4. Pearl Millet
Of all the world's cereals, pearl millet (Pennisetum glaucum) is
the sixth most important.
Descended from a wild West African grass, it was domesticated
more than 4,000 years ago, probably in what is now the heart of the Sahara
Desert. Long ago it spread from its homeland to East Africa and thence to India.
Both places adopted it eagerly and it became a staple.
Today, pearl millet is so important that it is planted on some
14 million hectares in Africa and 14 million hectares in Asia. Global production
of its grain probably exceeds 10 million tons a year, to which India contributes
nearly half. At least 500 million people depend on pearl millet for their lives.
Despite its importance, however, pearl millet can be considered
a "lost" crop because its untapped potential is still vast. Currently, this
grain is an "orphan" among the significant cereals. It is poorly supported by
both science and politics. In fact, few people outside of India and parts of
Africa have ever heard of it. As a result, it lags behind sorghum and far behind
the other major grains in its genetic development. For instance, its average
yields are barely 600 kg per hectare and it is almost entirely a subsistence
crop; perhaps for this last reason alone pearl millet has attracted little
research or industrial support.
Indeed, largely due to neglect, pearl millet is actually
slipping backwards. Production in West Africa during the last two decades has
increased by only 0.7 percent a year - the lowest growth rate of any food crop
in the region and far less than the population's growth rate. Furthermore, even
this meager increase has been mainly due to expanding the area cultivated rather
than to boosting yields. Elsewhere in Africa the decline has been even more
dramatic. Just 50 years ago, pearl millet was of almost incalculable value to
millions of rural people in eastern and southern Africa. But over the decades,
more and more farmers - especially in southern Africa - have abandoned it and
switched to maize.
There are several reasons for this. For one thing, international
research efforts have made maize more productive than pearl millet; for another,
government incentives have given maize an added financial advantage; and for a
third, easier processing has made maize more convenient to use. The momentum for
change has now gone so far that maize is often pushed into pearl millet areas to
which it is poorly suited and where it cannot perform reliably.
Now, however, a new era may be dawning. Pearl millet is
supremely adapted to heat and aridity and, for all its current decline, seems
likely to spring back as the world gets hotter and drier. Perhaps the best of
all "life-support" grains, pearl millet thrives where habitats are harsh. Of all
the major cereals, it is the one most able to tolerate extremes of heat and
drought. It yields reliably in regions too hot and too dry to consistently
support good yields of maize (or even sorghum). These happen to be the regions
most desperately in need of help.
It is there that the famines of recent decades have brought mass
devastation and death. It is there that expanding deserts are destroying the
productivity of perhaps 25 million hectares every year. And it is there that
agricultural development could have its greatest humanitarian benefits.
These reasons alone should be sufficient to make pearl millet
the target of a global initiative.
But this crop has even more promise. Rising climatic
temperatures are starting to concern almost all countries. And water is shaping
up as the most limiting resource for dozens of the world's nations - including
some of the most advanced. Agriculture is usually a country's biggest user of
water, so that crops that sip, rather than gulp, moisture are likely to be in
ever greater demand. Thus, even for economies that until now never heard of it,
pearl millet could quickly become a vital resource.
Agronomically, there is no reason why pearl millet could not
(like sorghum) become used worldwide. Indeed, recent research in the United
States is showing that its prospects are much higher than most people now think.
Already, the crop is showing promise for the heartland of America. It might also
become widely used in the hotter and drier parts of Latin America, Central Asia,
and the Middle East. It could have a bright future in dry areas of Australia and
other countries as well.
FIGURE: Pearl-millet-growing areas in
Africa. There are an estimated 14 million hectares of millet in this zone,
making it the third most widely grown crop in sub-Saharan Africa. The plant was
probably domesticated some 4,000-5,000 years ago along the southern margins of
the central highlands of the Sahara. It has since become widely distributed
across the semiarid tropics of Africa and Asia. Today, approximately one-third
of the world's millet is grown in Africa, about 70 percent of it in West Africa.
Africa's major pearlmillet producing countries include Nigeria, Niger, Burkina
Faso, Chad, Mali, Mauritania, and Senegal in the west; Sudan and Uganda in the
east. In southern Africa, the commercialization of agriculture has resulted in
maize partially or completely displacing this traditional food crop. (ICRISAT,
1987; each dot represents 20,000 hectares)
Pearl millet is easy to grow. It suffers less from diseases than
sorghum, maize, or other grains. Also, it has fewer insect pests.
The widespread impression that pearl millet grain is essentially
an animal feed, unpalatable to all but the desperately hungry, is wrong. The
grain is actually a superior foodstuff, containing at least 9 percent protein
and a good balance of amino acids. It has more oil than maize and is a
"high-energy" cereal. It has neither the tannins nor the other compounds that
reduce digestibility in sorghum.
Pearl millet is also a versatile foodstuff. It is used mainly as
a whole, cracked, or ground flour; a dough; or a grain like rice. These are made
into unfermented breads (roti), fermented foods (kisra and gallettes), thin and
thick porridges (toh), steam-cooked dishes (couscous); nonalcoholic beverages,
and snacks.
Grain from certain cultivars is roasted whole and consumed
directly. The staple food of the mountainous regions in Niger is millet flour
mixed with dried dates and dried goat cheese.
This nutritious mixture is taken on long journeys across the
Sahara and eaten mixed with water - no cooking required.
Grain from other types is used to make traditional beer. In
Nigeria, it is fermented, like maize or sorghum, to produce ogi - a traditional
weaning food that is still common.
In future, pearl millet may be used in many more types of foods.
The fact that it can be made into products resembling those normally produced
from wheat or rice should make it acceptable to many more people.
With new technology, there seem to be possibilities of using it
even to make raised breads (see Appendix C).
All this is not to say that pearl millet is perfect. Indeed, the
crop has several serious problems. For one, the raw grain is difficult to
process. Many consumers decorticate (dehull) the grain before grinding it into
various particle sizes for use in different products. Dehulling by traditional
hand pounding produces low yields of flour (around 75 percent) and the product
has poor storage stability.
Despite these impediments, this plant's promise is so great that
we have devoted the following two chapters to its various types. The next
chapter highlights its promise for subsistence farmers - the millions in Africa
and Asia to whom pearl millet means life itself.
The subsequent chapter highlights commercial pearl millets - the
types that are increasingly grown by farmers who produce a surplus to sell.
Bajra
About 3,000 years ago pearl millet crossed the Indian Ocean and
became a vital contributor to South Asia's food supplies. Today it is India's
fourth most important cereal, surpassed only by rice, wheat, and sorghum. Bajra,
as it is called, is currently grown on almost 10 percent of India's food-grain
area, and it yields about 5 percent of the country's cereal food.
Rajasthan, Maharashtra, Gujarat, and Uttar Pradesh account for
nearly 80 percent of the 14 million hectares planted and 70 percent of the 5
million tons of pearl millet grain produced each year.
India's farmers grow some pearl millet under irrigation during
the hot, dry months and routinely reap harvests as high as 3 or 4 tons per
hectare. But most grow it in the arid areas, particularly where the rainfall is
just insufficient for sorghum or maize. Here, the soils are usually depleted in
fertility and there is no irrigation. Some plots receive as little as 150 mm of
rainfall per year. But pearl millet survives and produces food.
FIGURE: Baira-growing areas in the
Subcontinent. (ICRISAT, 1987; each dot represents 20,000 hectares)
Indians commonly grind pearl millet and make the flour into
cakes or unleavened bread (chapati). Some goes into porridges, which may be thin
or thick. Much is cooked like rice.
The grain is sometimes parched and eaten, the product (known as
akohi, bhunja, lahi, or phula) being similar to popcorn. In some regions, the
green ears are also roasted and eaten like a vegetable.
Although small quantities of the grains are used for feeding
cattle and poultry, the plant is more often fed to animals as a green fodder. It
is well suited for this purpose because it is quickgrowing, tillers very freely,
lends itself to multiple cutting, and usually has thin and succulent stems.
All in all, pearl millet is not a neglected crop in India.
Authorities realize that it stabilizes the nation's food basket. Improved
strains, suited to various regions, have been created and released for
cultivation. Indeed, its potential is being increasingly exploited, especially
as the swelling population requires increased cultivation of marginal land.
Let Them Eat Millet Bread
Millet once played a greater role in the world of cereals for
many rural people in eastern and southern Africa, but it has declined in
importance over the last 30-50 years because of a preference for maize.
The decline has been compounded by increased research on maize
leading to greater productivity of the crop and by the incentives given to maize
production through government policies. Maize has been grown, as a result, in
dry conditions to which it is not adapted and it has failed too often in these
conditions. Governments have come to realize this as well as the farmers
themselves.
So it is now necessary to reestablish the importance of millet
and sorghum in these drier areas and to do so we must make the production of
these crops attractive enough so that they can compete with maize, not only in
the worst and most severe droughts but in at least a majority of years. Here is
work for the scientists in millet.
But in the long run, even in Africa, maize is not the problem at
all. The problem is wheat, or more correctly, bread. Politicians are going to
give the people bread. They have been saying this for a long, long time, and
they mean it. Technocrats may decry this trend, particularly in tropical areas
where wheat cannot be grown satisfactorily, but I can assure you that the
protestations will be to little avail. They may slow the process down but they
will not stop it.
The people of the cities want bread, and the elected officials
will ensure that they get it. The people are already exposed to bread and they
will ask for it, they will insist upon it, and they will get it.
In many tropical countries it will be very expensive to satisfy
this demand unless millet can become bread. And this, too, the politicians
recognize and they will support this demand whether efforts can be made to
decrease the cost of giving people the food that they demand. So here is
something else for the millet scientists to do. Don't ask me how you do it. You
know far better than I do. I am just telling you it's got to be done.
From an address by L.D. Swindale
Former Director-General,
ICRISAT
NUTRITION
Pearl millet's average composition is given in the tables on the
following pages. Some highlights are summarized below.
Carbohydrates usually make up about 70 percent of the dry grain,
and they consist almost exclusively of starch. The starch itself is composed of
about two-thirds amylopectin (the insoluble component that forms a paste in
water at room temperature) and one-third amylose (the soluble component that
forms a gel in aqueous solution).
Measurements made on several hundred types have shown that the
protein ranges from 9 to 21 percent, with a mean of 16 percent. However, the
varieties now used in farm practice have an average of about 11 or 12 percent.
Of the different protein types, prolamine constitutes 40 percent and globulins
20 percent; the presence of an albumin has been also reported, but no gluten.
The protein's biological value and digestibility coefficient have been measured
as 83 percent and 89 percent, respectively. The protein efficiency ratio has
been found to be 1.43, which is even better than that of wheat (1.2).
The grain has about 5 percent fat, roughly twice the amount
found in the standard cereals. It is composed of about 75 percent unsaturated
and 24 percent saturated fatty acids.
The vitamin values of pearl millet grain are generally somewhat
lower than those of maize, although the level of vitamin A is quite good. The
carotene value is also good - for a cereal.
Of the grain's edible portion, ash comprises about 3 percent, an
amount somewhat higher than in wheat, rice, or maize. The various mineral
constituents, accordingly, tend to occur in greater quantities as well. Compared
with maize, phosphorus (average 339 ma) is half again as much, iron (average 9.8
ma) is more than three times, and calcium (average 37 ma) is more than five
times as much. Traces of barium, chromium, cobalt, copper, lead, manganese,
molybdenum, nickel, silver, strontium, tin, titanium, vanadium, zinc, and iodine
have also been noted.
In feeding teals, pearl millet has proved nutritionally superior
to rice and wheat. A review of research in India states that a diet based on
pearl millet and pulses is somewhat better at promoting human growth than a
similar diet based on wheat. In one trial, for instance, researchers made up
vegetarian diets typical of those eaten by the poor. When pearl millet partially
or completely replaced rice, the nutritive value increased appreciably.
Studies conducted on children showed that all the subjects fed
diets based on pearl millet maintained positive balance with respect to
nitrogen, calcium, and phosphorus. The protein's apparent digestibility was
about 53 percent, an amount close to that for finger millet and sorghum
proteins, but less than that of rice protein (65 percent). It was also found
that pearl millet could replace 25 percent of the rice in a child's diet without
reducing the amount of nitrogen, calcium, or phosphorus its body absorbed.
NUTRITIONAL PROMISE
The pearl millet grain is nutritious. It has no husk, no tannin,
contains 5-7 percent oil' and has higher protein and energy levels than maize or
sorghum. The unsaturated fatty acids making up the oil are oleic (20-31
percent), linoleic (40-52 percent), and linolenic (2-5 percent). The saturated
fatty acids are palmitic (18-25 percent) and stearic (28 percent).
In general, pearl millet has a higher protein content than other
cereals grown under similar conditions. In 180 pearl millet lines tested in
1972, protein contents ranged from 9 to 21 percent with a mean of 16 percent. It
has an excellent amino acid profile and, depending on the variety and perhaps on
the growing conditions, the levels of the various amino acids making up the
protein can vary by as much as a factor of two. In general, however, the
reported values show higher tryptophan, threonine, and valine and lower leucine,
but otherwise similar essential amino acids in pearl millet compared with grain
sorghum. What is uncertain, however, is the digestibility of pearl millet
protein. It is possible that the actual amount of digestible protein is less
than that of other major grains.
Botanical Name Pennisetum glaucum (L.) R. Br.
Synonyms Pennisetum typhoides (Burm.f.) Stapf and Hubbard, P.
americanum (L.) Leeke, P. spicatum Roem and Schult.
Pearl millet is an erect annual, usually between 50 cm and 4 m
tall. Tillering and branching are not uncommon and are sometimes profuse. The
straw is coarse and pithy.
The numerous flowers are tucked tightly around a cylindrical
spike (rachis) that can range in length from 15 to 140 cm. This inflorescence is
usually greenish yellow, and it may be cylindrical throughout its length or may
taper at one or both ends.
The flowers can be either cross-pollinated or self-pollinated.
The female part (stigma) emerges before the male part is ready to shed its
pollen.
As a result, cross-pollination normally occurs. However, where
the timing overlaps, some self-pollination can occur.
Grain begins developing as soon as fertilization occurs and is
fully developed 20-30 days later. The whole process, from fertilization to
ripening, takes only about 40 days.
The seeds range in color from white to brown, blue, or almost
purple. Most are slate gray.
They are generally tear shaped and smaller than those of wheat.
The average weight is about 8 ma. Some thresh free from glumes, while others
require husking.
The seeds are quick to germinate. If conditions are favorable,
they sprout in about 5 days.
Freshly harvested seed may not germinate immediately; however, a
dormancy of several weeks after harvesting has been reported.
The two vast areas of West and East Africa where pearl millet is
prominent have already been mentioned.
Soon after its domestication, the crop became widely distributed
across the semiarid tropics of both Africa (15 million hectares) and Asia (14
million hectares). Pearl millet first became known in Europe about 1566 when
plants were raised in Belgium from seed said to have been received from India.
This form, sometimes known as Pennisetum spicatum, is still grown in Spain and
North Africa. Pearl millet was introduced into the United States at least as
long ago as the 1850s.
Pearl millet's extremely deep roots can reach down into soil
layers untapped by other plants. Tests in the southeastern United States have
revealed that it can pull up nutrients from residues that have accumulated below
the root zones of the previous farm crops.
This finding, should it prove more widely true, has profound
implications. Much of the fertilizer now put on crops leaches past their roots
where it is not only lost but becomes a pollutant. Having an annual crop that
can scavenge the lower layers gives farmers a second shot at the (expensive)
fertilizer as well as a tool for cleaning the environment. They might even make
a profit from it by selling the pearl millet.
There are vast numbers of types, differentiated by features such
as the following:
· Quick maturity (about 80 days), medium maturity (100 days
or so), or slow maturity (180 days or more)
· Height
· Amount of
tillering
· Stem thickness and branching
· Leaf size and
hairiness
· Seedhead size, shape, and "tightness"
· Number,
length, rigidity, brittleness, and hairiness of bristles
· Size, shape,
and color of grain
· The degree to which the glume adheres to the grain.
For pearl millet, the bulk of the systematic breeding has been
done in India, but substantial contributions have also come from several African
countries, France, and the United States.
Most yield improvements have resulted from incorporating genes
from African varieties into
Indian breeder stocks. However, a breakthrough came in the late
1950s when plants carrying cytoplasmic male sterility were discovered. This
genetic trait made hybrids a practical possibility. Today, singlecross
pearl-millet hybrids, using male-sterile seed parents, are the basis of vigorous
private and semi-public seed industries, especially in India.
Daylength Pearl millet is usually a short-day plant (see next
chapter), but some varieties are daylength neutral.
Rainfall Although the crop is grown where rainfall ranges from
200 to 1,500 mm, most occurs in areas receiving 250-700 mm. The lowest rainfall
areas rely mainly on early- maturing cultivars. Although very drought resistant,
pearl millet requires its rainfall to be evenly distributed during the growing
season. (Unlike sorghum, it cannot retreat into dormancy during droughts.) On
the other hand, too much rain at flowering can also cause a crop failure.
Altitude Pearl millet is seldom found above 1,200 m in Africa,
but occurs at much higher altitudes elsewhere (for instance, in western North
America).
Low Temperature The plant is generally sensitive to low
temperatures at the seedling stage and at flowering.
High Temperature High daytime temperatures are needed for the
grain to mature. In Africa's pearl millet zone, temperatures are typically above
30°C.
Soil Type Like most plants, pearl millet does best in light,
welldrained loams. It performs poorly in clay soils and cannot tolerate
waterlogging. It is tolerant of subsoils that are acid (even those as low as pH
4-5) and high in aluminum content.
Pearl millet has many relatives. A number are quite troublesome.
In much of Africa, for instance, wild Pennisetum species manage to get their
pollen in, and this cross-pollination quickly reduces the crop's productive
capacity. The hybrid swarms of weedy "half-breeds" (called shibras in West
Africa) are common contaminants in the farmer's crop. Whereas the cultivated
races have broad-tipped persistent spikelets and large, mostly protruding
grains, the wild species have narrower, pointed spikelets. Also, their grains
are smaller, entirely enclosed by husks, and prone to fall out (shatter).
Luckily, the weedy species did not accompany the crop to India.
Although hybridization and introgression between the crop plants
and the wild relatives is a problem for farmers, it can be a blessing for plant
breeders, giving rise to new forms both of the crop and of the weed.
