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OCR for page 11
Overview
Scientists exploring seashores, estuaries, and saline seeps have
found thousands of halophytes with potential use as food, fuel, fod-
der, fiber, and other products. Many have already been in tradi-
tional use, and there are also a number of plants that, although
not halophytes, have sufficient salt tolerance for use in some saline
environments.
Although economic consideration of halophytes and other salt-
tolerant plants is just beginning, they are now receiving increased
attention in arid regions where intensive irrigation has led to splinted
soils or where water shortages are forcing use of marginal resources
such as brackish underground water. This report wiD examine some
of the plants that may be suitable for economic production in saline
environments in developing countries.
There are four sections in this report. They highlight salt-
tolerant plants that may serve as food, fuel, fodder, and other prod-
ucts such as essential oils, pharmaceuticals, and fiber. In each of
these sections, plants are described that have potential for produc-
tive use. Each section also contains an extensive list of recent papers
and other publications that contain additional information on these
plants. A list of researchers currently working on these plants or
related projects is included at the end of each section.
11
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12
FOOD
Many halophytes survive saline stress by accumulating salt in
their vegetative tissues. The salt levels in the leaves and stems of
these plants can limit their direct consumption as food, but their
seeds are relatively salt-free, which may allow production of starchy
grains or oilseeds.
For example, the seeds of Zostera marina, a sea grass, were used
as food by the Seri Indians of the southwestern United States; in
recent tests, these seeds were ground to flour and used to make bread.
Seeds of Distichlis palmer), Palmer's saltgrass, were harvested from
tidal flats at the head of the Gulf of California by Cocopa Indians.
The seed, about the same size as wheat, has also been used for
making bread.
The production of vegetable oils from seed-bearing halophytes
appears prolonging. A number of these seeds have an oil content
comparable with that of better known sources of vegetable oils. A
Salicornia species is being evaluated as a source of vegetable oil in
field trials in the United Arab Emirates, Kuwait, and Egypt. Since
many developing countries import vegetable oils, the opportunity for
domestic production on currently unusable lands warrants investiga-
tion.
It may be possible as well to use the salt-containing vegetative
parts of some halophytes to produce salt-free leaf protein. In this
process, any inorganic salts in the leaves are separated from the
protein. Leaf protein production may help improve the nutritional
quality of foods in developing countries.
There are also traditional food crops that are grown commer-
cially using underground brackish water for irrigation. These include
tomatoes, onions, and melons. Asparagus also appears to grow well
with brackish water irrigation.
FUEL
More than a billion people in developing countries rely on wood
for cooking and heating. In most developing areas, the rate of de-
forestation for fuelwood and for agricultural expansion far exceeds
the rate of reforestation. Increasing needs for agricultural land to
feed growing populations make it unlikely that land suitable for food
crops will be used for tree planting. One alternative, therefore, is to
use marginal or degraded lands to produce more fuelwood.
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13
Fue~wood and building materials can be produced from salt-
tolerant trees and shrubs employing land and water unsuitable for
conventional crops. Fuel plantations established on saline soils or
irrigated with saline water would allow more fertile land and fresh
water to be reserved for food or forage production. With careful
planning, trees and shrubs can help rehabilitate degraded lands by
stabilizing the ecosystem and providing niches and protection for
other plants and animals.
In Australia, a consortium of business and academic groups is
developing a program to market salt-tolerant trees for fuel and pulp.
The project will screen Australian tree species for growth rates,
salt tolerance, and drought tolerance. Root fungi associated with
these trees, which help the trees obtain nutrients from the soil, will
be screened for salt tolerance and their influence on tree growth.
Trees with superior growth on saline soils will be tissue cultured and
inoculated with salt-tolerant root fungi. These cloned trees will then
be tested for field performance in Australia and developing countries.
FODDER
Halophytic grasses, shrubs, and trees are all potential sources
of fodder. Trees and shrubs can be valuable components of grazing
lands and serve as complementary nutrient sources to grasses in arid
and semiarid areas.
Among the grasses, kalIar grass (Leptochioa fusca) tolerates wa-
terIogging and recovers well from cutting and grazing. Its economic
value as fodder for buffalo and goats has already been demonstrated
in Pakistan and is now being examined in other countries. Members
of the Spartina genus (corUgrasses) have also been used as fodder.
These tough, Tong-leaved grasses are found in tidal marshes in North
America, Europe, and Africa. The salt-tolerant grass Sporobolus
virginicus has also been used as cattle forage.
Distichlis spicata has been used as forage for cattle in Mexico.
Introduced in the area of a dry salt lake outside Mexico City, D.
spicata reduced windblown dust while serving as cattle feed.
In arid and semiarid zones, trees and shrubs for fodder have sev-
eral advantages over grasses. They are generally less susceptible than
grasses to fire and to seasonal variation in moisture availability and
temperature. Usually less palatable than grasses, they can provide
reserve or supplementary feed sources.
Among the shrubs, saltbushes (Atriplex spp.) grow throughout
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14
the world. They tolerate salinity in soil and water, and many are
perennial shrubs that remain green all year. They are especially
useful as forage in arid zones.
Among trees, Acacia species are widely used in arid and saline
environments as supplementary sources of fodder. Acacia pods pro-
vide food for livestock in large areas of the semiarid zone of Africa.
Acacia Cyclops and A. bivenosa tolerate salt spray and salinity. They
grow on coastal dunes as small trees or bushy shrubs. Pods and leaves
of both are consumed by goats.
Leucaena [eucocephala is a tree legume widely cultivated In trop-
ical and subtropical countries. Leaves, pods, and seeds are grazed by
cattle, sheep, and goats. In Pakistan, it has been grown on coastal
sandy soil through irrigation with saline water. When seawater com-
prised 20 percent of the irrigation water, yields were reduced by 50
percent, however.
The leaves and pods of mesquite (Prosopis spp.) have been used
as forage for cattle, goats, sheep, and camels in countries throughout
the world-P. juliflora and P. cineraria in India, P. chilensis in
South America, P. glandulosa In the United States, and P. pallida in
Australia.
About 20 years ago the Chilean government began to improve
the salt-afflicted Pampa de} Tamaru gal in the northern part of the
country by growing tamarugo (P. tamarugo). In some cases, these
trees were planted in pits dug through the salt into the soil. Although
watering was required for the first year, after that the plants sur-
vived by capturing moisture from the ground and air. About 23,000
hectares are now covered with tamarugo forest. The tamarugo leaves
and fruit are used as feed for sheep and goats.
FIBER AND OTEE11 PRODUCTS
Salt-tolerant plants can also be used to produce economically
important materials such as essential oils, flavors, fragrances, gums,
resins, oils, pharmaceuticals, and fibers. They may also be marketed
for use in landscape gardening, and for their foliage or flowers.
In India, peppermint of} and menthol have been produced in
saline environments. The salt-tolerant Kenya, a common species of
screwpine, is used to produce perfume and flavoring ingredients.
Sesbania bispinosa, commonly known as dhaincha in India, is an
important salt-tolerant legume and fodder crop. In addition to use of
the stalks as sources of fiber and fuel, the seeds yield a galactomannan
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15
gum that can be used for sizing and stabilizing applications, and a
seed meal that can be used for poultry and cattle feed.
Grindelia camporum is a salt-tolerant resinous perennial shrub.
It produces large amounts of aromatic resins that have properties
similar to the terpeno~;ds in wood and gum rosins, which are used
commercially in adhesives, varnishes, paper sizings, printing inks,
soaps, and numerous other industrial applications.
Jojoba (Simmondsia chinensis) is a perennial desert shrub with
seeds that contain a unique of! similar to that obtained from the
sperm whale. This of! and its derivatives have been used prunarily
in cosmetics, but broader use in lubricants and waxes will probably
develop if prices come down. Jojoba is relatively salt tolerant. In
Israel, jojoba is growing wed near the Dead Sea with brackish water
· · ~
Irrigation.
Phragmites australis, common reed, Is an ancient marsh plant
that has served in roofing, thatching, basketmak~ng and fencing, as
well as being used for fuel. It grows throughout the world in water-
saturated soils or standing waters that are fresh or moderately saline.
In Egypt, two salt-tolerant rushes, Juncus rigidus and ]. acutus, have
been investigated with particular emphasis on their potential use in
papermaking.
Many attractive halophytes can be used as landscape plants,
especially in areas with constraints on the use of fresh water for
watering or irrigation. In Israel, salt-tolerant trees and shrubs are
sold for amenity planting. In addition, other salt-tolerant plants have
potential for cut-flower production.
Although the salt-tolerant plants described in this report typify
those that are currently being evaluated or appear to deserve ad-
ditional attention, the inventory is far Tom complete. Many other
species may have equal or greater potential. In some cases in this
report, specific companies or products are identified. This is for
convenience and floes not constitute endorsement.
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Representative terms from entire chapter:
saline environments
