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Advice on Publications Available.A preliminary investigation
Maboko Samuel Mposi
University of the North
South Africa
Email: MPOSIM@unin.unorth.ac.za
[These notes have been extracted from a report prepared by Mr Mposi following his six months as a Masters exchange student with the New Crops Group at the University of Queensland Gatton College, from July to December, 1998.]
The genus Amaranthus consists of nearly 60 species that can be broadly categorised into grain, green leaf vegetable and weed types.
Amaranth is cultivated as a minor food crop in Central and South America, Mexico and parts of Asia and Africa and is extensively grown as a green leaf vegetable in many tropical countries. There is no distinct separation between the vegetable and grain type since the leaves of young grain type plants can be eaten as greens.
In Africa, Amaranthus hybridus and Amaranthus thunberghii are the species most commonly used for this purpose. They are grown occasionally by farmers in west Africa but not in southern Africa.
Amaranthus hybridus is grown for grain or vegetable production in the south-western United States, China, India, Africa, Nepal, the South Pacific islands, in the Caribbean region, Greece, Italy and Russia.
Amaranthus hybridus is fast growing, requires little cultivation, is resistant to moisture stress and produces a good yield of grain in Sorghum-like heads.
However, it is a very difficult crop to establish because its grain is small and needs to be planted in a shallow seedbed to ensure germination. Since the seeds are so close to the surface, rain or irrigation can wash out recently planted fields.
There is less research on Amaranthus thunberghii. It has been classified as an aphid-trap plant and as a broadleaf weed by the commercial farmers of other crops. However, it grows very fast and is resistant to water stress. It is also tolerant to many insect pests such as aphids, fall army worm etc.
Amaranthus thunberghii has a more prostrate growth habit than its relatives and tends to be frequently seen growing on roadsides and in gardens, than in cropping areas.
These two species of Amaranth have not caught the imagination of the scientific research establishment in the southern African countries even though they are consumed by the rural-based indigenous people.
The genus Amaranthus consists of approximately 60 species. Only a few of these are cultivated types, while most are considered weedy species.
The origin of Amaranth is obscure. Some authors believe that amaranth originated in Central and South America because it was a staple crop of the ancient Aztec and Inca civilizations.
Nigeria has also been claimed as the centre of diversity, collaborated by the prevalent use of local names and the enormous genetic diversity available there.
Amaranth germplasm is available in at least eleven different countries and several thousand germplasm accessions are available in the United States.
The principal Amaranth weed, red ragwort is Amaranthus retroflexus.
Amaranthus retroflexus is one of the world's most cosmopolitan weeds.
Amaranth is a C4 plant, and this characteristic is believed to have contributed to the plant's wide geographic adaptability to diverse environmental conditions.
However in cultivation, every aspect of production requires special attention and consideration. Twentieth century Amaranth production is vastly different from that of earlier civilisations and from modern day primitive agriculture systems.
Amaranth prefers soils with pH above 6 and soil temperatures above 15 C for establishment. Seeding rates of 1.2 to 3.5 kg seed/ha planted to an average depth of 1.3 cm are recommended. The most accurate commercial seeding rates have been achieved by using vegetable seeders which use seed plates of appropriate size to metre the seed.
The most commonly advised fertility guide for Amaranth has been 112 to 135 kg/ha of total available N, with a soil test of 15 to 30 ppm P and 80 to 120 ppm K. Fertility needs vary significantly in higher rainfall areas.
Established plant population density has a significant effect if the amaranth is being grown for grain yield, with the highest yields achieved at the lowest populations.
Harvesting for vegetable use is usually carried out by cutting the plants above the second leaf from the ground, at a height of about 7.5 cm, after they have attained a marketable size. Cutting is done at various lengths (15 to 23 cm) in the first instance, and subsequently, branches are included. The height from the ground and time intervals between harvests are not standardised and these parameters affect the yield.
Alternatively, harvesting is done by uprooting the whole plant at an earlier stage and bunching together for sale after washing the roots. The quality of the vegetable is affected by flowering. Plants that are flowering are not harvested but are left to seed.
Amaranth has shown that it benefits from intercropping with species such as Celosia and/or Corchorus.
Pests and diseases can be important problems with amaranth production.
At the National Horticultural Research Institute in Nigeria, many amaranth lines have failed due to wet rot of leaves and young stalks, caused by Choenephora cucurbitarium.
A principal insect pest is the lygus bug (Lygus lineolarius), which can extensively damage the flowering head. Under Australian conditions, the Lixus weevil (Lixus masterii) can cause severe damage to the stems of plants.
Amaranth can also suffer injury from the Fall Armyworm (Spodoptera frugiperda) and the curly top virus disease, which is transmitted by the beet leafhopper (Circulifer temellus).
If the leaves are harvested, it is traditional in west Africa to soak the plant in water before transporting it to the market as this gives the leaves a fresh look. The leaves are arranged in bunches that are usually spread on a raffia tray in the market stalls or else hawked in the street. Since evaporation takes place rapidly, more water is sprinkled on the leaves at regular intervals.
Amaranth is one of the very few double-duty plants.
The grain contains a high level of protein, perhaps averaging 15%, with an amino acid balance that means it can supplement the amino acids found in a diet that is high in cereals (which are deficient in lysine) and legumes (which are deficient in the sulphur amino acids).
The leaves can be used as a tasty leafy vegetable, often preferred to spinach by some people.
Amaranth leaf protein contains more lysine than the best high-lysine corn and more methionine than soybean meal. Vegetable amaranth can also be used in feed lots for cattle or other intensively reared animals.
Amaranthus species demonstrate high levels of variability in leaf size, leaf shape, bolting pattern, growth and regrowth ability, number of economic branches, and colour.
Amaranth offers more genetic diversity in its present undeveloped state than do many widely grown crops.
The wide geographical spread of the genus has resulted in the evolution of many land races in widely separated areas. The huge gene pool will be very important to the future development of the crop.
The success of the South African amaranth industry must be based on the areas where the crop is in high demand.
Such areas would be rural areas where the crop is known well by the consumers and this can only be done properly if a marketing chain is developed with active links at each level.
Reading
Becker, R, EL Wheeler, K Lorenz, AE Stafford, OK Grosjears, AA Betschart and RM Sanders (1981) A composition study of amaranth grain. Journal of Food Science 46: 1175-1180.
Brenner, D and Haupti, H (1990) Seed shattering control with indehiscent utricles in grain amaranth seed oil. Legacy 3: 2-3. American Amaranth Institute, Bricelyn, Minnesota, USA.
Bharat, PS and FW Wayne (1991) Population density and soil pH effects on vegetable amaranth production In J Janick and JE Simon (ed) 'New crops' John Wiley and Sons Inc. pp 562-4.
Feine, LB, RR Harwood, CS Kauffin and JP Senft (1979) Amaranth, gentle giant of the past and future. In GA Ritchie (ed) 'New agricultural crops' Westview Press, Boulder, Colorado, pp 41-63.
Grubben, GJH (1976) Cultivation of amaranth as a tropical leaf vegetable Amsterdam, Department of Agriculture, Royal Tropical Institutes, p 67.
Ikeorgu, JEG (1990) Glasshouse performance of three leafy vegetables grown in mixtures in Nigeria. Scientia Horticulturae 43: 181-8.
Makus, DJ (1989) Aluminium accumulation in vegetable amaranth grain in a soil with adjusted pH value. Hortscience 24: 460-3.
National Academy of Sciences (1985) Amaranth: Modern prospects for an ancient crop. National Academy of Sciences, Washington DC.
Opeke, LK (1963) Final report of the vegetable breeding programme of the Research Division of the Moore Plantation, Ibadan, Nigeria.
Whiting, MM (1994) Genetic variability in grain amaranth, including response to attack by the Lixus weevil (Lixus mastersi). Final Year Study project, The University of Queensland Gatton College.
Any claims made by authors in the Australian New Crops Newsletter are presented by the Editors in good faith. Readers would be wise to critically examine the circumstances associated with any claims to determine the applicability of such claims to their specific set of circumstances. This material can be reproduced, with the provision that the source and the author (or editors, if applicable) are acknowledged and the use is for information or educational purposes. Contact with the original author is probably wise since the material may require updating or amendment if used in other publications. Material sourced from the Australian New Crops Newsletter cannot be used out of context or for commercial purposes not related to its original purpose in the newsletter
Contact: Dr Rob Fletcher, School of Land and Food, The University of Queensland Gatton College, 4345; Telephone: 07 5460 1311 or 07 5460 1301; Facsimile: 07 5460 1112; International facsimile: 61 7 5460 1112; Email:
r.fletcher@mailbox.uq.edu.au[
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