultivos multiples. Yuca, Investigaci�n, Producci�n y Utilisaci�n (Dominguez, C. E., ed.), pp. 261-315. Cali, Colombia: Centro International de Agricultura Tropical, 659 pp.

L�ON, J. 1977. Origin, evolution and early dispersal of root and tuber crops. Proceedings of the 4th Symposium of the International Society for Tropical Root Crops (Colombia, 1976), IDRC-080e (Cock, J., MacIntyre, R. and Graham, M., eds), pp. 20-36. Ottawa, Canada: International Development Research Centre, 277 pp.

LOZANO, J. C. and BELLOTTI, A. C. 1982. Control integrado de enfermedades y pestes en la yuca. Yuca, Investigaci�n, Producci�n y Utilisaci�n (Dominguez, C. E" ed.), pp. 463-473. Cali, Colombia: Centro Internacional de Agricultura Tropical, 659 pp.

LOZANO, J. C. and BOOTH, R. H. 1982. Enfermedades de la yuca. Yuca, Investigaci�n, Producci�n y Utilisaci�n (Dominguez, C. E., ed.), pp. 421-461. Cali, Colombia: Centro Internacional de Agricultura Tropical, 659 pp.

LOZANO, J. C., HERSHEY, C. H., BELLOTTI, A. and ZEIGLER, R. 1984. A comprehensive breeding approach to pest and disease problems of cassava. Proceedings of the 6th Symposium of the International Society for Tropical Root Crops (Peru, 1983), pp. 315-320. Lima, Peru: International Potato Center, 672 pp.

LOZANO, J. C., TORO, J. C., CASTRO, A. and BELLOTTI, A. C. 1982. Selecci�n y preparaci�n de estacas de yuca pare siembra. Yuca, Investigaci�n, Producci�n y Utilisaci�n (Dominguez, C. E., ed.), pp. 209-229. Cali, Colombia: Centro Internacional de Agricultura Tropical, 659 pp.

LULOFS, R. B. 1969. A study of methods and costs for commercial planting of tapioca in Kedah. Incorporated Society of Planters, Proceedings of Conference on Crop Diversification (Malaysia) (Blencowe, E. K. and Blencowe, J. W., eds), pp. 149-166. Kuala Lumpur, Malaysia: Yau Seng Press, 300 pp.

MAHENDRANATHAN, T. 1971. Potential of tapioca (Manihot utilissima Pohl) as a livestock feed - a review. Malaysian Agricultural Journal, 48 (1), 77-89.

MANER, J. N., BUITRAGO, J. and JIMENEZ, I. 1967. Utilization of yuca in swine feeding. Proceedings of the International Symposium on Tropical Root Crops (Trinidad, 1967) (Tai, E. A., Charles, W. B., Haynes, P. H., Iton, E. F. and Leslie, K. A., eds), Vol. 2, Section VI, pp. 62-71. St. Augustine, Trinidad: University of the West Indies (2 vole).

MARTIN, F. W. 1970. Cassava in the world of tomorrow. Tropical Root and Tuber Crops Tomorrow: Proceedings of the 2nd International Symposium on Tropical Root and Tuber Crops (Hawaii, 1970) (Plucknett, D. L., ed.), Vol. I, pp. 53-58. Honolulu, Hawaii: College of Tropical Agriculture, University of Hawaii, 171 pp. (2 vole).

MCFARLANE, J. A. 1982. Cassava storage. Part 2: Storage of dried cassava products. Tropical Science, 24, 205-236.

MONTALDO, A. 1967. Bibliograf�a de ra�ces y tub�rculos tropicales. Revista del Facultad Agronomico, Universidad Central de Venezuela, 13, 152-270; 515-516; 528-533; 543-545.
MONTALDO, A. 1972. Yuca o Mandioca. Cultivo de ra�ces y tub�rculos tropicales, pp. 51 - 136. Lima, Peru: Instituto Interamericano de Ciencias Agricolas de la OEA, 284 pp

NARTEY, F. 1978. Manihot esculenta (cassava). Cyanogenesis, ultrastructure and seed germination. Copenhagen, Denmark: Munksgaard: 262 pp.

NESTEL, B. and MACINTYRE, R. (eds). 1973. Chronic cassava toxicity:

Proceedings of an interdisciplinary workshop (London, 1973), IDRC-010e. Ottawa, Canada: International Development Research Centre, 162 pp.

NITIS, I. M. and SUARNA, M. 1977. Undersowing cassava with stylo grown under coconut. Proceedings of the 4th Symposium of the International

Society for Tropical Root Crops (Colombia, 1976), IDRC-080e (Cock, J., MacIntyre, R. and Graham, M., eds), pp. 98-103. Ottawa, Canada: International Development Research Centre, 277 pp.

NWEKE, F. I. 1981. Consumption patterns and their implications for research and production in tropical Africa. Tropical Root Crops: Research Strategies for the 1980s: Proceedings of the 1st Triennial Root Crops Symposium of the international Society for Tropical Root Crops - Africa Branch (Nigeria, 1980), IDRC-163e (Terry, E. R., Oduro, K. A. and Caveness, F., eds), pp. 88-94. Ottawa, Canada: International Development Research Centre, 279 pp.

OKE, D. L. 1968. Cassava as food in Nigeria. World Review of Nutrition and Dietetics, 9, 227-250.

PHILLIPS, T. P. 1973. Cassava utilisation and potential markets, IDRC-020e. Ottawa, Canada: International Development Research Centre, 182 pp.

PRAMANIK, A. 1971. Prospects for tapioca cultivation and pelletisation in Malaysia. Planter, Kuala Lumpur, 47 (543), 240-246.

PURSEGLOVE, J. W. 1968. Manihot Mill. Tropical crops: Dicotyledons 1, pp. 171-180. London: Longmans, Green and Co. Ltd, 332 pp.

RICKARD, J. E. 1985. Physiological deterioration of cassava roots. Journal of the Science of Food and Agriculture, 36, 167-176.

RICKARD, J. E. and COURSEY, D. G. 1981. Cassava storage. Part 1: Storage of fresh cassava roots. Tropical Science, 23, 1-32.

ROBERTS, A. T., TAYLOR, H. and MARGAI, M. 1983. Gari processing in Sierra Leone: an economic appraisal. Abstracts of the 6th Symposium of the International Society for Tropical Root Crops (Peru, 1983), p. 58. Lima, Peru: International Potato Center, 113 pp.

ROGERS, D. J. 1965. Some botanical and ethnological considerations of Manihot esculenta. Economic Botany, 19, 369-377.

ROGERS, D. J. and APPAN, S. G. 1973. Manihot, Manihotoides (Euphorbiaceae). Flora Neotropica, Monograph, No. 13, New York: Hafner Press, 272 pp.

SINGH, K. K. and MATHUR, P. B. 1953. Cold storage of tapioca roots. Bulletin of the Central Food Technological Research Institute (Mysore), 2, 181-182.

STRASSER, J., ABBOTT, J. A. and BATTEY, R. F. 1970. Process enriches cassava with protein. Food Engineering, 42 (5), 112; 114-116.

SUBRAMANYAM, H. and MATHUR, P. B. 1956. Effect of a fungicidal wax coating on the storage behaviour of tapioca roots. Bulletin of the Central Food Technological Research Institute (Mysore), 5, 110-111.

TERRY, E. R. and HAHN, S. K. 1982. Increasing and stabilizing cassava and sweet-potato productivity by disease resistance and crop hygiene. Root crops in Eastern Africa: Proceedings of a Workshop (Rwanda, 198O), IDRC-177e, pp. 47-52. Ottawa, Canada: International Development Research Centre, 128 pp. (Plant Breeding Abstracts, 53, 2340).

THAMPAN, A. K. 1979. Cassava. Trichur, Kerala, India: Kerala Agricultural University, 242 pp.

TORO, J. C. and ATTLEE, C. B. 1982. Practicas agronomicas pare la producci�n de yuca; una revisi�n de la literature. Yuca, Investigaci�n, Producci�n y Utilisaci�n (Dominguez, C. E., ed.), pp. 367-391. Cali, Colombia: Centro Internacional de Agricultura Tropical, 659 pp.

VARGHESE, G., THAMBIRAJAH, J. J. and WONG, F. M. 1977. Protein enrichment of cassava by fermentation with microfungi and the role of natural nitrogenous supplements. Proceedings of the 4th Symposium of the International Society for Tropical Root Crops (Colombia, 1976), IDRC-080e (Cock, J., MacIntyre, R. and Graham, M., eds), pp. 250-255. Ottawa, Canada: International Development Research Centre, 277 pp.

WALTERS, P. R. 1983. Cassava's markets - where next? World Crops, 35, 130-134.

WILLIAMS, C. N. 1972. Growth and productivity of tapioca (Manihot utilissima): crop ratio, spacing and yield. Experimental Agriculture, 8, 15-23.

Chavar (Hitchenia caulina)

Common name

CHAVAR

Botanical name

Hitchenia caulina (Grah.) Baker syn. Curcuma caulina (Grah.).

Family

Zingiberaceae.

Other names

Arrowroot lily, Chowar, Indian arrowroot'.

Botany

A tuberous herb with a leafy stem, 0.9-1.2 m high, with oblong-lanceolate, fibrous leaves 30-50 cm long and 7.5-10 cm broad. The yellow flowers, which possess a long peduncle, are borne on a central spike.

Origin and distribution

The plant is native to India and is found mainly growing wild on the table land of the Mahabaleshwar plateau and neighbouring regions in forest areas with high annual rainfall.

Cultivation conditions

Hot moist conditions are essential: rainfall of upwards of 500 cm per annum characterises its natural habitat, though it may be grown on the banks of irrigation canals.

Planting procedure

Chavar is easily propagated by tuber cuttings, which are planted in raked soil at the beginning of the monsoon, frequently in arecanut plantations and on the banks of rivers and irrigation channels. It is often planted very densely to prevent soil erosion, in some areas up to 50 000 plants per hectare.

Growth period

For maximum yields of starch a 2 year rotation should be practiced and the tubers harvested when they are 20-24 months old.

Harvesting and handling

The tubers are dug by hand.

Primary product

Tubers - these are normally the size of an orange with white flesh and covered with fibrous roots.

Main use

The tubers yield a white edible starch, which has sometimes been used as a substitute for arrowroot starch.

Secondary and waste products

It has been suggested that the leaves could be used for papermaking.

Special features

The tubers have a starch content of 10.9-18.3 per cent (fresh weight basis). On average the tubers yield about 13 per cent of starch, 60 per cent of which is of superior quality and very similar to that of arrowroot.

Processing

The harvested tubers are washed and the fibrous roots removed, after which the cleaned tubers are grated and the resultant pulp washed thoroughly, sieved and then re-washed, and the starch allowed to settle out. It is then sun-dried.

Major influences

Although formerly used locally as a source of 'arrowroot starch', nowadays it is not normally economic to prepare starch commercially from chavar, but the crop can yield a high quality starch, and it could be of value in high rainforest areas to prevent soil erosion.

Bibliography

KHAIRNAR, M. S. 1945. Hitchenia caulina (Chavar) as a source of arrow root. Indian Forester, 71, 126-127.

SASTRI, B. N. (ed.). 1959. Hitchenia. The wealth of India: Raw materials, Vol. 5 (H-K), PP. 101-102. New Delhi, India: Council for Scientific and Industrial Research, 332 pp.

Chinese water chestnut (Eleocharis dulcis)

Common names

CHINESE WATER CHESTNUT, Matai, Waternut.

Botanical name

Eleocharis dulcis (Burm. f.) Trin. Ex Hensch. var. tuberosa (Schult.) Koyama syn. E. tuberosa Schult.

Family

Cyperaceae.

Other names

Ap�lid, Buslig (Philipp.); Cabezas de negrito (Sp.); Ch�taigne d'eau (Fr.); Chikai, Dekang (Indon.); Kalangub (Philipp.); Kohekohe (Haw.); Mati (China); Nilaga (Philipp.); O-kuroguwai (Japan); O-yu, Peci (China); Pipi-wai (Haw.); Pi't'si (China); Potok (Philipp.); Po-tsai (China); Sibosibolasan (Philipp.); Tek�, Teki-tik� (Indon.); Wu-yu (China).

Botany

A variable, annual, stout, tufted, aquatic, sedge plant, characterised by its lack of leaves, their photosynthetic activity having been transferred to the numerous upright tubular septate stems, 50-100 per plant, which normally reach a height of 0.9-1.5 m. Inflorescences containing about 50 insignificant flowers are produced at the top of these stems. The female (pistillate) flowers appear when the stem tips reach 15 cm above the water and are followed later by the male (staminate) flowers. Tiny 'seeds', in fact achenes, are produced but are of no economic importance. Two types of subterranean rhizomes are produced. Rhizomes spread from the base of the plant: the first appear 6-8 weeks after planting, grow horizontally under the surface of the soil, and then turn upwards to form suckers and ultimately daughter plants; others, starting somewhat later, bend down and produce corms at the tip (one per rhizome), about 12 cm below the soil surface. The young corms are white, becoming scaly and brown when mature, subglobose, somewhat flattened, 1-4 cm across.

Two very distinct forms of E. dulcis are recognised. One is a wild form, which generally grows in stagnant water, produces very small, very dark skinned, almost black secondary corms and is sometimes referred to in the literature as E. plantaginea or E. plantaginoides. The second form occurs only under cultivation and produces larger, sweeter, secondary corms and was originally described as a separate species. E. tuberosa.

Origin and distribution

Eleocharis dulcis grows wild in many parts of India, South-East Asia and Polynesia. It was first cultivated in South-East China in humid monsoon areas and is now also grown commercially in Japan, Hong Kong, the Philippines, Hawaii and other Pacific islands, India and the southern USA.

Cultivation conditions

Temperature - a long warm growing season is required, with at least 220 frost-free days, and a soil temperature of 14-15.5°C is necessary for germination of the corms.

Rainfall - the plant is aquatic and thrives in areas where there are well-controlled irrigation facilities giving a continuous supply of water throughout the year.

Soils - for optimum yields a rich clay or peaty soil with a pH of 6.9-7.3 is required; slightly more acid soils may be successfully neutralised with limestone. It has been shown that this crop has a high uptake of certain nutrients; in experiments in which corm production was approximately 4 700 kg/ha the uptake in kg/ha was nitrogen 108, calcium 6.9, magnesium 37.5, though requirements for phosphorus and potassium are relatively low. In the USA the application of a high grade complete fertiliser (including magnesium) at a total rate of 2.5 t/ha, one third or one half before planting, another third 8-10 weeks after planting, and the balance just prior to the development of the corms, has been recommended.

Altitude - the crop may be grown at altitudes from sea level up to 1 200 m.

Planting procedure

Material - small corms are used.

Method - the corms may be planted directly into the field or, usually in the more temperate climates, started in protected nursery beds and hand transplanted when the top growth is 20-30 cm high. If planted direct in the field, the corms are planted in rows in holes 10-12.5 cm deep. This is often done manually with a hand trowel, but in larger plantings in the USA, the furrows are opened with a plough or courter and the corms dropped in at intervals of 75 cm and then covered with a covering plough or hiller. After planting the fields are flooded for 24 hours and then allowed to drain naturally; as soon as top growth reaches 20-30 cm the fields are again flooded and the water level kept to at least 10-12.5 cm throughout the growing season. Weeds are not usually a problem provided the soil has been well-tilled just before planting. In the USA the use of preemergence herbicides has been tried with success: 2,4-D amine at 1.9 kg/ha gave good weed control and was effective for 3 months.

Field spacing - in the USA a spacing of 75 x 75 cm has been recommended. In China a triangular spacing of 45-60 cm and 45 cm between plants is common practice.

Seed rate - approximately 500 kg of corms are used to plant one hectare.

Pests and diseases

Chinese water chestnuts are not normally subject to serious attacks from pests and diseases, though when grown on acid soils, ph 5.5, the plants may be attacked by a stem fungus, Cylindrosporium spp. In Florida, the most serious insect pest is the billbug, Calendra cariosa, and the crop is also attacked by a stem nematode, Ditylenchus spp. and by the awl nematode, Dolichodorus heterocephalus. In the Philippines, the crop is sometimes attacked by a grasshopper, Aiolopus thalassinus, but this pest has been effectively controlled by spraying with 2 per cent aldrin. Rodents, especially rats, can cause considerable crop losses at harvest, unless effectively controlled.

Growth period

Chinese water chestnuts require a long warm growing season and the corms usually reach maturity in about 7-8 months; in many areas of China this is after the first frost has killed the green culms.

Harvesting and handling

Harvesting normally takes place after the culms have turned brown or been killed off by frost and by this time the corms have acquired a characteristic deep chestnut-brown colour. In most areas irrigation is stopped at least 3-4 weeks before harvest so that the ground dries, and the corms are carefully dug out by hand to avoid bruising. In the USA, in the harvesting of small plots, the soil is carefully lifted on to a 0.9 cm wire mesh screen and worked over with rubber pads or paddles, when about 98 per cent of the corms are left on the screen. These are picked off and dropped into water to clean them. In larger plantings a small plough is used which turns a furrow to a depth of approximately 15 cm. The furrow is then raked with a potato rake having rubber-covered prongs. The corms are carefully picked out by hand, washed thoroughly, and all damaged ones removed before they are air-dried, preferably in the shade. Harvesting may be delayed, since the corms do not deteriorate in the soil provided that there are no severe frosts.

In the USA commercial supplies of the dried corms are usually packed in 64-litre moisture-proof containers, which are sealed but not airtight. They can be kept satisfactorily at temperatures between -1 and 4°C for up to 6 months; at a temperature of about 14°C sprouting occurs.

Primary product

Corms - the edible starchy corms have a dark chestnut-brown coloured outer skin and are usually rounded or onion-shaped and from I to 4 cm in diameter. The wild forms are usually the smallest and in general only corms 3 cm or more in diameter are commercially acceptable. The flesh is crisp and white with a characteristic flavour.

Yield

Yields in China are reported to average 20-40 t/ha and in the USA 28 t/ha.

Main use

Chinese water chestnuts are eaten as a vegetable either fresh or cooked and are an important ingredient of many Chinese food dishes. They are said to smell like sweet corn when boiled.

Subsidiary uses

Certain cultivars are sometimes used for the preparation of starch, while very small corms are useful for poultry feed.

Secondary and waste products

In China the corms are used in traditional medicine. The dry stems can be used for cattle feed, mulching, as a packing material for horticultural products and for making baskets, mats, etc.

Special features

The corms show considerable variation in composition; an approximate analysis of the edible portion of fresh Chinese corms has been given as: moisture 77.29 per cent; protein 1.53 per cent; fat 0.15 per cent; nitrogen-free extract 18.9 per cent; reducing sugars 1.94 per cent; sucrose 6.35 per cent; starch 7.34 per cent; fibre 0.94 per cent; ash 1.19 per cent; calcium 2-10 mg/100 g; iron 0.43-0.6 mg/100 g; phosphorus 52.2-65 mg/100 g; thiamine 0.24 mg/100 g; riboflavin 0.007 mg/100 g; niacin 0.94 mg/100 g; ascorbic acid 9.2 mg/100 g.

The starch is similar to that obtained from sweet potatoes or cassava and has large grains up to 27 microns in length which may be rounded, have regular geometric shapes or be completely irregular. The juice extracted from the corms has been shown to contain an antibiotic principle, designated puchiin.

Processing

Canning - the corms are first washed and peeled, usually by hand, and then processed in a manner similar to potatoes. The recommended processing times are 30 minutes for No. 2 cans, 35 minutes for No. 2 1/2 and 45 minutes for No. 10 at 115°C, after an initial heating before sealing to 60°C.

Quick freezing - the washed, peeled corms are blanched for 4 minutes in steam at 99-100°C in single layers on wire mesh trays; they are then cooled immediately in an air-blast, packed into cans and frozen in a blast freezer at - 32°C then held at - 18°C for periods up to 12 months.

Starch - in China starch is sometimes extracted from the corms by a very primitive method. The corms are washed, then crushed, and the resultant starchy mass put in a fine bamboo basket which is set in a filter cloth and hung over a wood fire. The basket is then placed in a pan, water added, and the contents thoroughly stirred for 15 minutes. Three parts of starch milk are collected; the first contains the largest proportion of starch and is set aside to allow the starch to separate out, the rest of the starch milk being re-used to wash more pulp. After about 5 hours the starch has separated out and is collected and dried in the sun on bamboo trays.

Production and trade

There is considerable trade in Chinese water chestnuts in Asia, and prior to the embargo on imports from China into the USA shipments averaged about I 000 tonnes a year. These have been partially replaced by domestic production in the southern states, eg Florida, but the demand is reported to be increasing.

Major influences

There is a growing demand for this speciality foodstuff, particularly in the USA, but the high cost of manual harvesting and the fact that the corms must be stored at low temperature to suppress sprouting are factors handicapping the commercial development of the Chinese water chestnut. It has been stated to be one of the more important crops that will thrive under Philippine conditions and is cultivated on a large scale in Laguna and Mindro (Luzon) and in Davon (Mindanao).

Bibliography

ANON. 1968. Citrus Magazine, 31(12), 15.

BATOON, M. P. 1965. There is money in growing Chinese water chestnut. Plant Industry Digest, 28(4-6), 6-7; 28.

CHEN, S. L., CHENG, B. L., CHENG, W. K. and TANG, P. S. 1945. An antibiotic substance in the Chinese water chestnut Eleocharis tuberosa. Nature, London, 156, 234.

CLOS, E. C. 1956. Nueva hortaliza pare el pais Heleocharis dulcis. [A new vegetable for Argentina, Eleocharis dulcis.] IDIA (100), 23-24.

EZUMAH, H. 1970. Miscellaneous tuberous crops of Hawaii. Tropical Root and Tuber Crops Tomorrow: Proceedings of the 2nd International Symposium on Tropical Root and Tuber Crops (Hawaii, 1970) (Plucknett, D. L., ed.), Vol. 1, pp. 166-171. Honolulu, Hawaii: College of Tropical Agriculture, University of Hawaii, 171 pp. (2 vole).

GROFF, G. W. 1950. The introduction into the United States and the culture of Eleocharis dulcis, the matai of China. Proceedings of the Florida State Horticultural Society, 63, 262-265.

HODGE, W. H. 1956. Chinese water chestnut or matai, a paddy crop of China. Economic Botany, 10, 49 - 65.

HODGE, W. H. and BISSET, D. A. 1955. The Chinese water chestnut. United States Department of Agriculture Circular, No. 956, 16 pp.

INTENGAN, C. Ll., CONCEPCION, I., SALUD, R. D., MANALO, J., DEL ROSARIO, I., GOMEZ, R., ARZAGA, V. and ALEJO, L. G. 1954. Composition of Philippine foods, II. Philippine Journal of Science, 83, 187-216.

L�ON, J. 1977. Origin, evolution and early dispersal of root and tuber crops. Proceedings of the 4th Symposium of the International Society for Tropical Root Crops (Colombia, 1976), IDRC-080e (Cock, J., MacIntyre, R. and Graham, M., eds), pp. 20-36. Ottawa, Canada: International Development Research Centre, 277 pp.

MCCORD, C. L. (Jr.) and LOYACANO, H. A. (Jr.). 1978. Removal and utilization of nutrients by Chinese waterchestnut in catfish ponds. Aquaculture, 13, 143-155.

MONTALDO, A. 1972. Pi't'si. Cultivo de ra�ces y tub�rculos tropicales, pp. 243. Lima, Peru: Instituto Interamericano de Ciencias Agricolas de la OEA, 284 pp.

NEUMANN, H. J., SHEPHERD, A. D., BOGGS, M. M. and HARRIS, J. G. 1966. Frozen Chinese water chestnuts: blanching, storage and quality. Food Technology, Champaign, 20, 1491 - 1494.

OSTOSAPAR and MERCADO, B. T. 1976. Morphology and anatomy of Eleocharis dulcis (Basur. f.) Trin. Kalikasan, 5 (3), 332-340.

RIGO, H. T. de. 1964. Pre- and post-emergence chemical weed control in Chinese water chestnut. Proceedings of the 17th Southern Weed Conference (Florida), pp. 333-336. (Horticultural Abstracts, 35, 3733.) (Weed Abstracts, 13, 1361).

RIGO, H. T. de and WINTERS, H. F. 1964. Effects of storage temperatures on physiological and chemical changes in Chinese water chestnut corms. Proceedings of the American Society for Horticultural Science, 85, 521 -525.

RIGO, H. T. de and WINTERS, H. F. 1968. Nutritional studies with Chinese water chestnuts. Proceedings of the American Society for Horticultural Science, 92, 394-399.

SASTRI, B. N. (ed.). 1952. Eleocharis. The wealth of India: Raw materials, Vol. 3 (D-E), pp. 142-143. New Delhi, India: Council for Scientific and Industrial Research, 236 pp.

SHEPHERD, A. D. and NEUMANN, H. J. 1958. New processed vegetables may diversify agriculture and diet: Chinese water chestnut. Chemurgic Digest, 17(11), 4-5.

TARJAN, A. C. 1952. Awl nematode injury on Chinese water chestnuts. Phytopathology, 42, 114.

TEODORO, G. N. and ABAYA, F. Q. 1939. Notes on the preliminary culture trial with Chinese water chestnuts (Eleocharis tuberosa Schultes). Philippine Journal of Agriculture, 10, 397-402.

TWIGG, B. A., STARK, F. C. and KRAMER, A. 1957. Cultural studies with matai (Chinese water chestnut). Proceedings of the American Society for Horticultural Science, 70, 266-272.

YU KING KEY. 1960. A trial culture of the Chinese water chestnut (E/eocharis dulcis) at the Araneta University experimental ground. Araneta Journal of Agriculture, 7, 116-128.

Chufa (Cyperus esculentus)

Common names

CHUFA, Earth nut, Tiger nut, Yellow nutsedge

Botanical name

Cyperus esculentus L.

Family

Cyperaceae.

Other names

Amande de terre (Fr.); Aya (Nig.); Chichoda (Ind.); Earth or ground almond, Enensa (Nig.); Erdmandel (Ger.); Imumu (Nig.); Kaseru (Ind.); Motha (Beng.); Omu (Nig.); Rush nut; Souchet comestible (Fr.); Zulu nut.

Botany

An erect perennial, grass-like sedge, usually 30-90 cm high, with long narrow dark-green leaves arranged in three rows around the triangular stem. The plant develops as a series of shoots, bulbs and stem tubers connected by brown wiry rhizomes which are strengthened by lignification of the inner cortex. Tubers are small, 1-2 cm in diameter, and are borne at intervals along the rhizomes. Basal bulbs grow from rhizome tips, producing shoot growth and new plants. The plant, when growing wild, is extremely difficult to eradicate and is stated to be the fifteenth worst weed in the world.

Origin and distribution

Chufa is thought to have originated in the Mediterranean area and western Asia but has spread (mainly as a weed) to many parts of the world. It will grow in a very wide range of climatic conditions, and occurs in the tropics, subtropics and warm temperate regions and is cultivated in several countries.

Cultivation conditions

Temperature - although the plant can be grown in relatively cool climates, optimum yields are obtained with moderately high temperatures throughout the growing season.

Rainfall - a moderate well-distributed rainfall is required for optimum yields. Although chufas are fairly drought resistant, commercial crops receive copious and repeated irrigation during the dry summer season (eg in Valencia, Spain) in order to ensure maximum yields.

Soil - maximum yield is obtained in light sandy loams of pH 5.5-6.5, but chufas can be grown on any well-drained soil. Alluvial sands containing relatively high quantities of manganese, sulphur, calcium, magnesium and boron are particularly suitable. They can be grown on saline soils in coastal areas and are of use in reclaiming such areas. There is little information on the precise fertiliser requirements of chufas but nitrogen is often limiting under natural conditions. The application of a 6:6:8 complete (NPK) fertiliser at the rate of I 000 kg/ha has been recommended. In many areas growers give a heavy dressing of FYM, if available, and wood ash, before or immediately after planting. In Florida, however, the crop has been found to respond very erratically to applications of fertilisers.

Planting procedure

Material - tubers are used for propagation.

Method - the tubers are soaked in water for 24-36 hours and then planted, either by hand or drill. Sprouting can be stimulated by treatment with ethylene at 3-10 ppm in air or by ethephon (ethrel) at 10-100 ppm in water.

Field spacing - spacing is extremely variable according to the soil conditions, local cultural methods and the purpose for which the crop is grown. Reports from Florida indicate that when grown for pig feed, chufas are usually drilled in rows 60-90 cm apart, with either 30 cm or 15 cm between the plants. Reports from other countries refer to tubers frequently being planted at 10 cm intervals along rows 60 cm apart. With spacing in the row of 10x60 cm a single tuber is placed in a hole and covered with 2.5-4 cm of soil, with IS x 60 cm spacing two tubers are used and at 30 x 60 cm, four tubers are used.

Seed rate - chufa tubers vary in size so that it is difficult to give even an approximate seeding rate; 16-22 kg/ha has been reported but calculations suggest that over 500 kg may be required when spacing is close and medium-sized tubers are used.

Pests and diseases

In Florida the negro bug, Thyreocoris pulicaria, has been reported to damage the crop; the larvae develop inside the tubers. Proper crop rotation is the best means of control. Chufas are seldom seriously affected by diseases.

Growth period

Chufas normally take 3-4 months to reach maturity.

Harvesting and handling

The tubers are ready for harvesting when the plants begin to die back; they are usually dug by hand or by running a small lifting plough under them. In Florida groundnut harvesters are sometimes used. The entire plant is laid on the soil and allowed to dry for 1-3 days before the tubers are separated for storage in thin layers in sheds. Tubers for human consumption are washed in running water and then dried either in the sun or artificially, after which they are graded and stored.

Primary product

Tubers - tubers are normally 1.5-2 cm in length, with a maximum diameter of approximately 1-2 cm. They have very thin skins and the flesh is slightly yellowish-white in newly-formed tubers, but darkens with increasing maturity; the flavour is sweet and nutty.

Yield

On sandy soils the yields of tubers are reported to average 800-900 kg/ha, although in Spain, with large-scale cultivation, yields as high as 8 000
14 000 kg/ha are reported.

Main use

The tubers are used as a foodstuff, particularly in Africa, where they are an important food crop with certain tribes. They may be eaten raw, baked as a vegetable, roasted like groundnuts or grated and used to make icecream, sherbets or a milky beverage which is known as 'horchata' in Spain and Latin American countries. In Spain the major proportion of the crop (approximately 1000 t) is used in this manner, and horchata continues to be a popular beverage, in spite of severe competition from carbonated drinks.

Subsidiary uses

Animal feeding - chufas can be used for animal feed and are grown as pig feed in parts of the southern USA.

Confectionery - chufas are sometimes used in certain types of confectionery, often as a substitute for almonds.

Coffee and cocoa adulterant - the ground tubers are sometimes used as a substitute or adulterant of coffee and cocoa.

Secondary and waste products

Oil - the tubers contain 20-28 per cent of a yellow non-drying pleasantly flavoured oil, similar to olive or sweet almond oil. It is used in Spain and Italy for culinary purposes and for the manufacture of soap.

Starch - chufa tubers are potentially a rich source of starch which may be extracted after the oil has been removed from the tubers.

Flour - the tubers can be ground to produce a nutritious flour, which can be used mixed with wheat flour in baking. It has the following composition: protein 3.4 per cent; fat 27 per cent; starch 38 per cent; ash 2.5 per cent.

Alcohol - chufa tubers can be used for the production of alcohol by fermentation. In Sicily, a cultivar with a very high sucrose content is grown and used commercially for this purpose.

Leaves - it has been suggested that the leaves of the chufa could be utilised for papermaking; simple digestion with soda lye will give a yield of 35-40 per cent of a deep-yellow coloured pulp.

Special features

Tubers - chufa tubers are rich in both starch and oil. They are variable in composition: the dry matter of fresh tubers is from about 70 per cent to about 90 per cent. Average analytical figures of the dry matter have been quoted as: residual moisture 9.3 per cent; protein 8.6 per cent; fat 21.8 per cent; carbohydrate 48 per cent; ash 1.7 per cent; magnesium 0.1 mg/100 g; phosphorus 211.5 mg/100 g; potassium 0.5 mg/100 g.

The carbohydrate consists of 33.4 g starch and 14.6 g total sugars. Quinones occur and have been used as an aid to the classification of the genus Cyperus.

Starch - chufa starch has the following approximate composition: moisture 9 per cent; nitrogenous material 0.3 per cent, fat traces; starch 89.8 per cent; cellulose 0.3 per cent; ash 0.5 per cent. It is a white flavourless product and when heated in water forms a transparent gelatinous paste.

Oil - the oil has the following characteristics: SG (15°C) 0.917-0.924; ND (20°C) 1.4680; sap. val. 190-194; iod. val. 74-89; acetyl val. 4.5-12; RM val. 0.2; Poll val. 0.3; unsap. 0.6 per cent. The oil consists of 17-18 per cent saturated acids of which 12 per cent is palmitic and 5 per cent stearic; of the unsaturated fatty acids present, 75 per cent is oleic acid and 6 per cent linoleic, though this varies to some extent with growing conditions and from cooler areas the proportions have been reported as 67.5 per cent and 15.2 per cent respectively, with a corresponding increase in the iodine value. Chufa oil is resistant to oxidative changes and it has been suggested that it could be added to oils such as coconut oil to retard rancidity.

Processing

Horchata, the milky white beverage, is prepared as follows:

(i) The tubers are left to soak in water for 12 hours and then thoroughly washed to remove adhering soil, etc.

(ii) The clean swollen tubers are ground in a crusher and the resultant paste stirred with water and passed through a 25 mesh sieve.

(iii) The residues left on the sieve are stirred with water twice more and the milky liquid obtained added to that from (ii).

(iv) The liquids from (ii) and (iii) are passed through a 100 mesh sieve and the residues pressed to obtain maximum extraction.

(v) Sucrose is then added to the extract at the rate of 150 g/litre and the product is bottled and kept at 0-5°C.

In general, about I kg of chufas will produce 5.5 litres of horchata.

A typical analysis of horchata is: total solids 22.8 per cent; fat 2.6 per cent; starch 2.4 per cent; sucrose 2.1 per cent; reducing sugars 0.03 per cent; ash 0.24 per cent; vitamin B 0.02 mg/100 g; ascorbic acid 0.27 mg/100 g. The pH is approximately 7 and Brix 18.3°.

When prepared on a commercial scale and stored at 0.5°C horchata quickly ferments and has a storage life of only 48 hours; for this reason attempts have been made to produce a more stable commercial product, eg by the production of frozen concentrates or using infra-red radiation. Pasteurisation before bottling is stated to extend the storage life of the chilled product to about four weeks without adverse effect on flavour.

Freeze drying is a promising (though costly) technique, which, with the incorporation of the antioxidant EDTA (ethylenediaminetetracetate) and packaging in nitrogen, gives a product of excellent quality with a storage life of four months at 37°C or about one year at 25°C. Spray drying has also been investigated.

Major influences

Although most of the literature on chufa is concerned with its eradication as a weed, there is continuing interest in the plant as a food and as a drink in the form of horchata. Certain vegetarian organisations have promoted chufa tubers as a complete food, in spite of the fact that their protein content is relatively low and their high cellulose content is nutritionally detrimental.

Bibliography

ABDEL-AKHER, M. and NICHALINOS, A. N. 1963. Separation and purification of starch from chufa nut tubers (Cyperus esculentus). Die Starke, 15, 329-334.

ALLAN, R. D., WELLS, R. J., CORRELL, R. L. and MACLEOD, J. K. 1978. The presence of quinones in the genus Cyperus as an aid to classification. Phytochemistry, 17, 263-266.

AMARGOS, J. L. 1946. El cultivo de la chufa. Revista de Agricultura, Habana, 29, 77-79; 82.

BARBER, S. 1981. Recent contributions to research in the Valencia region on local products in food science and technology. Revista de Agroqu�mica y Tecnolog�a de Alimentos, 21, 175-184

BARKO, J. W. and SMART, R. H. 1979. The nutritional ecology of Cyperus esculentus, an emergent aquatic plant grown on different sediments. Aquatic Botany, 6(1), 13-28.

BLAIM, K. 1955. Charakterystyka chemiczna bulwek migdala ziemnego, Cyperus esculentus L. [Chemical characterisation of the tubers of the earth almond.] Przemysl Spozywczy, 9, 328-330. (English summary p. 330). (Food Science Abstracts, 28, 1901).

CHEEOWSKI, J. AND LEONCZUK, K. 1978. [Evaluation of usefulness of Cyperus esculentus for processing.] Przemysl Spozywczy, 32, 468-469.

CHOUDHURY, J. K. 1961. Essential oil-bearing plants of India: a review of the monocotyledons. Indian Perfumer, 5(2), 87.

DANGUGUWA, A. A. 1963. Cultivation of tiger nuts (Cyperus esculentus) by some tribes in Bauchi. Samaru Agricultural Newsletter, 5, 86-87.

GAD, A. M. and OSMAN, F. A. 1961. Chemical constituents of the Egyptian chufa. Journal of Chemistry of the United Arab Republic, 4, 119-131.

GARCIA OLMEDO, R., VALLS PALLES, C. and DIAZ MARQUINA, A. 1979. [Study of the oil of Cyperus esculentus tubers. I. fatty acid composition.] Anales de Bromatologia, 31, 339-347. [II. Unsaponifiable oils.] Anales de Bromatologia, 31, 348-356.

GOODING, E. G. B. 1962. The storage behaviour of dehydrated foods. Recent Advances in Food Science: Papers read at the Residential Summer Course (C/asgow, 1960) (Hawthorn, J. and Leitch, J. M., eds), Vol. 2, Processing, pp. 22-40. London: Butterworths, 317 pp.

IRVINE, J. R. 1969. Chufa. West African agriculture, 3rd edn, Vol. 2, West African crops, p. 187. London: Oxford University Press, 272 pp.

JACKSON, E. K., JANGAARD, N. O. and JAMES, A. L. 1971. The stimulation of nutsedge tuber sprouting with ethylene. Plant Physiology, 47, Abstract 87.

KILLINGER, G. B. and STOKES, W. E. 1946. Chufas in Florida. University of Florida Agricultural Experiment Station Bulletin, No. 419, 16 pp.

LAFUENTE, B. and ALONSO, I. 1965. Quality of horchata concentrate as influenced by storage temperature. Food Science and Technology: Proceedings of the 1st International Congress of Food Science and Technology (London, 1962) (Leitch, J. M., ed.), Vol. IV, pp. 679-686. New York: Gordon and Breach Science Publishers, 809 pp. (5 vole).

LAFUENTE, B., ALONSO, I. and LOPEZ, J. J. 1965. Pasteurizaci�n de la horchata con radiaciones infrarrojas. [Pasteurisation of horchata by infrared radiation.] Revista de Agroqu�mica y Tecnologia de Alimentos, 5, 92-98.

LOCASCIO, S. J. and COOLS, W. G. 1979. World's worst weed pests (Cyperus rotundus, Cyperus esculentus) can be stopped. Sunshine State Agricultural Research Report, V, 23(1), 6-7.

MATTHIESSEN, R. L. and STOLLER, C. W. 1978. Tuber composition in yellow nutsedge (Cyperus esculentus) and variants. Weed Research, 18, 373-377.

MENSIER, P. H. 1957. Cyperus esculentus. Dictionnaire des huiles v�g�tales, pp. 203-204. Paris: P. Lechevalier, 763 pp.

MOKADY, Sh. and DOLEV, A. 1970. Nutritional evaluation of tubers of Cyperus esculentus L. Journal of the Science of Food and Agriculture, 21, 211-214.

NAVARRO, J. L., SCHWARTZ, M., GASQUE, F., ALBEROLA, J., PEREZ, R. and LAFUENTE, B. 1983. Evoluci�n de las caracter�sticas analiticas de la chufa (Cyperus esculentus L.) a lo largo del periodo de recolecci�n. Revista de Agroqu�mica y Tecnolog�a de Alimentos, 23, 387-394.

NAVARRO, J. L., SCHWARTZ, M., GASQUE, F., ALBEROLA, J., PEREZ, R. and LAFUENTE, B. 1984. Influencia de la �poca de recolecci�n de la chufa (Cyperus esculentus L.) sobre las caracter�sticas analiticas y sensoriales de la horchata. Revista de Agroqu�mica y Tecnolog�a de Alimentos, 24, 199-208.

PIERAERTS, J. 1921. Le souchet comestible: Donn�es botaniques, chimiques, culturales et commerciales. L'Agronomie Coloniale, 6(37), 18-30; (47), 152-156.

PIERAERTS, J. 1923. Le souchet comestible. L'Agronomie Coloniale, 9(67), 7-21.

PINAGA, F., LAFUENTE, B. and PRIMO, E. 1975. Horchata en polvo III. Estudio de la estabilidad en el almaceniamento de la horchata liofilizada. Revista de Agroquimica y Tecnolog�a de Alimentos, 15, 374-382.

PRIMO, E. and LAFUENTE, B. 1965. This is horcata. Food Science and Technology: Proceedings of the 1st international Congress of Food Science and Technology (London, 1962) (Leitch, J. M., ed.), Vol. IV, pp. 687-691. New York: Gordon and Breach Science Publishers, 809 pp. (5 vole).

SCHWARTZ, M., COSTELL, E. and GASQUE, F. 1984. Efecto de los tratamientos de estabilizaci�n de la horchata de chufa (Cyperus esculentus L.) sobre su color y su viscosidad. Revista de Agroqu�mica y Tecnolog�a de Alimentos, 24, 271 -277.

SCHWARTZ, M., VILA, R., GASQUE, F., NAVARRO, J. L. and LAFUENTE, B. 1982. Mejora de la estabilidad de la horchata de chufas por tratamientos t�rmicos. Revista de Agroqu�mica y Tecnolog�a de Alimentos, 22, 531-538.

STAMPA, G. 1932. The edible cyperus and its industrial uses. International Review of Agriculture, (7), T259-270.

WILLIAMS, R. D. 1982. Growth and reproduction of Cyperus esculentus L. and Cyperus rotundus L. Weed Research, 22, 149-154.

WILLS, G. D., HOAGLAND, R. E. and PAUL, R. N. 1980. Anatomy of yellow nutsedge (Cyperus esculentus). Weed Science, 28, 432-437.

WILLS, J. B. 1962. Tigernut (Cyperus esculentus L.). Agriculture and land use in Ghana (Wills, J. B., ed.), p. 378. London: Oxford University Press for Ghana Ministry of Food and Agriculture, 504 pp.

WINTER, H. 1957. Die Proteine der Erdmandel (Cyperus esculentus). [The proteins of the earth almond.] Zeitschrift fur Lebensmittel-Untersuchung und -Forschung, 105, 200-206. (Food Science Abstracts, 29, 2604).

East Indian arrowroot (Tacca leontopetaloides)

Common names

EAST INDIAN ARROWROOT, Fiji arrowroot, Indian arrowroot', Polynesian arrowroot, Tacca, Tahiti arrowroot, Williams arrowroot.

Botanical name

Tacca leontopetaloides (L.) Kuntze syn. T. pinnatifida Forst., T. involucrata Schum. and Thonn.

Family

Taccaceae.

Other names

Kabitsa (Madag.); Katjandong (Indon.); Loki (Polyn.); Lukeh (Mal.); Makmok, Mokmok (Mar. Is.); Masoa (Sam.); Pia (Haw.); Tavolo(s), Tavolo-kabija (Madag.); Vitian (Tah.); Yabia, Yabyaban (Philipp.).

Botany

East Indian arrowroot is a perennial herb with a tuberous rhizome, from which a single petiole, 60-90 cm long arises, bearing deeply lobed leaf blades consisting of three main segments, each further divided in a pinnate manner; the blades are about 30 cm across. The inflorescence is borne on a long stalk, also arising from the basal tuber, and is terminated by an umber of small green flowers surrounded by six or more bracts each about 3-4 cm long and numerous thread-like purplish inner bracts. The fruit is an ovoid, smooth, yellowish berry, about 3.5 cm long, with six ribs. Two distinct types have been reported from the Pacific Islands, one producing a single large tuber, the other with a number of smaller (potato-sized) tubers.

Origin and distribution

East Indian arrowroot was introduced into the Pacific Islands from its origin in South-East Asia very early, and was subsequently introduced throughout tropical Asia, tropical Africa and tropical Australia. Its importance has declined; it is not cultivated in Africa and only sporadically elsewhere, though it has persisted throughout its range of early distribution in a wild state.

Cultivation conditions

Tacca leontopetaloides is a tropical plant but there is little precise information on its cultural requirements, though it appears to thrive best on low-lying (up to 200 m), friable soils, particularly near the seashore; weeding is important and partial shade is beneficial.

Planting procedure

Material - propagation is by division of the small tuberous rhizomes which form at the base of the plant and often remain in the soil when the larger ones are harvested.

Field spacing - the tubers are often planted about 15 cm deep at a distance of 45 cm in rows 75-90 cm apart.

Pests and diseases

Few diseases or insect attacks have been recorded from cultivations of East Indian arrowroot as a reserve food crop in the Pacific.

Growth period

In Hawaii, the leaves appear in the early spring and the crop is mature by the end of the summer, approximately 8 months from planting, though under some conditions the crop can take up to 10 1/2 months to reach maturity.

Harvesting and handling

The tuberous rhizomes are ready for harvesting when the leaves begin to wither and fall. They are dug and sometimes stored in pits, but are liable to sprout.

Primary product

Tuberous rhizomes - most plants produce many starchy tubers, similar in appearance to potatoes, usually 10-15 cm in diameter, but they can reach 30 cm on rich soils. They normally weigh from 70 to 340 g but can reach 1 kg. The tubers have eyes, a pale-yellow skin and dull-whitish flesh, and are usually bitter and almost inedible when raw.

Main use

The tubers were in the past a staple foodstuff in Polynesia, and in the 19th century were used as a source of starch rather similar to that of arrowroot, often given in the treatment of dysentery and for feeding infants. In Tahiti, they are used to make 'poi' ('poke' in the Cook Islands), a traditional food which consists of a mixture of fruit pulp and starch, flavoured with vanilla and lemon and cooked in an oven.

Subsidiary uses

Wild plants are regarded as a famine food in parts of West Africa.

Secondary and waste products

In the 19th century the leaves were marketed in Europe for the manufacture of hats.

Special features

The tubers contain 20-30 per cent of starch which can be easily extracted in a pure state and was formerly marketed in Europe and used in the Philippines for breadmaking. An analysis of Tahitian tubers has been given as: water 60.59 per cent; skin 2.5 per cent; starch 30.6 per cent; fibre 6.3 per cent.

An analysis of African tubers on a dry weight basis has been given as: protein 5.1 per cent; ether extract 0.2 per cent; carbohydrate 89.4 per cent; cellulose 2.1 per cent; fibre 8.8 per cent; ash 3.2 per cent; calcium 0.27 per cent; phosphorus 0.2 per cent.

The principal amino acids present in the protein are arginine, glutamic and aspartic acids, leucine, Iysine and valine.
The starch obtained from the tubers is very white and similar in many respects to that of cassava or arrowroot; the grains are simple polyhedrons or semi-hemispheres, with diameters ranging from 8 to 40 microns, average 20 microns. In addition, the tubers contain about 2.2 per cent of a bitter extract, and a bitter principle taccalin has been isolated from the dried tubers.

Processing

Starch - the tubers are peeled, grated, and the resultant pulp washed in water several times, finally in a sieve or cloth. The aqueous starch solution is collected and the starch grains allowed to settle out, collected and dried in the sun.

Major influences

The demand for East Indian arrowroot starch has never been high and there seems no prospect of its expansion in the future. In Tahiti it has been largely replaced by cassava starch in the preparation of 'poi'.

Bibliography

ALLEN, R. N. 1929. Photomicrographs of Philippine starches. Philippine
Journal of Science, 38, 251-252.

BATES, W. N. 1963. Root crops. Mechanization of tropical crops, pp. 268-279. London: Temple Press Books, 410 pp.

BURKILL, I. H. 1935. Tacca pinnotifida. A dictionary of the economic products of the Malay peninsula. Vol. II (I-Z), pp. 2118-2119. London: The Crown Agents for the Colonies, 2402 pp.

BUSSON, F. 1965. Taccac�es. Plantes alimentaires de l'ouest Africain: �tude botanique, biologique et chimique, pp. 436-438. Marseille, France: L'Imprimerie Leconte, 568 pp.

EZUMAH, H. 1970. Miscellaneous tuberous crops of Hawaii. Tropical Root and Tuber Crops Tomorrow: Proceedings of the 2nd International Symposium on Tropical Root and Tuber Crops (Hawaii, 1970) (Plucknett, D. L., ed.), Vol. I, pp. 166-171. Honolulu, Hawaii: College of Tropical Agriculture, University of Hawaii, 171 pp. (2 vole).

HAUDICOURT, A. 1942. Les tacca, plantes utiles. R�vue Botanique Appliqu�e et d'Agriculture Tropicale, 22, 76-81.

JUMELLE, H. 1910. Les plantes � arrowroot et � f�cules similaires Tacca pinnatifida. Encyclop�die scientifique: Les plantes � tubercules alimentaires, pp. 243-249. Paris: O. Doin et firs, 372 pp.

MASSAL, E. and BARRAU, J. 1956. Polynesian arrowroot. Food plants of the south sea islands. South Pacific Commission Technical Paper, No. 94, pp. 11-12. Noumea, New Caledonia: South Pacific Commission, 51 pp.

MONTALDO, A. 1972. Pia. Cultivo de ra�ces y tub�rculos tropicales, pp. 254-256. Lima, Peru: Instituto Interamericano de Ciencias Agricolas de la OEA, 284 pp.

PURSEGLOVE, J. W. 1972. Taccaceae. Tropical crops: Monocotyledons 2, pp. 517-518. London: Longman Group Ltd, 607 pp. (2 vols).

RAKOTO-RATSIMAMANGA, A., BOITEAU, P. and MOUTON, M. 1968. Elements de pharmacop�e malagasy, amidons: amidon de Tacca pinnatifida Forst. Bulletin de Madagascar, 18 (268), 735-736.

SPROAT, M. N. 1968. A guide to subsistence agriculture in Micronesia. Agricultural Extension Bulletin, No. 9. Saipan, Mariana Islands, Trust Territory of the Pacific Islands: Division of Agriculture, Department of Resources and Development, 142 pp.

STONE, E. L. 1951. Polynesian arrowroot, 'Makmok'. The agriculture of Arno Atoll, Marshall Islands. Atoll Research Bulletin, No. 6, pp. 24-25. Washington, DC: Pacific Science Board, 46 pp.

WILDEMAN, E. de. 1906. Tacca pinnatifida. Plantes utiles ou int�ressantes du Congo, Vol. 2, pp. 148-151. Bruxelles, Belgium: Veuve Monnom, 268 pp.

Elephant yam (Amorphophallus spp.)

Common names

ELEPHANT YAM, Elephant bread, Elephant foot yam, Suran, Sweet yam.

Botanical name

Amorphophallus spp.

Family

Araceae.

Other names

Anto (Philipp.); Arsaghna, Balukund (Ind.); Chena (Mal.); Daga (Fiji); Ilis-ilis, Kand godda (Indon.); Karak-kavanai (Tamil); Karnai kilangu (Mal.); Kidaran (Ind.); Koe (Polyn.); Konjac, Konniaku, Konnyaku (Japan); Mo-yu (China); Ol (Assam); Ol kuchu (Bangl.); Oroy, Po�gapong, Pu�gapung (Philipp.); Sooweg (Indon.); Suron (Fiji); Tamari (Sol. Is.); Telinga potato (Ind.); Teve (Tah.); Tigi (Philipp.); Waloor (Indon.); Zaminkund (Ind.).

Botany

A robust herbaceous plant, with an erect solitary stem usually 1-2.5 m in height and bearing at the top one or two tripartite leaves, each part of which is deeply dissected into numerous segments. Towards the end of the plant's cycle (usually 4-6 years) a large terminal inflorescence is produced, consisting of a short stalk and spathe and a spadix, which emits a malodorous smell, reminiscent of rotten meat. The corms are large globose depressed tubers, usually dull-yellow or brownish-yellow in colour, and these produce 5-10 cormels at the end of each growing season.

The genus Amorphophallus consists of about 90 species, but the most important and widespread in the tropics is Amorphophallus paeoniifolius (Dennst.) Nicolson (syn. A. campanulatus Decne) and according to some authorities this exists in two forms, the wild one, var. sylvestris, recognisable by its rough petioles, while the cultivated form, var. hortensis, has much smoother petioles. In Indonesia two closely related species A. oncophyllus Prain and A. variabilis Bl. occur and are utilised. In addition, A. konjac C. Koch (syn. A. rivieri Durien var. konjac (C. Koch) Engler) is cultivated and utilised in Japan and the warmer parts of China, and is also referred to as elephant yam in these areas.

Origin and distribution

The genus is indigenous to tropical Asia and Africa and A. paeoniifolius is found widely distributed in thickets and secondary growth forests at low and medium altitudes in the Philippines, Malaysia, Indonesia, Sri Lanka and the South-East Asia subcontinent. A. konjac originated in the Vietnam-southern China region and was introduced into Japan in the 10th century.

Cultivation conditions

A. poeoniifolius is a tropical and subtropical crop and requires an average temperature of 25-35°C, preferably fairly equable during its growing period. The rainfall should be evenly distributed and between 100 and 150 cm, although the plant can be grown with a rainfall as low as 65 cm provided irrigation facilities are available. Warm humid conditions favour leaf growth and dry conditions favour the development of the corms. A. konjac requires cooler conditions with temperatures in the range 18-30°C, and is normally grown between latitudes 34°N and 43°N.

For optimum yields, deep loamy soils worked to a fine filth are necessary, preferably not alkaline. Good drainage is essential as the crop cannot stand waterlogging and heavy clays are therefore unsuitable. In India, it has been recommended that the crop should receive 25 t/ha of FYM, in addition to nitrogen 40 kg/ha, phosphorus 40 kg/ha and potassium 80 kg/ha. If no FYM is used additional nitrogen is advised, about 50 kg/ha in July and again in August for a fourth year crop.

Planting procedure

Material - both A. paeoniifolius and A. konjac are propagated from small corms (cormels) or buds produced below ground from the base of the shoot; in A. paeoniifolius the cormels appear during the fourth year but in A. konjac they appear in the second or third year. A weight of 100-120 g per piece is usual for planting. Both species have a dormancy period of 2-3 months. A crop may be obtained in one year from A. paeoniifolius if a four year old corm is cut into sections, each of which weighs 1-1.2 kg and carries at least one cormel and planted. Viable seeds have been produced experimentally and may be used for breeding work.

Method - the soil should be well tilled. Frequently planting is on the flat, after paddy culture, but planting on ridges is also common. The corms are usually planted 10-15 cm deep. The crop often receives little cultural atten tion, although mulching or shading during the first 3-5 weeks of growth, followed by weeding and earthing up, is recommended. In India it is often grown mixed with other crops, such as arecanuts (Areca catechu), ginger (Zingiber officinale), methi (Trigonella foenum-graecum), cluster bean (Cyamopsis tetragonoloba) and bananas (Musa sp.). In parts of India, eg Bombay, the corms are usually dug at the end of each growing season, stored and then replanted, but in other areas, such as Japan, where A. konjac is grown, the corms are left in the ground for the whole growth cycle. It is essential for the corms of both species of Amorphophallus to be allowed a period of natural dormancy of 2-3 months. Amorphophallus has been recommended for intercropping with coconuts.

Field spacing - trials in India using cut pieces of four year old corms gave the highest yield per hectare when planted at 90x 120 cm. With seed pieces a spacing of 60x 120 cm has been recommended if accompanied by fertilisers.

Seed rate - approximately 1 600-2 000 kg/ha of corms or buds are required: when cut pieces of four year old corms are used the rate is about 10 000 kg/ha.

Pests and diseases

Reports from India indicate foot rot (caused by Rhizoctonia solani) as a serious problem. Drenching the soil around affected plants at monthly intervals with 0.2 per cent captan or 0.1 per cent quintozene was highly effective and led to almost double the tuber yields of untreated plants. Little has been reported from elsewhere.

Growth period

The growth cycle of the corms normally takes about 8-12 months but the tubers are small and unmarketable after only one season and 3-4 seasons are required for an economic crop, except when planted from four year old corms as described.

Harvesting and handling

The corms are dug by hand when the leaves begin to wither and die, and weigh from 3 to 9 kg, depending upon the number of growing seasons. They are usually carefully cleaned and are stored in heaps preferably in well-ventilated sheds. Corms of A. paeoniifolius can lose as much as 25 per cent of their initial weight in the first month of storage, but can be successfully stored at 10°C for several months. Alternatively, they may be left in the ground until required, with a little irrigation if necessary. Corms dipped for I minute in a 4 per cent fungicidal emulsion can be stored at room temperature for about 2 months with minimal loss of weight or sprouting. In Japan corms of A. konjac that are to be replanted must be protected in store from low winter temperatures, since it has been found that if they are subjected to temperatures of - 5°C germination is affected.

Primary product

Corms - the depressed globose corms often have a diameter of 30 cm or more, and under good cultural conditions can weigh 7-9 kg by the fourth season.

Yield

In India the average yield ranges between 12 and 22 t/ha; as an intercrop with coconuts 13 t/ha. However, under experimental conditions over 60 t/ha has been reported, and 36 t/ha in mixed cropping.

Main use

The corms and cormels of A. paeoniifolius are usually boiled or baked and eaten as a vegetable: in Japan A. konjac is mainly eaten as konnyaku, a gel-like food with an elastic texture made from konjac mannan flour (see Processing). The small one year old corms of A. konjac are considered to be a delicacy. Wild forms must be soaked in water for some time before cooking, and boiled for a lengthy period in order to remove the bitterness.

Subsidiary uses

In the Philippines, the corms are sometimes boiled and fed to pigs. They may be used as a source of starch and alcohol and have been used to prepare a flour for breadmaking. In Indonesia, the species A. onchophyllus is used to produce flour for industrial purposes, and the Japanese species A. konjac is used as a commercial source of mannose. A glucomannan from species of Amorphophallus has been proposed for thickening food products such as ice cream or mayonnaise.

The konjac mannan flour from A. konjac is used to make paste that does not separate when frozen and thawed, and is not eaten by insects. It is also employed in the manufacture of paper, and in textiles it is used in the same manner as starch. Cotton and other fabrics are waterproofed by coatings based on konjac mannan flour. Cosmetics such as those for chapped skin, beauty creams and hair pomades may contain the flour.

Secondary and waste products

The young petioles and leaf blades may be boiled and eaten as a vegetable which is reported to resemble asparagus. Older, tougher petioles are used for livestock feeding, while the corms are reported to be used for medicinal purposes in parts of India.

Special features

The composition of the edible portion of the corms of A. paeoniifolius has been reported as: energy 330 kJ/100 g (approx); water 72-79 per cent; protein 1.7-5.1 per cent; fat 0.2-0.4 per cent; carbohydrate 18-24 per cent; fibre 0.�-0.8 per cent; ash 0.7-1.3 per cent; calcium 50-56 mg/100 g; iron 0.6-1.4 mg/100 g; phosphorus 20-53 mg/100 g; vitamin A 434 IU/100 g; thiamine 0.04-0.06 mg/100 g; riboflavin 0.05-0.08 mg/100 g; niacin 0.07-0.075 mg/100 g; ascorbic acid trace-3 mg/100 g. Most of the carbohydrate is starch (75-80 per cent); the starch granules vary in shape and size (about 5.5-19 microns).

A. konjac is reported to have a higher water content (80-90 per cent), with only about 10 per cent of the carbohydrate as starch but up to 65 per cent as glucomannan.

A. paeoniifolius and A. konjac contain calcium oxalate crystals; the wild forms of A. paeoniifolius contain more than the cultivated and are strongly acrid.

Processing

No processing methods for A. paeoniifolius have been described, but A. konjac corms are commonly air-dried in the sun; the dried corms may be stored for long periods, or made into flour. The following procedures apply only to A. konjac.

Flour (konako or konjac mannan flour) - the corms are peeled, sliced and skewered onto bamboo sticks 60 - 90 cm long, 2 or 3 cm apart, and placed in the sun. After about one week the slices are crushed and then ground in a mortar and pestle run by a waterwheel. During the grinding a flap attached to the mortar blows away the fibre and cell debris (and some of the flour). The flour is known as konako: about 12 kg of konako is obtained from 100 kg of fresh tubers. The proximate composition of konako has been given as: water 17 per cent; fat 0.6 per cent; carbohydrate 68 per cent; fibre 2.3 per cent; ash 4.5 per cent. The flour is used in many recipes.

Konnyaku - konako flour is made into konnyaku by the following process:

(i) Water is stirred into the flour until it becomes uniformly soft and gelatinous.

(ii) The paste is allowed to stand, stirred, and allowed to stand for a further period of time.

(iii) A dilute, strained suspension of slaked lime is stirred into the gel, and mixed thoroughly until it thickens.

(iv) The mass is poured into shallow trays, allowed to stand until further thickening has developed, then cut into squares (often with about 10 cm sides).

(v) The squares are boiled in water for about 20 minutes, allowed to cool in the cooking water and then stored, refrigerated, in the same water. Konnyaku is reported to last indefinitely if the water is not changed.

Shirataki - the lime-treated gelatinous mass (step (iii) in the production of konnyaku) is pressed through a die (or sieve) before cooking, forming noodles called shirataki.

Konnyaku and shirataki are an important part of the Japanese diet and may be eaten fresh (or refrigerated), or canned. Published analytical figures for Hawaiian and Japanese konnyaku are:

Hawaiian konnyaku (fresh): energy 50 kJ/100 g; water 96.6 per cent; protein 0.09 per cent; carbohydrate 3.07 per cent; fibre 0.06 per cent; ash 0.24 per cent; calcium 63 mg/100 g; iron 0.3 mg/100 g; magnesium 7 mg/100 g; phosphorus 7 mg/100 g; potassium 10 mg/100 g; sodium 38 mg/100 g; thiamine 0.021 mg/100 g; niacin 0.02 mg/100 g; ascorbic acid 0.5 mg/100 g.

Japanese konnyaku (fresh): water 97.4 per cent; protein 0.1 per cent; carbohydrate 2.3 per cent; fibre 0.1 per cent, ash 0.2 per cent; calcium 43 mg/100 g; iron 0.4 mg/100 g; phosphorus 5 mg/100 g; sodium 10 mg/100 g.

Japanese konnyaku (canned): energy 54 kJ/100 g; water 96.48 per cent; protein 0.04 per cent; fat 0.01 per cent; carbohydrate 3.28 per cent; fibre 0.37 per cent, ash 0.19 per cent; calcium 63 mg/100 g; iron 0.28 mg/100 g; magnesium 3 mg/100 g; phosphorus 3 mg/100 g; potassium 18 mg/100 g; sodium 2 mg/100 g; ascorbic acid 0.1 mg/100 g.

The figures for shirataki would be similar.

Konnyaku in the diet is reported to lower plasma cholesterol.

Production and trade

Very little information is available: in Japan the area under A. konjac was estimated to be about 15 000 ha in 1979, with production of 90 000 t, and in India about 800 ha of A. paeoniifolius is reported.

Major influences

Although the elephant yam continues to be a popular root crop in parts of India and eastern Asia, production is limited mainly because of the four year crop cycle. However, in Japan, breeding and selection aimed at improved disease resistance, higher yields, earlier maturity and higher mannan contents, are in progress.

Bibliography

ANON. 1939. Note sur une plante � tubercles amylac�s - l'Ilis-Ilis de Java (Amorphophallus campanulatus Blume). Agronomie Coloniale, 28 (255), 48-87.

ANON. 1960/1961. Effect of waxing on elephant yam, Amorphophallus campanulatus. Annual Report of the Central Food Technological Research Institute (Mysore), 3-4.

ARKERI, H. R. 1950. Seed production in suran (Amorphophallus campanulatus). Dharwar Agricultural College Magazine, 3, 3-4.

CHAUGULE, B. A. and KHOT, B. D. 1957. Four years with suran. Indian Farming, 7 (9), 27-31.

CHAUGULE, B. A. and KHOT, B. D. 1963. Effect of size of seed corm and spacing on growth and yield of fourth year suran (Amorphophallus campanulatus Blume). Indian Journal of Agronomy, 7 (4), 310-318.

CHEVALIER, A. 1931. Les amorphophallus et leurs usages. Revue Botanique Appliqu�e et d'Agriculture Tropicale, 11 (122), 809-816.

COURSEY, D. a. 1968. The edible aroids. World Crops, 20 (4), 25-30.

DEKKER, G. H. W. D. and HALEWIJN, E. K. E. 1940. De bereiding van ilesmannaanmeel uit Amorphophallus oncophyllus. [Preparation of meal from Amorphophallus oncophyllus.] Bergcultures, 14 (22), 708-718.

FORD, D. M. and CHEYNEY, P. A. 1983. UK Patent Application NU GB 2 100 967 A (Food Science and Technology Abstracts, 45, 1441).

IYER, N. A. 1935. A note on the cultivation of elephant yam (Amorphophallus campanulatus) in Chittoor Taluk. Madras Agricultural Journal, 23, 451-454.

KOREGAVE, B. A. 1964. Effect of mixed cropping on the growth and yield of suran (Elephant yam, Amorphophallus campanulatus Blume). Indian Journal of Agronomy, 9, 255-260.

KUNDU, B. C. 1967. Some edible rhizomatous and tuberous crops of India. Proceedings of the International Symposium on Tropical Root Crops (Trinidad, 1967) (Tai, E. A., Charles, W. B., Haynes, P. H., Iton, E. F. and Leslie, K. A., eds), Vol. 1, Section 1, pp. 124-130. St. Augustine, Trinidad: University of the West Indies (2 vole).

LAMBERT, M. 1982. The cultivation of taro Amorphophallus campanulatus Blume. Taro Cultivation in the South Pacific. South Pacific Commission Handbook, No. 22 (Lambert, M., ed.), pp. 101-102. Noumea, New Caledonia: South Pacific Commission, 146 pp.

L�ON, J. 1977. Origin, evolution and early dispersal of root and tuber crops. Proceedings of the 4th Symposium of the International Society for Tropical Root Crops (Colombia, 1976), lDRC-080e (Cock, J., Maclntyre, R. and Graham, M., eds), pp. 20-36. Ottawa, Canada: International Development Research Centre, 277 pp.

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.

MASSAL, E. and BARRAU, J. 1956. Taros and taro-like plants. Food plants of the south sea islands. South Pacific Commission Technical Paper, No. 94, pp. 6-11. Noumea, New Caledonia: South Pacific Commission, 51 pp.

MONTARDO, A. 1972. Teve. Cultivo de ra�ces y tub�rculos tropicales, pp. 247-249. Lima, Peru: Instituto Interamericano de Ciencias Agricolas de la OEA, 284 pp.

MOTTE, M. J. 1932. Le konnyaku in Japan. Annales du Mus�e Coloniale de Marseille, 40th ann�e, 10 (4), 1-22.

NAIR, P. K. R. 1979. Intensive multiple cropping with coconuts in India. Principles, Programmes and Prospects. Berlin, Germany: Verlag Paul Parey, 147 pp. (Herbage Abstracts, 50 (10), 4724).

OCHSE, J. J. 1931. Amorphophallus campanulatus. Vegetables of the Dutch East Indies. pp. 48-51. Buitenzorg-Java: Archipel-Drukkerij, 1005 pp.

PANCHO, J. V. 1959. Notes on cultivated aroids in the Philippines: the edible species. Baileya, 7 (1), 63-70.

PE�A, R. S. de la. 1970. The edible aroids in the Asian-Pacific area. Tropical Root and Tuber Crops Tomorrow: Proceedings of the 2nd International Symposium on Tropical Root and Tuber Crops (Hawaii, 1970) (Plucknett, D. L., ed.), Vol. I, pp. 136-140. Honolulu, Hawaii: College of Tropical Agriculture, University of Hawaii, 171 pp. (2 vole).

PLUCKNETT, D. L. 1970. Status and future of the major edible aroids, Co/ocasia, Xanthosoma, Alocasia, Cyrtosperma and Amorphophallus. Tropical Root and Tuber Crops Tomorrow: Proceedings of the 2nd International Symposium on Tropical Root and Tuber Crops (Hawaii, 1970) (Plucknett, D. L., ed.), Vol. I, pp. 127-135. Honolulu, Hawaii: College of Tropical Agriculture, University of Hawaii, 171 pp. (2 vole).

PLUCKNETT, D. L. 1977. Current outlook for taro and other edible aroids. Regional meeting on the production of root crops (Fiji, 1975): Collected Papers. South Pacific Commission Technical Paper, No. 174, pp. 36-39. Noumea, New Caledonia: South Pacific Commission, 213 pp.

PURSEGLOVE, J. W. 1972. Tropical crops: Monocotyledons 1, pp. 58 - 74. London: Longmans Group Ltd, 334 pp.

QUDRAT-I-KHUDA, M., MUKHERJEE, B. D., HOSSAIN, M. A. and KHAN, N. A. 1960. Cereals and cereal products: Properties of certain starch varieties and their sources in East Pakistan. Pakistan Journal of Scientific and Industrial Research, 3, 159- 162.

RASHID, M. M. and DAUNICHT, H. J. 1979. Chemical composition of nine edible aroid cultivars of Bangladesh. Scientia Horticulturae, 10, 127-134.

REANTASO, C. G. 1935. Pu�gapu�g as a source of starch and alcohol. Philippine Agriculturist, 24, 239-248.

ROTAR, P. P., PLUCKNETT, D. L. and BIRD, B. K. 1978. Bibliography of taro and edible aroids. University of Hawaii Agricultural Experiment Station Miscellaneous Publication, No. 158. Honolulu, Hawaii: University of Hawaii, 245 pp.

SAKAI, W. S. 1983. Aroid root crops: Alocasia, Cyrtosperma and Amorphophallus. Handbook of Tropical Foods (Chan, H. J. (Jr.), ed.), pp. 29-83. New York: Marcel Dekker Inc., 639 pp.

SIVAPRAKASAM, K., KANDASWAMY, T. K. and NARAYANASAMY, P. 1982. Effect of certain fungicides on the control of foot rot of yam. Tuber crop research in Tamil Nadu (Muthukrishnan, C. R., ed.), pp. 197-198. Coimbatore, India: Tamil Nadu Agricultural University.

False yam (Icacina senegalensis)

Common name

FALSE YAM.

Botanical name

Icacina senegalensis A. Juss.

Family

Icacinaceae.

Other names

Bankanas (Sen.); Basouna (W. Afr.); Kouraban (Sen.); Manankaso (Gam.); Pan� (Sud.); Takwara (Gh.).

Botany

False yam is a shrubby perennial, variable in form, which sends up glabrous or pubescent erect leafy shoots from a large, underground fleshy tuber. The aerial stems are light green, and may reach about I m in height.
The leaves are simple, ovate or obovate, pointed or rounded at the apex, 5-10 cm long and 4-7 cm broad, light green when young, but becoming leathery and dark green on the upper surface and dull green on the lower.
The flowers are inconspicuous, usually white or cream and pedunculate, ascending or erect, corymbose cymes, collected into a terminal leafless panicle, or the lower peduncles arising from the axis of reduced leaves. The calyx is in five divisions, the pointed lobes are bright green; the corolla is composed of 5 narrow, white or creamy-white petals, covered with silky hairs on their outside surface. The fruit is a bright-red ovoid berry, approximately 2.5-3 cm in length and 2-2.5 cm in width. It is covered with very short hairs and contains a thin layer of white pulp, approximately 0.2 cm thick, surrounding a single spherical or ovoid seed.

Origin and distribution

Icacina senegalensis is indigenous to west and central Africa and is found growing wild on light sandy soils in the savanna areas of Senegal, The Gambia, northern Ghana, Guinea and parts of the Sudan.

Cultivation conditions

The plant requires light soils and a marked wet and dry season, but with only moderate rainfall in the wet season (80-100 cm).

Planting procedure

The plant usually occurs wild, and is seldom cultivated. However, it is occasionally planted in Africa and it is reported from Senegal to be propagated by pieces of tuber, planted before the wet season, at about 440 plants/ha.

Pests and diseases

No pests and diseases have been reported.

Harvesting

The tubers are harvested by hand as required; owing to their size and the fact that they can penetrate to about 25-30 cm below the surface they are difficult to dig out and at one time the plant was nicknamed 'abub ntope' or 'break hoe' in northern Ashanti.

Primary product

Tubers - these resemble large turnips or beetroots and show considerable variation in size, ranging from 30 to 45 cm in length up to 100 cm, with a diameter of about 30 cm, and weighing from 3 to 25 kg. The tubers are greyish in colour with a thin skin enclosing white flesh, which is usually speckled with yellow spots that correspond to bundles of xylem. They contain a bitter toxic principle.

Yield

In Senegal yields have been reported to average 2-3 t/ha, although in some parts of west Africa yields are reported to reach 20 t/ha.

Main use

The tubers are used mainly as a famine food and sometimes as a source of starch or flour.

Subsidiary uses

In western Ashanti the tubers are reported to be used medicinally.

Secondary and waste products

The fruits are often eaten by children and the seeds are sometimes dried and pounded to yield a flour, especially at times of food scarcity.

Special features

The tubers contain about 10-15 per cent of starch, the grains of which are irregular in shape, some spherical and some elliptical, with lengths varying from 12 to 50 microns. Flour manufactured from the tubers has the following approximate composition: water 11.7 per cent; protein 10.3 per cent; fat 0.7 per cent; carbohydrate 74.5 per cent; ash 2.8 per cent; calcium 150 mg/100 g; iron 7 mg/100 g; thiamine 0.04 mg/100 g; riboflavin 0.18 mg/100 g; niacin 1.4 mg/100 g. In addition, a bitter toxic principle, reported to be a gum resin, is present in quantities ranging from 0.9 to 2.8 per cent.

Flour obtained from the seeds has the following approximate composition: water 12-13 per cent; protein 8 per cent; fat 0.1 per cent; carbohydrate 72-73 per cent; ash 0.5 per cent.

Processing

When used as a foodstuff the tubers are cut up and placed in clean running water for several days, to remove the bitter principle and to facilitate maceration. They are then dried, pulverised and sieved to give a greyish-white or creamy-yellow flour. The yield of flour from the raw tuber is approximately 8-10 per cent.

Major influences

The false yam is a common weed in many savanna areas of West Africa, particularly where the true yam has been cultivated. It could be utilised to provide a source of commercial starch in certain areas and would be of value in those areas where crop failures causing a shortage of subsistence foods are likely to occur.

Bibliography

CERIGHELLI, M. R. 1919. La farine des graines et la f�cule des tubercules de l'Icacina senegalensis. Annales du Mus�e Coloniale de Morseille, 7, Ser 3 (1), 169 - 178.

DALZIEL, J. M. 1948. Icacina. The useful plants of west tropical Africa, p. 291. London: The Crown Agents for the Colonies, 612 pp.

IRVINE, F. R. 1930. Plants of the Gold Coast, p. 236. London: Oxford University Press, 521 pp.

TOURNIER, J. L. 1951. Une plante � amidon de l'ouest Africain: le bankanas (lcacina senegalensis). 1er Conference internationale d'Afrique Ouest, 2 (85), 100-103. Dakar: Institute Francais d'Afrique Noire.

WOOT-TSUEN WU LEUNG, BUSSON, F. and JARDIN, C. 1968. Food composition table for use in Africa, p. 35. Rome: Food and Agriculture Organization of the United Nations, 306 pp.

Giant taro (Alocasia macrorrhiza)

Common name

GIANT TARO.

Botanical name

Alocasia macrorrhiza (L.) G. Don.

Family

Araceae.

Other names

Alavu, Alooku, Alu (Ind.); Ape (Polyn.); Babai' (Kiri.); Big� (Philipp.); Birah (Mal.); Boro (Assam); Brak (Mal.); Dokuimo (Japan); Hog tannia (Guy.); Inhame gigante (Braz.); Kape (Pacif. Is.); Manaka, Mankachu, Mankanda (Ind.); Oht (Pon.); Pindu (N. Cal.); Puluka (Tuv.); S�nt� (Indon.); Talanu (Sam.); Toyoeu (Braz.); Uvea (Polyn); Vaaga, Via (gaga), Viamiloa (Fiji).

Botany

Giant taro is a tall succulent herbaceous plant, reaching 4.5 m in height, with a thick cylindrical stem arising from a basal corm. The leaves are borne on long petioles which arise from the stem and are sheathing on the lower half, but the blades are more or less heart-shaped with rather rounded basal lobes: the blades point upwards forming a straight line with the petiole (unlike Colocasia or Xanthosoma spp. in which the blades point downwards to form an acute or right angle with the leaf stalk). The leaf blades have a conspicuous midrib, raised on the upper surface, and grow up to about I m in length. They are usually green, but there are variegated forms which are blotched or mottled with white. The spathe has a glaucous, yellowish-green blade. Cormels are formed around the basal corm. The plant contains latex.

Origin and distribution

The giant taro is thought to have originated in Sri Lanka, but has become widely distributed in the South-East Asia subcontinent, Malaysia, Indonesia and Polynesia, and has spread to parts of tropical America.

Cultivation conditions

Temperature - the species is essentially tropical and temperatures below 10°C are detrimental to growth.

Rainfall - taro requires a reasonably high (in excess of 170 cm per year) evenly-distributed rainfall and cannot survive a long period of drought. It is frequently found naturally along river banks, but cannot stand waterlogging.

Soil - the plant grows well in medium to heavy soils provided drainage is adequate. Response to nitrogen fertilising has been demonstrated.

Planting procedure

Material - suckers are commonly used, but shoot tips with a few inches of stem and rolled up young leaves, or sections of stem having two or three buds are also frequently employed.

Method - planting is in holes 15-25 cm deep for suckers or 8-15 cm deep for cormels.

Field spacing - Alocasia is commonly an intercrop with yams, and the spacing is usually 3.5 x 3.5 m. In pure stand 60 x 60 cm to 1.5 x 1.5 m is used.

Pests and diseases

The giant taro is resistant to most pests and diseases, although in India considerable losses have been reported due to an unidentified bacterial leaf spot disease.

Growth period

The crop life is usually 12-18 months, but harvesting can be delayed for up to four years.

Harvesting and handling

The giant taro is normally dug by hand; the plant can remain in the ground for about 3 months after reaching maturity without any deterioration and is in fact often 'field-stored'.

Primary product

Stems - unlike most other edible aroids, in which the edible parts are subterranean, it is the fleshy aerial stems of the giant taro that provide the primary product. These stems may be up to I m long and 20 cm in diameter, normally weighing 8-10 kg, though 20 kg or more is not uncommon.

Yield

In the Pacific islands harvesting is usually after 18-24 months but the plant may be allowed to grow for up to 4 years, producing corms weighing about 18 kg. Theoretically, yields for pure stands could be almost 200 t/ha at this stage, but no yields for the Pacific region have been reported as all normal planting is intercropped. Much lower yields are reported from Sri Lanka, where harvesting is usually at 11 months, giving about 7-11 t/ha per crop (1.8-2.7 kg per plant) though when grown over coconut husks 6-7 kg per plant is obtained.

Main use

The stem tuber is peeled, cut into pieces and eaten as a vegetable after cooking, usually in curries or stews. Older stems may require prolonged cooking with several changes of water to remove acridity.

Subsidiary uses

Giant taros are sometimes used as a source of a very white easily-digested starch or flour. The underground corms and cormels are also used for food after thorough cooking, particularly in times of scarcity. The leaves may be eaten (eg fried with onions, garlic, chili, etc). Alocasias are widely grown in certain areas, eg Florida, as ornamental foliage plants.

Secondary and waste products

The corms and leaf juices (latex) are reported to be used for medicinal purposes in India and the Pacific islands. The plant was formerly cultivated in Brazil, where it was utilised as a pig feed. It has also been investigated as a possible raw material for the production of alcohol.

Special features

The food value of the edible portion of the raw stem tubers of giant taro has been reported as: energy 293-599 kJ/100 g; water 63-81 per cent; crude protein 0.6-3.3 per cent; fat 0.1-0.2 per cent; carbohydrate 17-27 per cent; ash 1.1-1.3 per cent; calcium 46-153 mg/100 g; iron 0.5-1 mg/100 g; phosphorus 45-72 mg/100 g; niacin 0.4 mg/100 g; riboflavin 0.02-0.03 mg/100 g; thiamine 0.09-0.1 mg/100 g; ascorbic acid trace. Much of the calcium is in calcium oxalate crystals.

Composition changes with age, older material having lower moisture content and higher solids. Few figures have been published showing starch content but there may be substantial quantities of other carbohydrates associated with it. The starch grains are small, irregularly-shaped polygons of four or five sides, 1-5 microns in length, with approximately 21 per cent amylose and 79 per cent amylopectin. Several cultivars of A. macrorrhiza are reported to be cyanogenic; the cyanogenic glycoside is not present in the corms or stems, but the young leaves have been found to contain up to 0.018 per cent of hydrogen cyanide.

Major influences

The giant taro is a minor crop in most Asian countries and production is not likely to expand.

Bibliography

ALLEN, R. N. 1929. Photomicrographs of Philippine starches. Philippine Journal of Science, 38, 247.

ASTHANA, R. P. 1946. Bacterial leaf-spot on arum. Current Science, 15 (12), 356.

BARRAU, J. 1957. Les arac�es � tubercules alimentaires des �les du Pacifique sud. Journal d'Agriculture Tropicale et de Botanique Appliqu�e, 4 (1), 34-52.

COURSEY, D. G. 1967. The edible aroids. World Crops, 20 (4), 25-30.

DOI SHINJI. 1944. Value of dokuimo as a raw material for the fermentation industry. Journal of the Agricultural Chemical Society of Japan, 20, 457-464. (Chemical Abstracts, 43(3), 11468).

FURTADO, C. X. 1941. Alocasia macrorrhiza and its varieties. Gardens' Bulletin of the Straits Settlements, II, 244-257.

HAUDRICOURT, A. 1941. Les colocasi�es alimentaires (taros et yautias). R�vue de Botanique Appliqu�e et d'Agriculture Tropicale, 21, 40-65.

KUNDU, B. C. 1970. Some edible rhizomatous and tuberous crops of India. Proceedings of the International Symposium on Tropical Root Crops (Trinidad, 1967) (Tai, E. A., Charles, W. B., Haynes, P. H., Iton, E. F. and Leslie, K. A., eds), Vol. 1, Section 1, pp. 124-130. St. Augustine, Trinidad: University of the West Indies (2 vole).
L�ON, J. 1977. Origin, evolution and early dispersal of root and tuber crops. Proceedings of the 4th Symposium of the International Society for Tropical Root Crops (Colombia, 1976), IDRC-080e (Cock, J., Maclntyre, R. and Graham, M., eds), pp. 20-36. Ottawa, Canada: International Development Research Centre, 277 pp.

MASSAL, E. and BARRAU, J. 1956. Taros and taro-like plants. Food plants of the south sea islands. South Pacific Commission Technical Paper, No. 94, pp. 6-11. Noumea, New Caledonia: South Pacific Commission, 51 pp.

MONTALDO, A. 1972. Ape. Cultivo de ra�ces y tub�rculos tropicales, pp. 244-245. Lima, Peru: Instituto Interamericano de Ciencias Agricolas de la OEA, 284 pp.

NAHRSTEDT, A. 1975. Cyanogenes der Arac�en. Phytochemistry, 14, 1339-1340.

NOZI�RES, M. 1982. The cultivation of taro, Alocasia macrorrhiza (L.) Schott. 2. The cultivation of 'kape' in Wallis. Taro Cultivation in the South Pacific. South Pacific Commission Handbook, No. 22 (Lambert, M., ed.), pp. 87-89. Noumea, New Caledonia: South Pacific Commission, 144 pp.

OPUTE, F. I. and OSAGIE, A. U. 1978. Identification and qualitative determination of the lipids of Alocasia macrorrhiza tubers. Journal of the Science of Food and Agriculture, 29, 1002-1006.

OSAGIE, A. U. 1977. Phytosterols in some tropical tubers. Journal of Agricultural and Food Chemistry, 25, 1222-1223.

PANCHO, J. V. 1959. Notes on cultivated aroids in the Philippines: the edible species. Baileya, 7 (1), 63-70.

PARHAM, B. E. V. 1942. Some useful plants of the Fiji islands. Fiji Agricultural Journal, 13 (2), 41.

PE�A, R. S. de la. 1970. The edible aroids in the Asian-Pacific area. Tropical Root and Tuber Crops Tomorrow: Proceedings of the 2nd International Symposium on Tropical Root and Tuber Crops (Hawaii, 1970) (Plucknett, D. L., ed.), Vol. 1, pp. 136-140. Honolulu, Hawaii: College of Tropical Agriculture, University of Hawaii, 171 pp. (2 vole).

PLOWMAN, D. L. 1969. Folk uses of new world aroids. Economic Botany, 23, 100.

PLUCKNETT, D. L. 1970. Status and future of the major edible aroids, Co/ocasia, Xanthosoma, Alocasia, Cyrtosperma and Amorphophallus. Tropical Root and Tuber Crops Tomorrow: Proceedings of the 2nd International Symposium on Tropical Root and Tuber Crops (Hawaii, 1970)

(Plucknett, O. L., ed.), Vol. 1, pp. 127-135. Honolulu, Hawaii: College of Tropical Agriculture, University of Hawaii, 171 pp. (2 vole).

PLUCKNETT, D. L. 1977. Current outlook for taro and other edible aroids. Regional meeting on the production of root crops (Fiji, 1975): Collected Papers. South Pacific Commission, Technical Paper, No. 174, pp. 36-39. Noumea, New Caledonia: South Pacific Commission, 213 pp.

PURSEGLOVE, J. W. 1972. Araceae. Tropical crops: Monocotyledons 1, pp. 58-74. London: Longman Group Ltd, 344 pp.

RASHID, M. M. and DAUNICHT, H. J. 1979. Chemical composition of nine edible aroid cultivars of Bangladesh. Scientia Horticulturae, 10, 127-134.

REARK, J. B. 1953. Cultivation of the genus Alocasia in Florida. Proceedings of the Florida State Horticultural Society, 66, 326-331.

ROTAR, P. P., PLUCKNETT, D. L. and BIRD, B. K. 1978. Bibliography of taro and edible aroids. University of Hawaii Agricultural Experiment Station Miscellaneous Publication, No. 158. Honolulu, Hawaii: University of Hawaii, 245 pp.

SAKAI, W. S. 1983. Aroid root crops: Alocasia, Cyrtosperma and Amorphophallus. Handbook of Tropical Foods (Chan, H. C. (Jr.), ed.), pp. 29-83. New York: Marcel Dekker Inc., 639 pp.

SOYZA, D. J. de. 1938. Yam cultivation in the Kegalla district. Tropical Agriculturist, 90, 71-79.

SRIVASTAVA, S. K. and KRISHNAN, P. S. 1959. Oxalalte content of plant tissues. Journal of Scientific and Industrial Research, 18C, 146-148.

SUNATHE, S. and PATTABIRANAN, T. N. 1977. Natural plant enzyme inhibitors V. A trypsin/chemotrypsin inhibitor from Alocasia macrorrhiza tuber. Biochimica et Biophysica Acta, 485 (1), 167-178.

VALENZUELA, A. and WESTER, P. J. 1930. Composition of some Philippine fruits, vegetables and forage plants. Philippine Journal of Science, 41, 85-102.