Sorghum
2007 Schools Wikipedia Selection. Related subjects: Plants
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About 30 species, see text |
Sorghum is a genus of about 30 species of grasses raised for grain, native to tropical and subtropical regions of Eastern Africa, with one species native to Mexico. The plant is cultivated in Southern Europe, Central America, North America and Southern Asia. Other names include Durra, Egyptian Millet, Feterita, Guinea Corn, Jowar, Juwar, Milo, Shallu and Sudan Grass.
Origin
Sorghum is a grass of East African origin, a drought-resistant, heat-tolerant member of the grass family.
Although wild species of sorghum are attested as early as 8000 years ago in the Nilotic regions of southern Egypt and the Sudan, the location of its true domestication within East Africa is still speculative. It is widely held that genetic separation of domesticated S. bicolor from its progenitor did not occur much before 2000 years ago somewhere in East Africa, possibly the Ethiopian Highlands, but more likely further west. The presence of true domesticated S. bicolor is claimed much earlier than this (3700-4900 years ago) in India, Oman, and Yemen, although the identity of the remains as full domesticates is still disputed. It is well adapted to growth in hot, arid or semi-arid areas. The many subspecies are divided into four groups - grain sorghums (such as milo), grass sorghums (for pasture and hay), sweet sorghums (formerly called " Guinea corn", used to produce sorghum syrups), and broom corn (for brooms and brushes). The name "sweet sorghum" is used to identify varieties of sorghum, Sorghum bicolor (L.) Moench, that are sweet and juicy. A United States patent officer introduced sweet sorghum to America in 1853.
Cultivation and uses
Sorghum is used for food, fodder, and the production of alcoholic beverages. It is drought tolerant and heat tolerant and is especially important in arid regions. It is an important food crop in Africa, Central America, and South Asia, and is the "fifth most important cereal crop grown in the world" . African slaves introduced sorghum into the U.S. in the early 17th century.
| Top Sorghum Producers - 2005 (in million metric tons (MMT)) |
|
|---|---|
 United States |
9.8 |
 India |
8.0 |
 Nigeria |
8.0 |
 Mexico |
6.3 |
 Sudan |
4.2 |
 Argentina |
2.9 |
 China |
2.6 |
 Ethiopia |
1.8 |
 Australia |
1.7 |
 Brazil |
1.5 |
| World Total | 58.6 |
| Source: UN Food & Agriculture Organisation (FAO) |
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The FAO reports that 440,000 square kilometres were devoted worldwide to sorghum production in 2004. In the US, sorghum grain is used primarily as a maize substitute for livestock feed because their nutritional values are very similar. Some hybrids commonly grown for feed have been developed to deter birds, and therefore contain a high concentration of tannins and phenolic compounds, which causes the need for additional processing to allow the grain to be digested by cattle. In arid, less developed regions of the world sorghum is an important food crop especially for subsistence farmers. It is used to make such foods as couscous, sorghum flour, porridge and molasses.
Bhakri, a variety of unleavened bread made from sorghum, is the staple diet in many parts of India such as Maharashtra and northern Karnataka. Bhakri is also sometimes made out of millet (" Bajari" in Marathi) flour.
In China, sorghum is the most important ingredient for the production of distilled beverages such as Maotai and kaoliang, as seen in the film Red Sorghum.
In the cuisine of the Southern United States, sorghum syrup is used as a sweet condiment, usually for biscuits, corn bread, pancakes, hot cereals or baked beans. It was used as the unavailable maple syrup is used in the North, although it is uncommon today.
Sorghum straw (stem fibres) can also be made into excellent wall board for house building, as well as biodegradable packaging. It does not accumulate static electricity, so it is also being used in packaging materials for sensitive electronic equipment.
Little research has been done to improve sorghum cultivars because the vast majority of sorghum production is done by subsistence farmers. The crop is therefore mostly limited by insects, disease and weeds, rather than by the plant’s inherent ability. To improve the plant’s viability in sustaining populations in drought prone areas, a larger capital investment would be necessary to control plant pests and ensure optimum planting and harvesting practices.
Recently, however, the US Congress passed the Renewable Fuels Standard, with the goal of producing 30 billion litres (8 billion gallons) of renewable fuel (ethanol) annually by 2012. This bill should noticeably increase the demand for ethanol producing crops for at least the next decade. Sorghum produces the same amount of ethanol per unit as maize, therefore in hot areas where sorghum can out-produce maize this bill should result in an increase in grain sorghum cultivation. Sorghum growers are hoping that this will create just the market they need to take off with production. Currently, 12% of grain sorghum production in the US is used to make ethanol, and growers are hoping for an increase.
Sorghum was used in Italian folk religions by the malevolent witches that fought the Benandanti.
Sorghum and beer
In Nigeria, Lesotho and South Africa, sorghum is used to produce beer, including the local version of Guinness. In recent years, sorghum has been used as a substitute for other grain in gluten free beer. Although the African versions are not " gluten free", as malt extract is also used, truly gluten free beer using such substitutes such as sorghum or buckwheat are now available. Sorghum is used in the same way as barley to produce a " malt" that can form the basis of a mash that will brew a beer without gliadin or hordein (together " gluten") and therefore can be suitable for coeliacs or others sensitive to certain glycoproteins.
Growing grain sorghum
Sorghum requires an average temperature of at least 25 °C to produce maximum grain yields in a given year. Maximum photosynthesis is achieved at daytime temperatures of at least 30 °C. Night time temperatures below 13 °C for more than a few days can severely impact the plant’s potential grain production. Sorghum cannot be planted until soil temperatures have reached 17 °C. The long growing season, usually 90–120 days, causes yields to be severely decreased if plants are not in the ground early enough.
Grain Sorghum is usually planted with a commercial corn seeder at a depth of 2–5 cm, depending on the density of the soil (shallower in heavier soil). The goal in planting, when working with fertile soil, is 50,000 to 300,000 plants per hectare. Therefore, with an average emergence rate of 75%, sorghum should be planted at a rate of 2–12 kg of seed per hectare.
It has been found that yields can be boosted by 10-15% when optimum use of moisture and sunlight are obtained by planting in 25 cm rows instead of the conventional 1 m rows. Sorghum, in general is a very competitive crop, and does well in competition with weeds in narrow rows. However, herbicides are still required to control the weed problem so that the plants produce an economically viable crop of grain.
Insect and diseases are not prevalent in sorghum crops. Birds, however, are a major source of yield loss. Hybrids with higher tannin content and growing the crop in large field blocks are solutions used to combat the birds. The crop may also be attacked by corn earworms, aphids, and some Lepidoptera larvae including Turnip Moth.
It is a very high nitrogen feeding crop. An average hectare producing 6.3 tonnes of grain yield requires 110 kg of nitrogen, but relatively small amounts of phosphorus and potassium (15 kg of each).
Sorghum’s growth habit is similar to that of maize, but with more side shoots and a more extensively branched root system. The root system is very fibrous, and can extend to a depth of up to 1.2 m. The plant finds 75% of its water in the top metre of soil, and because of this, in dry areas, the plant’s production can be severely affected by the water holding capacity of the soil. The plants require up to 70–100 mm of moisture every 10 days in early stages of growth, and as sorghum progresses through growth stages and the roots penetrate more deeply into the soil to tap into hidden water reserves, the plant needs progressively less water. By the time the seed heads are filling, optimum water conditions are down to about 50 mm every 10 days. Compacted soil or shallow topsoil can limit the plants ability to deal with drought by limiting its root system. Since these plants are designed to grow in hot, dry areas, it is essential that the soil is kept from compacting and that they are grown on land with ample cultivated topsoil.
Wild species of sorghum tend to grow to a height of 1.5–2 m; however, due to problems this height created when the grain was being harvested, in recent years cultivars with genes for dwarfism have been selected, resulting in sorghum that grows to between 60 and 120 cm tall.
Sorghum's yields are not affected by short periods of drought as severely as other crops such as maize because it develops its seed heads over longer periods of time, and short periods of water stress do not usually have the ability to prevent kernel development. Even in a long drought severe enough to hamper sorghum production, it will still usually produce some seed on smaller and fewer seed heads. Rarely will you find a kernelless season for sorghum, even under the most adverse water conditions. Sorghum's ability to thrive with less water than maize may be due to its ability to hold water in its foliage better than maize. Sorghum has a waxy coating on its leaves and stems which helps to keep water in the plant even in intense heat.
Species
- Sorghum almum
- Sorghum amplum
- Sorghum angustum
- Sorghum arundinaceum
- Sorghum bicolor
- Sorghum brachypodum
- Sorghum bulbosum
- Sorghum burmahicum
- Sorghum controversum
- Sorghum drummondii
- Sorghum ecarinatum
- Sorghum exstans
- Sorghum grande
- Sorghum halepense
- Sorghum interjectum
- Sorghum intrans
- Sorghum laxiflorum
- Sorghum leiocladum
- Sorghum macrospermum
- Sorghum matarankense
- Sorghum miliaceum
- Sorghum nitidum
- Sorghum plumosum
- Sorghum propinquum
- Sorghum purpureosericeum
- Sorghum stipoideum
- Sorghum timorense
- Sorghum trichocladum
- Sorghum versicolor
- Sorghum virgatum
- Sorghum vulgare
Hybrids
- Sorghum × almum
- Sorghum × drummondii