J M J de Wet. Cambridge World History of Food. Editor: Kenneth F Kiple & Kriemhild Conee Ornelas. Volume 1. Cambridge, UK: Cambridge University Press, 2000.
Grain sorghum (Sorghum bicolor [Linn.] Moench) is a native African cereal now also widely grown in India, China, and the Americas. Sorghum ranks fifth in world cereal grain production, and fourth in value (after rice, wheat, and maize) as a cereal crop. It is grown on 40 to 50 million hectares annually, from which up to 60 million metric tons of grain are harvested. In Africa and Asia traditional cultivars are grown, usually with low agricultural inputs, and average yields are below 1 metric ton per hectare. But more than 3 metric tons of grain are harvested per acre in the Americas, where farmers plant modern sorghum hybrids. Sorghum is more tolerant to drought and better adapted for cultivation on saline soils than is maize. It holds tremendous promise as a cereal to feed the rapidly expanding populations of Africa and Asia. In the Americas it is replacing maize as an animal feed.
Morphology and Distribution
The grass genus Sorghum Moench is one of immense morphological variation. It is taxonomically subdivided into sections Chaetosorghum, Hetero-sorghum, Parasorghum, Stiposorghum, and Sorghum (Garber 1950), and these sections are recognized as separate genera by W. D. Clayton (1972). The genus Sorghum is here recognized to include: (1) a complex of tetraploid (2n = 40) rhizomatous taxa (S. halapense [Linn.] Pers.) that are widely distributed in the Mediterranean region and extend into tropical India; (2) a rhizomatous diploid (2n = 20) species (S. propinquum[Kunth] Hitchc.) that is distributed in Southeast Asia and extends into adjacent Pacific Islands; and (3) a nonrhizomatous tropical African diploid (2n = 20) complex (S. bicolor [Linn.] Moench) that includes domesticated grain sorghums and their closest wild and weedy relatives (de Wet and Harlan 1972). Genetic introgression is common where wild rhizomatous or spontaneous nonrhizomatous taxa become sympatric with grain sorghums, and derivatives of such introgression have become widely distributed as weeds in sorghum-growing regions.
The domesticated sorghum complex is morphologically variable. It includes wild, weed, and domesticated taxa that are divided by J. D. Snowden (1936, 1955) among 28 cultivated species, 13 wild species, and 7 weed species. Following the classification of cultivated plants proposed by Jack R. Harlan and J. M. J. de Wet (1972), the wild taxa are recognized as sub-species verticilliflorum (Steud.) de Wet, the weed taxa as subspecies drummondii (Steud.) de Wet, and the grain sorghums as subspecies bicolor (de Wet and Harlan 1978).
Subspecies verticilliflorum includes races verticilliflorum, arundinaceum, virgatum, and aethiopicum. These grade morphologically and ecologic ally so completely into one another that they do not deserve formal taxonomic rank. This subspecies is indigenous to tropical Africa but has become widely distributed as a weed in tropical Australia (de Wet, Harlan, and Price 1970). It differs from grain sorghum primarily in being spontaneous rather than cultivated and in being capable of natural seed dispersal.
Verticilliflorum is the most widely distributed, and morphologically the most variable, race of the sub-species. It extends naturally across the African savannah, from Senegal to the Sudan and South Africa. It is distinguished from the other races by its large and open inf lorescences with long and spreading branches. Verticilliflorum is an aggressive colonizer of naturally disturbed habitats, and it often forms large continuous populations in flood plains. It is commonly harvested as a wild cereal in times of scarcity.
Race arundinaceum is distributed along the margins of tropical forests of the Congo basin. It is sympatric with verticilliflorum along the transition zone between savannah and forest, and the races introgress. Derivatives of such hybridization aggressively colonize areas of forest that are cleared for agriculture. Arundinaceum is typically characterized by large and open inflorescences with long branches that become pendulous at maturity.
Race virgatum occurs along stream banks and irrigation ditches in arid regions of tropical northeastern Africa. Wild populations are harvested as a cereal during times of famine. It is widely sympatric with race verticilliflorum, and gene exchange between them is common. It typically has smaller inflorescences than verticilliflorum.
Race aethiopicum is drought tolerant. It extends across the West African Sahel and into the Sudan. In flood plains, it frequently forms large continuous populations and is harvested as a wild cereal. The distribution and habitat of aethiopicum rarely overlap with the other races. It is characterized by large spikelets that are densely tomentose.
Subspecies drummondii is an obligate weed derived through introgression between subspecies verticilliflorum and cultivated grain sorghums. It became widely distributed across tropical Africa as part of cereal agriculture. Morphological variation is extensive as a result of hybridization among the different races of grain sorghum and different races of close wild relatives. Stabilized derivatives of such introgression accompanied the cereal to India and the highlands of Ethiopia. Weeds often resemble grain sorghums in spikelet morphology, but they retain the ability of natural seed dispersal.
Grain sorghums also introgress with the Eurasian S. halepense to form diploid or tetraploid weedy derivatives. Johnson grass of the American Southwest and some sorghums of Argentina are tetraploid derivatives of such introgression. Diploid derivatives of hybridization between grain sorghum and Johnson grass have recently become obnoxious weeds in the American corn belt.
Subspecies bicolor includes all domesticated grain sorghums. The 28 cultivated species recognized by Snowden (1936) are artifacts of sorghum cultivation. They represent selections by farmers for specific adaptations and food uses, and they do not deserve formal taxonomic rank. Grain sorghums are classified by Harlan and de Wet (1972) into races bicolor, kafir, caudatum, durra, and guinea. Sorghums belonging to different races hybridize where they are grown sympatrically, and cultivars have become established that combine characteristics of two or more of these races. Extensive racial evolution took place in Africa before sorghum was introduced as a cereal into Asia (Harlan and Stemler 1976).
Race bicolor resembles spontaneous weedy sorghums in spikelet morphology, but all cultivars depend on harvesting for seed dispersal. Mississippi chicken corn probably represents a derivative of abandoned cultivated race bicolor that entered America during the slave trade. It is spontaneous and must have regained the ability of natural seed dispersal through mutation. Bicolor sorghums are characterized by open inflorescences, having spikelets with long and clasping glumes that enclose the grain at maturity. Some cultivars of race bicolor are relics of the oldest domesticated sorghums, whereas others are more recent derivatives of introgression between evolutionally advanced cultivars and spontaneous sorghums.
Bicolor sorghums are widely distributed in Africa and Asia but are rarely of major economic importance because of their low yield. Cultivars survive because they were selected for specific uses. They are grown for their sweet stems (chewed as a delicacy), for the high tannin content of the grains (used to flavor sorghum beer), and for use as fodder. Cultivars often tiller profusely, which tends to make their sweet stems desirable as fodder for livestock in Africa.
Race kafir is the most common cultivated sorghum south of the equator in Africa. It never became widely distributed in India and China, probably because of limited trade between southern Africa and India or the Near East before colonial times. Race kafir is characterized by compact inflorescences that are cylindrical in shape. Spikelets have glumes that tightly clasp the usually much longer mature grain. Sorghum has been replaced by maize in areas with high rainfall, but kafir sorghums remain the most important cereal crop of the southern savannahs in areas with between 600 and 900 millimeters (mm) of annual rainfall. At the drier limits of agriculture, sorghum is replaced as a cereal by pearl millet. In the wettest parts, sorghum competes as a food cereal not only with maize but also with finger millet. The grain of kafir sorghums is commonly high in tannin. This provides partial protection against bird damage and confers resistance to grain molds that reduce grain quality. Tannin also, however, reduces the digestibility of porridges produced from kafir sorghums, which today are grown mainly to produce malt for the making of a highly nutritious beer. This beer is commercially produced in Zimbabwe and South Africa.
Race caudatum is distinguished by its asymmetrical grains. The grain is usually exposed between the glumes at maturity, with the embryo side bulging and the opposite side flat or concave. Inflorescences range from very compact to rather open with spreading branches. Caudatum cultivars are highly adaptive and are grown in areas with as low as 350 mm and as high as 1,000 mm of annual rainfall. Selected cultivars are resistant to fungal leaf diseases, to ergot of the grain, and to infestation by insects or the parasitic striga weed. Caudatum sorghums are a major food source of people speaking Chari-Nile languages in the Sudan, Chad, Uganda, northeastern Nigeria, and Cameroon (Stemler, Harlan, and de Wet 1975). Along the flood plains of the Niger River in Chad, caudatum sorghums are grown in nurseries and transplanted to cultivated fields as flood waters recede (Harlan and Pasguereau 1969).The grains are ground into flour from which a fermented porridge is produced. Caudatum sorghums are also commercially grown in Nigeria for the production of malt used in the brewing industry.
Race durra is the most drought tolerant of grain sorghums. Selected cultivars mature in less than three months from planting, allowing escape from terminal drought stress in areas with short rainy seasons. The name durra refers to the Arabic word for sorghum, and the distribution of durra sorghums in Africa is closely associated with the spread of Islam across the Sahel. The grain is also extensively grown in the Near East, China, and India. Inflorescences are usually compact. Spikelets are characteristically flattened and ovate in outline, with the lower glume either creased near the middle or having a tip that is distinctly different in texture from the lower two-thirds of the glume. Grains are cooked whole after decortication or are ground into flour to be prepared as porridge or baked into unleavened bread.
Race guinea is distinguished by long glumes that tightly clasp the obliquely twisted grain, which becomes exposed between them at maturity. Inflorescences are large and often open, with branches that become pendulous at maturity. These are adaptations for cultivation in areas with high rainfall, and guinea is the principal sorghum of the West African Guinea zone with more than 800 mm of annual rainfall. Guinea sorghums are also grown along the high-rainfall highlands from Malawi to Swaziland and in the ghats of Central India. It is a principal food grain in West Africa and Malawi. In Senegal, the small and hard grains of an indigenous cultivar are boiled and eaten, similar to the way rice is prepared and consumed in other parts of the world. In Malawi, the sweet grains of a local cultivar are eaten as a snack while still immature. Guinea sorghums are valued for the white flour that is produced from their tannin-free grains.
Intermediate races recognized by Harlan and de Wet (1972) include sorghum cultivars that are not readily classifiable into any one of the five basic races. They combine characteristics of race bicolor with those of the other four basic races, of guinea and cau-datum, or of guinea and kafir. Cultivars with intermediate morphologies occur wherever members of basic races are grown sympatrically in Africa. Intermediate cultivars have become widely distributed in India. Modern high-yielding sorghum hybrids combine traits of races kafir, durra, and caudatum in various combinations.
Domestication and Evolutionary History
Cereal domestication is a process, not an event. Domestication is initiated when seeds from planted populations are harvested and sown in human-disturbed habitats (in contrast to naturally disturbed habitats), and it continues as long as the planting and harvesting processes are repeated in successive generations (Harlan, de Wet, and Price 1973). The initial ability to survive in disturbed habitats is inherent in all wild grasses that were adopted as cereals. In fact, as aggressive colonizers, they can form large continuous colonies in naturally disturbed habitats. This weedy characteristic of these plants facilitates harvesting and eventually leads to their domestication. Sowing in cultivated fields reinforces adaptation for survival in disturbed habitats, and harvesting of sown populations selects against mechanisms that facilitate natural seed dispersal. Thus, domesticated cereals have lost the ability to compete successfully for natural habitats with their wild relatives. They depend on farming for suitable habitats and on harvesting and sowing for seed dispersal.
There is little doubt that subspecies verticilliflorum gave rise to grain sorghums under domestication. This spontaneous complex of tropical African sorghums is an aggressive colonizer of naturally disturbed habitats, and because it forms large continuous stands, it remains a favorite wild cereal of nomads as well as farmers during times of food scarcity. Snow-den (1936) and R. Porteres (1962) have suggested that race arundinaceum (of forest margins) gave rise to guinea sorghums, the desert race aethiopicum to durra sorghums, and the savannah race verticilliflorum to kafir sorghums. Distribution and ethnological isolation certainly suggest three independent domestications of grain sorghum. This, however, is unlikely. Close genetic affinities between specific cultivated races and the spontaneous races with which they are sympatric resulted from introgression. Such introgression continues between grain sorghums and their close, spontaneous relatives. Racial evolution of advanced cultivated races resulted from selection by farmers who grew bicolor sorghums for specific uses, and from natural adaptations to local agro-ecological environments.
The wild progenitor of cultivated sorghums is the widely distributed race verticilliflorum. It could have been domesticated anywhere across the African savanna. Jack Harlan (1971) proposes that sorghum was taken into cultivation along a broad band of the savanna from the Sudan to Nigeria, where verticilliflorum is particularly abundant. H. Dogget (1965) previously had suggested that the initial domestication occurred in the northeastern quadrant of Africa, probably undertaken by early farmers in Ethiopia who learned from the ancient Egyptians how to grow barley and wheat. These two Near Eastern cereals have been grown in Egypt and along the Mediterranean coast of North Africa since at least the fifth century B.C. (Clark 1971).
Tropical agriculture in Africa must have started in the savannah along the southern fringes of the Sahara (Clark 1976, 1984). Archaeological evidence indicates that pearl millet (Pennisetum glaucum [Linn.] R. Br.), sorghum, and finger millet (Eleusine coracana [Linn.] Gaertn.) were among the earliest native cereals of the savannah to be domesticated.
J. S. Wigboldus (1991) has suggested that there is little evidence to indicate cereal cultivation south of the Sahara before the ninth century of the Christian era. Archaeological evidence, however, indicates that cereal agriculture in the African savanna is much older than this. Inhabitants of the Dhar Tichitt region of Mauritania, extending from the middle of the second to the middle of the first millennium B.C., evidently experimented with the cultivation of native grasses (Munson 1970). During the first phase of settlement, bur grass (Cenchrus biflorus Roxb.) seems to have been the most common grass harvested as a wild cereal. It is still extensively harvested in the wild as a source of food during times of scarcity. In the middle phases, Brachiaria deflexa (Shumach.) Hubbard, now cultivated on the highlands of Mali (Porteres 1976), and Pennisetum glaucum, now grown as pearl millet across the Sahel, became equally common, as shown by their impressions on potsherds. In later phases, starting about 1000 B.C., impressions of what is almost certainly domesticated pearl millet became dominant (Munson 1970). It is not possible, however, to determine whether pearl millet was domesticated at Dhar Tichitt or whether this cereal was introduced to these settlements from other parts of the West African Sahel.
Tropical African grasses were also grown as cereals in eastern Africa before the beginning of the Christian era. Potsherds from a Neolithic settlement at Kadero in the central Sudan, dated to between 5,030 and 5,280 years ago, reveal clear impressions of domesticated sorghum and finger millet spikelets and grains (Klichowska 1984). Both cereals are today extensively grown in eastern and southern Africa. Indirect evidence of early sorghum and finger millet cultivation in Africa comes from the presence of these African cereals in Neolithic settlements of India, dated to about 1000 B.C. (Weber 1991). Other archaeological evidence indicates that sorghum cultivation spread from eastern Africa to reach northeastern Nigeria not later than the tenth century A.D. (Connah 1967) and, together with pearl millet and finger millet, reached southern Africa not later than the eighth century A.D. (Shaw 1976).
That native grasses were grown as cereals not less than 3,000 years ago along the southern fringes of the Sahara is not surprising. Wheat and barley were grown in Egypt and along the Mediterranean coast of North Africa by the latter part of the fifth millennium B.C. (Shaw 1976), and the knowledge of cereal agriculture reached the highlands of Ethiopia some 5,000 years ago. These Near Eastern cereals cannot be grown successfully as rain-fed crops in lowland tropics. Experimentation with the cultivation of native grasses in the semiarid tropical lowlands seems a logical next step in the development of African plant husbandry. Nor is the absence of domesticated sorghum in West Africa before the tenth century A.D. surprising. Sorghum is poorly adapted to the arid Sahel, where finger millet was domesticated and remains the principal cereal, and an abundance of wild food plants and animals probably made agriculture in the Guinea zone less productive than hunting and gathering during the beginnings of plant husbandry in tropical Africa. Racial evolution gave rise to races guinea, caudatum, durra, and kafir and is associated with adaptation to agro-ecological zones and the isolation of different ethnic groups who adopted sorghum cultivation. Morphological differentiation took place in Africa, except for race durra that may have evolved in Asia after sorghum cultivation became established in southwestern Asia.
Race guinea’s open panicles and spikelets with widely gaping glumes are adaptations for successful cultivation in high-rainfall areas. The glumes enclose the immature grain to protect it from infection by grain molds, but they gape widely at maturity to allow the grain to dry rapidly after a rain and thus escape damage. Guinea sorghums, which probably evolved in Ethiopia, are still grown in the Konso region, and from there they may have spread along the mountains south to Swaziland and west to the Guinea coast. Cultivated sorghum belonging to race guinea was already growing in Malawi during the ninth century A.D. (Robbinson 1966). Today, almost half the sorghum production in Nigeria comes from guinea sorghums.
Kafir sorghums evolved south of the equator and never became widely distributed outside the southern African savanna. They are probably relatively recent in origin. Kafir sorghums became associated with Iron Age Bantu settlements only during the eighth century A.D. (Fagan 1967; Phillipson and Fagan 1969). Kafir sorghums are genetically more closely allied to local verticilliflorums than to other spontaneous sorghums. This led Y. Schechter and de Wet (1975) to support Snowden’s (1936) conclusion that race kafir was independently domesticated from other sorghums in southern Africa. It is more likely, however, that kafir sorghums were derived from introduced bicolor sorghums that introgressed with local wild sorghum adapted to the arid southern savanna.
As already mentioned, race durra is the most drought-tolerant of all grain sorghums. Their wide distribution in semiarid Asia caused Harlan and A. B. L. Stemler (1976) to propose that durra sorghums evolved in West Asia from earlier introductions of race bicolor. Archaeological remains indicate that bicolor sorghums were grown in India not later than the early first millennium B.C. (Weber 1991). Durras remain the common cultivated sorghums in semiarid Asia. In Africa, they are grown across the Sahel, and their distribution seems to be associated with the expansion of Islam across North Africa.
The cultivation of caudatum sorghums is closely associated in Africa with the distribution of people who speak Chari-Nile languages (Stemler, Harlan, and de Wet 1975). Caudatum sorghums probably represent selections from race bicolor in the eastern savannah during relatively recent times. Bicolor sorghums were important in the Sudan as late as the third century A.D., and archaeological sorghum remains from Qasr Ibrim and Jebel et Tomat in the Sudan belong to race bicolor (Clark and Stemler 1975).The beautifully preserved sorghum inflorescences from Qasr Ibrim date from the second century (Plumley 1970). The only known archaeological remains of caudatum are those from Daima, dated A.D. 900 (Connah 1967). Introgression of caudatum with durra sorghums of the Sahel and with guinea sorghums of West Africa gave rise to a widely adapted complex that is extensively used in modern sorghum breeding.
The spread of sorghum as a cereal to Asia is poorly documented. Carved reliefs from the palace of Sennacherib at Nineveh are often cited as depicting cultivated sorghum (see Hall 1928, plates 30 and 32). But these plants were actually the common reed (Phragmites communis Trin.) growing along the edges of a marsh with pigs grazing among them, certainly not a habitat for growing sorghum. Similar plants appear in imperial Sassanian hunting scenes from Iran (for illustrations, see Reed 1965).
In the Near East, sorghum is an important cereal only in Yemen. Sorghum probably reached India directly from East Africa during the latter part of the second century B.C. (Vishnu-Mittre and Savithri 1982), and in India, race durra evolved. From India durra sorghum was introduced to China, probably during the Mongol conquest (Hagerthy 1940), and to the Sahel during the expansion of Islam across northern Africa. Introduction into the New World most likely started with the slave trade between Africa and the Americas. The weedy Mississippi chicken corn may represent an escape from cultivation dating back to colonial times.
Sorghum as a World Cereal
Sorghum is an important rain-fed cereal in the semi-arid tropics. Production in recent years has been between 50 and 60 million metric tons of grain harvested from around 45 million hectares. The major production areas are North America (excluding Mexico) with 34 percent of total world production, Asia (32 percent), Africa (26 percent), and South America (6 percent).The Caribbean, Meso America, and South America together account for about 17 percent of world sorghum production, with Mexico producing almost 59 percent of this amount. Potential yield of improved sorghum hybrids under rain-fed agricultural conditions is well over 6 metric tons per hectare. Actual maximum yields are closer to 4 metric tons, and average yields are about 1.5 metric tons per hectare. Sorghum is often grown on marginal agricultural land. In Africa and Asia, where local cultivars are still extensively grown with a minimum of agricultural inputs, average yield is well below 1 metric ton per hectare. Sorghum is grown as a cereal for human consumption in Africa and Asia and as animal feed in the Americas and Australia. Sorghum is also extensively grown as a fodder crop in India.
Sorghum production in Africa extends across the savanna in areas with as little as 300 mm and as much as 1,500 mm of annual rainfall. At the drier limits of its range, sorghum is replaced in Africa by pearl millet, in India by pearl millet or foxtail millet (Setaria italica [Linn.] P. Beauv.), and in China by foxtail millet. In areas with more than 900 mm of annual rainfall, maize has replaced sorghum across tropical Africa since its introduction from America during the sixteenth century.
Major factors limiting yield in Africa are infestation of cultivated fields by Striga (a parasitic weed) and the abundance of birds that feed on sorghum grain before it is ready for harvest. Some degree of resistance to bird damage is conferred by high tannin content in developing grains. Tannin, unfortunately, reduces the desirability of sorghum as a cereal grain. Digestibility is improved through fermentation, and fermented food products produced from sorghum grain are extensively used where high tannin cultivars are grown.
Striga is parasitic on most cereals and several broad-leaved crops grown in Africa and India. It produces large numbers of seeds and can become so abundant that fields eventually have to be abandoned. Control of Striga requires high agricultural inputs, the most important of which is high soil fertility and weeding. Neither is affordable under conditions of subsistence farming. Some local sorghum cultivars are resistant to Striga, but these have low grain yield. Attempts to transfer genes for resistance into more desirable genotypes of sorghum are high in priority for breeding projects in West and East Africa, where Striga has become a particularly obnoxious weed.
In Asia, the major sorghum-producing countries are China, India, Thailand, Pakistan, and Yemen. In Thailand, sorghum is grown as a dry-season crop, after a rain-fed crop, usually maize, has been harvested. In India, sorghum is grown as a rain-fed crop (kharif) or a dry-season crop (rabi), usually following rice or cotton on soils with good moisture retention. Kharif sorghum is usually mixed with pigeon pea in the field. Sorghum matures and is harvested after 90 to 120 days, allowing the season-long–developing pigeon pea an opportunity to mature without competition.
Kharif sorghums were selected for their ability to mature before the end of the rainy season in order to escape terminal drought stress that severely reduces yield. These cultivars are highly susceptible to infection by grain molds, which greatly reduces the desirability of kharif sorghum as a cereal grain. Market samples have revealed that in central and southern India as much as 70 percent of food sorghum grown during the rainy season is infected with grain molds. Cultivars with high tannin content in developing grains are resistant to infection by grain molds, but their flour yields a poor-quality unleavened bread, the major product of sorghum preparation as a food in India. Long-term breeding programs to produce grain-mold–resistant sorghums with grain acceptable to consumers have consistently failed.
Rabi sorghums escape infection by grain molds as they are grown in the dry season, but yields are low because of terminal drought stress. Prices in the market for these sorghums, however, are sufficiently attractive to make rabi sorghum a major crop in India. Production is well below demand, and attempts to shorten the growing season of rabi sorghums to escape drought and at least maintain yield potential are showing promise. Terminal drought stress commonly leads to lodging of these sorghums because of a combination of infection by stem rot fungi and plant senescence. Lodging makes harvesting difficult and contributes to reduced grain quality. To improve stalk quality and overcome lodging, plant breeders in India introduced genes for delayed senescence into high-yielding cultivars. This allows grain harvest when the stalk is still juicy and the leaves are green. Delayed senescence also greatly improves fodder quality. The stalks of both kharif and rabi sorghums are in demand as animal feed. Around urban areas, the demand by the dairy industry for fodder far exceeds the supply, and farmers often derive a higher income from sorghum stalks than sorghum grain.
Shortage of sorghum grain as a food largely excludes its use as animal feed in Africa and Asia.The grain is eaten in a variety of preparations that vary within and between regions. Grains are ground into flour from which unleavened bread is baked, or the flour is used to produce both fermented and unfermented porridges. The grains are also cracked or decorticated and boiled like rice, or whole grains are popped in heated oil.
Commercial grain sorghum production in Africa and Asia is determined by the availability of reliable supplies of the much-preferred rice, wheat, or maize. Only where these three cereals are not available at competitive prices is sorghum an important commercial crop. In China, sorghum is commercially grown for the production of a popular alcoholic beverage. It is used as a substitute for barley malt in the Nigerian beer industry. In southern Africa, a highly nutritious, low-alcohol beer is commercially produced from sorghum malt and flour, and in Kenya sorghum is used to produce a widely accepted baby food. However, attempts in many countries to replace wheat flour partially with sorghum flour in the baking industry have, so far, met with limited success, even though the quality of the bread is acceptable.
In the Americas, sorghum production is determined by demand for the grain as an animal feed. World feed use of sorghum has reached 40 million metric tons annually, with the United States, Mexico, and Japan the main consumers (Food and Agriculture Organization 1988). These three countries used almost 80 percent of the world’s sorghum production in 1993. Although North American demand for sorghum grain has stabilized, in South America, where more than 1 million hectares are under sorghum cultivation, demand exceeds production by about 10 percent annually. This shortfall, predicted to increase throughout the next decade, is now mostly made up by imports from the United States. In the quest for self-sufficiency in animal feed, sorghum cultivation in South America is expanding into areas too dry for successful production of maize and into the seasonally flooded Llanos (with acid soils), where sorghum is more productive than maize.
In Asia, the area under sorghum cultivation is declining to make room for the production of fruits, vegetables, and other foods needed to supply rapidly increasing urban populations. Grain production, however, has remained essentially stable in Asia during the last decade because farmers increasingly grow improved cultivars associated with improved farming practices. This allows production to keep pace with demand, except during drought years when the demand for sorghum as human food far exceeds production.
In several African countries, population increase exceeds annual increase in food production. The Food and Agriculture Organization of the United Nations predicted that 29 countries south of the Sahara would not be able to feed their people as the twenty-first century opened. The concomitant increase in demand for cereals will have to be met by the expansion of production into marginal agricultural land, the growing of improved cultivars, and improved farming practices. Pearl millet is the cereal of necessity in areas with between 300 and 600 mm of annual rainfall, and sorghum is the most successful cereal to grow in areas with between 600 and 900 mm of annual rainfall. Because of that, the future of sorghum as a food cereal in Africa and Asia, and as a feed grain in the Americas and Australia, seems secure.