3. Sorghum and millet new roles for old grains.
SPORE, 29, 1992, p. 6
As Africa strives to close the gap between population and food production, sorghum and millet will become of increasing importance.
This will be especially so where weather patterns are unpredictable because maize is much less adaptable to inadequate erratic rainfall.
There are two broad categories of sorghum; red or brown sorghums, which often contain bitter tasting tannins in the seed coat, and white sorghums, which do not. The tannins deter predators but must be removed in order to make grain acceptable for human consumption.
Sorghum is both drought-resistant and able to tolerate waterlogging better than maize because of its deep and well-branched root system. It is also remarkably pest-resistant, but unfortunately the compounds that help protect the crop from birds and insects make the grain and the stover less palatable and less digestible for people and livestock.
There are also two major types of millet; finger millet and bulrush millet. They are very different in appearance. The grain of finger millet is contained in a "hand" of digits (hence the name) and the plant seldom grows higher than 1.3 metres. Bulrush millet can grow to 3 metres. Millets are even more drought resistant than sorghum and can give good yields on infertile, sandy soil which would be unsuitable for most cereals. But millets are very susceptible to bird damage and, as more children attend school and are not available to scare birds, this can cause considerable losses. Farmers are also inclined to switch to maize, as has happened in Kenya and Tanzania, because millets and sorghum demand a great deal more work to harvest, store and process.
Sorghum and millet are very similar to maize in their nutritional value.
Traditionally both grains are prepared by pounding to remove the husks but, millet and sorghum flour does not keep well and fresh flour has to be prepared regularly. New techniques for easier processing are urgently needed and there have been some promising developments in mechanical decortication.
A dry abrasive technique for milling of the husk off sorghum was developed from a Canadian design and promoted by the International Development Research Centre (IRDC). About 40 machines were made locally and installed in Botswana, and trials and demonstrations set up in several other SADCC countries. These decorticators proved well-suited to small-scale operations, as the cost of equipment is low. The cost of transportation of grain and products to and from the mill is minimized, employment is created in rural areas and, when milling a reasonably pure strain of white sorghum, a high yield of excellent quality product can be obtained. However, it is more difficult to process mixed crops to acceptable levels of colour and taste.
An alternative technique for semi-wet milling of sorghum has been developed by the UK Natural Resources Institute (NRI). The whole sorghum grain is wetted with up to 25% water and after 12 hours the conditioned grain is milled in a roller mill in the same way as maize or wheat. Even in highly bird resistant varieties of red sorghum the endosperm is normally white, and using this technique the white endosperm is effectively separated, leaving the bran and most of the coloured layers clean and almost intact.
Semi-wet milling is not the answer for all situations, however, since it is unlikely that the process will be economically viable at a throughout of less than two tonnes per hour. Also, the meal produced has over 20% moisture and is unsuitable for long-term storage.
If techniques can be perfected to make sustainable use of much larger quantities of millet and sorghum (particularly red sorghum), which can be grown on the extensive and still under-utilized semi-arid lands of Africa, the consequences will be profound and far reaching: on food security, on rural employment and on agricultural income in many parts of the continent.
Pearl millet (Pennisetum glaucum) f.e. like sorghum was domesticated in Africa but can withstand more heat and drought stress and yet reliably produce a nutritious grain crop. While new advances can be made in the forage crop using recently discovered low lignin bmr genes, pearl millet has many attributes which are being used to transform it into a summer combine grain crop for temperate agriculture. These include a very large and varied germplasm resource base, a high growth rate, efficient nutrient utilization, major dwarfing genes, earliness, good heterosis, and several cytoplasmic-genic malesterile systems for hybrid seed production. Seed is produced commercially in India of semi-dwarf grain hybrids which cover 2 million ha annually. Under optimum conditions, the yield potential of these early maturing (85-90 days) hybrids is high - 5000 kg/ha.
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Review, book, developing countries, arid regions, saline agriculture, salt tolerant plants, food, fuel, fodder, fiber
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