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Original:Root Crops 19
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Root crops (NRI, 1987, 308 p.)
Hausa potato (Solenostemon rotundifolius)
HAUSA POTATO, Coleus potato, Country potato.
Solenostemon rotundifolius (Poir.) J. K. Morton syn. Coleus rotundifolius Chev. and Perrot.
Fra-fra potato (Gh.); Innala (Sri La.); Kembili (Mal.); Ketang (Indon.); Koorka (Ind.); Madagascar potato (Fr.); Ratala (Sri La.); Saluga (Nig.); Sudan potato, Tumuku (Nig.); Vatke (Eth.).
A small, herbaceous annual, IS-30 cm high, prostrate or ascending, with a succulent stem and somewhat thickish leaves having an aromatic smell resembling that of mint. Flowers are small, pale violet in colour, produced on an elongated terminal raceme. Small dark-brown tubers are produced in clusters at the base of the stem.
Origin and distribution
The hausa potato is believed to have originated in central or east Africa, but was early spread throughout tropical Africa and into South-East Asia, including India, Sri Lanka, Malaysia and Indonesia, where it is cultivated on a small scale.
Temperature and rainfall - the plant is suited to high rainfall areas; evenly-distributed rainfall and low night temperatures favour the development of tubers. It is grown in India as a monsoon crop and is sometimes grown under irrigation in West Africa.
Soil - optimum yields are obtained on well-drained, sandy loams; heavy clay soils are unsuitable. The plant cannot stand waterlogging and is usually grown on ridges, except in very well-drained soils. Waterlogging causes deformities to the tubers and reduces yields considerably. The inclusion of 25 t/ha of FYM at planting is recommended, and subsequently application of a 16:8:8 complete (NPK) fertiliser at the rate of 125 kg/ha.
Material - generally propagated by suckers obtained from germinating tubers.
Method - selected tubers from the previous harvest are usually planted in raised, well-manured, nursery beds, approximately 90-120 cm wide and any convenient length. The tubers are planted in rows 5 x 15 cm about 4 cm deep. If the soil is dry the beds are irrigated to start growth and this is continued if necessary. The tubers germinate in 10-15 days, and give rise to a cluster of sprouts, which are ready for transplanting to the field after about 3 months. In Sri Lanka three methods of planting out are commonly used: Ordinary planting - cuttings about 15 cm long and having three or four leaves at the top end are planted 7 cm deep in rows down the ridges 22 cm apart. Coiled planting - cuttings about 22 cm long are used and about 12 cm of the more mature portion is coiled and planted in holes about 7 cm wide and 5 cm deep. Horizontal planting - cuttings about 30 cm long are placed horizontally across the ridge, two at a time, in opposite directions and almost touching each other. About 22 cm of the cuttings remain on the ridge and 7 cm outside and there is about 7 cm between each pair of cuttings. Of these three methods, coiled planting is reported to give the best results.
In some areas, eg Madras (India), the seed tubers are planted in a corner of the field and about a month after germination the top suckers, with four or five leaves, are ripped off and planted 15-20 cm apart in another part of the field. These quickly become established and in about another fortnight a further set of suckers is available for planting out. In this way in about 2 months a hectare of planting material is obtained from an initial 0.2 ha, and relatively few tubers.
Once planted out the crop is normally cultivated twice to control weeds, once about 3 weeks after planting, and then one month later. At the latter, the plants are earthed up to encourage the production of tubers.
Field spacing - in Sri Lanka the hausa potato is usually planted at about 22 cm spacing on ridges 90 cm apart; in India a slightly closer spacing of 15-20 cm along the ridge is sometimes used.
Seed rate - in Sri Lanka about 50 000 plants/ha are required: these are obtained from cuttings taken from nurseries and raised in three different ways. The following figures indicate the number of tubers planted in the nursery to provide the necessary number of cuttings to plant one hectare: ordinary planting 20 000 tubers; coiled planting 40 000 tubers; horizontal planting 60 000 tubers.
In India, where top suckers are taken at intervals from a nursery bed, 2 500 tubers will produce enough suckers to plant one hectare.
Pests and diseases
The hausa potato is relatively free from pests and diseases though Pycnarmon cribata, Phostria piasusalis and a leaf folder, Hymenia curvalis, have been reported from India as being important. These have been controlled by spraying with pesticides such as dimethoate.
The crop normally reaches maturity in 5-6 months in Sri Lanka, West Africa and Malaysia, and 6-8 months in India. (It has been reported that tuber initiation may be accelerated by about 2 weeks by treatment of the young plants with chlormequat or ethephon (ethrel).)
Harvesting and handling
The tubers are ready for harvesting when the leaves begin to wither, and are normally dug by hand. Harvesting cannot be delayed as the mature tubers deteriorate rapidly if left in the soil, but they can be stored successfully in dry sand or in a cool, well-ventilated shed.
Tubers - these resemble the potato, but are smaller, with an aromatic sweetish flavour. In Sri Lanka, two main types are recognised, the small-tubered type favoured for its delicate flavour and the larger type that produces heavier crops which are easier to harvest. In West Africa, there are three recognised types: nigra, widespread in Mali, with small tubers and blackish skin; rubra, with small reddish-gray or reddish-yellow tubers; and alba, which is whitish.
Yields normally range from 7 to 15 t/ha, although under very favourable conditions they may reach 18-20 t/ha.
The tubers can be used as a potato substitute and are usually cooked in a curry and eaten with rice, but they can also be boiled, baked or fried similarly to potato chips.
In Africa, the hausa potato is sometimes used in the treatment of dysentery and in the treatment of certain eye disorders.
The composition of the edible portion of the tubers has been quoted as: water 75 per cent; protein 1.4 per cent; fat 0.5 per cent; carbohydrate 21 per cent; fibre 0.7 per cent; ash I per cent; calcium 17 mg/100 g; iron 6 mg/100 g; thiamine 0.05 mg/100 g; riboflavin 0.02 mg/100 g; niacin 1 mg/100 g; ascorbic acid Img/100 g. The principal amino acids in the protein are arginine, aspartic and glutamic acids.
Although formerly of considerable importance as a staple foodstuff in tropical Africa, the hausa potato has been largely replaced by other starchy foodstuffs, such as cassava and potatoes, and production has declined to such an extent that it has almost disappeared in many areas.
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