Innovative biological technologies for lesser developed countries

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Innovative biological technologies for lesser developed countries workshop proceedings
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Agricultural innovations -- Congresses -- Developing countries ( lcsh )
Agricultural innovations -- Congresses ( lcsh )
Biological productivity -- Congresses -- Developing countries ( lcsh )
Biological productivity -- Congresses ( lcsh )
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Full Text
Q?7 /71

Innovative Biological

Technologies for Lesser

Developed Countries

Workshop Proceedings

o Office of Technology Assessment
Washington, D. C. 20510

i? t'

Office of Technology Assessment

Congressional Board of the 99th Congress

TED STEVENS, Alaska, Chairman

MORRIS K. UDALL, Arizona, Vice Chairman

South Carolina
Rhode Island


H&Q Technology Partners
DAVID S. POTTER, Vice Chairman

University of Alaska
General Accounting Office


Advisory Council

California Land Commission
University of Pittsburgh
Library of Congress

University of Arizona
Midwest Research Institute
University of Wisconsin
Memorial Sloan-Kettering
Cancer Center



This is an OTA Workshop Proceeding that has neither been reviewed nor
approved by the Technology Assessment Board

Innovative Biological

Technologies for Lesser

Developed Countries

Workshop Proceedings

S p Office of Technology Assessment
Washington, D. C. 20510

Recommended Citation:
Innovative Biological Technologies for Lesser Developed Countries-Workshop Pro-
ceedings (Washington, DC: U.S. Congress, Office of Technology Assessment, OTA-
BP-F-29, July 1985).

Library of Congress Catalog Card Number 85-600550

For sale by the Superintendent of Documents
U.S. Government Printing Office, Washington, DC 20402


Oversight of the Agency for International Development (AID) is the responsi-
bility of the House Committee on Foreign Affairs. In 1980, under Chairman Cle-
ment Zablocki, the Committee requested the Food and Renewable Resources
Program of the congressional Office of Technology Assessment (OTA) to review
innovative biological technologies that AID could use to help lesser developed coun-
tries (LDCs) enhance the productivity of their soils, reduce their need for costly
chemical fertilizers, and increase food supplies.
In response to the committee's request, OTA hosted a workshop that brought
together some 40 leading scientists, AID representatives, and congressional and
executive branch staff for 2 days of presentations and discussions on November
24 and 25, 1980 (see attendees list). On the first day of the workshop each scientist
presented a paper about innovative biological technologies and responded to ques-
tions. The second day was devoted to discussing AID and its role in using, promot-
ing, and developing innovative biological technologies. Chapters I and II of this
report summarize those two days of discussion. Chapters III through XII contain
the scientific papers that were presented at the workshop.
These Workshop Proceedings were first released by the Committee on Foreign
Affairs in 1981. Continued requests for copies of the proceedings spurred this
reprinting. Although the papers have been edited slightly for style, they have not
been updated. OTA wishes to thank the authors of the papers, the other workshop
participants, reviewers, and the many people worldwide who have requested copies.

Workshop Participants

James Duke
Germplasm Resources Laboratory
Building 001, Room 131
Beltsville, MD 20705
Peter Felker
Ceasar Kleberg Wildlife Research Institute
College of Agriculture
Texas A&I University
Kingsville, TX 78363
Stephen R. Gliessman
Agroecology Program
Board of Environmental Studies
University of California
Santa Cruz, CA 95064
Jake Halliday
Battelle Kettering
Research Laboratory
150 East South College St.
Yellow Springs, OH 45387
William Liebhardt
Rodale Research Center
RD1 Box 323
Kutztown, PA 19530
Thomas A. Lumpkin
Department of Agronomy and Soil Science
Washington State University
Pullman, WA 99164-6420

Cy McKell
Director of Research
417 Wakara Way
University Research Park
Salt Lake City, UT 84108
John Menge
Department of Plant Pathology
University of California
Riverside, CA 92521
Frederick Mumpton
Department of the Earth Sciences
State University of New York
Brockport, NY 10003
Donald Plucknett
World Bank
1818 H St., N.W.
Room K1045
Washington, DC 20433
Noel Vietmeyer
National Academy of Sciences
National Research Council
JH 213
2101 Constitution Ave., N.W.
Washington, DC 20418

OTA Workshop Staff on Innovative Biological Technologies
for Lesser Developed Countries

Joyce C. LashofI and Roger Herdman,2 Assistant Director
OTA Health and Life Sciences Division

Ogechee Koffler, Division Assistant

Walter E. Parham, Food and Renewable Resources Program Manager

Bruce Ross, Project Director

Chris Elfring
Hugh Bollinger

Chris Elfring

Administrative Staff
Phyllis Balan3 and Patricia Durana,4 Administrative Assistant
Elizabeth Galloway, Secretary
Gillian Raney, Secretary
Nellie Hammond, Secretary
Carolyn Swann, Secretary

'Until December 1981.
2Current Assistant Director.
'Until September 1984.
"From October 1984.


Chapter Page
I. The Potential of Innovative Technologies ............................ 3
II. The Role of the Agency for International Development ................ 23
III. Underexploited Plant and Animal Resources for Developing Country
Agriculture (Noel Vietm eyer) ....................................... 37
IV. Native Plants: An Innovative Biological Technology
(Cyrus M M cK ell) ................................................ 51
V. Multiple Cropping Systems: A Basis for Developing an Alternative
Agriculture (Stephen R. Gliessman).................................. 69
VI. Development of Low Water and Low Nitrogen Requiring Plant
Ecosystems for Arid Developing Countries (Peter Felker) ........ ...... 87
VII. Azolla, A Low Cost Aquatic Green Manure for Agricultural Crops
(Thomas A. Lumpkin and Donald L. Plucknett) ....................... 107
VIII. Using Zeolites in Agriculture (Frederick A. Mumpton) ................. 127
IX. Agrotechnologies Based on Symbiotic Systems That Fix Nitrogen
(Jake H alliday) .................................................... 161
X. Mycorrhiza Agriculture Technologies (John A. Menge) ................. 185
XI. A Low Fertilizer Use Approach to Increasing Tropical Food Production
(W illiam C. Liebhardt) ............................................. 207
XII. The Gene Revolution (James A. Duke) ............................... 227

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Introduction ....................................................... ... 3
What Do Innovative Technologies Offer? ..................................... 4
The Workshop's Conclusions ............................................... 5
Innovative Biological Technologies: Highlights of the Workshop ................. 6
Underexploited Plant Resources ......................................... 6
M multiple Cropping .................... ........................... 7
Agroforestry .................................. ............. ........... 8
Azolla/Algae Symbiosis .................... .. ......................... 10
Underexploited Animal Species ................................... .... 12
Zeolites ............................................................. 13
Biological Nitrogen Fixation ...................... ...................... 14
Mycorrhizal Fungi ....................................... ............ 17

_ __ _

Chapter I

The Potential of

Innovative Technologies


Fertile soil is the key to productive agricul-
ture, whether for an Illinois corn farmer or a
subsistence farmer in Ghana, Haiti, India, or
other less developed country (LDC). The farm-
ers know this; they know their soil must have
good tilth, hold water, and be rich with the nec-
essary nutrients and minerals. They learn these
principles through education or, more likely,
through tradition and experience. But for most
LDC farmers, the old ways of maintaining soil
quality may no longer be adequate. Population
pressures and rising expectations force them
to demand more from the land, to shorten the
traditional fallow periods, and to open mar-
ginal lands that past generations could avoid
using. The farmers may turn to modern agri-
cultural methods-e.g., commercial fertilizers
-only to find that the rising costs of these in-
puts prohibit even this option. This predica-
ment is common throughout LDCs.
Most LDCs, with their growing populations,
are concentrated in a belt roughly 30 degrees
north and south of the Equator. These tropi-
cal and subtropical lands contain diverse eco-
systems: mountains, rainforests, semiarid re-
gions, and deserts, and house some 45 percent
of the Earth's people. The concentration of
LDCs in the Tropics is not a coincidence but
stems in large part from inherent physical
limitations caused by climatic and soil con-
straints. As the populations of these nations
have grown, many LDCs have come to face a
myriad of severe resource problems: degraded
soil fertility, deforestation, soil erosion, water
pollution, and land-use conflicts. Concomitant
social problems-including malnutrition, pov-
erty, and political instability-are common as

The humid tropical regions have some of the
Earth's most productive ecosystems-lush
forests that are the result of eons of long grow-
ing seasons and abundant rainfall. But this
apparent fertility is often superficial. Tropical
forests have been called "deserts covered by
trees." In fact, natural soil fertility in the wet
tropical latitudes is extremely low because
most of the minerals have been leached from
the soil by ages of rain and weathering. The
nutrients are trapped in the vegetation itself;
as the greenery dies and decays on the forest
floor, the nutrients are released, then quickly
absorbed into new growth.
Arid and semiarid regions face different
problems. Lack of water limits the type and
amount of crops that can be grown. Wind ero-
sion, salinization, and temperature extremes
all work to limit the land's productivity.
Agriculture in tropical latitudes must con-
tend with these and other physical dictates. It
must work within increasingly severe eco-
nomic constraints, too, as the costs of energy,
water, equipment, and various other agricul-
tural inputs, from seed to fertilizer, continue
to rise.
Conventional agricultural methods, many of
which were developed for use in temperate
areas, are not wholly suitable for tropical con-
ditions. It is not that conventional agriculture
cannot work in the Tropics; it can, in the short
run. But without continuous fertilizer inputs,
poor tropical soils cannot sustain temperate
farming methods. Also, in arid and semiarid
regions temperate farming technologies require
costly irrigation systems. Thus, with the in-
creasing expense of irrigation development

and fertilizers derived from natural gas, it
seems inevitable that LDC farmers will look for
new ways to sustain soil fertility and to ensure
continued agricultural productivity.
The Agency for International Development
(AID) is one mechanism by which the United
States can help LDCs meet development and
resource challenges. AID has been commended
for many of its programs, but it also has been

cited for its reluctance to change and for its
lack of innovative vision at a time when in-
novation seems most necessary. This workshop
reviewed a number of innovative biological
technologies that might help LDCs enhance
their agricultural productivity and it takes a
special look at the role AID plays, and could
play, in developing these technologies.


The innovative biological technologies cho-
sen for discussion in the workshop represent
only a sample of the diverse and adaptable ap-
proaches being studied by scientists here and
abroad. The workshop examined the following:

Promoting underexploited plant species,
especially native species already adapted
to local climates and conditions. Nature
is a storehouse of genetic possibilities in-
cluding plants with potential as food, fod-
der, oil seeds, and export goods. Native
plants can be integrated into cropping sys-
tems, reducing the need for fertilizer and
water and enhancing resistance to pests
and disease. There is also promise in plant
breeding efforts and tissue culture, where
native stocks are used to adapt crops to
less than ideal environments. This reduces
the need to alter the environment with fer-
tilizer, irrigation, and other expensive
Developing multiple-cropping and inter-
cropping systems suitable for specific trop-
ical environments as a way to maximize
land productivity. Multiple cropping is in-
tensive agriculture-growing two or more
crops that share space and resources and
can produce more per unit of land than
monoculture. Proper design of the crop-
ping pattern-e.g., using legumes-ensures
and enhances soil quality while providing
farmers with a range of products.
Designing integrated agricultural systems
that take advantage of the special benefits
provided by leguminous trees. Various spe-

cies of nitrogen-fixing trees (e.g., Prosopis
and Acacia) could be used to revegetate
deforested landscapes while providing
food, fodder, cash crops, fuelwood, and in-
creased soil fertility. Unlike legumes used
in temperate agriculture (e.g., alfalfa),
many of these tree species can fix nitro-
gen under arid conditions.
* Cultivating "green" fertilizer for rice pro-
duction. Azolla, a small aquatic fern native
to Asia, Africa, and the Americas, shows
great promise as a green manure. The fern
provides nutrients and a protective leaf
cavity for a strain of blue-green algae,
which in turn converts atmospheric nitro-
gen into a usable form. The nitrogen-rich
azolla is grown in rice paddies, either
before or along with the rice crop. It also
can be harvested and transported to up-
land fields.
* Using underexploited animal species to
meet local needs for high protein food as
well as to provide local populations with
innovative cash crops. For instance, in
Peru, guinea pigs are being produced as
an unconventional, but tasty and prolific,
protein source for local diets. And in
Papua, New Guinea, villagers are supple-
menting farm income by tending an addi-
tional garden crop-exotic butterflies for
* Exploring the use of natural mineral soil
amendments, e.g., zeolite minerals, that
improve soil properties and extend fer-
tilizer efficiency. Because of their struc-
ture, zeolites have unique properties. They

are used today primarily as molecular
sieves in industrial processes, but they
show promise in agriculture. They seem
able to help maintain nitrogen availability
in soils and help plants resist water stress.
More immediate benefits may show in ani-
mal agriculture, where zeolites can serve
as feed additives and as decontaminants
for feedlot wastes, and in fish farming.
Zeolite deposits are thought to be wide-
spread in many LDCs.
SReducing the need for commercial nitro-
gen fertilizer by inoculating suitable crops
with beneficial soil bacteria-rhizobia-
that biologically take nitrogen from the air
and convert it to a usable form for the
plant. Legume rotations, of course, were

fundamental to agriculture before the de-
velopment of commercial fertilizers. These
rotations relied on the natural abundance
of rhizobia, but improved strains might
garner even better results. Legume in-
oculants are used commercially in U.S.
agriculture and suitable strains are being
developed for LDC environments.
Increasing a plant's capacity to absorb
nutrients by encouraging the growth of
beneficial micro-organisms-mycorrhizal
fungi-that live in association with some
plants. The mycorrhizae significantly in-
crease the root's surface area-the part of
the plant that assimilates nutrients from
the soil.


Workshop participants shared a general feel-
ing that a range of promising, innovative tech-
nologies exists in various stages of develop-
ment that could help LDCs sustain soil fertility
with reduced fertilizer inputs. However, these
technologies are underused and many impor-
tant ones are being ignored by the development
community. Many of the innovative approaches
discussed are "technologies" in the broadest
sense; they are new management systems, not
new pieces of hardware.
Research on such innovative techniques gen-
erally is underfunded, perhaps because of tech-
nological complexity, human reluctance to
stray too far from the norm, or well-intentioned
skepticism about radically new or unproven
approaches to agriculture. Thus, it is all the
more difficult to document their worth. Most
of the technologies, while promising, need
pilot-scale testing in appropriate environments
to determine potential problems or necessary
alterations before they can be promoted on a
wide scale. Also, workshop participants thought

that much of the development of innovative
technologies is occurring outside of, and per-
haps in spite of, the national and international
institutions normally considered responsible
for maintaining natural resources and for deal-
ing with problems of land quality and produc-
A particularly interesting facet of these new
technologies is that many of them could bene-
fit not only LDC agriculture but also U.S.
agriculture by providing opportunities for eco-
nomic diversification, reducing soil degrada-
tion, and bolstering production while lower-
ing capital costs.
No new technology, of course, can be a pan-
acea. The importance of innovation lies in the
fact that each new approach increases the
number of options available to deal with prob-
lems. More choices thus provide increased
adaptability to changing social, economic, and
physical conditions.


This planet is believed to house some 80,000
species of edible plants. Man, at one time or
another, has used 3,000 of those for food. But
only about 150 plants have been cultivated on
a large scale, and less than 20 crops currently
provide almost 90 percent of the world's food.
It is clear that mankind could exploit more
fully the range of botanical diversity found on
Earth. In developing countries, various inno-
vative uses of plant resources show great prom-
ise and could help enhance land productivity
and increase food supplies. First, it is possible
to expand the range of crops grown by using
underexploited plant species, especially native
species already adapted to local climates and
conditions. Second, special attention could be
devoted to the potentials of leguminous spe-
cies, including leguminous trees, that are ca-
pable of converting atmospheric nitrogen into
a usable form and thus enhancing soil fertility
while reducing reliance on expensive com-
mercial fertilizers. Further, innovative and
conventional crops could be used together in
multiple cropping or intercropping systems de-
signed for specific tropical environments to
maximize efficient resource use and land pro-
The first day of the two-day OTA workshop
was devoted to discussions of particular inno-
vative biological technologies-their potential
advantages for LDC users and problems limit-
ing their use or development. Here are high-
lights of those discussions.

Underexploited Plant Resources
Every culture, of course, has indigenous spe-
cies that have been used traditionally for food,
fuel, livestock feed, construction, fiber, medi-
cine, and other purposes either gathered from
the wild or cultivated in various small farm-
ing systems. But until recently, these traditional
crops in LDCs had been lost in the shadows
of the Green Revolution and westernized farm-
ing techniques.

Now, however, there is renewed optimism
about the agricultural potential of many of
these plant resources. Native plants can be
innovative sources of a wide range of goods-
food for people and livestock, fuelwood for
cooking and warmth, materials for homes and
clothing, even oil seeds and other exports. The
benefits provided are compounded because
native plants can require fewer total inputs of
fertilizer, herbicides, insecticides, energy, and
in some cases water. This is because native spe-
cies are adapted to local environmental con-
ditions-soil type and quality, climate and
terrain. Indigenous species often are more re-
silient to stress, as well; they have evolved
defenses for local disease and pest organisms
and evolved to be efficient users of available
resources, whether water, soil nitrogen, or
other necessary nutrients. The native plant
concept is a reversal of the old philosophy of
using inputs to change the soil to suit the crop.
Here the crop is chosen to suit the soil. Ex-
amples of innovative plants include:
Winged bean (Psophocarpus tetragonolobus):
Generally identified as a "poor people's crop"
in developing countries, the winged bean's nu-
tritional potential has been vastly underrated.
Actually, this plant, sometimes called a "super-
market on a stalk," has at least six edible parts.
The leaves are used like spinach as a vegetable
or salad; the flowers are edible, tasting some-
what like mushrooms; the pods, similar to
green beans, are nutritious and palatable; the
seeds are similar to soybeans and are com-
posed of 17 percent oil and 42 percent protein;
the tendrils are also edible and taste like aspar-
agus; and the below-ground tubers contain four
times the protein of potatoes.
Amaranth (Amaranthus hypochondriacus):
Once the mainstay of certain ancient South
American cultures, amaranth is a fast-growing,
cereal-like crop that produces high-protein
grains in large, sorghum-like seed heads. The
grain is also exceptionally high in lysine-one
of the critical amino acids usually deficient in

plant protein. Amaranth grain is usually parched
and milled to be used for pancakes, cooked for
gruel, or blended with other flours. Its leaves
can be eaten as a spinach substitute.
Leucaena (Leucaena leucocephala): Of all
tropical legumes, leucaena probably offers the
widest assortment of uses. It is a fast-growing
tree that produces good, dense firewood; it
fixes nitrogen in the soil; and its leaves make
nutritious cattle forage. This leguminous tree
is especially valuable in reforestation efforts.
Any change in the use of fertilizer, pesticides,
irrigation, or machinery would depend entirely
on the nature of the native plant chosen for
cultivation-whether the particular plant could
be used on an intensive or extensive basis, the
degree to which the plant is susceptible to
pests, and many other variables.
Water needs, too, would vary with the spe-
cific species chosen for cultivation. Species
adapted to tropical soils and moist climates
should not require irrigation provided that ade-
quate rainfall occurs during the critical stages
of plant development. In regions of less than
optimal precipitation, farmers can choose
native plants with low water requirements
such as jojoba, atriplex, guayule, buffalo gourd,
guar, cassia, and acacia species. It is also pos-
sible to enhance the effectiveness of water use
through management (alternate fallow periods,
spaced planting, etc.), water harvesting, and
drip irrigation. Where land is not the limiting
factor, enhanced water harvesting is showing
high potential for fostering plant production
under desert conditions. The most suitable
plants for these technologies are deep-rooted
tree crops, drought adapted species, and bio-
mass plantings.
Some native species also offer hope for in-
tensive agriculture as certain plants could be
developed for large-scale operations. If a low-
value crop can be replaced with a high-value
new crop, irrigation may even be justified.
Close plantings, tillage, pest control, and fer-
tilization may then be needed to optimize pro-
duction and under certain circumstances
might be economically viable. Grain amaranth,
winged bean, and guar are possible species for

intensive development, but many others may
be considered.
Equipment and labor needs also vary de-
pending on the specific native plant in ques-
tion. Some species (e.g., guar or guayule) are
amenable to mechanical harvesting. Many
others, however, require manual labor, which
could be an advantage where excessive un-
employment exists.
To develop the potential of native plant re-
sources, more effort needs to be devoted to
identifying valuable species and adapting them
to modern needs. Once identified, researchers
need to look for opportunities to expand the
plant's use into similar environments else-
where in the world. Perhaps a better under-
standing of the plant diversity available world-
wide will lead to more innovation and also an
acceptance that folkways are often valid and
could be incorporated into a productive com-
promise between old and new customs.

Multiple Cropping
Multiple cropping is intensive agriculture
where two or more crops share space and re-
sources, enhancing both land-use efficiency
and long-term productivity. It is not a new tech-
nology but rather is at its roots an ancient tech-
nique that mimics the diversity of natural eco-
Today's multiple cropping systems vary
greatly depending on the character of the site
being farmed. In general, multiple cropping
systems are managed so that total crop produc-
tion from a unit of land is achieved by grow-
ing single crops in close sequence, growing
several crops simultaneously, or combining
single and mixed crops in some sequence. Both
"sequential cropping," which is growing two
or more crops in sequence on the same land,
and "intercropping," which refers to various
ways of growing two or more crops simulta-
neously on the land, are included in the
broader term "multiple cropping."
Generally, productivity on multiple cropped
land can be more stable and constant in the
long run than in monocultures. Although each

crop in the mixture may yield slightly less than
in monoculture, combined production per unit
area can be greater with multiple cropped
fields. The overall increased yields result be-
cause the component crops differ enough in
their growth requirements so that overlapping
demands-whether for sunlight, water, or
nutrients-are minimal. Multiple cropping, in
effect, broadens the land's productive capac-
ity by more fully exploiting the dimensions of
time and space.
It is important to point out that not all crop
mixtures will produce better yields when multi-
ple cropped. Certain combinations make bet-
ter overall use of available resources and will
be more successful; these crops are considered
"complementary." One of the main ways to
achieve such complementarity is by varying the
crop components temporally-i.e., using se-
quential planting to achieve a multiple crop-
ping system that avoids antagonistic interac-
tions between the components. Such systems
require special management-timely harvest-
ing, the use of proper varieties, alteration of
standard planting distances, special selection
of herbicides so as not to create antagonisms
or residual effects.
Another way of complementing crop com-
ponents is through intercropping based on
relay planting. Direct competition is avoided
by planting a second crop after the first one
has completed the major part of its develop-
ment, but before harvest. Research on relay
cropping in Mexico and Latin America shows
definite yield advantages, especially for corn
and beans. The success of relay intercropping
depends on the correct combinations of tim-
ing and other variables so as to avoid shading,
nutrient competition, or inhibition brought
about by toxicity produced by the decomposi-
tion of previous crop residues. Research in
these areas is inadequate.
Finally, farmers can get maximum comple-
mentarity in systems where two or more com-
patible crops are grown simultaneously, either
in rows, strips, or mixed fields. For example,
traditional corn, bean, and squash systems
grown in Mexico show how three species can

benefit from multiple cropping. All three crops
are planted simultaneously, but mature at dif-
ferent rates. The beans, which begin to mature
first, followed by the corn, use the young corn
stalks for support. The squash matures last. As
the corn matures, it grows to occupy the up-
per canopy. The beans occupy the middle
space and the squash covers the ground. Re-
search shows that the system achieves good
weed and insect control. And while the beans
and squash suffer a distinct yield reduction,
corn yields are significantly higher than in
comparable monocultures. It is still uncertain
whether the higher yields are the result of more
efficient resource use or if some mutually ben-
eficial interaction is occurring among the crop

Agroforestry is a multiple cropping manage-
ment technology that combines tree crops with
food crops, animal agriculture, or both. Like
other multiple cropping systems, its goal is to
optimize land productivity while maintaining
long-term yields. In the past, small-scale tradi-
tional agriculture often included trees as part
of the farm design, but interest in agroforestry's
place in modern agriculture is just beginning.
Agroforestry systems can be used to bring mar-
ginal lands into production-lands with steep
slopes, poor soils, or widely fluctuating rain-
fall. But tree-crop combinations can also be
used on prime agricultural or grazing land to
further increase productivity. The main limita-
tions to widespread use of agroforestry prac-
tices is lack of knowledge and expertise, and
unwillingness in the agricultural establishment
to accept the idea of long-term, diversified
The key to multiple cropping's benefits is the
intensity of the cropping pattern-drawing as
much as possible from the land resource. De-
spite the intense demands, such systems need
not abuse the land; through proper design and
operation, multiple cropping management can
sustain and actually enhance soil fertility. De-
pending on the multiple cropping system used,
advantages can include:

more efficient use of vertical space and
time, imitating natural ecological patterns
and permitting more efficient capture of
solar energy and nutrients;
more biomass (organic matter) available to
return to the soil;
more efficient circulation of nutrients, in-
cluding "pumping" them from deeper soil
profiles when deep-rooted species are
possible reduced wind erosion because of
surface protection;
promise for marginal areas because multi-
ple cropping can take better advantage
of variable soil types, topography, and
steeper slopes;
less susceptible to climatic variation
(especially precipitation, wind, and tem-
reduced evaporation from soil surface;
increased microbial activity in the soil;
more efficient fertilizer use through the
more diverse and deeper root structure in
the system;
improved soil structure, less likelihood to
form "hardpan," and better aeration and
reduced fertilizer needs because legume
components fix atmospheric nitrogen for
themselves and associated nonlegumes;
heavier mulch cover aids in weed control;
better opportunities for biological control
of insects and diseases because of compo-
nent plant diversity; and
potential benefits from mutualisms and
beneficial interactions between organisms
in crop mixture systems.
But as mentioned, not all crop combinations
lend themselves to successful multiple crop-
ping and not all forms of multiple cropping are
necessarily good for the land. Sequential crop-
ping, for instance, of two or three crops can
actually mine the land of nutrients and min-
erals if little thought is given to legume rota-
tions, green manures, animal manures, or other
fertility-building activities. And in light of the
biological and physical aspects of the agroeco-
system, other disadvantages in multiple crop-
ping might include:

competition for light, soil nutrients, or
possibility of allelopathic influences be-
tween different crop plants caused by
plant-produced toxins;
potential to harm one crop component
when harvesting other components;
difficulty building a fallow period into
multiple cropping systems, especially
when long-lived tree species are included;
difficulties in mechanizing various oper-
ations (tillage, planting, harvest, etc.);
increases in evapotranspiration caused by
greater root volume and larger leaf surface
possible overextraction of nutrients, fol-
lowed by their subsequent loss from the
agroecosystem if they are exported as agri-
cultural or forest products;
damage to shorter plants from leaf,
branch, fruit or water-drop from taller
higher relative humidity in the air that can
favor disease outbreak, especially of fungi;
possible proliferation of harmful animals
(especially rodents and insects) in certain
types of systems.
Even though it seems that the biological and
physical advantages of multiple cropping out-
weigh the disadvantages, there also is a range
of social and economic factors that would in-
fluence the acceptance and use of multiple
cropping technologies in various cultures. In
terms of social stability, multiple cropping is
advantageous because it leads to a diverse agri-
cultural system. Such a system is less suscep-
tible to climatic variation, environmental
stress, and pest outbreaks. It is also less vul-
nerable to swings in crop prices and markets.
Multiple cropping also demands more constant
use of local labor and provides a more constant
output of harvested goods over the course of
the year. And because such systems are highly
adaptable, they can be melded into many dif-
ferent types of culture without undue stress on
existing local customs. Multiple cropping also
provides farmers with a large variety of useful
products, depending on the type and complex-

ity of their systems. And, of course, multiple
cropping systems can reduce the need for fer-
tilizers and other energy imports, thus giving
LDC farmers improved economic stability and
Reported lower yields, complexity of activi-
ties and management, higher labor demands,
and difficulty mechanizing operations are all
factors that discourage modern farmers from
multiple cropping. Conventional agriculture is
looking for short-term profits rather than at
maintaining constant income over the long
term, although it appears that the economics
of farming may be changing to favor such inno-
vative systems, especially in the LDCs.
Although there exists the tangible disadvan-
tage of potentially lower yields, most of the dis-
advantages involved in multiple cropping are
derived from lack of experience and knowledge
about the workings of complicated agroeco-

Azolla/Algae Symbiosis
Rice-one of the most important staple crops
in the world-demands rich, fertile soil. But
traditional legume crops do not make good
green manures for rice farmers; they are reluc-
tant to devote part of the valuable growing
season to a relatively slow-growing legume
crop. Furthermore, most legume crops cannot
grow or fix nitrogen in flooded or waterlogged
soils. But these disadvantages can be avoided.
Through the use of azolla, a small aquatic fern
native to Asia, Africa, and the Americas, rice
farmers can produce a fast-growing green
manure that thrives in paddy-like conditions.
Azolla is a genus of small ferns that live nat-
urally in lakes, swamps, streams, and other
bodies of freshwater. Its tremendous agricul-
tural potential lies in the fact that azolla lives
in a symbiotic relationship with a nitrogen-
fixing blue-green algae, Anabaena. The delicate
azolla fern provides nutrients and a protective
leaf cavity for the Anabaena. In turn, the algae
produce enough nitrogen to meet the needs of
both plants, plus some extra. Under the right
conditions, the fern/algae combination can ac-

tually double in weight every 3 to 5 days and
fix nitrogen at a higher rate than most legume
Rhizobium symbionts. In 25 to 35 days, azolla
can fix enough nitrogen for a 4 to 6 ton/ha rice
crop during the rainy season or a 5 to 8 ton/ha
crop under irrigation during the dry season.
The nitrogen fixed by the fern/algae combina-
tion becomes available to the rice after the
azolla mat is incorporated into the soil and its
nitrogen is gradually released as the plants
Azolla's value as a green manure for flooded
crops has been known for centuries by the peo-
ple of the People's Republic of China and Viet-
nam. But its use was relatively limited; few
families knew the intricate techniques needed
to overwinter and oversummer the sensitive
fern successfully, and these families controlled
the distribution of starter-stocks in the spring.
After the revolutions in China and Vietnam,
the new governments eventually recognized
the value of azolla and began promoting its use,
but their efforts were minimal and progress
was slow. It is only recently that worldwide at-
tention has focused on the plant and serious
efforts have been made to search for hardier
varieties for widespread use.
Azolla's ability to enhance soil fertility oc-
curs both because it is an input of nitrogen and
of organic matter. Nitrogen, of course, is a nec-
essary plant nutrient. Humus, the rich organic
material formed through plant decomposition,
increases the water-holding capacity of the soil
and promotes better aeration and drainage.
Organic matter also can bind soil particles to-
gether, thereby improving the soil structure.
Azolla also can be important in the cycling
of nutrients. While it is growing, the plant not
only fixes nitrogen but absorbs nutrients out
of the water, nutrients that otherwise might be
washed away. Some of both the nitrogen and
nutrients are stored in the living plant matter
until the fern/algae mat is incorporated into the
soil and begins to decompose. Because it has
a high lignin content, azolla decomposes rela-
tively slowly-6 weeks or more before all the
nutrients are released. This natural slow re-
lease is ideal for a developing rice crop.

In addition, it seems that azolla suppresses
the growth of certain aquatic weeds-in part
because the thick azolla mat deprives young
weeds of sunlight and in part because the in-
terlocking mat physically inhibits weed emer-
gence. Rice seedlings are not harmed because,
when transplanted, they stand above the azolla
Using any green manure crop requires some
adjustments in a farmer's crop management
system. Depending on the local environments,
azolla can be grown as a monocrop, intercrop,
or both. If the fern is grown as a monocrop,
it is grown and incorporated into the soil before
the rice is harvested or it is grown and trans-
ported for use on upland crops. Azolla is often
intercropped in areas where the growing
season is too short for successful monocrop-
ping. One method grows two rows of rice
planted about 4 inches apart with Azolla grow-
ing in two-foot spaces on either side of the dou-
ble rows. The azolla is incorporated by hand
or with a rotary rice weeder. Combining mono-
cropped and intercropped azolla provides ni-
trogen before transplanting and throughout the
growing season. At present, azolla's primary
role is as a spring green manure and its sec-
ondary role is as a fall manure. It is highly sus-
ceptible to pests and temperature extremes and
generally is not grown crops in summer.
To be successful, azolla requires phosphorus
fertilizer (0.5 to 1.0 kg P/ha/week), but this is
not necessarily an increase over the fertilizer
needed to produce a rice crop. Rice also re-
quires phosphorus; so, rather than applying it
directly to the rice the fertilizer can be given
to the azolla in small weekly doses. Once the
azolla is incorporated into the soil and begins
to decompose, the phosphorus becomes avail-
able to the rice crop. Other inputs that enhance
azolla growth in certain soils (e.g., potassium)
are usually also applied for a high-yielding rice
crop and so can be cycled in a similar way.
Water is the primary environmental con-
straint on azolla cultivation. As a freefloating,
aquatic fern, azolla can only grow in areas with
abundant, stable water supplies. Although it
can last for months under refrigeration, the

plant cannot survive for more than a few hours
on a dry soil surface under direct summer sun.
The azolla varieties available are not very stress
tolerant; azolla cannot live in water outside a
00 to 400 range, and for adequate growth the
daytime temperature should stay within 150 to
350 C. Humidity and pH also affect azolla
Because the technology to grow azolla from
seeds (spores) does not exist, some plants (1 to
10 percent of those needed for startup) must
be maintained throughout the year. Because of
azolla's sensitivity to temperature stress, the
overwintering and oversummering periods are
critical. The plant is also susceptible to a num-
ber of insect and disease pests. The pests are
especially destructive during the summer and
must be carefully controlled. In fact, the pri-
mary reason why azolla is not cultivated dur-
ing the summer is because of the destruction
caused by rampant insects.
There are also cultural and economic con-
straints on azolla cultivation. As with any in-
novation, it can be difficult for people to ac-
cept an idea that is foreign to their traditions.
The idea of growing an aquatic legume is fun-
damentally different from most farming soci-
eties' norms; and in many hungry countries,
the idea of growing a crop just to plow it under
seems utterly impractical. Azolla cultivation
may be slow in gaining acceptance, too, be-
cause it demands a year-round commitment
not usually required of rice farmers. And be-
cause azolla cultivation is not applicable in
areas where rice is broadcast-sown, it is not a
viable technology for those regions that do not
plant rice in rows.
Finally, social and political factors can work
both for and against azolla's use. In some re-
gions, especially where there are unfavorable
land ownership patterns, low prices or other
strong disincentives, farmers are not willing
to shift from their immediate-subsistence,
"plant and harvest" approach, because they do
not see the long-term benefits. Political sys-
tems, too, can have an effect. The successful
azolla programs in China and Vietnam depend
heavily on specially trained "azolla teams"

made possible by the structure of their farm-
ing communes and cooperatives. Societies less
centrally organized could have difficulty adopt-
ing and transferring azolla cultivation tech-
One of the major constraints on the devel-
opment of azolla technologies is simply lack
of information. Although it is an ancient agri-
cultural system, its use has always been limited
and it has not received much scientific atten-
tion. Research efforts are disorganized, scat-
tered, and often repetitious. There has never
been an international discussion of azolla re-
search priorities. And once again, traditional
segmented research approaches have proven
inadequate because many of the problems that
remain require a multidisciplinary approach.
As of 1980, azolla was cultivated as a green
manure on about 2 percent of the harvested
rice area of China and about 5 percent of the
spring rice crop. In Vietnam, azolla grows as
a winter green manure for 8 to 12 percent of
the total harvested area, and about 40 to 60 per-
cent of the irrigated spring rice in the Red River
delta. But these two countries are only two of
many that might tap azolla's potential. With re-
search, strains could be found that are less sen-
sitive to summer insects and temperature and
cultivation could increase substantially. In
essence, using azolla in rice production ex-
changes labor for nitrogen fertilizer. In coun-
tries with a shortage of cash but plentiful la-
bor, azolla technology could be a step toward
sustainable agriculture productivity.

Underexploited Animal Species
People interested in helping developing
countries better their standards of living tend
to promote resources and technologies with
which they already have experience. One hears
much, for example, of how genetic engineer-
ing can be expected to make possible self-
fertilizing varieties of conventional crops such
as wheat and corn. While understandable, this
preoccupation with increasing the productivity
of "mainstream" species overlooks a vast po-
tential. Indigenous species often have the

advantage of being relevant to the customs and
values of local people.
Just as there are unfamiliar plants ripe for
development as sources of food, feed, fiber, and
fuel, so are there also unfamiliar animal spe-
cies at least as promising. People traditionally
have relied on a small number of animals that
have been domesticated since prehistoric
times. But domestication of some different spe-
cies could pay tremendous dividends. In some
countries, in fact, this is already beginning.
For instance, small animals are particularly
suited to domestication in many developing
countries because they require little space, they
fit well into village or urban life, and they re-
quire no refrigeration since they can be eaten
in one meal. Moreover, many of these species
tolerate the climates of developing countries
better than do sheep, cattle, and pigs, and they
thrive on readily available diets. Thus, snail
farming in Nigeria, giant toad farming in Chile,
and guinea pig farming in Peru are all being
developed to provide native people with much-
needed high-quality protein at affordable costs.
In addition, at least some of these ventures
can become the basis of new industries. Thanks
to the efforts of researchers at the La Serena
campus of the University of Chile, for exam-
ple, intensive methods have been developed
that furnish grocery stores, restaurants, and
canneries with 10 to 15 tons of giant toad legs
a year. Because the meat is an attractive white
and tastes like a blend of chicken and lobster,
it could prove to be a lucrative export as well.
Giant toads are reportedly easy and inexpen-
sive to rear. Kept in isolated ponds (so that they
will not cannabilize other aquatic life) and sup-
plied with insects attracted by flowers, shrubs,
and rotten fruit, they require little attention and
reach their market weight of about half a pound
in 2 years.
The domestication of exotic species is, in
fact, already producing foreign exchange for
at least one poor country-Papua New Guinea.
There, people who used to hunt crocodiles in
the wild are now more profitably rearing hatch-
lings in captivity for the world skin market.

And in remote jungle villages butterflies are be-
ing raised on "farms without walls" to meet
the rising international demand from mu-
seums, entomologists, private collectors, or-
dinary citizens, and the decorator trade.
Both the crocodile and butterfly projects
demonstrate that development and the conser-
vation of natural resources can go hand in
hand. They also demonstrate something else:
that to succeed, such projects need not only a
concern for development but also a sensitivity
to local environmental conditions and knowl-
edgeable inputs of science and sociology.
In Papua New Guinea, for instance, the in-
troduction of western-style cattle ranching
could threaten the fragile tropical forest eco-
system. And such imported technologies would
be completely unfamiliar to local people. By
contrast, crocodile and butterfly farming that
can be based on sound biological principles,
would make it worthwhile for local people to
use indigenous renewable resources wisely.

Zeolites are natural, three-dimensional, fine-
grained silicate minerals composed of alkali
and earth metals crystals that have an ability
to separate gas molecules on the basis of size
and shape. Over 100 forms have been synthe-
sized and are now the mainstay of multimil-
lion-dollar molecular sieve businesses that are
important for industrial purposes in chemical
and petrochemical firms in the United States
and abroad.
Zeolites, however, also occur abundantly in
nature. Almost 50 species have been identified
from volcanic sedimentary deposits on every
continent. Their widespread dispersion and
special properties make them of interest to
countries wishing to rely less on costly im-
ported inputs to produce food because they ap-
pear promising as a means to improve animal
husbandry, fish production, and crop yields.
Zeolites have such promise primarily because
they act as traps for nitrogen.
Zeolites get their name from the classical
Greek words "boiling stones" because they

froth when exposed to intense heat. Although
their existence has been known to scientists
since 1756 and they have been used since an-
tiquity as building materials, their potential
agricultural and aquacultural applications
were virtually ignored until about 20 years ago.
Even now this technology must be said to be
suffering from neglect.
When added to animal feed, for example,
zeolites have both inhibited the development
of mold during storage and increased the
growth rates of swine, rabbits, poultry, beef,
and dairy cattle. Moreover animals raised on
zeolite-enriched rations tend not to be subject
to diarrhea or other ills. These minerals are
thus a possible alternative to the controversial
use of antibiotics in livestock feed.
Besides thriving on zeolite-supplemented
diets, animals fed these minerals produce ex-
crement that is at once almost odorless and ex-
ceptionally good fertilizer. This is because
zeolites capture the ammonia ion from the fe-
ces and thus retain the biological availability
of the nitrogen in animal wastes. Direct zeolite
treatment of manure to reduce odor and im-
prove its efficacy as fertilizer is also feasible,
as is using the adsorption properties of natu-
ral zeolites to obtain pure methane for energy
purposes from animal or other organic wastes.
In summary, the application of zeolites to
animal husbandry holds some promise from
the perspectives of livestock production, pol-
lution control, crop yields, and energy alter-
Zeolite technology also has potential for the
commercial fish breeding and farming. For one
thing, the rations now fed to fish in such enter-
prises are quite expensive. As the nutritional
requirements of fish are similar to those of
poultry, the indications are that zeolite supple-
ments could be expected to reduce feeding
costs. For another, many fish species are raised
in closed or recirculating water systems where
the accumulations of nitrogen from their waste
and the decay of uneaten food commonly
causes sterility, stunted growth, and high mor-
tality. Although various means already are used
to deal with these problems, zeolite regulation

of the nitrogen content of fish ponds has been
reported to be cheaper and, under low temper-
ature conditions, more reliable.
Similarly, the affinity of zeolites for nitrogen
may be important in ponds and small lakes
where eutrophication results in an oxygen-poor
environment detrimental to fish life. Evidence
suggests that the ability of these minerals to in-
troduce free oxygen into stagnant water might
increase the number of fish that can be raised
or transported in a given volume of water.
The properties of zeolites also improve the
performances of chemical fertilizers and pes-
ticides, fungicides, and herbicides. For exam-
ple, zeolite-treated soils retain the nutrients
supplied by chemical fertilizers longer than
soils treated with the fertilizers alone. The pres-
ence of zeolites as soil conditioners (also
known as soil amendments) also has been
found to regulate the release of critical nutri-
ents from fertilizers. Improved yields of wheat,
apples, eggplant, carrots, sorghum, radishes,
chrysanthemums, and sugar beets have been
Controlled release of micronutrients from the
soil itself-e.g., iron, zinc, copper, manganese,
and cobalt-has also been found when zeolites
are used in conjunction with chemical fer-
tilizers; this also prevents them from caking
and hardening during storage.
Zeolites added to pesticides, herbicides, and
fungicides seem to enhance their effectiveness.
They can also be exploited to remove toxic
heavy metals from the soil, thus preventing the
toxic wastes from moving up the food chain
from plants to animals and, ultimately, to
Nonetheless, the commercial use of zeolites
in agriculture has generally been on only a rela-
tively small scale and then predominately in
Japan and other parts of the Far East. Even
though a number of domestic companies have
undertaken preliminary zeolite studies, little in-
formation is available on the long-term bene-
fits or adverse impacts of these minerals on
food production or the environment. Further-
more, even such information as has been

developed is often proprietary. Though the de-
sire of the private sector to keep its data con-
fidential is understandable, this cannot help but
lead to duplication of effort and slow progress.
Developing countries of course would be
eager to reduce their costly dependence on im-
ported fertilizers, fuels, and livestock feed. Co-
operative ventures between the United States
and these countries could improve knowledge
of zeolite technology and, importantly, under-
take long-term or large-scale testing projects
under field conditions.

Biological Nitrogen Fixation
One very promising multiple cropping strat-
egy is the use of leguminous plants. Legumes
can provide food, livestock fodder, and wood
while concurrently improving soil fertility. Le-
guminous plants-e.g., temperate species such
as alfalfa, soybeans, and clover-have the ca-
pacity to provide their own nitrogenous fer-
tilizer through bacteria (Rhizobia) that live in
nodules on their roots. The bacteria chemically
convert atmospheric nitrogen into a form that
the plant can absorb and use. The nitrogen also
is available in the root zone for nonleguminous
companion or follow-on crops to use.
The use of legumes is not new; generations
of farmers relied on rotations of legume plants
to restore nitrogen in the soil long before the
advent of cheap commercial fertilizers. Now,
as energy costs skyrocket and fertilizer costs
become prohibitive in many developing coun-
tries, legume use-green manure-may be the
best remaining option for maintaining soil fer-
tility and agriculture productivity.
Leguminous species could not only help pro-
tect LDCs from burgeoning energy costs but
could also improve local nutrition. Nutri-
tionally, legume seeds (beans or pulses) are two
to three times richer in protein than cereal
grains. Many have protein contents between
20 to 40 percent. A few even range up to 60
percent. This is particularly important because
there is chronic protein deficiency in virtually
every developing country.

Inoculant Technologies: Nitrogen can be
converted into forms usable by plants through
industrial processes, but only at great cost,
especially as energy prices escalate. But bio-
logical nitrogen fixation (BNF) by symbiotic
associations of plants with micro-organisms
may be an economically and environmentally
sound approach to sustainable agriculture.
Farmers can capitalize in two ways on cer-
tain plants' innate ability to fix nitrogen bio-
logically. First, of course, like countless past
generations of farmers they can use legumes
in their cropping systems and benefit from the
nitrogen produced. But recent innovations also
can help farmers maximize nitrogen fixation.
Using inoculant technology, selected legumes
can be inoculated with specific strains of
Rhizobium, the soil bacterium that associates
with legume roots and fixes nitrogen. This way
farmers can more fully exploit the plant's fer-
tilizing capabilities.
Most soils harbor various native rhizobial
populations and these strains will associate
with sprouting legumes. But because these
strains differ greatly in their effectiveness, it
can be to the farmer's advantage to plant leg-
ume seeds that have been inoculated with
proven strains of Rhizobium. The objective of
inoculation technologies is to introduce suffi-
ciently high numbers of preselected strains of
rhizobia into the vicinity of the emerging root
so that they have a competitive advantage over
any indigenous soil strains of lesser nitrogen-
fixing ability.
Commercial-scale inoculant use is common
in the United States and Australia. Brazil,
Uruguay, Argentina, India, and Egypt also pro-
duce inoculants. But while demand for in-
oculants is growing in many countries, it is not
enough to simply import U.S. or other in-
oculants because they may not be suitably
adapted to the LDCs climate, soils, and farm-
ing systems. BNF can be improved by select-
ing effective Rhizobium strains from the local
environment and culturing these.
The major scientific constraint on develop-
ing BNF technologies is inadequate under-
standing of the interactions among specific

host legumes, rhizobial strains, and various
environments. This results in an inability to
predict whether a given legume will respond
to inoculation in a particular region. A lack of
trained personnel in tropical regions also acts
to limit research and development efforts. And
because inoculant development and use re-
quires some technical training, it may not be
an easy technology for LDCs to adopt widely.
But while legume use holds potential in all
segments of agriculture, inoculant technology
at present should only be advocated when there
is a known need to inoculate.
Most legumes in the Tropics fix about 100
kg/ha/yr of nitrogen, although the forage tree
leucaena can fix as much as 350 kg/ha/yr and
some other species can fix as much as 800
kg/ha/yr. However, the benefit to nonlegumes
is small when compared to the effects of nitrog-
enous fertilizer as applied in the intensive
cereal production systems of the developed
world. It is unrealistic to think that biologically
fixed nitrogen will replace commercial fer-
tilization of cereal and root crops. These crops
are known to respond to levels of nitrogen far
in excess of those that could currently be sup-
plied through legume BNF. Thus, it would be
profitable to determine ways to increase the
contribution of legume BNF as a complement
to nitrogen fertilizers rather than as an alter-
Although legumes seem unlikely to replace
commercial fertilizers, fertilizer savings through
the use of legumes could represent a signifi-
cant savings in foreign exchange, reduce de-
pendence on energy-rich nations, and lend
more stability and diversity to LDC agriculture.
Leguminous Plants: A great variety of legu-
minous plants-both food crops and species
useful for fuelwood, fodder, and other needs-
exist that could be cultivated in moist and
arid/semiarid tropical climates. Winged bean
is one extraordinarily valuable leguminous spe-
cies. Tarwi, tepary bean, and yam beans are
also nitrogen-fixing species with potential in
moist tropical environments.
But not all leguminous species have high
water requirements. Adapted plant species

could be used in arid and semiarid regions as
well, serving not only to enhance land produc-
tivity but also to stimulate depressed econ-
omies. For example, leguminous trees such as
Acacia, Leucaena, and Prosopis could be im-
portant, fast-growing fuelwood sources. Be-
cause 80 percent of the wood consumed in the
Third World is used as fuel, and wood short-
ages are of crisis proportions in some areas,
the potential of agroforestry should not be un-
In arid/semiarid regions, of course, water
availability is a key factor in agricultural pro-
ductivity. But problems are compounded in
some dry environments because soils also have
low fertility. In these areas, drought-adapted,
deep-rooted, nitrogen-fixing tree species (e.g.,
Acacia albida and Prosopis cineraria), peren-
nial arid-adapted herbaceous legumes (e.g.,
Zornia and Tephrosia), and shrubby legumes
(e.g., Palea species) could increase soil fertility
and triple water use efficiencies. By bolstering
soil fertility with tree species, it is possible to
create a system where production of food
staples is water-limited rather than fertility-
limited. And intercropping traditional, annual
food staples such as millet, sorghum, ground-
nuts, and cowpeas with leguminous trees can
actually stimulate crop yields.
Livestock fodder and cash crops, too, can be
obtained from arid species. Arid-adapted, salt-
tolerant shrubs (e.g., saltbush-Atriplex spe-
cies), the pods of leguminous trees (e.g., Acacia
tortilis, Acacia albida, and Prosopis species),
and even cactus (Opuntia and Cereus) can ex-
pand the amount of forage available for local
livestock while improving soil quality and en-
hancing the stability of the grazed ecosystems.
LDC farmers also could benefit from grow-
ing perennial, arid-adapted plants as cash
crops. The species Jojoba is under development
in southern California, Arizona, Mexico, and
various semiarid LDCs. It produces seed that
contains a rancidity-resistant, nonallergenic,
liquid wax with lubricating properties equiva-
lent to oil from the endangered sperm whale.
Another desert plant, guayule, contains natu-
ral rubber and could become a major semiarid

crop. Other potential lies with various species
of drought-adapted leguminous trees that might
be useful for the gums they exude, cacti that
produce table-quality fruits, and a number of
other innovative plant resources.
Surprisingly, relatively little work is being
done to further current knowledge about some
of these highly promising plant resources. But
as energy, fertilizer, irrigation, and other costs
escalate, it seems inevitable that farmers in arid
and semiarid regions will look more to adapted
Optimal water-use efficiency in an arid/
semiarid agroecosystem demands a mix of
nitrogen-fixers and water-to-dry matter conver-
sion specialist plants. For instance, cacti are
a better supplier of the energy portion of live-
stock feed than legumes because they have a
fivefold greater efficiency converting water to
dry matter. However, legume leaf litter is im-
portant to create good soil fertility so the cactus
can achieve its maximum water-use efficiency.
Thus, a mix of plants is needed. And because
livestock need both energy and protein, both
energy- and protein-producing plants are re-
Similarly, appropriate use of arid-adapted
legumes can increase fertilizer-use efficiency.
Adapted legumes do not require nitrogen them-
selves and when properly incorporated into a
diversified agroecosystem they will reduce ni-
trogen needs for nonlegumes as well. Many
arid-adapted plants, both legumes and non-
legumes, have very deep root systems-an
advantage because they are thus capable of ex-
tracting nutrients and minerals from deep sub-
surface soil layers. Also, the deeper rooted spe-
cies should capture a higher portion of any
fertilizers applied because the nutrients are not
as likely to leach beyond their deep root zone.
As an added benefit, wind and perhaps water
erosion might be reduced, as many of these
plants are perennials and thus keep the soil
more adequately protected.
There are no major scientific constraints to
using arid-adapted plant resources in LDC agri-
culture, but there is great need for expanded
research and development efforts. The poten-

tial paybacks could be great. Environmental
impacts, too, are overwhelmingly positive, in-
cluding the potential to slow desertification.
Political and social constraints, however, ex-
ist that might limit the use of innovative plants.
Cultural traditions, for instance, are not easily
changed and innovation must blend into ex-
isting values systems and local behavior. If, as
in Sahelian Africa, free-roaming goats devour
young tree seedlings because tradition allows
that goats can forage unrestrained, then refor-
estation attempts must consider this and devise
goat-proof protection for the young trees.
Other social influences also can make the
acceptance and use of innovation all the more
difficult. This is especially clear in research
centers run by scientists either from or trained
in developed countries; consciously or not,
they often strive to promote their own cultural
values and ignore the methods and effective-
ness of native farming systems. As was the case
with Acacia albida, the scientists may not be
broadly trained-the agronomists failing to see
the tree's food potential and the foresters un-
derestimating its potential because it does not
grow in forests and hence is not part of stand-
ard sylviculture concepts. It is not lack of con-
cern that causes this problem. Rather, some
agricultural scientists tend to be overspecial-
ized and limited in their experience. Also,
administrative structures often thwart attempts
to develop integrated, innovative programs.
In practical terms, such innovative biologi-
cal technologies offer real hope for LDC farm-
ers. And the scale need not be big. A farmer,
for instance, could plant 1 hectare with 200
Prosopis trees at 15 cents each for a total cost
of $30. Land, a shovel, and buckets for water-
ing the seedlings are the only prerequisites.
With protein and nitrogen contents of 12.5 and
2.0 percent, respectively, pods from the trees
could in 2 or 3 years produce 60 kg of nitro-
gen and return the $30 initial investment.
Many of the innovative systems now receiv-
ing attention from the scientific community are
actually widely used by subsistence farmers in
the developing countries. However, the plants

under cultivation now are of unselected genetic
stock. It is comparable, in fact, to the use of
unselected races of maize and wheat that were
in use in the late 1800s in the United States and
Europe. Subjecting the innovative species to
a rigorous research and development effort
could be expected to produce yield increases-
perhaps twofold and threefold in 15 years-
and other beneficial refinements of immense
value to the people of the Third World. And
yield increases in tree legume production,
fuelwood production, cash crop production,
soil fertility, and ensuing staple food produc-
tion would have repercussions throughout the
economy-more income; greater demands for
goods; a larger tax base to support roads,
schools, and health services; and increased em-
ployment. By working within the bounds of the
ecosystems, innovative plant resources can
help agrarian societies ensure sustainable and
stable agriculture.

Mycorrhizal Fungi
Nitrogen is only one of the nutrients essen-
tial to plant growth. So another approach to
enhancing LDC agriculture without inputs of
commercial fertilizers is to find ways to in-
crease the effectiveness of the plant's use of the
other nutrients available in the soil.
Selective plant breeding, of course, still holds
great potential for developing varieties of inno-
vative and traditional crops that are more
resistant to environmental stress. Geneticists
have made extraordinary strides in breeding
varieties that respond to commercial fertilizer
inputs; similar efforts could help locate and de-
velop plants that would grow and prosper
under less than ideal conditions-marginal
lands, variable climates, or deficient soils. This
potential amplifies the importance of preserv-
ing native plant resources, both in seed stor-
age facilities and in their natural habitats, be-
cause geneticists necessarily turn to hardy,
native stocks as sources of genetic material to
improve cropped varieties.
There is another "biotic fertilizer" that might
aid LDCs in their quest for sustainable agro-

ecosystems. Mycorrhizal fungi are beneficial
soil fungi that live symbiotically with a vast
range of plants. Mycorrhizae are the structures
formed-part plant, part fungus-by the sym-
biosis. These structures can extend up to 8 cm
from the root into the surrounding soil, pro-
viding a bridge to transport nutrients back to
the roots. The host obtains nutrients via the
mycorrhizal fungi, while the fungus obtains
sugars or other foods from the plant. The asso-
ciation results in a marked increase in the host
plant's growth.
There are many species of mycorrhizal fungi
that form mycorrhizae and can enhance plant
growth. These fungi are so common, in fact,
that literally any field soil sample from the Arc-
tic to the Tropics will contain some. The most
common type, vesicular-arbusula (VA) mycor-
rhizae, occur on liverworts, ferns, some con-
ifers, and most broad-leaved plants including
agronomically important species such as wheat,
potatoes, beans, corn, alfalfa, grapes, date
palms, sugar cane, cassava, and dryland rice.
Only 14 plant families are considered primar-
ily nonmycorrhizal.
The fungi essentially increase the surface
area of the plant's roots for absorbing nutrients.
They actually can increase the plant's absorp-
tive area by as much as 10 times. The fungi also
extend the host plant's range of uptake; nutri-
ent ions that do not readily diffuse through the
soil-e.g., phosphorus, zinc, and copper-can
be tapped from beyond the normal root zone
by the fungi. Absorption of immobile elements
can be increased by as much as 60 times by the
plant-fungi symbiosis. Perhaps the most impor-
tant benefit provided by mycorrhizal fungi is
increased phosphorus uptake. They also stim-
ulate plant absorption of zinc, calcium, cooper,
magnesium, and manganese. Plant uptake of
mobile soil nutrients such as nitrogen and
potassium is rarely improved because normal
soil diffusion typically supplies adequate amounts
of these regardless of root size.
Mycorrhizal fungi also can enhance water
transport, prevent water stress under some
conditions, enhance salt tolerance, and in-

crease symbiotic nitrogen-fixing bacteria such
as Rhizobium.
The potential offered by mycorrhizal fungi
as biotic fertilizers, however, is not as vast as
it might seem. Mycorrhizal fungi already occur
in most soils and thus already grow in asso-
ciation with most agronomic crop plants. Be-
cause these fungi are so widespread, immedi-
ate needs for inoculation are limited. The
inoculants currently available are for use on
disturbed sites (strip-mined areas where in-
digenous mycorrhizal populations have been
destroyed), on fumigated soils (any forest or
crop nursery or plot that has been treated to
remove soil-borne pests), and in greenhouses
(because sterile soils lack native mycorrhizal
fungi). In these situations, inoculation with
mycorrhizal fungi has proven beneficial-e.g.,
in fumigated sand or soil, VA mycorrhizal
fungi will increase the growth of citrus, soy-
beans pine, and peaches. Growth improve-
ments also show in cotton, tomatoes, corn,
wheat, clover, barley, potatoes, and many other
But even though large-scale field inoculations
with mycorrhizal fungi are rare because of ade-
quate indigenous populations and because
there is limited inoculum available, it seems
likely that such applications might be much
more valuable if, for instance, scientists de-
velop mycorrhizal fungi inoculants that are
superior to native populations. Because many
indigenous mycorrhizae are relatively ineffi-
cient symbionts, improved strains of fungi
could enhance plant growth, even in nonsterile
soils. And because huge expanses of tropical
soils (e.g., the Brazilian Cerrado) are either defi-
cient in phosphorus or immobilize added phos-
phorus fertilizers, mycorrhizal fungi could im-
prove the productivity of the marginal lands,
if fungi having the ability to extract small quan-
tities of fertilizer were developed and added
to the soil.
Even though mycorrhizal fungi inoculants
are used commercially in some circumstances,
their importance is limited and many questions
about their effectiveness remain unanswered.

For instance, fumigating fields with methyl
bromide, a biocide that is extremely toxic to
mycorrhizal fungi, often is followed by stunted
growth in following crops. Yet little work has
been done to determine the feasibility of field-
scale application of inoculants. And even in
nursery crops grown on sterile, nonmycor-
rhizal soils, inoculations receive limited use in
part because detailed information regarding
their value is lacking. For tree crops, however,
some of the answers may be coming; the U.S.
Forest Service is conducting a testing program
using commercial inoculum on tree nursery
sites throughout the country. When the tests
are complete they should indicate the commer-
cial feasibility of producing and using mycor-
rhizal inoculum in fumigated tree nurseries.
Three major obstacles hinder further devel-
opment of this biotic fertilizer. First, no large-
scale field experiments using mycorrhizal
fungi under normal agricultural conditions

have been conducted, yet such work is a nec-
essary forerunner to actual use of the fungi.
Second, cost-benefit analysis is warranted to
determine the economics of mycorrhizal ap-
plications. And finally, agriculture itself must
shake loose of some conventionality; it seems
locked to practices for increasing soil fertility
that only involve use of commercial chemical
Because mycorrhizal fungi increase the effi-
ciency of fertilizer use, they can be thought of
as biotic fertilizers and might be substituted for
some fertilizer components. Considering esti-
mates that 75 percent of all the phosphorus ap-
plied to crops is not used within the first year
and thus reverts to forms unavailable to plants,
especially in tropical soils, it appears that fur-
ther work on improving mycorrhizal fungi ef-
fectiveness could aid LDCs in developing sus-
tainable agricultural systems.

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Chapter II

The Role of the Agency

for International Development


During the second day of the workshop, AID
staff reviewed their agency's agricultural de-
velopment activities and the various con-
straints under which AID operates when car-
rying out its agricultural mandates. Their

discussions were candid and are summarized
in the following text. An organizational chart
in effect for AID in November 1980 appears
at the end of this chapter.


In 1980, AID carried out about $600 million
in agricultural projects and research related to
solving agricultural problems and developing
agricultural opportunities in LDCs. Further,
AID spent an additional $43 million to trans-
fer fertilizer, much of it going to Sri Lanka,
Zambia, and Bangladesh.' During the first
quarter of FY '81, fertilizer transfers to India,
Kenya, Zambia, and Bangladesh were $105 mil-
lion. AID's main thrust in agriculture is to help
LDCs increase agricultural productivity, espe-
cially of the locally accepted basic food crops.
By doing so, AID's goal is to help LDCs im-
prove their economy, nutrition, and the gen-
eral well-being of their people.
But for AID to step beyond traditional ap-
proaches and promote innovative technologies
to solve LDC food and agricultural problems
is risky. AID is not a research agency; its goal
is development. Therefore, AID commonly
supports research that holds promise of high
immediate payoff and tends to avoid research

'AID's financed fertilizer purchases for FY '80 were at the lowest level
since 1965.

that may have long-run payoffs. Similarly, AID
feels that its development projects should focus
on the short term, have high visibility, and
show positive results quickly. It is not surpris-
ing that some AID agriculturalists believe that
"when you only have $2 to bet you don't go
for long shots." To compound the problem,
AID's small budget for innovative activities is
often one of the first targets during budget cuts.
The United States, on the basis of its gross
national product (GNP), in 1980 ranked 14th
of those countries that provide development
assistance to LDCs. For example, Sweden con-
tributes 1.0 percent of its GNP whereas the U.S.
contributes 0.19 percent.
AID's budget dilemma is complicated further
by a growing list of competing development
needs such as forestry, women-in-development,
and environmental concerns. AID has been
many things to many people, but it has not been
perceived by Congress as a technical transfer
agency. AID stressed that there remains a lack
of understanding among the public and Con-
gress about how science and technology relate
to economic development.


During the workshop, AID participants pre-
sented a brief overview of some of their cur-
rent activities involving various innovative
biological technologies. Examples included
biological nitrogen fixation, tissue culture, and
applied soybean research. In addition, through
a collaborative effort, AID, the Joint Research
Committee (JRC), the Board on International
Food and Agricultural Development (BIFAD),
and 30 land-grant colleges and universities
have developed three Collaborative Research
Support Programs (CRSP) to study small
ruminants, sorghum and millet, and bean/cow
pea production systems. The activities involve
30 U.S. universities, six international agricul-
tural research centers, and one foundation.
Work is carried out at 28 LDC sites with col-
laboration of the local LDC institution. Two
new CRSPs are being developed in nutrition
and soils. These activities will expand the num-
ber of participating U.S. universities by eight
and LDC sites by ten.
CRSPs are viewed as long-term research
endeavors, at least five years in duration. AID
funds up to 75 percent of the CRSP and the
collaborating U.S. colleges and universities
contribute from 25 to 50 percent. At least 50
percent of AID's CRSP budget is spent in par-
ticipating countries. AID's minimum budget
for FY '82 CRSP activities is $11 million. AID
plans to invest a minimum of $88.3 million in
CRSP activities from FY '82 through FY '87.
Biological nitrogen fixation (BNF) is not a
new technology; it was recognized in Biblical
times that when certain legumes were grown
in alternate years, the yield of the following
year's crop was improved. After five years of
research, AID recognizes that BNF technology
still could be improved. Because it can provide
nitrogen to plants in a usable form without the
expense of commercial nitrogen fertilizers, it
has important potentials for LDCs and devel-
oped countries alike.
Rhizobia, nitrogen-fixing bacteria that live in
nodules associated with the roots of certain
plants, can be used in some instances to in-

oculate the roots of plants to enhance nitrogen
production. No infallible technique to inoculate
seeds is known, but this is an area of research
AID is addressing. (The information of BNF
summarized elsewhere in this report is based
on research at the University of Hawaii spon-
sored in part by AID). BNF in tropical grasses
also is being studied. AID is working on in-
country testing of BNF technology, building in-
oculation production and distribution systems,
developing profitable BNF cropping systems,
and providing continued help in improving
BNF technology for LDC use.
AID believes that commercial fertilizers play
an important role in LDC agriculture but also
believes that BNF technology can help these
countries reduce their need for commercial ni-
trogen fertilizers. Considering that commercial
nitrogen fertilizer may cost as much as $1 a
pound by the year 2000, BNF, which ultimately
may reduce the need for commercial nitrogen
fertilizers in LDCs by 25 percent, could help
AID is supporting some research on tissue
culture to supplement its traditional research
on standard crop-breeding practices. AID
believes tissue culture to be an inexpensive
technology and one that has good potential for
use in LDC agriculture.
In the past, agriculturalists selected superior
plants for reproduction by handpicking those
few individual plants having certain desirable
characteristics out of many thousands of the
less desirable specimens. Space and time
severely limit the number of plants screened
this way. With tissue culture, desirable plants
can be selected and propagated quickly and
easily. For example, an agriculturally desirable
plant can be used as a cell source for a desired
special characteristic such as salt tolerance
needed for growth in irrigated areas. A tiny
slice of the plant can be used to grow large
clusters of cells that can be separated in the
laboratory and screened to find the cells hav-
ing the required characteristics. These cells in
turn can be grown to full plants that themselves

can be used for seed sources. Research has
demonstrated that the new plants will survive
the particular soil stresses for which they were
screened. This technique enhances our ability
to design plants for the especially harsh envi-
ronments in LDCs and holds real promise for
improving LDC agriculture.
AID provides support for the International
Soybean Program (INTSOY) as part of its ef-
fort to support innovative biological technol-

ogies. INTSOY works to improve and adapt
soybeans for tropical developing countries
through germplasm selection. Some of their ap-
plied research deals with finding improved
ways to store seed for extended times in LDCs
and improving soybean processing using sim-
ple technologies. INTSOY also is studying the
role of soybeans in the LDC farming economies
and in the national economy as well.


Two sharply different approaches to apply-
ing innovative biological technologies to LDC
agricultural problems, particularly the problem
of rising fertilizer costs, surfaced during the
workshop's discussions. The first might be
called an "agroecosystem approach" and was
stressed by most non-AID participants. The
second reflected a "conventional production
approach" and was mainly an AID viewpoint.
The "agroecosystem approach" focuses on
applying biological technologies that are tai-
lored to fit the biological, physical, and social
limitations of the local environment so that
sustainable agriculture can exist within the
constraints of the natural resource base. This
approach includes a concern for energy con-
servation and a desire for interdisciplinary re-
search and development.
The "agroecosystem approach" to LDC re-
quirements for food, fodder, and fuel also
focuses on developing new agricultural sys-
tems and on accepting rediscovered, and per-
haps improved, agricultural systems. A wide
spectrum of agricultural crops is considered
including a number that might be viewed as
nontraditional. This approach emphasizes re-
storing, maintaining, and improving the natu-
ral resource base while offering the farmers a
reasonable chance for economic betterment.
In comparison, the "conventional production
approach" stresses production and increased
yields. It tends to focus on a more limited num-

ber of crops for which a market already exists.
The ecosystem is adjusted to provide high pro-
duction of these crops by using intensive in-
puts of commercial fertilizers, pesticides,
pumped water, and petroleum-powered farm
equipment. Some such systems commonly are
categorized as "green revolution" technologies.
Major efforts have been devoted to mainstay
crops such as rice, corn, sorghum, and soy-
beans, and production increases generally have
been outstanding.
The variety of crops dealt with in this ap-
proach is more limited than in the "agroeco-
system approach" and monocultures often are
economically advantageous. Production efforts
typically attempt to foster crop growth by over-
coming local environmental constraints such
as infertile soils or water scarcity. In many
cases the technologies promoted are adapta-
tions of technologies that have been used suc-
cessfully in developed countries and temperate
There are, of course, instances where the two
approaches overlap, but these are exceptions.
Proponents of both approaches are trying to
help LDCs improve the well-being of the popu-
lace-their methods, however, include quite
different agricultural styles and practices. The
workshop focused on the opportunities shown
by each of the approaches for helping LDCs re-
duce their need for expensive commercial fer-
tilizers while enhancing soil productivity.

The Need for Cooperative Ventures
Participants agreed that agricultural research
and its appropriate implementation in lesser
developed countries is an AID/LDC coopera-
tive venture and that good communication is
essential for success. They discussed the in-
herent difficulties involved in using U.S. ex-
pertise in LDC projects because many U.S.
experts lack the special training that is appro-
priate to the physical and biological environ-
ment. Many U.S. technical experts used by AID
are drawn from U.S. land-grant universities
and consulting firms where there is little
familiarity and experience with LDCs. And be-
cause the United States historically has little
experience in LDC-i.e., tropical-agriculture,
AID has difficulty finding contractors who are
able to grasp LDC agricultural problems
quickly and recognize the appropriateness or
inappropriateness of temperate region agricul-
tural solutions.
AID has provided grants and other support
to numerous U.S. universities to help them de-
velop their teaching/research expertise so that
it can be tapped to help solve LDC agricultural
problems. Many of these universities have set
aside land for use in agricultural research and
teaching, but again agricultural research re-
sults commonly are not readily transferable
from region to region. Further, because pilot
studies often are cumbersome to conduct, take
considerable time, and lack significant recog-
nition, few university scientists are eager to
devote effort to projects relevant to LDC agri-
culture, even though certain aspects may also
hold indirect promise for improving U.S. agri-

The Need for Field Demonstrations
Pilot projects, demonstrations, and field ex-
periments carried out in LDCs by U.S. and
host-country interdisciplinary teams on inno-
vative biological technologies are essential first
steps before new technologies can be used
widely. Section 103A of the Foreign Assistance
Act directs AID to carry out pilot studies. Fur-
ther, workshop participants agreed that the pri-
vate sector, whether U.S. or LDC, should be

encouraged to participate in biological technol-
ogy development and its transfer to potential
users. Only where new technologies can be
shown to be economically profitable is there
the likelihood of their being pursued and
adopted by the private sector. For example,
Thailand established several innovative pro-
grams in alcohol production from cassava
through direct links between the private sec-
tor and Thai research institutions. It was also
pointed out that in many places, farmers learn
new agricultural techniques from salesmen.
AID believes that during the 1980s it will em-
phasize technology transfer but hopes to spon-
sor increased adaptive field research and do
cooperative research with LDC scientists. The
Agency sees the need for multitiered develop-
ment efforts but recognized the difficulty in co-
ordinating them. There is an acute need for
LDCs to establish their own national research
priorities rather than having the donor com-
munity do so.
Pilot-scale activities that receive partial sup-
port from AID do exist at the international agri-
cultural centers. But whether or not all such
institutions strongly emphasize the "agroeco-
system approach," especially agricultural tech-
niques that are aimed at enhancing soil fertility
and reducing reliance on expensive commer-
cial fertilizers, was debated. AID believes that
much of the work carried out at the interna-
tional centers is innovative, but many of the
non-AID participants felt that these centers pay
little attention to low fertilizer, low-energy agri-
cultural systems.

The Need for Innovative Research
Further, AID was criticized for spending $43
million of its $650 million agricultural efforts
on the transfer of expensive commercial fer-
tilizers to LDCs without providing incentives
to try new agricultural methods that minimize
fertilizer use. LDCs must develop the resources

to continue appropriate fertilizer use, but along
with this should go development of efficient
new agriculture systems that rely on biologi-
cal processes to complement soil nutrient avail-
ability. The use of mycorrhizal technologies,

for instance, seems to hold great promise for
reducing fertilizer needs, but AID is not work-
ing with this technology. Although AID agri-
cultural professionals in the Development Sup-
port Bureau have tried to initiate mycorrhizal
research, it has failed to place high enough on
their priority list to warrant funding in each
of the last two years. AID interest in biologi-
cal technologies has expanded, but the Agency
staff feels funds remain the limiting factor.
They feel their involvement in biotechnology
research might help speed transfer and imple-
mentation of its results.
Workshop participants encouraged AID to
place agricultural scientists from nonconven-
tional fields of study on AID peer review panels
.of field projects and research activities. Be-
cause AID seemed committed to conventional
agriculture, some workshop participants
believed that AID needs fresh ideas to help
their agricultural professionals move away
from conventional paths and into new areas
having potential for high payoff for LDCs.
AID's peer review was likened to "an old boy
system," one in which acceptance of new ideas
was slow. Non-AID members also viewed the
U.S. Department of Agriculture (USDA) dimly
in the field of innovative biological research
because they felt that USDA, too, primarily is
committed to conventionality. Some partici-
pants thought USDA was not helping AID with
the question of how to maintain productive
soils in LDCs while reducing the input of ex-
pensive commercial fertilizers.
In the view of "agroecosystem" proponents,
AID and some international agricultural
centers place the greater part of their efforts
on a few traditional food crops but do little to
develop underexploited, nutritionally impor-
tant new food crops. AID was viewed as hav-
ing no interest in these "odd-ball" crops even
though such foods contribute significantly to
LDC diets. Proponents of the "agroecosystem
approach" proposed looking into any food
crops that fit into the local ecological system.
Therefore, the resulting mix of crops might be
radically different from the crop mix recom-
mended by the "production approach," but one

that could be sustained with lower fertilizer
An agroforestry system might be instituted
that would integrate, for example, tree crops
for food, fodder, firewood, and erosion control;
native food crops; microbiological systems
such as mycorrhiza and rhizobium; and local
mineral resources such as zeolites into a low-
energy consuming system. Participants en-
couraged AID to set aside a certain percent-
age of its appropriations each year to look for
new, low-energy agricultural systems. The
Agency could continue to back its efforts in
"bread and butter" crops-corn, rice, etc.- but
should be willing to commit some of its re-
sources to nonconventional approaches. All
participants agreed that AID should be en-
couraged to take some risks and not merely to
back "winner" crops.

The Need for Flexibility
Most non-AID participants, as well as some
AID staff, believed that the Agency needs a
more flexible mechanism to provide funding
for small-scale innovative activities. Currently,
AID seems unable to transfer small amounts
of money quickly or easily for such projects or
experimental activities. The Agency claims that
processing a small amount of money is as time-
consuming as processing large grants or proj-
ects. Pressure within AID to obligate program
dollars rapidly makes dealing with small proj-
ects bothersome. AID's agricultural profes-
sionals in the Development Support Bureau,
for example, may wish to support certain in-
expensive innovative activities, but they are
discouraged by internal AID procedures and
the program office's strong control. Conse-
quently, scientists outside of AID who have
special useful knowledge and who wish to par-
ticipate in solving LDC agricultural problems
feel that AID is neither open nor interested in
outside assistance. Yet most participants felt
that many aspects of both the "conventional
production approach" and "agroecosystem ap-
proach" could be integrated with positive

38-846 0 85 2

The non-AID scientists elaborated on how it
is generally difficult for them to obtain needed
support for innovative approaches to low-
energy agricultural systems. The picture was
similar for the varied researchers. First, there
seems to be little support for funding the broad
range of innovative biological technologies that
may help improve LDC agricultural systems.
This is particularly true at most U.S. univer-
sities because the universities find it difficult
to support international activities that seem
remote. Then, too, researchers who rely on the
university for their salary commonly do not
want to jeopardize their security by conduct-
ing nonmainline research.
Some of the non-AID researchers admitted
that to carry out their chosen areas of LDC-
related research they sometimes resort to using
small amounts of money from other projects
that are not LDC-related ("bootlegging"). Other
common small funding sources for LDC-re-
lated research include a variety of Federal
agencies other than AID, although AID does
provide significant support for the biological
nitrogen fixation work at the University of Ha-
waii. An AID grant provides partial support for
azolla/algae research. Because Federal support
for LDC-related research has the habit of

vanishing suddenly, non-AID researchers face
constant doubt about the continuity of their
funding. The National Science Foundation,
some United Nations institutions, small univer-
sity grants, and private industry and institu-
tions sometimes are funding sources as well.
Private industry support seemed lacking for ap-
plied research in these fields.

The Need for Trained Aid Staff
Underlying all of the above problems was the
strong need for a significant increase in the
number of technically trained professionals in
agriculture and natural resource areas in AID
and its Missions overseas. Existing technical
professionals need to spend increased time on
the substance of their projects and less deal-
ing with bureaucratic constraints. Without
such an environment, AID may find it increas-
ingly difficult to maintain or expand technical
competence within its Washington offices or
Missions in LDCs. A need for improved com-
munication between scientists and the Con-
gress was restated several times during the
workshop, and activities similar to this work-
shop were cited as a step in the right direction.


AID's major efforts in innovative agricultural
research are directed primarily to the 13 inter-
national agricultural research centers to which
AID contributes financial support. Much of the
AID activity, however, depends on the work
of the AID Missions and the ability of the pro-
fessional staff to relate to the scientific com-
munity at large and to the Missions and re-
gional or geographic bureaus. A number of
problems in these areas were identified by the
workshop participants.

Mission Agricultural Activities
AID Missions largely are removed from cur-
rent science and technology developments in
the academic and private sectors. Conse-

quently, AID faces a difficult task in channel-
ing new science and technology to field activ-
ities in most LDCs. In addition, AID staff at the
workshop explained that many Missions feel
that adequate technology already exists and
that new science and technology are not
needed. The Missions want AID technical peo-
ple to solve the problems that the Missions
identify using established technologies. This
approach frustrates AID professional staff, in-
cluding staff in the Agriculture Office.

AID considers its contribution to the Con-
sultative Group on International Agricultural
Research (CGIAR) valuable and feels that the

nonbureaucratic institution functions very well
in addressing agricultural development prob-
lems and in implementing research results.
AID sees Korea as a model of successful de-
velopment where effective technology transfer
has occurred, and feels that the Korea exam-
ple should be used as a model for development
activities by other LDCs.

Agricultural Staff
AID agricultural professionals attempt to
maintain close contact with agricultural ex-
perts in the scientific community both within
and outside of USDA. But the number of agri-
cultural scientists in AID is so small that main-
taining regular contact with their scientific col-
leagues can be difficult. AID employs about
4,000 people yet its Development Support Bu-
reau (DSB), the bureau that provides technical
support to all of AID's regional or geographic
bureaus, has only 25 agricultural professionals.
These 25 people managed about $70 million in
agricultural projects in FY '80. Further, only
about 10 percent of AID Mission personnel
worldwide are agricultural officers even
though some 50 percent of AID's development
programs are agriculturally oriented. Because
AID commonly reassigns its agricultural pro-
fessionals to new Missions or back to the U.S.
about every three to four years, many agricul-
tural programs suffer from the lack of conti-
nuity. AID's workshop participants felt person-
nel rotations occur too frequently.
AID workshop participants felt that the
Agency's emphasis on natural resource man-
agement should be increased but that this area
is not receiving much Agency attention. Nat-
ural resource management requires an inter-
disciplinary approach, but because AID is
segmented into numerous administrative com-
partments it is extremely difficult to conduct
interdisciplinary activities. For example, agro-
forestry activities were to be transferred re-
cently to DSB's Office of Forestry, Environ-
ment, and Natural Resources, the successor to
the Office of Science and Technology (OST).
Agroforestry, by definition, combines aspects
both of agriculture and forestry, yet in the new

arrangement, agroforestry is separated from
The mandate to identify and test innovative
and/or emerging science and technology and
to transfer promising ideas to AID's Missions
and Regional Bureaus belonged to the dis-
banded Office of Science and Technology. This
office served as AID's "window" to the science
and technology community and gave AID the
opportunity to tap a broad array of innovative
science and technology to help solve LDC
A problem that AID workshop participants
highlighted repeatedly was that of the ex-
panded role of AID program officers in deci-
sionmaking and priority-setting for agriculture
projects and research. Program officers com-
monly are generalists having little or no tech-
nical agricultural training. Organizationally,
they sit between top bureau administrators and
agriculturalists and other professionals and ex-
ert a strong influence on AID's agricultural ef-
forts. AID agricultural professionals feel that
they are continually second-guessed by pro-
gram office generalists and that the technical
content of proposed agricultural projects and
research many times is adversely affected by
the actions of the program office.
Program officers commonly evaluate project
or research activities. But AID's evaluation
process seems to foster a strong desire to have
evaluations that show positive results. Without
positive evaluations, the difficulty of moving
subsequent projects through the AID system
and, therefore, through the program office may
increase. This perception, whether true or not,
discourages some technical professionals from
pursuing innovative opportunities because the
element of risk in innovative activities gener-
ally is higher than in traditional approaches.
The overall effect of having an inordinately
strong program office is that agricultural pro-
fessionals introduce fewer innovative technol-
ogies into AID agricultural programs.

2As of May 1981, a new Bureau for Science and Technology was formed.
(See section on AID organization changes.)

Fall 1984 Addendum

Demand for the original House Foreign Af-
fairs Committee publication on innovative
biological technologies was high in the United
States as well as many other countries and by
1984 copies were no longer available. Con-
tinuing requests for the publication have pro-
mpted OTA to reprint the document in its
workshop series. Described below are some
relevant policy changes that have occurred at
AID since the 1980 workshop.
The atmosphere at AID today is more fa-
vorable toward new biological technologies.
The current administration has expanded
work on tissue culture and sees potential in
other related areas. The attitude toward inno-
vative crops, however, remains essentially un-
changed and few resources are directed
toward new crop development.
In its overseas Missions and within AID-
Washington, there is still a scarcity of profes-
sional agriculturalists. Those that are on staff
have many, diverse responsibilities so that
innovative biological technologies do not re-
ceive much attention. Nevertheless, the Na-
tional Academy of Sciences Board on Science

and Technology for International Develop-
ment (BOSTID) receives AID funds to seek
new biological opportunities for developing
countries. Since the 1980 workshop, research
received increased attention in AID, however,
the substantial budget cuts recently proposed
in 1985 may adversely affect this trend.
One problem identified at the 1980 work-
shop concerned AID's inability to support
small scale activities. AID appears to have im-
proved some in this area. A new small grants
program-the Program in Science and Tech-
nology Cooperation (PSTC)-has been estab-
lished in the Office of the Science Advisor.
The program is designed to stimulate new out-
side research on problems that confront de-
veloping nations. Priority funding is directed
to five areas: Biotechnology/Immunology,
Plant Biotechnology, Chemistry for World
Food Needs, Biomass Resources and Conver-
sion Technology, and Biological Control of
Disease. This type of competitive, small grants
program is an important step toward provid-
ing a more flexible mechanism to support
innovative and small-scale research and tech-
nology development.


Summarized below are a variety of sugges-
tions generated by the 40 participants during
the course of the workshop discussions. Some
of these topics received considerable attention
and others much less. The participants were
encouraged to express their points of view
freely on any issues they felt were relevant. By
doing so, the participants touched upon a va-
riety of topics, many of which deserved more
detailed examination than could be accom-
plished in two days. The issues that surfaced,
however, should help the House Committee on
Foreign Affairs in their oversight responsi-
bilities of the Agency for International Devel-
opment and in determining the role that inno-
vative biological technologies could play in
enhancing soil fertility, improving food pro-

duction, and reducing the need for expensive
commercial fertilizers throughout the world.

* AID should greatly increase the number of
in-house agricultural professionals in Wash-
ington and in the missions, especially in
decisionmaking positions.
* AID should increase the number of Mission
directors who are agricultural professionals.
Similarly, effort should be made to encour-
age the selection of an increased number of
people with professional agricultural train-
ing as ambassadors for LDCs.
* AID should encourage the U.S. and LDC pri-
vate sector to participate in pilot-scale proj-
ects testing and developing innovative bio-
logical technologies.

* AID should appoint some outside experts in
nonconventional agricultural technologies to
its advisory committees and to its peer re-
view panels.
* AID should broaden its inventory of scien-
tists who might help AID expand its efforts
into nonconventional agricultural practices.
* AID should streamline its procedures to en-
courage increased outside participation by
U.S. scientists and technologies in small-
scale innovative agricultural activities.
* AID should set aside a certain percentage of
each agricultural project to integrate some
new, innovative biological technology into
the project.
* AID should fund some small-scale, pilot-type
projects on the kinds of innovative biologi-
cal technologies presented at this workshop
and encourage the participation of outside
scientists to work on the project as members
of interdisciplinary teams. The need for pilot
testing of a wide variety of innovative bio-
logical technologies by AID was stressed
heavily and the need for risk-taking was en-

* AID should increase its activities in agro-
forestry systems. These activities should be
expanded to include both humid tropical re-
gions and arid/semiarid regions. Pilot testing
of the arid/semiarid systems could be carried
out in the Southwest United States and
* An expanded inventory of innovative bio-
logical technologies that could help LDCs re-
duce their need for expensive commercial
fertilizers should be prepared, and institu-
tions and individuals who have the skills for
these technologies could be identified.
* OTA could conduct a full assessment of a
broad range of innovative biological technol-
ogies that could help LDCs reduce the need
for their use of expensive commercial fer-
* AID should emphasize the transfer of tech-
nical information to LDCs and to AID mis-
sion agriculturalists, particularly on innova-
tive biological technologies that might help
LDCs reduce their need for expensive com-
mercial fertilizers.


The Administrator for the Agency for Inter-
national Development (AID) on May 21, 1981,
announced a reorganization for the structure
of AID (see following chart). One major change
was the formation of a new Bureau for Tech-
nology and Science to replace the old Bureau
for Development Support. Structurally, this
change gives greater prominence to the role of

science and technology in AID than has existed
previously. Unlike the other AID bureaus for
Science and Technology. Unlike the other AID
bureaus which are headed by Assistant Ad-
ministrators, the Bureau for Science and Tech-
nology is headed by a Senior Assistant Admin-
istrator, thus giving added strength to science
and technology in AID.



I I -


-I. -- -^ ^ ^




Effctiv Date: May 27, 190O

List of Atendees


Dr. James Duke
Germplasm Resources Laboratory
Building 001, Room 131
Beltsville, MD 20705

Dr. Peter Felker
Ceasar Kleberg Wildlife
College of Agriculture
Texas A & I University
Kingsville, TX 78363

Research Institute

Dr. Jake Halliday
Battelle Kettering
Research Laboratory
150 East South College Street
Yellow Springs, OH 45387

Dr. William Liebhardt
Rodale Research Center
RD1 Box 323
Kutstown, PA 19530
Dr. Cy McKell
Director of Research
Native Plants, Inc.
417 Wakara Way
University Research Park
Salt Lake City, UT 84108
Dr. John Menge
Full Professor
Department of Plant Pathology
University of California
Riverside, CA 92521
Dr. Fred Mumpton
Department of Earth Sciences
State University College
Brockport, NY 14420




Dr. Donald Plucknett
Scientific Advisor
World Bank/CGIAR
Room K1045
1818 H Street, N.W.
Washington, DC 20433
Dr. Noel Vietmeyer
National Academy of Sciences
National Research Council
2101 Constitution Avenue, N.W.
Washington, DC 20418
Dr. Stephen R. Gliessman
Agroecology Program
Board of Environmental Studies
University of California
Santa Cruz, CA 95064
Dr. Thomas A. Lumpkin
Department of Agronomy and Soil
Washington State University
Pullman, WA 99164-6420

Other Participants
Mr. Tony Babb
U.S. Agency for International Development
Dr. Hugh Bollinger
Native Plants, Inc.
University Research Park
Mr. Douglas W. Butchart
U.S. Agency for International Development
Dr. Mary Clutter
National Science Foundation
Mr. Stan Dundon
Office of Rep. George Brown
U.S. House of Representatives
Dr. Lloyd Frederick
U.S. Agency for International Development
Ms. Margaret Goodman
Foreign Affairs Committee
U.S. House of Representatives

Mr. George Ingram
Foreign Affairs Committee
U.S. House of Representatives
Dr. Howard Minners
U.S. Agency for International Development
Mr. Donald Mitchell
Office of Personnel Management
Mr. Stephen D. Nelson
Foreign Affairs Committee
U.S. House of Representative
Ms. Julia Nickles
Legislative Assistant
State of California
Dr. Palmer Rogers
Office of Basic Energy Sciences
U.S. Department of Energy
Dr. Charles Simkins
U.S. Agency for International Development
Mr. Skip Stiles
Legislative Assistant
Office of Rep. George Brown
Dr. James Walker
U.S. Agency .for International Development
Mr. Henry Williams
Congressional Fellow
Office of Sen. Mathias

OTA Staff
Dr. John H. Gibbons
Dr. Joyce Lashof
Assistant Director
Dr. Walter E. Parham
Program Manger
Mr. Bruce Ross
Project Director
Ms. Barbara Lausche
Natural Resources Lawyer
Dr. Betty Williams
Nutrition Project Director

Ms. Chris Elfring
Congressional Fellow
Ms. Judith Randal
Congressional Fellow

Dr. Omer Kelly
Dr. Michael Phillips
Project Director

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Chapter III

Underexploited Plant

and Animal Resources for

Developing Country Agriculture


The 1940s was the decade of wonder chem-
icals. The miraculous properties of DDT, sulfa
drugs, herbicides, nylon, and plastics blinded
us to the potentials of nature. Laboratories
were limitless, nature seemed limited. Man-
made was modern, nature seemed passe. Sub-
sequent decades seemed to confirm the eu-
phoric view; we gave up seeking our new prod-
uct needs in the kingdom of nature, the
previous wellspring for civilization's advances.
As a result, as we move toward the 21st cen-
tury, we rely on fewer and fewer plants and
animals. We ignore, or have forgotten, thou-
sands of useful species that could broaden and
balance our fount of resources. All this, in face
of the recognition that within a few short dec-
ades the petrochemical explosion that began
in the 1940s will be snuffed out.
However, a big change is now occurring in
the scientific community. Researchers are
returning to nature's storehouse to take stock
of its genetic possibilities; to scrutinize species
that could make useful new crops and domes-

tic animals. Some of them are species that are
wild and untested, some even poorly identified.
Though they work largely out of the public eye,
these dedicated researchers are quietly ger-
minating ideas and laying roots that will grow
with and shape our future. Some natural prod-
ucts now virtually unknown are likely to be-
come mainstays of world agriculture.
Decisionmakers, entrepreneurs, and the gen-
eral public should pay more attention to these
researchers' results. A groundswell of support
for the development of new species could lead
to a cornucopia of new foods, fuels, and indus-
trial feedstocks. It may help extend productive
agriculture to vast regions that today are not
arable. It may help raise from despair the ever
increasing numbers of humans in developing
countries who waste their lives away in mal-
nourished poverty. It may show how to cul-
tivate crops that produce raw materials that
now come from petroleum. It's a challenge. But
some of the future's best resources are out there
waiting in nature.


Botanists and ethnobotanists can reel off long
lists of obscure plants that seem to warrant rec-
ognition. Respondents to recent questionnaires
sent out by the National Academy of Sciences
named over 2,000 plant species that deserve
much greater recognition. Almost none have
been given agronomic attention. A few strik-
ing examples are given below.

Poor People's Plants

A friend recently told me that he had dis-
cussed the winged bean with an influential
Filipino family. "They were incredulous that
such a miraculous plant could exist," he said.
"So, on a hunch, I took them out back to the
servant's quarters. There, climbing along a

fence, was a winged bean plant laden with
'But that's just sequidillas,' they said, dis-
appointment echoing in their voices. 'It's only
a poor man's crop!' "
It is a universal phenomenon that certain
plants are stigmatized by their humble associa-
tions. Scores of highly promising crop plants
around the world receive no research funding,
no recognition from the agricultural commu-
nity; they are ostracized as "poor man's crops."
For information on a poor people's crop one
has to turn, more often than not, to botanists
and anthropologists; only they will have taken
an interest in the plant. Often there has been
no agricultural research on it at all-no vari-
eties collected or compared, no germination or
spacing trials, no yield determinations or even
nutritional analyses. And yet the crop actually
may be crucial to the lifestyle-even the sur-
vival-of millions of people.
Just 50 years ago, the soybean itself was a
poor people's crop. In the United States, it was
spurned by researchers for more than a cen-
tury after Benjamin Franklin first introduced
seeds from the Jardin des Plantes in Paris. To
be a soybean advocate then was to risk being
considered a crackpot. Early in this century,
Americans still considered the soybean a sec-
ond-rate crop fit only for export to "poor peo-
ple" in the Far East. But then, in the 1920s,
University of Illinois researchers established
a comprehensive soybean research program
that helped sweep aside this discrimination.
The soybean acquired new status as a "legiti-
mate" research target, and its development
gained so much momentum that it is now the
world's premier protein crop.
Nowhere is the neglect of poor people's crops
greater than in the Tropics-the very area
where food is most desperately needed. The
wealth and variety of tropical plant species is
staggering. Some of the Third World's best
crops are waiting in the poor people's gardens,
virtually ignored by science. Merely to have
survived as useful crops, suggests that the
plants are inherently superior. Moreover, they

are already suited to the poor person's small
plots and mixed farming, as well as to poor
soils, and the diet and way of life of the family
or village. Examples are the winged bean and
Winged Bean
Perhaps no other crop offers such a variety
of foods as the winged bean. Yet it, remains
a little-known, poor person's crop, used exten-
sively only in New Guinea and Southeast Asia.
A bushy pillar of greenery with viny shoots,
blue or purple flowers, and heart-shaped
leaves, the winged bean resembles a runner-
bean plant. It forms succulent green pods, as
long as a man's forearm in some varieties. The
pods, oblong in cross-section, are green, pur-
ple, or red and have four flanges or "wings"
along the edges. When picked young, the green
pods are a chewy and slightly sweet vegetable.
Raw or boiled briefly, they make a crisp and
snappy delicacy. Pods are produced over sev-
eral months and a crop can be collected every
two days, providing a continuous supply of
fresh green vegetables.
If left on the vine the pods harden, but the
pea-like seeds inside swell and ripen. When
mature, the seeds are brown, black, or mottled.
In composition they are essentially identical
to soybeans, containing 34 to 42 percent pro-
tein and 17 to 20 percent of a polyunsaturated
oil. The protein is high in the nutritionally crit-
ical amino acid lysine.
In addition to the pods and seeds, the winged
bean's leaves and shoots make good spinach-
like potherbs. Its flowers, when cooked, are a
delicacy with a texture and taste reminiscent
of mushrooms.
But perhaps the most startling feature of the
plant is that, below ground, it produces fleshy,
edible tuberous roots. These are firm, fiberless,
ivory-white inside and have a delicious and
delicate nutty flavor. The winged bean is there-
fore something like a combination of soybean
and potato plants. And winged bean tubers are
uniquely rich in protein-some contain more
than four times the protein of potato.

Amaranths-major grain crops in the tropi-
cal highlands of the Americas at the time of
the Spanish Conquest. They were staples of
both Aztec and Inca. But the conquistadores
banned the cultivation of amaranths because
the grain was a vital part of native religion and
culture. With this political move the Spanish
struck a blow for their church but they also
crushed the crop. For 500 years little has been
done to study or promote it.
Amaranths belong to a small group of plants,
termed C4, whose photosynthesis is exception-
ally efficient. The sunlight they capture is used
more effectively than in most plants and ama-
ranths grow fast. Vigorous and tough, ama-
ranths have been termed self-reliant plants that
require very little of a gardener. They germi-
nate and adapt well to the rural farmer's small
plots and mixed cropping. Furthermore, they
are relatively easy to harvest by hand and to
Amaranths are annuals that reach six feet in
height and have large leaves tinged with
magenta. They are cereal-like plants produc-
ing full, fat, seed heads, reminiscent of sor-
ghum. The seeds are small but occur in prodi-
gious quantities. Their carbohydrate content
is comparable to that of the true cereals, but
in protein and fat amaranths are superior to
the cereals.

When heated, amaranth grains burst and
taste like popcorn. In many regions, however,
the grains are more often parched and milled.
Amaranth flour is high in gluten and has ex-
cellent baking qualities; bread made from it
rises and has a delicate nutty flavor.
Recently, W. J. S. Downtown, an Australian
researcher, has found that the grain of at least
one amaranth (Amaranthus caudatus var.
edulis) is rich in protein and exceptionally rich
in lysine, one of the critical amino acids usu-
ally deficient in plant protein. Indeed, the
amount of lysine exceeds that found in milk
or in the high-lysine corn now under devel-
It is very hard to get grants for research on
poor person's plants. Funding agencies resist;
the plants are unknown to most of them, and
the literature to support any claims may be
Nonetheless, it is now time for agricultural
research facilities throughout the world to in-
corporate poor person's crops into their re-
search efforts. Third World agricultural devel-
opment needs this balance, for only when his
own crops are improved will the poor man be
able to feed his family adequately. In future
decades it may be-as in the case of the soy-
bean-that today's poor person's plants will be
feeding the world.


Man has deforested one-third of South
America's native forests, one-half of Africa's,
and two-thirds of Southeast Asia's. It is criti-
cally urgent that the remaining forest cover be
protected from indiscriminate harvest and that
many now-deforested regions be reforested. A
"thin green line" of fast-growing leguminous
trees may be either our last line of defense or
our first line of attack.
To most people legumes are limited to the
dining table, but to plant scientists legumes in-
clude not only vegetables but shrubs, vines, and

thousands of tree species, most of them in-
digenous to the Tropics. Actually, the family
Leguminosae is the third largest in the plant
kingdom. But out of the 18,000 different spe-
cies of legumes, farmers extensively cultivate
only about 20 species including peas, beans,
soybeans, peanuts, clover, alfalfa, and even lic-
orice. Foresters cultivate almost none.
The potential of tree legumes as useful plan-
tation species remains largely unrecognized,
yet they offer a particularly promising area for
exploration in these days of devastating defor-

station. Indeed, they seem to have special at-
tributes that could put them in the front lines
of the battle to reclothe the scarred hillsides
throughout the Tropics.
Legumes, for example, are nature's pioneers
in plant succession. They are among the first
plants to colonize bare land. It therefore seems
ecologically wise for man to deliberately ex-
ploit them for the same purpose: to quickly
revegetate eroding or weed-smothered terrain,
to halt erosion, and to provide protective
ground cover under which slow-growing,
climax-forest species can regenerate. Further-
more, many wood requirements might be met
by these quick-growing small trees and they
could help spare the last remnants of the nat-
ural forests.
Many woody legumes have a hardy, irre-
pressible character, suited to a wide range of
soils, climates, altitudes, and environments.
Like other pioneer species, they have a preco-
cious nature and grow quickly in an attempt
to overtop and preempt the space of their plant
Because of this innate competitiveness, many
tree legumes are easy to establish and cultivate.
Some can be direct-seeded (avoiding the ex-
pense of nurseries and transplanting fragile
seedlings), and in some tests even spraying
their seed out of aircraft has proven a suitable
way to establish plantations. Many occur nat-
urally in dense, pure stands, suggesting that
they probably can be grown in monoculture
without being decimated by pests.
A most important feature of many legume
species is that nodules on their roots contain
bacteria, which chemically convert nitrogen
gas from the air into soluble compounds that
the plant can absorb and use. Thus, for aver-
age growth these species require little or no ad-
ditional nitrogenous fertilizer. Some produce
such a surfeit of nitrogen-largely in the form
of protein in their foliage-that they make ex-
cellent forage crops and the soil around them
becomes nitrogen rich through the decay of
fallen foliage.

To give an idea of the potential of this class
of trees, three species of fast-growing legumes
are mentioned below. Not one of these trees
is widely exploited so far.

In the 1960s, University of Hawaii professor
James Brewbaker found in the hinterland of
Mexico certain varieties of Leucaena leuco-
cephala that grow into tall trees. This was un-
expected because the plant was previously
known only as a weedy bush. In tropical cli-
mates, Brewbaker's varieties have grown so tall
and fast that they can be twice the height of
a man in just six months; as high as a three-
story building in two years; and as tall as a six-
story building with a trunk cross-section as
large as a frying pan in only six or eight years.
In the Philippines, one hectare of these tall
leucaenas has annually produced over 10 times
the amount of wood per acre that a well-man-
aged pine plantation produces in the United
States. Even among the world's champion fast-
growing trees, this is exceptional.
Leucaena wood is thin barked and light col-
ored. For such a fast-growing species, it is
remarkably dense (comparable to oak, ash, or
birch), strong, and attractive. Its fiber is accept-
able for paper-making and the wood can be
pulped satisfactorily and in high yield.
But leucaena, a multipurpose plant par ex-
cellence, also has other uses. It can supply for-
age, for example, and researchers in Hawaii
and tropical Australia have found that cattle
feeding on leucaena foliage may show weight
gains comparable to those of cattle feeding on
the best pastures. Leucaena wood also makes
excellent firewood and charcoal. Further, the
plant is a living fertilizer factory for if its
nitrogen-rich foliage is harvested and placed
around nearby crops they can respond with
yield increased approaching those effected by
commercial fertilizer.
Although arboreal leucaena varieties have
been cultivated for only a decade or so, they

are already being planted over tens of thou-
sands of hectares in the Philippines. The World
Bank has funded one large program. Batangas
Province has a nursery producing 10,000 leu-
caena seedlings daily. The province's dynamic
governor, Antonio E. Leviste, has decreed that
other nurseries be set up throughout his prov-
ince: in churchyards, cemeteries, school-
grounds, roadsides-any idle ground. No gov-
ernment employee gets a paycheck until he has
set up a leucaena plantation with at least 20
trees to produce seed. The consequent green-
ing of Batangas has made citizens keenly ap-
preciative of deforestation's ugliness and prob-
lems, as well as reforestation's rewards. Tree
planting now interests the Batangas public
intensely-not entirely for the sake of revegetat-
ing eroding watersheds, but for the income and
benefits from exploiting leucaena forage, fuel-
wood, and "green manure." That the program
has been adopted with gusto by the citizenry
demonstrates the relevance of tree legumes to
tropical problems as a sort of "appropriate
In more remote southern islands of the
Philippines, leucaena (Filipinos call it ipil-ipil)
is being planted over huge areas of former
green-deserts, wastelands lost to coarse, sharp-
edged "cutting-grasses." With its vigor and per-
sistence, leucaena-if given a little care-can
overtop the grasses, shading them out of ex-
istence, and converting waste ground to pro-
ductive forest. It is essentially a permanent
forest because after felling, the stump of a leu-
caena tree regrows with such vigor that the
plant is said to literally "defy the woodcutter."

Calllandra Calothyruas
In 1936, horticulturists transported seed of
this small Central American tree to Indonesia.
They were interested in it as an ornamental,
for like other Calliandra species, it has flowers
that are gorgeous crimson powder-puffs, glow-
ing in the sunlight like red fireballs. But Indo-
nesians instead took up Calliandra calothyrus
as a firewood crop. Indeed, for 15 years stead-
ily expanding fuelwood plantations of it have
been established until they now cover over
75,000 acres in Java.

This small tree-barely taller than a bush-
grows with almost incredible speed. After just
one year it can be harvested. The cut stump
resprouts readily giving new stems that can be
10 feet tall within six months. Some trees in
Indonesia that are 15 years old have been har-
vested 15 times!
Calliandra wood is too small for lumber, but
it is dense, burns well, and is ideally sized for
domestic cooking. It is also useful for kilns
making bricks, tiles, or lime and for fueling
copra and tobacco dryers.
Indonesian villagers now cultivate Callian-
dra calothyrus widely on their own land, often
intercropping it with food crops. The plant's
value is dramatically exemplified by the village
of Toyomarto in East Java. There, land that was
once grossly denuded and erosion-pocked is
now covered with calliandra forest and is fer-
tile once more. Today the villagers actually
earn more from selling calliandra firewood
than from their food crops.

These are brief descriptions of only two spe-
cies of small leguminous trees that have re-
cently proven useful in combating deforesta-
tion in Southeast Asia. There are many other
exciting species. In South Korea, foresters in-
tercrop bushy Lespedeza species to provide
firewood during the early years of the estab-
lishment of pine and other forests. In Central
America, there are Enterolobium cyclocarpum
and Schizolobium parahyba, in South Amer-
ica, Mimosa scabrella (M. bracatinga),
Schizolobium amazonicum, Tipuana tipu, and
Clitoria racemosa; and in the Pacific Islands,
Albizia minahassae and Archidendron
oblongum. In Africa, several fast-growing
Albizia (A. adianthifolia, and A. zygia, for ex-
ample) are indigenous, and two legume trees
introduced from India, Acrocarpus frax-
inifolius and Dalbergia sissoo, have shown ex-
ceptional growth rates on appropriate sites. In
Asia, there are also Acacia auriculiformis and
Sesbonia grandiflora.
In foresters' terms many of these species
have "poor form." Their trunks may be too nar-

row or too crooked for construction timber or
veneer. But, these are species for "peoples' for-
estry." Their role is for:
farms, backyards, pasture lands, roadsides,
canal banks and fencelines;
village woodlots and energy plantations to
fuel kilns, electricity generators, cooking
stoves, and crop dryers;
agrisilviculture (agroforestry), because
they provide a wealth of products includ-
ing forage, green manure, and food;

* use in shifting cultivation, because the nat-
ural drop of protein-rich leaves, pods, and
twigs contributes nitrogen organic matter
and minerals to upper soil layers and can
markedly speed up the rebuilding of worn
out soils;
* quick-rotation cash crops, both for the pri-
vate landowner and the government for-
est department; and
* utility purposes such as beautification,
shade, and shelter belts.


When early farmers discovered that animals
could be tamed and managed, they eagerly ex-
perimented with many of the species surround-
ing them. In Asia and the Americas, the silk-
worm, yak, camel, water buffalo, llama, alpaca,
and guinea pig were selected. Egyptian tomb
paintings at Saqqara painted in 2500 B.C. show
addax, ibex, oryx, and gazelle wearing collars
and obviously domesticated. Ancient Egyp-
tians apparently domesticated hyenas and ba-
boons, as well.
But then the process essentially stopped.
Today's farmers raise the same animals their
Neolithic forebears were familiar with more
than 10,000 years ago. (One exception is the
rabbit, which French monks tamed between
the 6th and 10th centuries because the Church
considered newborn rabbits to be fish and they
could be eaten when the Church calendar
demanded abstinence from meat.) Although
the world's menagerie contains some 4,000 spe-
cies of mammals alone, only a mere six domes-
tic animals produce virtually all of the world's
meat and milk.
As agricultural man spread himself about the
globe, he dragged with him this handful of spe-
cies. He carried them beyond their natural
boundaries, forced them upon strange and
often fragile environments-usually driving out
the native species that previously predom-
inated there, and often drastically changed the
environments to accommodate them.

Very little meat is eaten in developing coun-
tries and because most of them are in the Trop-
ics, it is not possible to change that much with
cattle, sheep, and pigs. These animals have an
evolutionary adaptation to the temperate envi-
ronments from which they originated and are
limited in their ability to adapt to new ones.
But the world's fauna is a rich genetic bank that
may be tapped to increase world food produc-
tion. Some of the potential species are unex-
pected ones, as highlighted below.

Toads, Snails, and Guinea Pigs
In rural areas of developing countries, it is
important to produce small animals. They fit
better into village life and they can be eaten
at one meal, so the lack of refrigeration is no
hindrance. In Chile, there's a shiny, olive green
toad (Calyptocephalella caudiverbera). It is a
giant toad that can weigh three pounds or
more. Its meat tastes like a cross between lob-
ster and chicken. It grows to be a foot long or
more and lacks the toxic skin glands and warty
appearance of other toads. Because of its su-
perb and enigmatic taste, the wild toad has long
been a delicacy of Chilean gourmets. But now,
researchers at the La Serena campus of the
University of Chile are learning how to farm
In 1975, the University's Institute of Food
Technology started farms large enough to pro-

duce 100,000 of the choice toads every two
years. The intensive methods they developed
have made it feasible to supply 10 to 15 tons
of scallop-sized toad legs each year to grocery
stores, restaurants, and canneries.
The Institute also has dug production ponds
out of otherwise useless swampland. The eggs,
larvae, tadpoles and adults are all kept apart
because the voracious toads have no hesita-
tions about cannibalism. Normally, however,
they feed on small fish, crabs, crawfish, and
aquatic plants. The ponds are surrounded with
flowers and shrubs to attract insects and boxes
of rotten fruit are placed nearby to draw fruit
flies to the area. With their long sticky tongues,
the toads eagerly capture the insects. Other
than this, the toads reportedly are given little
attention and in two years they reach market
size: about 7 inches long and weighing one-half
Researchers are ecstatic over the ease and
cheapness of toad farming, and they are look-
ing toward the lucrative international frog meat
market to export the tender, white drumsticks
of these unique Chilean toads.
In Nigeria, the Institute of Oil Palm Research
is developing another potentially valuable new
resource: the giant African Land snail
(Achatina species). This snail grows rapidly
and may weigh up to half a pound. It is eaten
widely in West Africa and is immensely popu-
lar in parts of Nigeria and Ghana. The meat
has as much protein as beef, but it has consider-
ably more of the important amino acids, lysine,
and arginine, than even eggs contain. The In-
stitute has found the snails suitable for "farm-
ing" in shaded enclosures under the trees in
rubber, cocoa, or oil-palm plantations. With
proper proportions of males and females, it has
produced as much as 150 pounds of snail meat
in the small enclosures each year.
In Peru, scientists are looking to their in-
digenous fauna too. One of Peru's serious and
permanent problems is a lack of beef. Two-
thirds of the steaks of which Peruvians are so
fond are imported despite the nation's chronic
dollar shortage. The situation became so seri-
ous that five years ago the military junta put

a ban on beef consumption 15 days in every
month. Chicken production was once believed
to be the answer to the problem, but although
it has grown fast, so has the population. Big
hopes were placed on fish, too, but the coun-
try lacks the financial resources to install the
facilities needed for national marketing. The
guinea pig is now believed to be the best
answer so far to the problem posed by the short
supply of animal proteins.
Guinea pig is a traditional staple. Although
domesticated in the time of the Inca, it has not
previously attracted much research attention.
Yet guinea pig is widely consumed in Peru. The
nutritional value of its meat compares favor-
ably with that of other meats. The animals can
be raised in urban areas and in villages, where
larger animals are scarce or impossible to keep.
The fast growth and rapid reproduction makes
the guinea pig a sensible resource in the Peru-
vian environment. Added to this is the fact that
guinea pigs can live off vegetation that is of
inadequate nutritive value for feeding other
These resources are strange-even repug-
nant-to the majority of specialists working to
increase food production and improve human
nutrition in developing countries. But to the
local inhabitants they are traditional foods that
are much sought and enjoyed.

In Africa, South and Southeast Asia, Aus-
tralia, and South America, the populations of
crocodiles, alligators, and caimans are fast
headed for extinction. In Papua New Guinea
(P.N.G.) in the 1960s, the two native crocodile
species were headed the same way. But not
today. In the last five years, a remarkably inno-
vative project in this, one of the newest and
most underdeveloped nations, has caused a
dramatic turnaround in the crocodile's dras-
tic decline there. Though the P.N.G. story has
not been told widely, it is one with immense
implications for the survival of crocodilians
elsewhere. It is also a demonstration of how
resources can be managed to conserve a spe-
cies, to minimize impact on a fragile environ-

ment, and to provide wealth in remote villages
in a developing country.
The P.N.G. program is based on an appreci-
ation for crocodile biology. Each year, a female
may lay between 30 and 70 eggs. Although
most of them hatch, predators so relish the ten-
der and remarkably vulnerable young hatch-
lings that almost none survived the 15 years
needed to reach breeding size. In nature, then,
there can at any time be found a plethora of
tiny crocodiles, but a paucity of breeders. Com-
mercial hunting worsens the imbalance be-
cause hunters always seek the biggest speci-
mens, regardless of the resulting damage to the
breeding populations.
Recognizing that a ban on hunting would be
largely unenforceable in remote areas (and
grossly unpopular where man-eaters some-
times occur), the P.N.G. Government decided
in 1970 to restructure the trade so that shoot-
ing breeders would lose its attraction and the
profit would come from exploiting the hordes
of tiny hatchlings that would result. This was
done through a law banning the sale of large
skins, supplemented by a stiff tariff on small
Today, villagers in the steamy swamps of
P.N.G. have tens of thousands of tiny croco-
diles in their care. They raise them for a year
or two and can sell them for up to $100 each.
Crocodile farming has already become the
main cash earner for the people there. I per-
sonally met a village leader in Wewak who had
come to oversee shipment of $14,000 worth of
skins headed to New York by airfreight.
The P.N.G. crocodile project is characterized
*Good Science: Despite popular "man-
eater" impression, crocodiles live mainly
on fish, though the researchers in P.N.G.
have found that young ones also grow well
on frogs, snails, and beetles. The feeding
efficiency is astounding: One and one-half
pounds of food gives one pound of weight
gain, and foot-long animals can grow to be
five and six feet long in less than two years.
(Conventional domestic livestock require

five to eight pounds of food to produce one
pound of weight gain.) Crocodile farming
is also space efficient: dozens of animals
are raised in an area the size of a house-
hold living room; in a swamp or jungle,
that's important.
Good Conservation: Because the program
is based on harvesting young hatchlings
from the wild, the economic value of the
wild populations and their habitats be-
comes forcefully apparent. The program's
future depends on them. It gives economic
value to wildlife protection. Out of pure
self-interest, the people become guardians
and conservers of habitats and wildlife. In
a sense, the farming project is just a tool
for conserving the species in its own wild
Good Sociology: The villagers have a so-
phisticated knowledge of the crocodile; the
animal is part of their culture and heritage.
They don't have to be taught how or where
to catch crocodiles, and they take quickly
to the program. Introducing cattle or West-
ern-style crop-raising would require mas-
sive and tedious education and training.
Good Environmental Management: The
program is based on living with the exist-
ing landscape and resources. It requires
none of the bush-clearing fencing, forage-
grass planting, or pesticide spraying that
rearing other domestic animals would de-
mand. That's important in a fragile tropi-
cal rainforest ecosystem.
Good Economic Development: What other
agricultural product could give a $14,000
income in a remote jungle village?

In remote jungle towns in the north of Papua
New Guinea are operating butterfly farms-
some of the most unusual farms in the world.
Around the edge of a field, flowering shrubs
are planted to attract the adult butterflies
whose mouthparts are adapted for drinking
nectar from flowers. These butterfly "forages"
include hibiscus, flame-of-the-forest, and the
strange, pipe-like aristolochia. Within half-acre
circlets of these flowers are planted leafy plants

that the caterpillars feed on. The combination
provides a complete habitat where butterflies
find everything they need for their life cycle.
Thus few leave, and the farmer retains his live-
stock without fencing or walls.
Butterflies may seem exotic livestock to us,
but even in the remotest P.N.G. jungle, a vil-
lager knows and understands their habits, loca-
tion, and lifestyle. And butterflies don't require
bank loans, veterinary services, artificial in-
semination, or the other impediments of con-
ventional livestock. Also, when farming in-
sects, the villager can work when and if he
wants to: there are no deadlines. No hard la-
bor and no danger, either. To a Papua Guin-
ean, the strange thing is that people are will-
ing to pay for a butterfly.
And pay well they do. Ounce for ounce, ex-
otic butterflies are far more valuable than cat-
tle. And worldwide demand for butterflies is
rising. Millions are caught each year and sold
to museums, entomologists, private collectors,
and perhaps most of all, to ordinary citizens.
The fragile, iridescent creatures, mounted in


The fuels paradise of recent decades has
blinded us to the possibilities of alternative
energies, especially those for powering ve-
hicles. The internal combustion engine, how-
ever, remains the most immediately practical
prime mover for motor transport. Finding alter-
native energy sources for it poses one of the
most severe problems facing the world. The
world is not so much running out of energy as
it is running out of liquid and gaseous fuels.
Living plants that produce liquid fuels would
indeed be boons for the future. Farmers would
become energy producers. Today this is al-
ready a distantly glimpsed possibility. Two ex-
amples are given below.
The Gasoline Plants
Near Irvine in southern California can be
found a field of what is perhaps the most

plastic, decorate purses, trays, tabletops,
screens, and other ornamental objects.
With their butterfly farms many rural Papua
New Guineans are for the first time participat-
ing in a cash economy and butterflies are be-
ginning to improve the welfare of many villages.
At Bulolo, the government has established an
insect-buying agency to help the butterfly
farmers of Papua New Guinea. It purchases in-
sects from farmers and fills specific orders re-
quested by overseas buyers. Profits go to the
Perhaps the most striking feature of the pro-
gram is that it is actually conserving, and even
increasing, the numbers of butterflies. Basi-
cally, it is an exciting, pioneering conservation
project because it develops a tremendous eco-
nomic incentive to preserve populations and
habitats-the program relies on healthy wild
populations to keep the farms stocked.
Because of this, conservation organizations
are becoming excited by the program, seeing
in it a model that could be duplicated to help
save endangered exotic butterflies everywhere.

revolutionary and little-explored development
in modern agriculture. The crop is Euphorbia
lathyris and this field is the first attempt at cul-
tivating this wild cactus-like shrub. It is the
brainchild of Melvin Calvin, professor of
chemistry at the University of California at
Berkeley. Euphorbia lathyris and related spe-
cies produce a milky latex, one-third of which
is composed of hydrocarbons-compounds
similar to those found in crude petroleum oil.
Although there are as yet few hard facts on
which to base firm projections, Calvin esti-
mates that the plants might be capable of each
year producing 10 to 50 barrels of oil per acre.
The hydrocarbon in Euphorbia lathyris and
similar species is principally polyisoprene, the
same molecule that makes up rubber in the rub-
ber tree. But in Euphorbia, it is liquid rather
than solid. This is because it is a smaller mol-

ecule, but Calvin points out that its hydrocar-
bon molecules are similar in size to those found
in crude oil. He thinks that Euphorbia type
hydrocarbons might even be processed into
fuels and petrochemicals in existing oil
A distinguished scientist, Calvin received the
1961 Nobel Prize for Chemistry in recognition
of his achievements in unraveling the chemi-
cal processes of photosynthesis. Growing pe-
troleum plants is a new venture for him, but
already he projects that this country's vast pe-
troleum demands could be met by plantations
covering an area the size of the State of
Arizona. He calculates the costs of harvesting
petroleum from trees to be competitive with
current oil prices: a total of between $5 and $15
per barrel for growing and processing the
A plantation of such plants should be eco-
nomic in dry lands unsuitable for growing
food. Though little is known of their require-
ments or yields, Euphorbia species are hardy
and need little or no irrigation and care. Calvin
foresees that the plants will be mowed near the
ground and the harvested plants crushed to re-
lease latex in much the same fashion as is done
with sugar cane. The stumps quickly resprout
new stems so that replanting would be unnec-
This is truly a pioneering concept, and the
field near Irvine is the first small step in evalu-
ating its practicality. Already, larger planta-
tions are planned. The University of Arizona
has a million-dollar grant from the Diamond
Shamrock Corporation to develop Euphorbia
lathyris into a crop; the Government of Kenya
is investing (perhaps unwisely) $10 million in
plantations. If such projects are successful, this
obscure wild plant will enable the world's des-
ert countries to have oil fields on top of the

Diesel Fuel You Grow on the Farm
Ohio State University (OSU) in Columbus,
Ohio, transports students around its spread-out
campus using a fleet of buses. Nothing unusual

in that. But, this year (1980) OSU is using soy-
bean oil as fuel.
Over the past decade, various student proj-
ects at the OSU engineering school have shown
that vegetable oils can be used as fuel for diesel
engines. For a full year the university has run
a large, 60-passenger bus partly on soybean oil.
The experiment proved so successful that in
September the whole university fleet was
switched to the new fuel.
The soybean oil is collected from deep-fat
fryers in cafeterias and kitchens across the
University, filtered through muslin cloth by the
engineering students to remove gunk and
solids, and blended into diesel fuel. A ratio of
one part soybean oil to four parts diesel was
settled on as it gave a stable mixture, lowest
fuel consumption, and actually smoked less
than diesel fuel alone.
The first bus maintained its normal 40 hour
a week schedule. After 4,500 miles on the soy-
diesel blend the engine was taken apart and in-
spected. Little or no abnormal wear had oc-
curred. The engine was actually in such fine
shape that it was merely reassembled and
returned to service without further attention.
Although it is little-known to the general pop-
ulace that diesel engines can be run on vege-
table oils, this knowledge is not new. In the
1890s, Rudolf Diesel concluded that any ma-
terial that was injectable and would ignite at
the temperatures generated by compressing air
could serve as fuel for his engine.
During World War II this knowledge was put
to use. When Japan was cut off from petroleum
supplies, the 65,000 ton Yamoto, the largest and
most powerful battleship of its time, used edi-
ble, refined soybean oil as bunker fuel. Japa-
nese forces occupying the Philippines and
Allied troops trapped in northern Burma used
coconut oil for fueling diesel trucks and
Since then, that experience has been largely
forgotten. But in the U.S., South Africa, Aus-
tralia, Brazil, Canada, Thailand, Japan, and
perhaps elsewhere, individual researchers are
rediscovering that diesel tractors, buses, and

stationary engines can operate when fueled
with sunflower, soybean, peanut, rapeseed,
and other vegetable oils.
The experiences are usually solitary and
most involve only very short running times.
The practical potential of vegetable oils as com-
mercial diesel fuel substitutes is therefore un-
certain. But, at least in the short run, they work.
Of all the research laboratories testing diesel
engines fueled by vegetable oils, the South Afri-
can government's Division of Agricultural En-
gineering has the most experience. At its lab-
oratory near Johannesburg it is running 10
tractors on sunflower oil. Fiat, International
Harvester, John Deere, Landini, Massey Fer-
guson, and Ford tractors are being used. With
two exceptions the tractors started satis-
factorily on undiluted sunflower oil. All oper-
ated normally, delivered almost full power, and
had virtually the same fuel consumption as on
diesel fuel. A Ford 7000 tractor has run trouble-
free for almost 1,400 hours of operation on a
farm using a blend of 20 percent sunflower oil
and 80 percent diesel fuel. At the end of this
time it was found that deposits in the combus-
tion chamber, cylinders, and piston ring
grooves were no worse than those formed
burning normal operation on diesel fuel. On
the other hand, carbon deposits on the injec-
tor nozzles were worse and contributed to an
eventual 4 percent power loss and serious gum-
ming of the crankcase oil.
The rapid compression of fuel and air in the
cylinder of diesel engines generates enough
heat to ignite the mixture and power the en-
gine. Unlike a gasoline engine, no spark is

needed. Injecting the fuel into the combustion
chamber is the most crucial step in a diesel en-
gine. The fuel must be forced in against the
pressure of the compressed air and to make this
doubly difficult, the fuel has to be in the form
of mist. If not atomized, the fuel burns slowly
and unevenly, reducing engine efficiency, rais-
ing unburned pollutants in the exhaust and the
lubricating system, and even forming depos-
its of solid carbon in the engine itself.
Vegetable oils are more viscous and less eas-
ily atomized than diesel fuel and are therefore
more difficult to inject successfully. This is
probably why the injector tips suffered build-
ups of carbon. Coking and the resulting incom-
plete combustion diluted the lubricating oil and
gummed it up because vegetable oils will poly-
merize when they are hot and next to metal.
The South African engineers, however, have
found a way that seems to avoid these difficul-
ties. They slightly modify the sunflower oil in
chemical reactions using small amounts of
ethanol or methanol. The resulting ethyl or
methyl esters derived from sunflower oil
caused much less coking than diesel fuel itself.
Furthermore, they produced much less exhaust
smoke, and the engine ran quieter so that the
characteristic diesel knock was less audible.
And, against all expectations, the engine gave
more power with the new fuel than with diesel
fuel. Thus tractors were running on a renew-
able fuel grown by farmers and achieving bet-
ter results than on diesel fuel. Much yet re-
mains to be done to test the widespread
applicability of these results, but it is a line of
research that is bright with promise.


Development specialists usually promote re-
sources and technologies that are familiar to
their own lives. Most agronomists, foresters,
animal scientists, and nutritionists know little
about the wealth of plants and animals to be
found in the developing world. They all but ig-
nore the significance poor people's crops, le-
guminous trees, and animal resources such as

snails, guinea pigs, and butterflies. Instead they
recommend and sponsor the introduction of
species that are foreign and unconnected to the
lives of those they want to help.

This paper identifies just a few exciting un-
derexploited resources for developing country
agriculture. Detailed information on them and

many others can be found in the following Na-
tional Academy of Sciences reports (all of
which are available without charge from the
Commission on International Relations, JH
215, National Academy of Sciences, 2101 Con-
stitution Avenue, N.W., Washington, D.C.
The Winged Bean: A High Protein Crop
for the Tropics
Leucaena: Promising Forage and Tree
Crop for the Tropics Underexploited Trop-

ical Plants With Promising Economic
* Tropical Legumes: Resources for the
* Guayule: An Alternative Source of Natu-
ral Rubber
* Making Aquatic Weeds Useful: Some Per-
spectives for Developing Countries
* Firewood Crops: Bush and Tree Species
for Energy Production

2f. Y,jt

v, p

74 .. ........

qq t A. '42 . .



MC-L: ".j


A-4 I,


...... ...
. ..


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sal icaag .o.............. 2

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SW T-. -- _. -. .. .... b
Thud r~l~ldY~lr, It*?r te rtain

a .ent, i Sdeaas ould fielp Native
yPs T P tp.tial of4i.z.t- S 1.Vti . . . 61

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-. .. .' .- ... .... .- .- .

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_.._._ . ............... 62.
.. ...... t.62
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at t _~d* -CodtionsW wouldd _--
illetl -r.. ... .................................... 62
S ..... ................ ...........

sa'cR ,..... 63
... .... .... ............... .........
.--" .,

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-- ---..- -- -.-.. --. .. .. . ._.. ... . '. . . 6 4

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Xmon aTehnalogyAfetthe

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Now Zvi ............. ....... 65
. ... .. . . .

Table No Page
1.ittle UsedBut Potentially Useful ;Pat ... .............................. 54


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-i-;- -?

Chapter IV

Native Plants: An Innovative

Biological Technology


The concept of native plants reflects a new
direction in botanical development. The term
implies the idea that rather than adapting the
environment to the plant, an indigenous plant
expresses the best adaptation to an environ-
ment and improving on this expression will
yield various benefits. Bringing marginal lands
into widespread agricultural use often employs
technologies and plant species inappropriate
to these situations. This occurs with a total dis-
regard for the climatic limitations of the envi-
ronments. A new approach is required.
Development of native or indigenous plants,
particularly those adapted to tropical and sub-
tropical soils, could be beneficial at different
economies of scale. In some instances, their de-
velopment will be small and amenable to use
by individual farmers or farming groups. On
the other hand, there will be instances where
development will be large scale and have in-
ternational implications.
Native plants can be particularly useful in
sustaining fertility on depleted or marginal
soils and improving general productivity. They
use an "agroecosystem approach" to obtain
necessary production. Polycultural (mixed)
cropping systems are especially applicable in
tropical locations; they rely heavily on the po-
tential of adapted or indigenous plants. Native
plants represent an underused resource and
constitute an opportunity for positive botani-
cal developments.

The coordinated, integrated development of
indigenous plants could allow for multiple and
additional benefits greater than the initial goals
of soil fertility, food production, or raw mate-
rials. There is an immediate need for inventories
of existing native crops for their development
potential. The world's tropical and subtropical
germplasm is poorly known. Throughout the
world, knowledge of plants and their uses by
indigenous peoples is disappearing because
farming systems are being converted to mono-
cultural uses. Germplasm storage of potentially
valuable varieties and strains requires imme-
diate attention. Demonstration of practical
working models with specific native plants
must be performed.
One factor limiting the development of native
or other unconventional plants is an institu-
tional bias against them. The major emphasis
of plant research during the last 100 years has
been directed at the dozen or so primary food
crops-to the exclusion of almost everything
To overcome this institutional bias will re-
quire innovation in policy, research and devel-
opment, and program implementation. Devel-
opment of native or adapted plants should
allow for an integration of these concerns. The
capabilities of various governmental and non-
governmental institutions should be directed
toward the goal of sustaining soil productivity
in both the short- and long-term context.


The purpose of this paper is to present a non-
technical description and evaluation on the
utility of "native" plants as an innovative tech-

nology to improve productivity on soils in trop-
ical/subtropical areas. The paper addresses sev-
eral major questions that appear as subsections.

The term native plant needs clarification. All
plants may be considered native or indigenous
to some location on the earth, but when a plant
is taken to an area where it is not naturally
found, it becomes an introduced species. This
distinction is too constraining and can over-
look the importance of adaptation-judged ei-
ther from actual observation or from scientific
evidence of ecological similarity. In this report,
native species are those plant species growing
in an area that have not been exploited for com-
mercial development and export. Some native
species may have desirable attributes and a po-
tential for intensive use while others may
merely serve to "fill in the spaces" of the plant
community and have only minor development
potential. This paper is limited to indigenous
species that have not been extensively de-
Native plants hold great promise for meeting
the expanding needs of society for food, fiber,
fuel, and enhanced land productivity. In the
search for a plant or plant product to serve a
market or domestic need, plants native to a
given region may already express the range of
adaptation necessary for sustained use. But
they are often overlooked in favor of an im-
ported species. A good example of indigenous
plants being overlooked is in rangeland im-

provement programs in the Western United
States where native shrubs were removed in
order to plant introduced grasses (11). Al-
though plant exploration and introduction has
been emphasized by the economically devel-
oped nations, the search for new plant
materials has been directed along conventional
lines and the potential of native species has
been overlooked.
In the past, the common procedure has been
to examine existing files or materials found in
plant introduction stations to find new plants
and plant products rather than to explore lo-
cally for possible new products. Because of the
increase in energy costs and the energy com-
ponent in existing production activities, a new
look for alternatives is justified. A particularly
attractive opportunity to develop native plants
exist in tropical and subtropical areas. These
areas generally have not been of interest as a
source of plant materials because the devel-
oped nations are, to a large extent, located in
temperate climates. This has limited germ-
plasm collection, research testing, and intro-
duction of new crop species. Additionally,
most American primary crop species are in-
troductions from the Old World, and these
have been genetically developed over long peri-
ods of time for intensive agricultural use.


Native plants serve a traditional role in many
tropical and subtropical countries. Various in-
digenous species have been used for food, fuel,
livestock feed, construction, fiber, medicines,
and other purposes on a sustained yield basis.
The species are either gathered from natural
plant communities (forests, rangelands, marshes,
etc.) or harvested from small farmed plots
under various degrees of cultivation. Cultures
as diverse as Mexico, Sri Lanka, and Indone-
sia have well-documented histories of wide use
of indigenous plants for medicines, foods, and
other uses. Most of these native plants have not
reached a level of development sufficient to

make them commercially useful. Notable ex-
ceptions include rubber, corn, pineapple, and
potatoes. Most species, however, are unspec-
tacular in their attributes and find beneficial
use only in the day-to-day existence of the local

Overuse of native species brought about by
population increases and energy shortages is
creating adverse impacts on many species and
their systems of production. Where previously
a conservative level of plant use generally as-
sured their natural replacement and did not re-
duce their genetic diversity, exploitation of

land resources by overgrazing, intensive agri-
cultural development, forest clearing, indus-
trial development, and widespread soil degra-
dation threatens to eliminate many useful
For example, a recent National Academy of
Science assessment of environmental degrada-
tion of the groundnut basin of Senegal (12) in-
dicates that overuse due to population increase
and cyclic drought has resulted in the disap-
pearance of many native species used for fruit
and livestock fodder. Theoretically, some of
these species are still present in the noncul-
tivated bush areas. An example is Ziziphus
maritiana, a desirable fodder shrub, that had
essentially been eliminated from areas adjacent
to intensively cultivated farmlands by overuse.
At a conference in Australia on Genetic Re-
sources of the World, concern was expressed
that valuable genotypes and gene combinations
were being lost due to the impacts of human
population expansion. Associated with the di-

rect loss of genetic resources is a substantial
reduction in soil fertility and an increase in less
desirable plants.
Native plants also play an especially impor-
tant role in improving crop performance and
diversity. Indigenous or locally cultivated
relatives of many common crop plants offer
significant potentials for crop improvement
programs within the temperate and tropical
latitudes. Recent discoveries of wild perennial
relatives of corn (Zia mays) could prove ex-
tremely important to the future development
of this crop. Similarly, the expression of ex-
panded environmental adaption often inherent
in many native plants could allow for much
wider cultivation of the species while reduc-
ing artificial inputs. Recent work with salt tol-
erance in major grain crops and tomatoes re-
lies heavily on the adaptive qualities of various
native and overlooked indigenous relatives of
these important crops (13).


Native plants are being used all over the
world. Many species find extensive use in de-
veloped agriculture and some native species al-
ready enjoy limited commercial use in areas
of optimum adaptation (table 1). Opuntia cactus
fruits in central Mexico are collected and sold
locally. Fibers are removed from the Leghugea
cactus for use in making Mexican mats, shoes,
and baskets. Numerous species of native trees
such as Mangosteen (Garcinia mangostana) in
southeast Asia, Naranjilla (Solanum quitoense)
in Colombia and Ecuador, pejibaye peach palm
(Guiliema gasipaes) in Central America, and
soursop (Annona muricata) of the West Indies
produce exotic fruits for local markets.
The important point is that the usefulness of
some species is known only to local people or
is generally not appreciated by a wide au-
dience. A number of examples of fruit, vege-
table, fiber, oil, and forage species are de-
scribed by the National Academy of Sciences
in their studies on underexploited plants (18).

Such underdeveloped species may possess
unique features that could be useful in new ap-
plications or supplement existing crop plants
if they were screened for optimum size, shape,
product quality, and adaptability to various
management practices.
The genus Atriplex is an example of a group
of semiarid, subtropical plants currently used
but possessing significant potential for increas-
ing rangeland productivity. Various shrubby
Atriplex species are valuable as livestock for-
age during seasonal dry periods when most
grasses are below required levels of crude pro-
tein for animal nutrition. The protein content
in Atriplex is high and balanced. The exploitive
subsistence level grazing practices and exten-
sive gathering of Atriplex on the rangelands of
Syria, Iraq, and other Middle Eastern nations
has nearly caused the disappearance of these
palatable shrubs (23). An integrated develop-
ment program of collection and revegetation
with this native species and other adapted

Table 1.-Little Used But Potentially Useful Plants

Present Yield
Common Useful Potential Present Growing State of Per Hectare Time to First
Name Scientific Name Portion Use Areas Cultivation Per Year. Harvest


palm or
Taro and






A. Humid Tropic
Cocoyam Xanthosom suittlfollum

carbohydrate, Tropical Americas,
protein West Africa
carbohydrate, Central and Northen
oil, protein, South America
"heart of palm"
carbohydrate Egypt, Philippines,
Hawaii, Caribbean
oil, starch, Amazon Basin.
vitamins A and Venezuela,
C, timber, cork, Guianas
fiber, "heart of
oil, protein, Amazon Basin
oil, fuel Amazon Basin,




Gullelma gipses fruit a

Colocasia esculents tuber

Mauitia flex uon fruit
Orbignye martiana fruit a
Caryocar brasmienis fruit a

Jessenia polycarp fruit

hophocarpus tetrqo- pods,
nolobus tube
Duio zibethinut fruit

Garcinia mangostane fruit

Cirrus grndis fruit

Annona muricata fruit

riorouma ccrrmpiaefolia fruit

Cnidijcolus chayamansa leaves

Rochmcria nirev stems;
Calathea lutre leaves

L.euceena lrucocephela leaves,

Central Brazil,
Amazon Basin

Papua New Guinea.
Southeast Asia.
Sri LankU
Southeast Asia



30-60 tons
wet weight
3 tons

domesticated 22-30 tons
wet weight
mostly wild ?

mostly wild 1.5 tons

mostly wild ?



22 kg/tree
per year
2.5 tons of
dry beans

haphazardly ?

Southeast Asia domesticated 50 kg/tree
per year
Southeast Asia domesticated ?

Southern China.
Australia. Africa.
tropical Africa.
West Indies
Western Amaron

Mexico and
Central America
East and Southeast
Asia. Brazil
Amazon Basin.
Central America
Central America.
Mexico. Southeast
Asia. Northern
South America.
Australia. Hawaii.
East and West Africa,
Papua New Guinea,
Caribbean. India

domesticated 6-10 tons

wild ?

domesticated ?

domesticated 1.4 tons fiber.
20 tons feed
wild 0.8 tons
of wax
domesticated 12-20 tons
and wild of fo-ri.e,
20-50 tons
of wood

3-10 months

6-8 years

6-18 months


10-15 years

9 years

10 weeks

7 years

15 years

several years

3 years

2-3 months

2 months

9 months

less than 1 year
to more than
3 years,
depends on

B. Semiarid and Arid Tropics and Subtropics
Channel Echinochloa runerna seed. leaves,
mille? and stems

Buffalo Cucurhita foetidissima seed, root


Cyamopsis tetragonoloba seed. leaves.
and stem

protein, live-
stock feed
oil, protein.

gum. protein,
oil. livestock

Central Australia

Mexico. Southwestern
United States

United States.
Pakistan, India.
Ausralia. Brazil.
South Africa

wild ?

several months
after heavy

mostly 2.5 tons of 2 years
wild seed. 22 tons
domesticated 18-24 tons 3-5 months
green fodder.
0.9-2 tons

oil resembling
olive oil.
protein, oil.
livestock teed
fat; vitamins,
highly prized
large citrus

fruit and

leafy vegetable
and fiber and live-
ge stock feed
livestock feed,
. po-'s, timber, fuel.
.bark paper, soil
fertilizer, dye
stuffs, human
food, erosion
and watershed
control, nurse
tree, fire and
wind breaks


Table 1.-Little Used But Potentially Useful Plants-Continued

Present Growing

Present Yield
State of Per Hectr- Time to First
Cultivation Per Year H.rvest

Apple-ling Acacia albida
acacia tree
Ramon Brosimum alicastum

leaves, shoots, livestock feed. Tropical and
pods. seeds human protein Southern Africa
leaves, twigs, livestock feed, Central America,
nuu carbohydrate. Southern Mexico.
protein Caribbean Islands

wild 200 kg
niostly vadd

Cassi. Cassia sturdy leaves livestock feed Australia, Israel wild ndJ 1'2 mn dai
shrub cullivatcJ weight
Saltbush Atriplex spp. leaves and livestock feed worldwide in uild and 1-1.5 tons
shoots warm arid zones cultivated
Candclilla Euphorbia anrsyphilitica stems and hard wax United States and wild ?
shrub leaves Mexican deserts
Tamarugo IPosopis tamarugo podsandleaves high protein. Atacoma desert ol culttlvted 1O-2U sheep
tree livestock Ieed Chile, Canary islands
Jojoba Summondssa chinnsis seeds liquid wax United States and mostly wild 2 tuns
shrub identical to Mexican deserts,
sperm oil Israel
Guayule Parthenmum argentaum whole plant natural rubber United States. Mexican mostly wdd t.jj3 ton
shrub deserts. Spain. Turkey

C Alousntan inrionmcnrs of Low Latitudes
Grain Amaranthus caudatus, seed, leave. high lysuc. Andean regiun of
amaranth etc. high protein, South America
starh. vitamluu

Ouil-11 (Owintpodiusm quirn.
P)rl.vian Irrscada .rinr'iorrii.0
NYarsnlitll Sv'iaum Qfsit',ents

Wine.?l I'vipiarora,,'u rereara

15. Saiinr j~niaonme~srs
I "I ci'" 7nsrraO ma-i".

Pummnelr- (.irmv farnidi

I marupn P.'onpnr rama"Il
Sill vam. J'erpalum regtnura

Spirulina. Spirulin. pirmensir
blue-green 'Spirulina maxima

dumc~tseated 4tw.ei., di...

seed protein. Andean region of donmeticated '
carbohydrate South America
tubers, stems. carbohydrate. Andean region of domesticated '
leaves livestock feed South America
fruit fruit and juice Central and domesticated 1-2 tons
Northern Souith of fruit
pods. bean. protein, oil. Papua New Guinea. domesi ticated 2.5 tons of
tubers, carbohydrate. Southeast Asia. dry beans
foliate livestock feed Sri Lanka

seed carbohydrates. tidal fats and wild ?
protein estuaries in
al latitudes
fruit citrus fruit brackish marshy domesticated several years
areas in Thailand
leaves and high protein, worldwide, including mostly wild 1-1.5 tin" 2 vea.,,
shoots livestock feed salty soils and saline
irrigation waters
podsandleaves high protein. Atacama desert of cultivated 10-20 sheer 5 yeart
livestock feed Chile. Canary Islands
leaves and livestock feed, seacoasts from mostly wild ? I or 2 years
s*ems sand stabiliza- AustralL : :I 'p-
tion Argentina to Baia
entire alpg poultry feed. Lake Chad, Valley cultivated 3 tons several days
very high pro- of Mexico protein
tein human food


Scientific Name



several years

several years

1-1.5 yealI

2 ,r 3 year

2-5 years

5 years

3-5 years

I )ear

ever;l nitlnina

5-6 month<

10-14 month

6-12 months

In week

Atriplex species from similar climates could
substantially restore rangeland productivity to
this region.
Another example of a native plant that is re-
ceiving considerable attention on a pilot-scale
level is jojoba (Simmondsia chinensis), an ever-
green shrub indigenous to the Sonoran deserts
of the United States and Mexico. The plant is
valued for the liquid wax contained in its seeds.

The wax is similar to sperm whale oil and has
a potential for use in many industrial proc-
esses. Field test plantings have been made in
Arizona, California, Israel, Mexico, and Aus-
tralia. Because the plant is adapted to areas of
extremely low rainfall (less than 10 inches), it
could become an important cash crop for the
appropriate arid areas (10).


Research on native plants is being conducted
by many different groups ranging from private
individuals and companies to State, national,
and international agencies. However, no co-
ordinated research effort can be expected be-
cause of the diversity of potentially useful na-
tive species, the various countries where they
are growing and could be grown, and the risks
involved in developing new crops for ill-
defined markets.
As has probably been the case throughout
history, plant resources have been developed
to meet existing and short-term needs. The dif-
ference today is the high cost of bringing new
products into a highly competitive market. Op-
portunities for new products or uses from na-
tive plants can occur as a result of changes (or
potential for changes) in consumer preferences
or as existing products come into short supply
and can be replaced by a native plant product.
It is difficult to identify organizations per-
forming research on native plants, but they fall
into the following categories:
1. Broad spectrum agencies sponsoring ex-
ploration collection and evaluation. Ex-
USDA: plant introduction, plant
materials centers (nationwide).
FAO (Food and Agriculture Organiza-
tion of the United States) seed ex-
change, international development.
SIDA (Swedish International Develop-
ment Agency): sponsoring projects to
preserve genetic resources.

2. Agricultural experiment stations doing
work on individual plant species with lo-
cal concern. Examples:
University of California Agricultural
Experiment station, Riverside: jojoba
University of Hawaii Agricultural Ex-
periment Station: Leucaena trees.
3. Private organizations, agricultural enter-
prises working to develop products from
various species. Examples:
Firestone Rubber Company: guayule
for rubber development,
Native Plants, Inc.: developing new
technology for tissue culture propaga-
tion of various plants.
Jojoba International, Inc.: encourag-
ing commercial plantings of jojoba.
Funding of native plant research is very depen-
dent on the species in question. Obviously the
potential for some species is greater than others
depending on the scarcity and quality of the
expected product, the abundance of the plants,
and the needs of society. Currently, there is a
high interest in native plants with potential as
sources for biomass energy. Unfortunately,
there is little, if any, coordination in research
funding for native plant development or in the
establishment of priorities. As of 1979, the to-
tal U.S. funding for research and development
of underexploited plants was limited to less
than $10 million, half devoted to jojoba.
The uncertain path of development for a nat-
ural rubber product from the native shrub

guayule (Parthenium argentatum) illustrates
the problems of developing a native plant. The
National Academy of Sciences (13) pointed out
that in 1904 a company was formed to extract
rubber from the guayule bush. By 1910 this
company was the sixth largest in Mexico but
the wild stands of plants quickly became
depleted. Expelled from Mexico by Pancho
Villa, the company continued limited opera-
tions in Salinas, California. Cut off from natu-
ral rubber supplies from Southwest Asia in
1942, the United States took over the company
and planted over 12,000 hectares of production
and experimental plots of guayule. These fields
were just coming into production after the war
in 1945, but because natural rubber was again
plentiful and a fledgling synthetic rubber in-
dustry gained the Federal price supports, the
guayule fields were destroyed. Recognizing the
need for dependable supply of natural rubber,
Congress passed the Native Latex Commercial-
ization Act of 1978 which makes $30 million
in Federal funds available for research. Sub-
sequently, Firestone Tire and Rubber Company
and Goodyear Tire and Rubber Company have
initiated field trials of guayule in the South-
west. In Mexico, plans are underway for a nat-
ural rubber industry using guayule from native
stands and later from established plantations.
Obviously, a more integrated and organized
effort will be needed to bring the benefits of
other native plants into reality. The research
community and society simply cannot be sub-
jected to the vagaries of 70 years when a plant
of national value takes so long to be developed.
Coordination is needed to stimulate innovation
in policy planning, research and development
funding, and commercial implementation.
Substantial, integrated programs are neces-
sary to bring native plants into commercial
production. We know that genetic quality of
conventional crops and appropriate cultural
practices have been improved over a long
period of time. With this history of develop-
ment, we can expect that new crops/products
from native plants can be developed with even
greater efficiency. Significant breakthroughs
may take place (such as the application of va-
rious biotechnologies) but for the most part, re-

search funds, time, and vision will be needed
to unlock these new resources.
One of the first research steps must be to
identify promising native plants and describe
some of their characteristics. A survey spon-
sored by the National Science Foundation (22)
described six new crops with a potential for
development in the United States. A thorough
coverage was given to ten new agricultural
crops (20) that already have received some at-
tention. Goodin and Northington (8) helped
stimulate interest in native plants with their
conference on Arid Land Plant Resources.
Probably the greatest stimulus to the devel-
opment and use of native plants in recent years
has been the series of bulletins published by
the National Academy of Sciences. Underex-
ploited Tropical Plants With Promising Eco-
nomic Value. NAS (18) describes 36 tropical
and subtropical plants that have a high poten-
tial for use as cereal, root, vegetable, fruit, oil-
weed, forage, and fuel. The Winged Bean-A
High Protein Crop for the Tropics (17) provides
information on a tropical legume native to
Southeast Asia and New Guinea with a poten-
tial for improving human nutrition. Guayule:
An Alternate Source of Natural Rubber (14) is
a report on the development potential of a sub-
tropical desert shrub of Mexico and Southwest-
ern United States that produces a latex prod-
uct similar to natural rubber from Southeast
Asia. Leucaena: Promising Forage and Tree
Crop for the Tropics (15) provides information
on a vigorously growing tree and bushy plant
that produces nutritious forage as well as re-
storing soil fertility. Other benefits include tim-
ber, fuel, and pulpwood as well as soil conser-
vation and stabilization. Tropical Legumes,
Resources for the Future (13) reports the find-
ings of a group of legume specialists on 200
species that warrant research and development
to achieve their optimum potential. Products
From Jojoba (16) gives a review of the chemis-
try of the liquid wax obtained from this shrub
native to Southwestern U.S. deserts.
These publications all highlight the immense
potential existing within the botanical world
to benefit agriculture, forestry, and horticul-

ture, particularly in the developing countries.
These and other surveys consistently document
the immediate need to inventory indigenous
knowledge concerning native plants and their
uses, germplasm collection and storage, and

conservation of existing habitats. The rapid dis-
appearance of extensive semiarid, subtropical,
or tropical plant community compounds the
problem of collecting, researching, and devel-
oping these under-exploited plant resources.


Any change in the present use pattern of fer-
tilizer, pesticides, irrigation, and machinery
would depend completely on the nature of the
native plant being developed-whether the par-
ticular plant could be developed on an inten-
sive or extensive basis, or the degree to which
the plant is susceptible to insects and diseases.
However, any move to increase productivity
would generally require an increase in the level
of inputs. The adaptation of some indigenous
plants to multicropping systems or polycul-
tures could significantly reduce the need for
artificial inputs. The development of such pro-
duction systems is just in its infancy, however,
and models appropriate to widespread appli-
cation are virtually nonexistent.
Some specific examples of inputs required
by various native plants will illustrate their
variable nature.
Three possibilities for fertilizer use may be
1. Legume species may have minimal fer-
tilizer requirements, needing mainly phos-
phorus, sulfur, and micronutrients.
2. Some native species may not require high
levels of fertilizer because of their adap-
tation to low nutrient environments.
3. Non-legume species may require substan-
tial amounts of fertilizer to achieve optimal
production levels.
Leguminous native plants are particularly at-
tractive because they can serve to increase soil
nitrogen as well as provide useful products
such as fuel, forage, and wood biomass. Fast

growing Leucaena trees have been shown to
provide foliage containing 1,000 to 1,300 lbs.
of nitrogen a year and can restore the fertility
of tropical soils depleted of nitrogen and or-
ganic matter (15). Felker (15) suggested that
mature tree legume orchards receiving no ir-
rigation or nitrogen after establishment may in-
crease soil fertility up to four times greater than
non-leguminous tree species. Numerous leg-
ume shrubs and trees such as Acacia, Prosop-
sis, Desmodium, Cassia, and Stylosanthes
enhance soil fertility while at the same time
serving as live fences, crop interplantings, or
range and pasture fodder. Many examples of
soil fertility increase are presented in Tropi-
cal Legumes: Resources for the Future (13),
Tropical Pastures (21), and in papers presented
at the International Symposium on Browse in
Some native species may not require large
amounts of fertilizer because they are adapted
to soils of medium to low fertility. Under such
conditions, plant growth and production could
be expected to be correspondingly low. If high
yields for commercial production are desired,
the level of fertility must be increased accord-
ingly. Intensive cropping has been shown to
deplete soil fertility and any continuous pro-
duction in a new agricultural location would
eventually require regular soil fertilization.
Non-legume native plants may require large
increments of fertilizer to produce at levels
sufficient to be commercially attractive and to
cover costs of production and development.
These species are those requiring optimal soil
and water conditions. Possible requirements
for fertilizer and other inputs for such crops

are summarized in a report prepared for the
National Science Foundation (22).
Another potential strategy is represented by
the selection and development of native plants
adapted to saline environments. The ability to
tolerate environmental constraints and still
produce utilitarian byproducts is one potential
avenue for overcoming high fertilization in-
puts. This is an approach to native plant de-
velopment that has been virtually ignored in
plant research. The existence of salt tolerant
wild selections of existing crops could improve
the infertility tolerance of these species and
therefore reduce their needs for fertilization.
Such possibilities will require concerted efforts
to enhance the range of adaptability for most
crop species.

Very few, if any, of the native plants having
a high potential for development have been
studied from the aspect of insect, disease, or
weed problems normally associated with inten-
sive cultivation. Whereas many insect or dis-
ease organisms may be held in check in a di-
verse plant community, they may increase to
epidemic proportions when their host plant is
grown in a pure stand. An example of such an
epidemic occurred when black grass bug pop-
ulations nearly devastated pure stands of in-
troduced wheatgrasses that had been seeded
to replace sagebrush and other plants in west-
ern rangelands (9). Plantings of native species
will require research and plant protection
measures similar to those already necessary for
the production of conventional crops.
In tropical countries where multicropping
systems represent the most sustainable method
of farming systems, the pesticide requirements
could be minimized by host/predator interac-
tion within the farm plots (7). Testing and de-
velopment of such models needs to be greatly
expanded, however.


Requirements for irrigation will depend on
the kind of native plant selected. As a concept,
the use of native plants indicates an adaptabil-
ity to the specific environment and its con-
straints. Species adapted to tropical soils may
not require irrigation if the pattern of rainfall
is adequate and meets the critical stages of
plant development. Areas of subtropical soils
typically have periods of rainfall deficiency and
various strategies must be employed to obtain
production under such conditions. These strat-
egies include:
1. Choose native plants with low water re-
quirements that can be grown in desert or
semi-desert conditions. Some examples
are: jojoba, atriplex, guayule, buffalo
gourd, guar, cassia, acadia species (19).
2. Develop technologies to increase the effec-
tiveness of natural precipitation or irriga-
tion. Alternate fallow, spaced plantings,
water harvesting, or drip irrigation can be
effective. Where land is not a limiting fac-
tor, these extensive practices can be eco-
nomically effective. Evanari, et al. (4), dem-
onstrated how an ancient civilization
survived in the Negev desert by using pre-
cipitation optimizing practices such as
water harvesting and spaced plantings. Re-
cent work at the University of Arizona (6)
indicates high potential for using water
harvesting to foster plant production un-
der desert conditions. Biomass plantings,
deep rooted tree crops, and drought
adapted species would be most suitable for
these technologies.
3. Use available irrigation water to support
maximum production of new crops from
high yielding native plants. Where soils
with a high productive potential may be
available for intensive use, possibly by
replacing a lower value traditional crop
with a high value new crop, irrigation may

38-846 0 85 3

be justified. Close plantings, tillage, pest
control, and fertilization may also be
needed to optimize production. Grain
amaranth, winged bean, and guar are pos-
sible species for intensive development,
but many other may be considered.

Because of the varied nature of native spe-
cies available for development, no definite
statement can be made regarding machinery
requirements. Equipment for land preparation,
tillage, and transportation of crops to storage
and market would be needed. Harvesting may
be done by machinery in the case of a uniform
plant such as guar or guayule where leaves and
seeds are easily available. Where fruits, stems,

or roots are not uniformly exposed and are re-
tained on the plant, either hand labor or a spe-
cialized piece of machinery may be needed.
In regions of the world where hand labor is
abundant for planting, cultivating, and har-
vesting, the development of new native crops
that require hand labor rather than machinery
is most appropriate. In other nations, labor in-
tensifying machinery can be developed. This
has been the pattern followed in the develop-
ment of conventional crops.
It is important to recognize that the devel-
opment of native plants for their various uses
can be aimed at local needs as well as at wider
industrial and international markets. Machin-
ery and labor requirements will depend on
what level of development is pursued.


There is a high potential for some native
plants to positively affect food production on
tropical and subtropical soils. One of the most
promising strategies is the increased use of le-
guminous plants as food, livestock fodder, and
wood to concurrently improve soil fertility (21).
As fertilizer costs continue to escalate in re-
sponse to energy expenses, fertilizers will be-
come economically prohibitive in many devel-
oping countries. Incorporation in the cropping
system of a legume rotation, green manure, or
animal manures derived from legume feeds
may be the best remaining option to replace
fertilizers (12) and maintain agricultural
Non-legume native species have various
potentials for positive benefits to food produc-
tion. Many species are already known locally
but have not received sufficient notice to be in-
troduced or developed for use in other (simi-
lar) regions. To achieve such recognition will

1. A shortage in food from existing crop
2. Development of new lands that are better
suited for new crops.
3. Adaptation of new crops to compete eco-
nomically with conventional crops.
Some form of research and development in-
tervention will be needed to raise the perspec-
tive and incentives of local peoples. The like-
lihood of general use depends on the individual
species. For example, the general qualities of
seeds from the jojoba plant have been known
for many years (10) but only recently has any
development effort appeared substantial
enough to bring the plant into widespread use.
The shortage and cost of sperm whale oil is
a big factor motivating jojoba development in
more than five countries. Some applications
will be less spectacular, but no less needed.
Plantings of the legume tree Acacia albida in
Mali (24) hold considerable promise for im-

proving subsistence agricultural production
there, but the effort is but a "drop in the
bucket" compared with the needs in that area
of West Africa.
In view of the diversity of native plants avail-
able for development and the number of coun-
tries with suitable environments, judicious sup-
port of native plant development programs

seem justified. The likelihood of spontaneous
development or widespread use of native plant
resources seems unlikely without external en-
couragement. Otherwise, many useful native
plant species and ecotypes stand in jeopardy
of being lost as deforestation, land depletion,
industrial development, or other activities elim-
inates the natural plant communities.


Scenario A
The program of planting seedlings of Acacia
albida legume trees in Mali (24) serves as a
model for the development of the potential of
a native plant. In this program, CARE set up
production nurseries to produce tree seedlings
in soil-filled plastic tubes. Acacia albida is an
indigenous legume tree native to sub-Saharan
Africa. The tree has the unique feature of be-
ing leafless during the rainy season. This al-
lows for cultivation of other crops directly un-
der the tree. The leaves and pods provide
fodder and green manure and the roots fix ni-
trogen. It is an ideal candidate for selection,
improvement, and application to various semi-
arid agroforestry systems.
Teams of local farmers were employed to
plant the seedlings in preselected agricultural/
pasture areas of good soils. Planters were paid
on a per tree basis for planting and protection.
Subsequently, these local people were encour-
aged (in their work training orientation) to take
a special interest in the seedlings to see that
they received appropriate management and
protection to ensure their survival from graz-
ing animals. Benefits expected are increases
in soil productivity and livestock feed.

Scenario B
A scenario for planting a living fence of a leg-
ume shrub to enhance soil fertility by N-
fixation and livestock manure might be as fol-

lows. Seedlings could be propagated at a gov-
ernment research station after selection from
depleted stands of palatable shrubs. These
plants would then be distributed to village
elders for allocation to heads of families for
planting around the fields and houses in the
immediate vicinity of the village. This would
enhance kitchen garden production and feed
small livestock through the dry season. Excess
fodder could be used on the farm plots as green

Scenario C
A scenario to develop a high value, native
tree, fruit crop would logically start with a pro-
gram of selecting the most desirable biotypes
for their fruit quality, tree size and form, and
maturity pattern. Because of the long-term re-
quirements for genetic improvements that
would combine the best qualities in various
selections, a dual development program would
be undertaken. The first would be to vege-
tatively propagate (by rooted cuttings of a few
plants or by tissue culture for thousands) the
best selectionss. Propagules would normally
be grown in containers until ready for field
transplanting. Sufficient acreage would be
planted to provide experience in intensive
management and production for a local, re-
gional (city), or international cash market. As
experience is gained with product acceptance,
the criteria for the genetic breeding program

would be modified. By the time suitable genetic
materials would be available, the market re-
quirements would be sufficiently known to
guide large-scale development plantings and
improved cultural practices, possibly involv-
ing machinery.

Levels of capital and manpower needed
could be determined or extrapolated on the
basis of experience with a pilot program. Pi-
lot demonstration programs are a plausible
way to approach development of the most
promising native plants.


One of the most critical attitudinal problems
in developing new crops from native plants is
one of institutional interest in sustainable
and diversified plant development. Traditional
crops, mostly of temperate origin, have re-
ceived the majority of institutional attention
from government, research, and commercial
organizations. A new and more innovative ap-
proach to plant development is required when
referring to native or adapted plant develop-
ment. The various groups that directly affect
these development efforts include the fol-

All efforts should include the local farmers.
The objective would be to seek sufficient in-
volvement on planning, planting, and manage-
ment to bring local people to thinking that the
project is theirs-not something imposed from
outside by government. The active efforts of
an individual farmer in the Dakotas to bring
sunflower into widespread cultivation is an ex-
ample of the importance of this element in the
introduction of "new" crops.

Politicians should be encouraged to provide
a favorable and stable policy for product de-
velopment, to be optimistic but not raise
unrealistic expectations, and finally to be will-

ing to support financial needs of the pilot proj-
ect. The efforts of the Guayule Commission is
an example of this coordinated effort at pol-
icy and implementation.

Banks and bankers need to be educated about
the realities and potentials for development of
a new crop. Available capital for second phase
development would be needed if the private
sector is to follow the pilot development. Orien-
tation and involvement would be needed to
assure support when it is needed. Tax incen-
tives and loan guarantees may be useful ways
for financial institutions to foster more rapid
development and diversification of new crops.

Policymakers within the international donor
community need to understand the risks as
well as the opportunities for a successful pro-
gram. Stepwise project implementation is a
desirable approach where needed research and
development experience is gained as the pro-
gram develops. This approach could be imple-
mented directly by requiring agricultural, for-
estry, and horticultural development projects
to direct a certain percentage of the program
to native species or varieties. Means for involv-
ing host country politicians, research people,
and local farmers are crucial.


Obviously, the best place for a native plant
development project would be where it is

needed most. However, there are qualifications
to this simplistic statement.

Biophysical Conditions
To be successful, a native species needs a
high degree of adaptation to the climate, soils,
topography, and animal uses, including resis-
tance to parasites. From an ecological stand-
point, the approach should be to seek areas that
are ecologically equivalent to the original hab-
itat of the native plant species. This is usually
done by testing plantings in various locations
of similar climate. However, the time period
during which the plantings are under obser-
vation may not be sufficient to experience the
range of environmental extremes that is com-
mon to the area. Detailed experiments under
greenhouse and controlled environment cham-
bers may help to document the full range of
adaptation possessed by the species.

Cultural Conditions
For a new crop or agricultural product to be
successfully produced, it must not be contrary
to the cultural traditions of the people to grow,
consume, or use. For example, an improved
high protein maize (corn) variety was consid-
ered in India, where there were food shortages.
However, the yellow color of the seed coat was
objectional because it resembled a grain prod-
uct fed to animals (1). A social custom study
would be advisable to determine if any taboos,
customs, or adverse values exist regarding the
potential crop and its required production

Socioeconomic Conditions
Critical to the development of any new crop
from a native plant is whether the product is
socially acceptable and whether local people
can handle the costs of development. There is
less chance of gaining social acceptance of a
project if the payoff period is far into the fu-
ture. An early return on the investment may
be needed to maintain interest and commit-
ment to a project. Further, the amount of cap-
ital required may exceed the capacity of in-
dividuals or banks to handle. Thus, smaller
increments of development and interim returns
to investment may be necessary. An example
with animals should illustrate this point. A
farmer could finance the purchase of several
animals of an improved breed of goat or a pen
of rabbits, but he may not be able to finance
a cow or bull. There is also greater risk in hav-
ing a high amount of capital tied up in one in-
The above conditions are most likely to ex-
ist in the less developed tropical countries, in
the more rural and remote regions of such a
country, and with people of tribal or nomadic
social organization. The less educated people
would likely be more difficult to reach and less
willing to accept a development program.
Communication tools such as radio, news-
papers, and films could be used to help both
in the search for useful plants as well as dis-
seminate information on new uses and oppor-
tunities for economic diversification.


Development of a native plant species to
commercial or economically significant levels
would not be easily accomplished based on
current observations of jojoba and guayule.
Many constraints must be overcome to satis-
factorily develop the potential of a native plant.

Scientific Constraints

A major scientific problem in plant develop-
ment is lack of technical information. A suffi-
cient amount of general information is needed
to identify plants of high potential. Additional

species information can help determine feasi-
bility for development and the suitability of
products or uses to meet identified needs. Prog-
ress toward development may well depend on
technical data regarding planting, manage-
ment, harvest, processing, and conservation.
Pilot demonstration programs designed to an-
swer technical problems are essential.
Particularly needed are scientific studies on
ways to establish plants and obtain optimum
productivity under arid, semiarid, and tropi-
cal conditions. Problems dealing with micro-
organisms and plant growth, drought resis-
tance, physiology of stress, and application of
engineering to improve adaptation present
challenges for scientific research on indige-
nous plants.

Environmental Constraints
Existing land uses may pose one of the
largest constraints to native plant development.
But such commitments of land must be seen
in relation to the long-term values. Where de-
creasing soil fertility and vegetation degrada-
tion are occurring, a shift to a leguminous na-
tive plant could bring multiple benefits. For
native plants with industrial potential (i.e.,
guayule), processing may influence air and
water quality. Whether costs can be internal-
ized in the value of the product of plant use
must be determined. In most instances, the
environmental benefits of developing native or
adapted plants will most likely outweigh the
negative impacts. The potential to reduce ex-
isting environmental degradation and more
sustained land use must be considered positive

Culture Constraints
Native plant development may cause social
change, community growth, and increased
need for services. Such changes need to be ad-
dressed, but at this time little information is
available. In general, the cultural impacts from
developing new crops or practices from native
plants should be positive or neutral. In the con-
text of tropical countries, the perceptions of re-

gional, community, tribal, or family groups
must be considered. Resistance to change may
be manifested by refusal to cooperate or allow
project development. Involvement of local
leaders and decisionmakers is a necessity.

Economic Constraints
The major economic constraint to develop-
ment is probably the lack of seed money, ven-
ture capital, or government support to conduct
pilot-scale programs. From the pilot program,
cost data can be extrapolated for planting, pro-
duction, transportation, and marketing. From
these preliminary data, decisions can be made
toward major financing and long- or short-term
commitment of funds, either by the private sec-
tor or through government grants and loans.
Because of the generally speculative nature of
developing high potential native plants to meet
needs that are not clear, private sector fund-
ing may have to be government subsidized.

Political Constraints
A major political constraint is the instabil-
ity and short longevity of many political leaders
in less developed countries. Although a new
crop development program may be highly fa-
vored by one political leadership, the prospect
of change must be considered. Because agri-
cultural development is highly important and
not as politically sensitive as other sectors of
a country, it should be possible to work within
political constraints as long as the project does
not appear to run counter to current political
and social philosophy.
For example, pilot plantings of palatable fod-
der shrubs in Syrian rangelands by FAO and
the Syrian Ministry of Agriculture were de-
scribed as an extension of cooperative market-
ing and fattening units to increase meat pro-
duction and increase the stability of the
livestock industry (2). In reality, the system had
many free enterprise profitmaking opportuni-
ties to increase the incentive of individuals to
participate in the scheme. Yet political leaders
touted the success of this cooperative project
and declared it to be in harmony with the so-

cialistic philosophy mandated by the govern-
ment. New crops must not appear to compete
with existing production systems, but should
complement them. Constituents must be con-
vinced that the proposed developments will

provide benefits equitably. Additionally,
adapted crops that could represent a higher
cash return than traditional crops should re-
ceive special attention from the international
donor community.


Because of the varied types of native plants,
no specific capital requirements can be deter-
mined for all native plants. There is no doubt
that a native plant development program would
require significant inputs of technology and
capital. However, those plants that produce a
crop would require greater inputs than those
used for reforestation, improving soil fertility,
or increasing rangeland forage production.
Careful analysis of the infrastructure of a re-
gion or county may give an indication of avail-
able processing capacity. For example, vege-

table oil extraction facilities are available in the
groundnut basin of Senegal and might be avail-
able in the off-season to extract hydrocarbon
latex from giant milkweed plants that grow in
waste places and margins of fields. A small
pilot program with these native plants could
provide some of the data necessary to deter-
mine the feasibility of proceeding to larger
phases of development. In a like manner, any
proposed new crop should be analyzed for cap-
ital inputs and available facilities for produc-
tion processing and transport.


It would be false to assume that only a large
commercial-type farm or a family-sized farm
would be suitable for native plant development.
Much depends on the nature of the plant spe-
cies and the magnitude of development nec-
essary. From table 1, it can be seen that some
crops such as cocoyam and buffalo gourd
could easily be grown on small plots and col-
lected for commercial markets. In contrast, in-
dustrial feedstocks, biomass, and high volume
crops such as guayule, ramie, leucaena, and
guar would better be grown in large fields and
be harvested and treated mechanically.
Small field operations would cause little
change on socioeconomic structure except to
provide an additional income stream to com-
munities. Large operations may disrupt com-
munities by increasing their population or re-
quiring the establishment of new communities.
An excellent example in the United States is
the 110,000 acre Navajo Irrigation project near

Farmington, New Mexico. This large commer-
cial farm operation has left little opportunity
for community development of a traditional na-
tive culture, nor has it provided an opportu-
nity for family farm or cooperative group farm
development. The project has addressed only
the large-scale production-economic aspects of
development. Socioeconomic problems remain
unsolved as illustrated by the attempts being
made to resettle Navajo workers in a modern
subdivision quite foreign to existing patterns
of community settlement.
In summary, the various options available in
native plants of high potential for development
could enhance existing social and economic
patterns or could disrupt them with large de-
velopments depending on the suitability of the
land, the adaptability of native plants to given
locations, and the institutional insensitivity that
might prevail in their development.


1. Cummings, Ralph, personal communication
from the Rockefeller Foundation Project Direc-
tor in India, 1972.
2. Draz, Omar, personal communication while on
a field trip to Waddi Al-Azib Experiment Sta-
tion in Syria, 1978.
3. Epstein, E. et al., "Saline Caltese of Crops: A
Genetic Approach," Science 210:399-404, 1980.
4. Evanari, Michael; Shanan, Leslie; and Todmor,
Naphtali, The Negev, the Challenge of a Desert
(Cambridge, MA: Harvard University Press,
1971), 345 p.
5. Felker, Peter, "Mesquite, An All-Purpose Legu-
minous Arid Land Tree," pp. 89-132. In:
Ritchie, Gary A. (ed.) New Agricultural Crops,
AAAS Selected Symposium 38 (Boulder, CO:
Westview Press, 1979).
6. Frasier, G.W., "Proceedings of the Water Har-
vesting Symposium," U.S. Department of Agri-
culture, Agricultural Research Service, Western
Region (ARS) W-22, 1975, 329 pp.
7. Gliessman, S., "The Ecological Basis for the Ap-
plication of Traditional Agricultural Technol-
ogy in the Management of Tropical
Agroecosystems," Agroecosystem (in press),
8. Goodin, Joe R., and David Northington (eds.),
"Arid Land Plant Resources," Proc. of the In-
ternational Arid Lands Conference on Plant Re-
sources, Texas Tech. University, Lubbock, TX,
9. Haws, B. Austin (ed.), "Economic Impacts of
Labops hesparius on the Production of High
Quality Range Grasses," final report of Utah
Agric. Exp. Stn. to Four Corners Regional Com-
mission, Utah State University, Logan, UT,
1978, 269 pp.
10. Hogan, Le Moyne, "Jojoba, A New Crop for
Arid Regions," pp. 177-205. In: Ritchie, Gary
A. (ed.), New Agricultural Crops, AAAS
Selected Symposium Series 38 (Boulder, CO:
Westview Press, 1979).
11. McKell, C. M., "Shrubs-A Neglected Resource
of Arid Lands," Science 187:803-809, 1974.
12. National Academy of Sciences, "Preliminary
Report Assessment of Environmental Degrada-
tion and Agricultural Productivity in the

Senegalese Groundnut Basin," NAS report to
AID, Senegal, 1980.
13. National Academy of Sciences, Tropical Le-
gumes: Resource for the Future, report of ad
hoc panel of the advisory committee on tech-
nology innovation, 1979.
14. National Academy of Sciences, Guayule: An
Alternate Source of Natural Rubber, report of
ad hoc panel of the advisory committee on tech-
nology innovation, 1977.
15. National Academy of Sciences, Leucaena,
Promising Forage and Tree Crop for the Trop-
ics, report of ad hoc panel of the advisory com-
mittee on technology innovation, 1977.
16. National Academy of Sciences, Products From
Jojoba: A Promising New Crop for Arid Lands,
report of ad hoc panel of the advisory commit-
tee on technology innovation, 1975.
17. National Academy of Sciences, The Winged
Bean: A High Protein Crop for the Tropics, re-
port of ad hoc panel of the advisory committee
for technology innovation, 1975.
18. National Academy of Sciences, Underexploited
Tropical Plants With Promising Economic Val-
ue, report of ad hoc panel of the advisory com-
mittee on technology innovation, 1975.
19. Revelle, Roger, "Flying Beans, Botanical
Whales, Jack's Beanstalk and Other Marvels,"
National Academy of Sciences, Board on
Science and Technology for International De-
velopment, 1978.
20. Ritchie, Gary A., New Agricultural Crops,
AAAS selected symposium series 38 (Boulder,
CO: Westview Press, 1979), 259 p.
21. Sherman, P. M., "Tropical Forage Legumes,"
Food and Agricultural Organization of the
United Nations, Rome, Italy, 1977.
22. Soil and Land Use Technology Inc., "Feasibil-
ity of Introducing Food Crops Better Adapted
to Environmental Stress," National Science
Foundation Report NSF/RA 780289, 1978.
23. Thalen, D.C.P., Ecology and Utilization of Des-
ert Shrub Rangelands in Iraq (Dr. W. Junk Pub-
lishers, The Hague Netherlands, 1979), 448 p.
24. Weber, Fred, and Dulansey, M., "Midpoint
Evaluation, Chad Reforestation Project," Pre-
pared for CARE by Consultants in Develop-
ment, New York, NY 10014, 1978.


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Chapter V

Multiple Cropping Systems:

A Basis for Developing an

Alternative Agriculture


This paper presents a general discussion of
the concept of multiple cropping, including a
description of the different types of systems,
and the advantages and disadvantages of their
widespread use, both biological and socio-
economical. These systems are designed to in-
tensify agricultural production both in terms
of yields per unit area and through the more
efficient use of space and time.
Examples of yield increases with multiple
cropping systems are expressed in terms of
Relative Yield Totals (RYT) or Land Equivalent
Use (LER) where the production per unit area
with the multiple crops is greater than the sum
of equivalent areas planted to monocultures.
This increase in production is explained by
higher overall efficiency of resource use.

Specific examples of the effects of multiple
cropping systems on resource use, conserva-
tion, and management are discussed. Variables
considered include microclimate, light, soil,
water, pests, diseases, weeds, crop interac-
tions, space, and time. The special case of
agroforestry, which combines trees with crops
and grasses, is discussed.
In conclusion, the socioeconomic implica-
tions, both advantageous and disadvantageous,
are discussed. Also, the great potential for
multiple cropping systems in agriculture in the
United States is presented. Research needs to
be directed to test these alternatives.


Multiple cropping is not a new form of agri-
cultural technology, but instead is an ancient
means of intensive farming. Multiple cropping
has been practiced in many parts of the world
as a way to maximize land productivity in a
specific area in a growing season. Generally,
the practice of planting two or more crops on
the same field is more common in tropical re-
gions where more rainfall, higher tempera-
tures, and longer growing seasons are more
favorable for continual crop production. As
population has increased, increasing the need
for agricultural production, the use of multi-

cropping systems is more prevalent. Though
the history of multiple cropping is old, the con-
cept has received very little attention from agri-
cultural scientists, and what limited interest ex-
ists has come about very recently.
Why was this interest increased so dramat-
ically in such a short time? Food shortages in
many parts of the world, as well as the threat
of insufficient supplies in the near future, con-
tinues to stimulate more intensive agricultural
investigation in a search for more productive
alternatives. As a consequence, it appears that


we are about to embark on a new phase of agri-
cultural research. Exactly what form it will take
is still not known, but the reasons for this new
approach are rapidly becoming apparent.
First, we have begun to observe a leveling off
in yield increases brought about by the types
of genetic manipulation that gave us such rapid
and impressive yield increases during the
"Green Revolution." It is as if we have reached
a "yield plateau" with the current lines of re-
search and crop selections. Large-scale use of
single varieties (e.g., some of the International
Rice Research Institute (IRRI) varieties of rice),
with broad adaptability, produced major break-
throughs in yields. But it appears that these va-
rieties have almost reached their maximum
yield potentials. In many areas with specific
soil and climatic conditions, they have not per-
formed as well as hoped, especially on land
more difficult to mechanize or irrigate. Thus
we must begin to look for varieties with more
specific adaptability and selected for specific
environments, or else consider alternative
cropping systems.

best agricultural lands-areas with good soil
and easy water control. Future increases in
production, therefore, will demand a new and
innovative way of managing these highly pro-
ductive lands, as well as looking for methods
to make marginal lands increasingly produc-
tive. Only 20 percent of Asia rice land, for ex-
ample, is irrigated, and the new high yielding
rice varieties (which also require high levels of
fertilizers, water use, and pest control) have not
penetrated much beyond this boundary (16).
The third factor is the oil crisis. Oil prices
continue to soar, and with them, the cost of fer-
tilizers, pesticides, and fuel needed to build and
run farm equipment and move irrigation water.
Costs continue to mount for those inputs most
responsible for achieving the dramatic yield in-
creases of the "Green Revolution." We are
faced with the necessity of having to consider
other alternatives that might allow us to sub-
stitute innovative biological or agronomic prac-
tices and varieties for these high cost inputs.
Multiple cropping offers one of the most im-
portant and promising of these alternatives.

Second, most of the dramatic yield increases
during the past few decades have been on the


Multiple cropping systems use management
practices where the total crop production from
a single piece of land is achieved by growing
single crops in close sequence, growing sev-
eral crops simultaneously, or combining single
and mixed crops in some sequence. The most
important aspect of multiple cropping is the
intensification of crop production into addi-
tional dimensions. Multiple cropping includes
the dimensions of time and space; for exam-
ple, when two crops share the same space at
the same time.
A classification of types of multiple cropping
systems is presented in table 1. Note that
special emphasis is placed on the distinction
between intercropping, where two or more
crops are grown at the same time, and sequen-

tial cropping, where two or more crops are
grown on the same piece of land, but one fol-
lowing the other.
Some additional terms used in multiple crop-
ping are presented in table 2. Agroforestry, as
a particular type of intercropping system, will
be discussed in some detail. Also, "mixed crop-
ping," "polyculture," and "multiple cropping"
will be used interchangeably in this review. By
combining different aspects of simultaneous
and sequential cropping systems, it is possible
to visualize a truly complex pattern of different
multiple cropping systems. This classification
will be used throughout the following discus-
sion, based on a symposium sponsored by the
American Society of Agronomy, in support of
the need to standardize terminology (34).

Table 1.-Definitions of the Principal Multiple
Cropping Patterns

* Multiple Cropping: The intensification of cropping in time
and space dimensions. Growing two or more crops on the
same field in a year.
* Intercropping: Growing two or more crops simultaneously
on the same field per year. Crop intensification is in both
time and space dimensions. There is intercrop competi-
tion during all or part of crop growth. Farmers manage more
than one crop at a time in the same field.
-Mixed intercropping: Growing two or more crops simul-
taneously with no distinct row arrangement.
-Row intercropping: growing two or more crops
simultaneously with one or more crops planted in rows.
-Strip intercropping: Growing two or more crops simul-
taneously in different strips wide enough to permit in-
dependent cultivation but narrow enough for the crops
to interact agronomically.
-Relay intercropping: Growing two or more crops simul-
taneously during part of each one's life cycle. A second
crop is planted after the first crop has reached its
reproductive stage of growth, but before it is ready for
* Sequential Cropping: Growing two or more crops in se-
quence on the same field per year. The succeeding crop
is planted after the preceding one has been harvested. Crop
intensification is only in the time dimension. There is no
intercrop competition. Farmers manage only one crop at
a time.
-Double cropping: Growing two crops a year in sequence.
-Triple cropping: Growing three crops a year in sequence.
-Quadruple cropping: Growing four crops a year in se-
-Ratoon cropping: Cultivating crop regrowth after harvest,
although not necessarily for grain.
SOURCE: Andrews and Kassam, 1976 (5).

Table 2.-Related Terminology Used in Multiple
Cropping Systems

Single Stands: The growing of one crop variety alone in pure
stands at normal density. Synonymous with "solid plant-
ing," "sole cropping." Opposite of "multiple cropping."
Monoculture: The repetitive growing of the same crop on the
same land.
Rotation: The repetitive growing of two or more sole crops
or multiple cropping combinations on the same field.
Cropping Pattern: The yearly sequence and spatial arrange-
ment of crops, or of crops and fallow on a given area.
Cropping System: The cropping patterns used on a farm and
their interactions with farm resources, other farm enter-
prises, and available technology that determine their
Mixed Farming: Cropping systems that involve the raising
of crops and animals.
Cropping Index: The number of crops grown per annum on
a given area of land multiplied by 100.
Relative Yield Total (RYT): The sum of the intercropped yields
divided by yields of sole crops. The same concept as land
equivalent ratios. "Yield" can be measured as dry matter
production, grain yield, nutrient uptake, energy, or protein
production, as well as by market value of the crops.
Land Equivalent Ratios (LER): The ratio of the area needed
under sole cropping to the one under intercropping to give
equal amounts of yield at the same management level.
The LER is the sum of the fractions of the yields of the
intercrops relative to their sole-crop yields. It is equivalent
to RYT, expressed in commercial yields.
Income Equivalent Ratio (IER): The ratio of the area needed
under sole cropping to produce the same gross income
as is obtained from 1 ha of intercropping at the same
management level. The IER is the conversion of the LER
into economic terms.
SOURCE: Sanchez, 1976 (39).


Yield Advantages of Crop Mixtures

In areas of the world where multiple crop-
ping is a common aspect of agroecosystem
management, productivity generally is more
stable and constant in the long term (24,45).
Farmers often are able to achieve a combined
production per unit area greater with a crop
mixture than with an equal area divided among
separate crop units. In such cases the Relative
Yield Total (RYT) is greater than 1.0. It may
be that each crop in the mixture yields slightly
less than the monocultures, but the combined

yield of the mixture on less total land area is
the important aspect.

In one study (43), the results of 572 com-
parisons of crop mixtures demonstrated that
the majority (66 percent) had RYTs close to 1.0,
indicating no distinct advantage to the mixture
(fig. 1). On the other hand, 20 percent of the
mixtures had RYTs greater than 1.0, ranging
up to 1.7, indicating advantages to the mix-
tures. Only 14 percent had less than 1.0, in-
dicating distinct disadvantages. It must be
remembered that most of the cases studied

Figure 1.-Distribution of the Relative Yield Totals of
Mixtures Based on 572 Published Experiments

Table 3.-Biological and Physical Factors:
The Advantages and Disadvantages of Multiple
Cropping Systems Compared to Sole-Cropping or
Monoculture Systems (priority is not established)

9 50
a 40

5 30

c 20

SOURCE: Trenbath, 1974 (43).

were experiment
multiple cropping
tend to choose the
we have observed

1. It is possible to obtain a better use of vertical space and
: time, imitating natural ecological patterns in regards to
structure of the system, and permitting efficient capture
of solar energy and nutrients.
7i ~2. Greater amounts of biomass (organic matter) can be
:i .returned to the system, sometimes even of better quality.
3. There exists a more efficient circulation of nutrients, in-
cluding their "pumping" from the deeper soil profiles
when deeper rooted shrubs or trees are included.
4. The damaging effects of wind sometimes can be
;,t reduced.
5. Systems can be designed that are appropriate for (but
not restricted to) marginal areas because multiple crop-
ping systems can better take advantage of variable soil,
topography, and steeper slopes.
6. Multiple cropping systems are less subject to variabili-
ty in climatic conditions, especially extremes of rainfall,
temperature, or wind.
7. Reduction of water evaporation from the soil surface.
8. Increased microbial activity in the soil.
0.9 1.1 1.3 1.5 1.7 9. Avoidance or reduction of surface erosion.
10. Fertilizer use can be more efficient because of the more
diverse and deeper root structure in the system.
active yield totals (RYT) 11. Improved soil structure, avoiding the formation of a "hard
pan" and promoting better aeration and filtration.
12. Legumes (as well as a few other plant families) are able
to fix and incorporate nitrogen into the system.
13. Heavier mulch cover aids in weed control.
14. Better opportunities for biological control of insects and
1 planting and not actual 15. Crop mixtures better permit the functioning of complex
systems. Farmers would mutualisms and beneficial interactions between or-
systems that yield more, as ganisms.
16. Better use of time, with more crops per unit time in the
in traditional agroecosys- same area.

teams in the lowland tropical areas of southeast-
ern Mexico (24,25).

The fact that advantageous mixtures do ex-
ist demonstrate the need for detailed research
to take proper advantage of such systems. But
for such systems to be considered as actual
alternatives we need to understand thoroughly
the biological and agronomic basis responsi-
ble for the observed response, as well as the
advantages and disadvantages to their use.
Before beginning a discussion of each aspect,
a basic outline of such characteristics is pre-
sented, separated broadly into biological and
physical aspects (table 3) and socioeconomic
aspects (table 4). In many cases it is understood
that there may be overlap between the two
classifications, yet it is hoped that in the course
of the following discussion that such aspects
will be clarified.

1. Competition between plants for light.
2. Competition between plants for soil nutrients.
3. Competition between plants for water.
4. Possibility for allelopathic influences between different
crop plants due to plant-produced toxins.
5. Harvesting of one crop component may cause damage
to the others.
6. It is very difficult to incorporate a fallow period into multi-
ple cropping systems, especially when long lived tree
species are included.
7. It is sometimes impossible, and many times very difficult,
to mechanize multiple crop systems.
8. Increased evapotranspiration loss of water from the soil,
caused by greater root volume and larger leaf surface
9. Possible over-extraction of nutrients, followed by their
subsequent loss from the system with the increased ex-
portation of agricultural or forest products.
10. Leaf, branch, fruit, or water-drop fall from taller elements
in a mixed crop system can damage shorter ones.
11. Higher relative humidity in the air can favor disease out-
break, especially of fungi.
12. Possible proliferation of harmful animals (especially
rodents and insects).

Table 4.-Social and Economic Factors:
The Advantages and Disadvantages of Multiple
Cropping Systems Compared to Sole-Cropping or
Monoculture Systems (priority is not established)

1. Dependence on one crop is avoided so that variability in
prices, market, climate, and pests and diseases do not
have such drastic effects on local economics.
2. Less need to import energy, pay for fertilizers, pay for ex-
ternally produced materials, or depend on machinery.
3. Wildlife is favored, and with rational use it can be an im-
portant source of protein.
4. Greater flexibility of the distribution of labor over the year.
5. Recovery of investments can occur in much less time,
especially where trees are combined with short term
agricultural crops.
6. Harvest is spread over a longer period of time.
7. In areas and times of high unemployment, multiple crop-
ping systems can use much more labor.
8. Farmers can produce a large variety of useful products,
depending on the type and complexity of the multiple
cropping systems, such as firewood, construction mate-
rials, flowers, honey, crops for home consumption, thus
lowering the outflow of funds.
9. Certain multiple cropping systems permit a gradual
change from destructive farming practices to more ap-
propriate technologies, without a drop in productivity.
10. Multiple cropping can promote a return to the land, and
its maintenance.
11. In systems which include trees and/or animals, such com-
ponents can constitute a type of "savings" for the future,
while short term crops satisfy immediate needs.
12. Because of their diverse nature, multiple cropping sys-
tems promote interdisciplinary activities, stimulate inter-
change and group activities, and lead to social cohesion
in the long term.
1. The systems are more complex and less understood
agronomically and biologically. Statistical designs for ex-
perimental analysis are much more complex.
2. Yields sometimes are lower, providing only subsistence
level production.
3. In many systems, multiple cropping is not considered to
be economically efficient due to the complexity of ac-
tivities necessary.
4. These systems require more hand labor, which can be
considered a disadvantage in some circumstances.
5. Some mixed crop systems do not offer sufficient reward
to lower income farmers to raise their standard of living.
6. For producers with limited economic resources, it may
take longer to recover the entire initial investment.
7. Farmers initiating multiple cropping systems may en-
counter opposition from the prevalent social, economic,
and political system.
8. There is a shortage of trained personnel (technical and
scientific) capable of Installing and managing multiple
cropping systems.
9. There is a general lack of knowledge or understanding
of multiple cropping by "decision makers," affecting
especially funding for research to make such systems
viable alternatives.

General Resource Use

The most commonly accepted reason ex-
plaining why it is possible to obtain better
yields with crop mixtures is that the compo-
nent crops differ in their growth requirements.
Such combinations of components can be said
to be "complementary" (46).
A mixture makes better overall use of avail-
able resources. Negative influences (e.g., com-
petition for light, water, or nutrients) between
the component members of a successful multi-
ple cropping system would be reduced con-
siderably. To maximize the advantages of such
a system, it is important to maximize the de-
gree to which one component complements
another. With a greater range of requirements
between different elements of the mixture,
theoretically the greatest advantages would be
One way to achieve complementarity is by
varying the crop components temporally-
using sequential planting to achieve a multi-
ple cropping system that ensures that antag-
onistic interactions between the components
are avoided. Following a crop with another that
has different growth requirements would
enable the maximum use of resources. This
concept has been used for a long time and is
the basic rationale behind crop rotations.
The most advantageous use of soil, for ex-
ample, would be to follow one crop with
another that requires different soil nutrients.
A subsequent crop would thus be able to ab-
sorb fertilizer residues left over from the pre-
vious crop, thus reducing the need for fertilizer
applications. For the Eastern United States, it
has been concluded (31) that double cropping
systems such as soybeans after wheat or bar-
ley, or the production of silage crops after grain
corn or sorghum, can function well.
Depending on the length of the growing
season, numerous sequential plantings can take
place during a single year. Such systems re-
quire special management, with timely harvest,
use of proper varieties, alteration of the stand-

ard planting distance, special selection of her-
bicides so as to not create antagonisms or re-
sidual effects, and also the possibility of using
no-tillage planting with certain of the row
Another form of complementing different
crop components is through an intensification
of the sequential cropping system known as
relay planting. The same avoidance of overlap-
ping plant growth requirements is gained, as
well as the avoidance of direct plant inter-
ference, by planting a second crop after the
first one has completed the major part of its
development, but before harvest. Relatively lit-
tle research on relay cropping has been done
in the United States, and most has demon-
strated little if any yield advantage (31). On the
other hand, in Mexico and Latin America in-
numerable examples of relay planting with def-
inite yield advantages have been reported,
especially for corn and beans (35,39).
Again, the important, and as yet little stud-
ied, aspect of relay planting success depends
on the correct combinations of timing and va-
rieties so as to avoid shading, nutrient competi-
tion, or inhibition brought about by toxicity
produced by the decomposition of a previous
crop residue.
Finally, maximum complementarity can be
achieved by growing two or more crops simul-
taneously, either in rows, strips, or mixed, but
taking advantage of the spatial arrangement of
the different crops and knowledge of their in-
dividual growth requirements. Again, most ex-
amples of such systems come from outside the
United States. One particularly well-docu-
mented example is a traditional corn, bean, and
squash system in Tabasco, Mexico (4).
Corn is planted at a density of 50,000 plants/
ha, climbing beans in the same hole at a den-
sity of 40,000 plants/ha, and the squash inter-
mixed among the rows of corn and beans at
a density of 3,330 plants/ha. All are planted at
the same time in this case. Beans begin to
mature first, using the corn stalks for support;
the corn matures second; the squash is the last
to mature. Aerial space is divided such that

corn occupies the upper canopy, beans the
middle, and squash covers the ground. Better
weed control is achieved, and insect pests are
largely controlled by natural enemies. Corn
yield was significantly higher for the polycul-
ture as compared to different densities of
monocultures, but beans and squash suffered
a distinct yield reduction (table 5). Interest-
ingly, the LER (Land Equipment Ratio) value
of 1.73 tells us that the sum of the yields in the
mixture can only be equaled in monoculture
by planting 1.73 times the area divided propor-
tionally among the three sole crops.

Table 5.-Yields of Corn, Beans, and Squash (kglha)
Planted in Polyculture as Compared to Low and High
Densities of Each Crop in Monoculture
Total grain or fruit yields
Crop Monocultures Polyculture
Density .... 33,300 40,000 66,600 100,000 50,000
Yield ...... 990 1,150 1,230 1,170 1,720
Density.... 56,800 64,000 100,000 133,200 40,000
Yield ...... 425 740 610 695 110
Density.... 1,200 1,875 7,500 30,000 3,330
Yield ...... 15 250 430 225 80
Crop Total biomass dry weight
Corn ........ 2,822.
9 3,119.
4 4,477.5 4,870.9 5,927.2
Beans....... 852.9 895.1 842.6 1,390.4 253.1
Squash...... 240.9 940.9 1,254.0 801.9 478.3
Total Polyculture Biomass 6,658.6
LER (Land Equipment Ratio) = Sum of yields of each polyculture
Sum of highest yield each
LER = 1,720 + 110 + 80
1,230 740 430
LER = 1.73
SOURCE: Amador, 1980 (13).

The advantage of producing a greater yield
altogether on less land is obvious. The much
higher total yield of biomass in the mixture is
also important because much of this organic
matter is returned to the soil, bringing impor-
tant consequences in soil fertility, humidity
conservation, microbial activity, etc., all related
to the success of the following crops. Currently,

studies are being conducted to determine if the
higher yields are the result of more efficient
resource use, or if in fact some mutually ben-
eficial effect between crop components is tak-
ing place, for example, the bean producing ni-
trogen that the corn can absorb (12). This
example demonstrates the enormous potential
that multiple cropping systems offer for the

Specific Resource Use, Conservation,
and Management
An intensified land-use system of agriculture
will certainly put greater pressures on the avail-
able natural resources of our crop and range-
lands. Considerable discussion has focused on
the harmful or beneficial aspects of this inten-
sification, and a review of some of the more
important aspects can aid greatly in under-
standing this problem:
1) Microclimate and Light: In any agroeco-
system, a very important aspect of productivity
is related to the amount of light converted
directly to carbohydrate, hence to vegetative
material, through photosynthesis. Each crop-
ping system has a photosynthetic potential,
based on its capacity of conversion (2). Mono-
cultures, especially of annuals, generally have
a lower potential because either the plant cover
is not complete, or the soil is occupied only
during one short season, leaving the surface
bare of photosynthetic capacity until the next
crop is planted. Light is not like other re-
sources, where a reservoir exists and the plants
tap it as the need arises. Rather, it has to be
used when it is available, thus leaf area be-
comes a very important factor. A multi-layered
polyculture would be able to capture much
more light energy, raising efficiency, and po-
tentially, production.
Apart from the quantity of light absorbed, its
quality is also important. Light that has passed
through a leaf layer is altered as certain light
waves are absorbed and others penetrate.
Plants in the lower layers of the canopy need
to be adapted to this alteration-an aspect well
studied only in natural vegetation (7). For crop-

ping systems, light has been studied in detail
only for monoculture systems (2) from the point
of view of increasing effective photosynthetic
leaf area for the single crop. By manipulating
species with different light requirements,
greater photosynthetic potential can be achieved.
This is made easier by using dominant species
in the polyculture that do not develop a closed
canopy, allowing considerable penetration to
the next levels. The most shade-tolerant plants
should be in the lowest levels. In such a sys-
tem, the soil surface is in essence completely
covered by plants. This manipulation of plant
architecture has been studied in detail ecologi-
cally (28) and has considerable application in
multiple cropping systems.
Other aspects of the crop microclimate are
also affected. Crops in the lower layers would
be subject to less water stress, but care must
be taken that root system competition for water
does not become a problem. Water loss by soil
surface evaporation could be reduced, but tran-
spiration from leaf surfaces might be increased
in the crop mixture. Soil temperatures would
be lowered, an advantage especially in warmer
and drier environments, aiding in the conser-
vation and buildup of organic matter in the soil.
Protection from wind would be provided for
the lower canopy species. Care would need to
be taken that the increased humidity in the
lower canopies does not promote higher in-
cidence of certain diseases, especially fungi,
either of the roots or foilage.
2. Soil-Plant Relations in Multiple Cropping
Systems: Any time that we try to combine two
or more crops simultaneously in one area,
there exists the possibility for complex interac-
tions between the plants and their soil environ-
ment (39). When total complementarity is
achieved, the roots of the component species
occupy different soil horizons, reducing con-
siderably the potential competition between
species and increasing the efficiency of total
nutrient uptake. In combinations of deep-
rooted with shallow-rooted species, especially
when trees are planted with grasses or annual
crops, the trees are capable of absorbing un-
captured nutrients as they are leached into the

soil. Then, through their transport to foliage,
they can be deposited on the soil surface again
as the leaves drop (47).
Intercropping systems have been shown to
extract more nutrients from the soil than do
single crop plantings per unit area of land. In
a very complete study with corn and pigeon
peas in Trinidad (19) (table 6), various param-
eters of crop response were measured. The
highest single crop yields of grain were ob-
tained in monocultures, but by adding yields
of two crops planted mixed or in intercropped
rows, Relative Yield Totals (RYT) were higher.
Total dry matter production was higher in the
mixtures as well. The most interesting aspect
is the uptake of nutrients (N, P, K, Ca, and Mg).
The total uptake is based on the sum of the two
crops together, and in all cases the total nutri-
ent content of the dry matter production was
higher for the mixtures, demonstrating the
greater extractive capacity of the multiple crop-
ping system. Apparently, for corn and pigeon

peas, row intercropping gave the best results,
demonstrating that at times two crops together
can negatively influence each other, but the
total yield makes up for the reduction. Each
crop mixture needs to be examined in detail.
The greater uptake of nutrients in crop mix-
tures could deplete the soil more rapidly. But
an aspect of multiple cropping that needs to
be considered is what proportion of this nu-
trient content is removed from the system with
the harvest, as compared to the part reincor-
porated back into the system. In table 7, a
corn/bean polyculture is compared to a corn
monoculture. Total biomass production, as
well as yield removed from the system, is con-
siderably higher from the mixture (10.24 tons/
ha versus 6.68 tons/ha total biomass). The per-
centage of this total that leaves the system is
slightly lower for the mixture (61 percent
versus 66 percent), but the actual amount of
organic matter returned to the soil in the poly-
culture (3.98 tons/ha) as compared to the sole

Table 6.-Effects of Mixed and Row Intercropping on Yields and Nutrient Uptake of Corn (C) and Pigeon Peas
(PP) in St. Augustine, Trinidad, Expressed as Relative Yield Totals (RYT)
Sole crop Mixed intercrop Row intercrop
Parameter C PP C PP RYT C PP RYT
Grain yields (tons/ha) ............................. 3.1 1.9 2.0 1.7 1.54 2.6 1.8 1.78
Total Dry Matter (tons/ha) ......................... 6.4 5.1 4.2 3.8 1.40 5.0 4.9 1.74
N uptake (kg/ha) .............................. 66.0 119.0 48.0 100.0 1.56 54.0 127.0 1.88
P uptake (kg/ha) ............... ............... 13.0 6.0 9.0 5.0 1.52 11.0 7.0 2.01
K uptake (kg/ha).............................. 51.0 37.0 37.0 32.0 1.59 46.0 33.0 1.79
Ca uptake (kg/ha) .............................. 10.0 22.0 10.0 15.0 1.68 9.0 19.0 1.76
Mg uptake (kg/ha) .............................. 12.0 14.0 9.0 8.0 1.32 9.0 12.0 1.61
SOURCE: Adapted from Dala, 1974, (19), cited by Sanchez, 1976, (39).

Table 7.-Biomass Distribution (in tonslha) of Dry Matter in a CornlBean Polyculture
as Compared to a Corn Monoculture, in Tacotalpa, Tabasco, Mexico
Leaves (B) (B) (A)-(B)
and (A) Removed (A) Total
Crop Roots Crown stem Graina Total matter percent reincorporated
Corn 0.49 0.60 2.29 4.76b
plus 10.24 6.26 61% 3.98
Beans 0.15 0.00 0.45 1.50b
Alone 0.34 0.41 1.57 4.36b 6.68 4.36 65 % 2.32
weight of grain of corn is unhusked, including cob and husk, in the manner that the harvest is removed from the field In
this region.
blndicates the removed portion of the biomass.
SOURCE: Adapted from Gllessman and Amador, 1979 (24)

crop (2.32 tons/ha) demonstrates that although
more material is produced by the intercrop sys-
tem, a greater amount returns to this system.
This possibly offsets any increase in extraction
of soil nutrients and permits the long-term
management of the system.
Another way to increase the return of nutri-
ents to the system is to plant "nurse plants."
These plants do not contribute directly to the
biomass harvested and removed from the sys-
tem, but their capacity to capture nutrients and
continually recycle them in the soil would be
an advantage. Local farmers in Tabasco, Mex-
ico, use this concept in the management of
weeds (14), leaving those that don't interfere
with the crops and removing those that are
harmful. This practice also provides a constant
cover over the soil and helps maintain better
soil structure, conserves water, fosters more
microbial activity, and over the long run, re-
quires fewer chemical fertilizers. By including
plants that "trap" nutrients, such as legumes,
such benefits can be improved even more. The
widespread use of legume trees for shade in
coffee and cocoa plantations is a classic exam-
ple (27).
3. Water Use in Multiple Cropping Systems:
Any discussion of water use should consider
rooting patterns. In multiple cropping systems,
especially with several crops with differently
arrayed root systems, a greater volume of the
soil typically is occupied and thus water use
efficiency is higher. This is useful, on the one
hand, in areas where water supplies are lim-
ited. It also helps make more complete use of
costly irrigation water. It has been proposed
that cover crops in orchards stimulate deeper
rooting by the trees (10). Different peak peri-
ods of water use in the crop mixtures would
avoid competition and increase overall water
use efficiency (8). A crop such as corn that uses
relatively little water in its early stages of de-
velopment could be interplanted with an early
maturing crop that could take advantage of the
unused moisture (30).
In areas where water is severely limited, care
must be taken not to plant crops with over-
lapping water requirements because in dry

years one member of the mixture could be out-
competed by the other (36). Combining two
crops with slightly overlapping water needs,
on the other hand, could be used to an advan-
tage in areas with widely fluctuating rainfall
regimes. In a dry year, one component would
be favored, and in a wet year the other, guar-
anteeing profitable harvests of at least one crop
every year. Studies on water availability in each
region, coupled with studies of water needs of
each component crop of multiple cropping sys-
tems, are critical for proper management.
The important effects of multiple cropping
on the conservation of water and soil are pri-
marily achieved through the maintenance of
a more complete vegetative cover over the soil
(26,40). It is important to remember that apart
from improving cover while the crop is grow-
ing, multiple cropping systems aim toward
maintaining this cover between harvests. This
is achieved by reducing the time between
harvest and replanting in sequential systems,
planting a new crop into another in relay crop-
ping, and continually interplanting in an inter-
cropped system. The use of trees, either as
windbreaks, for soil stabilization on eroded
hillsides, or in areas subject to desertification,
can be enhanced greatly by combining them
with crops or pasture grasses (see discussion
on Agroforestry).
In summary, although it appears that multi-
ple cropping systems use more water, their
ability to obtain water not available to mono-
culture, use the water more efficiently, and
contribute significantly to soil conservation,
demonstrate a further potential for their more
widespread use.
4. Pest, Disease, and Weed Relations: As dis-
cussed, possibilities exist for multiple cropping
systems to be both advantageous and disadvan-
tageous in relation to problems of pests, dis-
eases, and weeds (29,32). The problem has to
do with the great complexity of environmental
factors and their dynamic interactions within
the cropping systems. Where capital is not
available or technical assistance has not been
accepted, we observe that the main means of
pest, disease, and weed control is through bio-

logical control, and through the management
of a great diversity of cropping patterns, both
in time and space (23).
It has been suggested that multiple cropping
systems permit such a control because they are
much less subject to attack (6,29,38). This
comes about because the mixed cropping sys-
tem: 1) prevents spread of diseases and pests
by separating susceptible plants; 2) one species
sometimes serves as a trap crop, protecting the
others; 3) associated species sometimes serve
as a repellant of the pest or disease to which
the other crops are subject; and 4) a greater
abundance of natural predators or parasites of
pests are present due to a higher diversity of
adequate microsites and alternate prey.
However, there are also reasons why a multi-
ple cropping system may be more susceptible
to attack: 1) reduced cultivation and greater
shading due to the presence of associated spe-
cies, 2) associated crops serve as alternate
hosts, and 3) crop residues from one crop may
serve as a source of inoculum for the others.
All of these advantages and disadvantages can
exist, and further study is necessary to achieve
the combinations that give the most positive
A few examples might serve to demonstrate
the potential of multiple cropping for biologi-
cal control. In one study (22), it was shown that
the planting of a locally used medicinal herb
(Chenodium ambrosioides) in sequence with
corn or beans reduced the incidence of nema-
tode populations in the soil, demonstrating a
potential for reducing attack on the roots of the
food crops. The herb added substances toxic
to the nematodes into the soil. In another study,
yields of cotton untreated with insecticides, but
interplanted with sorghum, were 24 percent
higher than sprayed monocultures. The reason
was that sorghum served as a microhabitat for
cotton bollworm predators (18). In another
case, fall army worms were less a problem on
corn associated with bush beans than on pure-
stand corn (21). Beans intercropped with corn
were attacked less by rust compared to beans
in pure stands, probably because corn func-

tions as a barrier to the dissemination of the
fungal spores (41).
Weeds, on the other hand, present another
problem. It has been reported that weeds are
much less a problem in multiple cropping sys-
tems, especially in intercropping (32), because
the space normally available to weeds is filled
with other crops. The aggressive nature of
weeds is well known (9), but recent work has
begun to show that weeds can fill an impor-
tant ecological role in cropping systems, by
capturing unused nutrients, protecting the soil,
altering soil fauna and flora, serving as trap
plants for pests and disease, and changing the
microhabitat to allow for high populations of
pest predators and parasites (3,17). In rural
tropical Mexico, farmers understand and use
a "non-weed" concept (14), where each is
classified according to positive or negative ef-
fects. We need to understand in more detail the
biological functions of each component of the
agroecosystem to establish the structure that
will allow adequate weed, pest, and disease
control. If part of this control can be achieved
by merely manipulating the crop mixture in
time and space, great strides toward more ef-
ficient agricultural management can be made.
5. Mutualisms and Crop Coexistence: In nat-
ural ecosystems, a great number of interactions
between different species are mutually bene-
ficial for those organisms involved, leading us
to believe that there is a strong selective pres-
sure operating to select combinations that
coexist rather than compete (37). On the long
term, such a coexistence permits a more effi-
cient use of resources, with the component
organisms aiding one another rather than in-
teracting negatively. This frees more energy for
growth and reproduction.
To a certain extent, nurse crops or compan-
ion plants function in this way. Legumes, be-
cause of their symbiosis with nitrogen-fixing
bacteria, can coexist with corn without com-
peting for nitrogen. In fact, part of the legume's
nitrogen may be available for the corn (12), re-
ducing overall need for fertilizers. Studies with
coffee and cocoa shade trees have demon-

strated the same relationship; the trees provide
shade, nitrogen, and an organic mulch over the
As mentioned, the presence of one crop may
have beneficial effects on others through altera-
tion in the microclimate, pest and disease pro-
tection, etc. Thus, apart from looking for crops
that complement one another by avoiding
overlap in requirements, we need also to look
for crops that are interdependent and that
mutually benefit from the association. This will
be a very stimulating challenge for crop selec-
tion programs.
6. Use of Space and Time: One of the most
important aspects of the management of multi-
ple cropping systems is the facility they offer
for the intensification of production through
manipulation of space and time. By achieving
the most ideal combination of the two, we will
achieve the greatest productivity. On the one
hand, we attempt to occupy the available re-
source space as efficiently as possible, combin-
ing species that complement each other, yet at-
tempting to avoid overlaps that lead to negative
Resource use in space is then combined with
its use in time, trying to achieve constant use
of the resources available. For this reason,
multiple cropping systems are intensified by
sequential, relay, and mixed planting that
establish constant resource use within the envi-
ronmental limits imposed by the ecological
conditions of each region. In this sense, we can
even visualize the possibility of including cold
resistant trees in association with annual crops
or pasture, so that during the winter the trees
continue to occupy the area. Thus, any yield
reduction during the normal frost-free grow-
ing season is compensated for by the long-term
tree production.
Additionally, multiple cropping systems per-
mit greater stability in production, despite
variability in climate or physical factors in the
planting area. Whatever the conditions in one
location and for one growing season, at least
one member of the multiple cropping system
will succeed. Since most of the better drained
and structured soils are already in production,

the more marginal lands will require special
technology to make them produce. We cannot
consider for the moment massive programs of
soil and water manipulation needed to install
mechanized high-yielding monocultures. To do
so is economically, if not ecologically, pro-
hibitive. The basic framework is available in
multiple cropping. Innovative combinations
need to be searched for and tested.

Agroforestry: A Multiple Cropping
Agroforestry is a technology of land manage-
ment that combines trees with agricultural
crops, with animals, or any combination of the
two. Combinations can be simultaneous, or
staggered in either time and space. The major
objective of agroforestry is to optimize produc-
tion for each unit of surface area, keeping in
mind the need to maintain long-term yield
(11,13,42). Small-scale, traditional agriculture
has always included trees as integrated ele-
ments of farm management, but only recently
has interest been revitalized in the application
of agroforestry practices into modern agri-
The renewal of interest in agroforestry is
based on many of the same reasons for multi-
ple cropping systems in general: the ever-
increasing demand for production, yet the ris-
ing cost of obtaining it. The explosive demand
for firewood and lumber has placed incredi-
ble pressures on the world's forests, especially
in tropical and subtropical regions. Deforesta-
tion continues at an accelerated rate (20,44).
But programs of reforestation or multiple-use
forest management do not satisfy basic needs
for food, clothing, and other necessities that
come from crop and range lands. It would
seem logical that these pressures for both for-
est and agricultural products would stimulate
their combination in agroforestry systems.
Agroforestry practices can be broadly clas-
sified into three types (15): 1) combined agro-
silvicultural (crop plus trees) systems, 2) com-
bined forestry and grazing, and 3) simultaneous
combinations of forestry with crops and graz-
ing. Examples of each of these classifications

are presented in table 8. The focus varies from
soil improvement, erosion control, wind breaks,
and shade to lumber, firewood, and reforesta-
tion. The combinations are essentially unlim-
ited, depending on the needs of each region.
At first glance it might appear that agroforestry
systems are most applicable on marginal lands,
on steep slopes, poor soils, or areas with widely
fluctuating rainfall regimes. But agroforestry
should also be considered for widespread ap-
plication, even on prime agricultural or graz-
ing land, because production needs to be in-
creased-both by opening up new areas and by
looking for innovative ways to increase produc-
tivity of lands already in use.
The principle limitations to widespread use
of agroforestry practices are economic and
technological. Ecologically, the advantages are
well known, but technically we still do not have
the information necessary to begin immediate
implementation. With the present focus in agri-
culture aimed at maximizing single crop yields,
there is a lack of acceptance of the idea that
yields need to be thought of more on a long-
term, diversified basis. Agricultural research
has not yet accepted the challenge that an in-
tegrated focus to forest and farm management

Socioeconomic Implications of
Multiple Cropping Systems:
Perspectives for the Future

In all of the aspects of multiple cropping sys-
tems that this review has considered-yield, re-
source use, pest and disease control, weeds,
use of space and time, types of planting sys-
tems-much of the evidence indicates that
generally there are more advantages than dis-
advantages of a biological, physical, or agro-
nomic nature. But we need to consider the
social and economic implications of the pos-
sible more widespread use of multiple cropping
systems in present day agriculture.
As was seen in table 4, the types of advan-
tages derived from multiple cropping are many
and varied. With a greater diversity of crops,

Table 8.-Classification and Examples of Agroforestry

Combined agrosilvlcultural systems (trees with crops):
1. Agrosilviculture-establishment of trees, intercropped
with agricultural crops during initial stages of tree growth,
until tree canopies close and force the elimination of the
crops. Production available in early stages of tree develop-
ment, and cultivation activities simultaneously benefit both
crops and trees.
2. Forest trees of commercial value in crop systems. Main-
tain trees in crop areas, either planted or natural, at low
densities that do not interfere, yet provide value in the
3. Fruit trees in crop systems. A system that allows fruit pro-
duction and grain or vegetable production simultaneously.
4. Trees that serve as shade for certain crops or improve the
soil through nitrogen fixation, organic matter incorpora-
tion, mulch, and microclimate modification.
5. Trees used as hedgerows, fence lines, or windbreaks
around cropping areas, where management is intimately
linked with the needs of the crops.
6. Trees around rivers, lakes, or artificial reservoirs or tanks,
integrated with fish or waterfowl management, providing
shade, food, and roosting.
Combined forestry and grazing systems (trees with grasses):
1. Grazing or forage production takes place within forestry
plantations, aiding in avoiding weed or brush build up,
lowering fire risk.
2. Grazing or forage production in young natural forests, with
same advantages as above.
3. Forest trees of commercial value in pastures, either planted
or natural, at densities that do not interfere with the pasture
4. Timber trees in pasture, either planted or natural, with the
capacity to fix nitrogen and improve soil, thus lowering the
need to fertilize and provide commercial value.
5. Trees in pastures that provide shade for the animals and
aid in improving the soil through nitrogen fixation and
nutrient extraction from deeper soil levels.
6. Trees, either in or around pastures, or in forests, that pro-
duce foliage of forage value for animal consumption. Can
allow the reduction of feed supplement for animals.
7. Fruit trees in pastures, allowing for commercial produc-
tion of both fruits and animals.
8. Trees around pastures as hedgerows, fence lines, or wind-
Simultaneous combinations of forestry with crops
and grazing:
1. Forest plantations planted with crops and grasses, permit-
ting the management of grazing animals, either free to
wander or enclosed in specific areas. Especially adapted
to smaller animals, such as ducks or pigs. Requires close
control of activities and use of specific crops.
2. Trees associated with crops and grazing, either planted or
natural, in densities that will not adversely influence the
crops. Trees scattered in and around cropping areas can
be periodically pruned and used as forage for animals, with
the timber harvestable at some later date.
3. Hedgerows or living fence lines around rural communities,
serving as shade, windbreak, property divisions, forage,
fruits, timber, and firewood. In this sense, the system is
truly multiple use.
SOURCE: Combe and Budowski, 1979 (15).

a farmer is less affected by market fluctuations
and is able to shift from one crop to another
depending on price and demand. At the same
time, the harvest is spread out over a longer
period of time. Less dependence on outside
energy sources has obvious advantages, espe-
cially in areas where capital is limited. Labor,
instead of being concentrated in certain peri-
ods of the year, can be more evenly distributed,
an important consideration in relation to the
migrant farm worker problem. In times of
higher unemployment, multiple cropping sys-
tems can offer more and steadier work.
Most of the economic disadvantages are
derived from our lack of experience and knowl-
edge with multiple cropping systems. Reported
lower yields, complexity of management activ-
ities, higher labor demands, and the difficulty
in mechanizing such systems are all important
factors that discourage modern farmers from
participating in multiple cropping practices.
An important aspect of this resistance comes
from the emphasis on large profits that governs
so much of modern agriculture today. Maxi-
mum profits in the short term, rather than con-
cern with maintaining constant income in the
long term, governs the decisionmaking proc-
ess on most American farms today. But with
the incredible rise in farm costs, a new focus
is necessary. All of these increases cannot be
passed on to the consumer. Many of the advan-
tages of multiple cropping systems definitely
need to be stressed more for use on farms
today. Smaller farms, with a greater diversity
of products and activities, can function quite

profitably because they are less dependent on
high-cost energy inputs. Lower costs mean
food can be produced at a lower price, the ben-
efits being transferred to the general popu-
Smaller farms would require more farmers.
To a certain extent multiple cropping systems
mean a return to the land, with the incentives
necessary to keep the farmers there. The great
diversity of activities in multiple cropping sys-
tems would promote an increase in interdis-
ciplinary activities in their investigation,
installation, management, and use in agricul-
ture. This stimulation of interchange and
collaboration can, in the long term, lead to
greater social cohesion. Rural regions might
once again take on the social importance they
enjoyed in the past. The problems of lack of
trained personnel, and social, political, and
economic restrictions on multiple cropping
systems, all can be overcome by thorough and
conscientious programs of research aimed at
determining the proper methods, varieties, and
practices necessary.
The belief that multiple cropping is only suit-
able for marginal or underdeveloped regions
ignores the fact that just a relatively short time
ago, such systems were the most common type
of agriculture. Only recently have they been
replaced by monoculture systems dependent
on the use of massive quantities of inexpensive
high energy inputs. For the moment, this time
has passed and we need to learn from the past
to reshape agriculture for the future. This will
be a great challenge for agricultural research.


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S Prodlction of Livestock i ad Forage .... ......................... 91
Intercropping Traditional Food Staples With Arid-Adapted Legumes to
Sustan High Food Staple Yields............ ....................... 92
Slowingthe Spread of Desert -tfon In Arid Regions.... ................ 93
,lebrttizer, Posticide,, Irrigation,.Ait Machinery Requirements ................... 93
S- lr ment-.. .... .... .. ... .. ......................... 93
S'i of s k dorae_.. .... ..... ............. 93

.... 94
Resetarch, Difer ipment aid o ln p eo ptatilon of Arid-Adapted
att Ecosystem Pioductian tehnologies ............................. 95
Contrain~ts Facing, Development and Implemnntation of Arid-Adapted
Plant Production Technologies .. ................... ... .................. 98
Effet of Technology Iplemaentatito oh Capital, Labor, and
Lndits sm ..t...... .....................................99
-P. ..... 99
t gy Irptfe ntatit on the Socioeconomic
,-,'.a Coutrs ............... ............. 100
.. .. .*. -.* . . . . .
.. .--. 103
,- .....--..... .......... ..................... 10

Table No. Page
I. t. Outlie of. Reseaith Procedure .......... ............................... 98

4 ." "

. *_


I~~-r;*m~a--~uc7n;r~i~~-i-r;rir~ ----ifi~-c~i----`l-2*~iilllll-------. _1LYI^IIII~-lllr.l~.I X-L Iliiliii- .li -i~-~ii~ -~II~IYU~

Chapter VI

Development of Low Water and

Nitrogen Requiring Plant Ecosystems

for Arid Land Developing Countries


This paper describes a low industrial input,
commodity-oriented approach to stimulating
economies of arid land countries using arid-
adapted plant species. It suggests legume tree
biomass farms using Acacia, Leucaena, and
Prosopis genera to provide increased fuelwood.
Increased soil fertility and ensuing water use
efficiency could be achieved by using deeply
rooted, drought-adapted species such as Acacia
albida and Prosopis cineraria that fix nitrogen.
Arid-adapted shrubs such as jojoba (Simmond-
sia chinensis), and guayule (Parthenium argen-
tatum) could provide stable production of cash
crops. Prosopis and Acacia pods, atriplex for-
age, Leucaena forage, and cactus pads could
increase livestock food supplies. Increased pro-
duction of traditional food staples such as mil-
let, sorghum and peanuts can be achieved by
intercropping them with arid-adapted legumes.
Aggressive management of these plants could
help reduce the spread of desertification.
Little government support has been made
available for these activities despite their wide-
spread use by indigenous farmers at subsis-
tence levels. A research and development pro-
gram is suggested that would establish living

germplasm collections and select and propa-
gate superior clones. Several months after
stand establishment, these plant systems can
be grown without supplemental irrigation by
using ground water within 10 m of the surface
or by using a minimum of 250 mm annual rain-
fall. Phosphate fertilizer, micronutrients, and
rhizobial inoculation are required, but the ni-
trogen needs will be provided by nitrogen fix-
ing plants. Less machinery will be needed to
till these systems.
Wide-scale implementation of these systems
would greatly enhance agricultural produc-
tivity at the local level, where it is most needed,
and indirectly stimulate nonagricultural sec-
tors of the economy. The increased economic
well-being of farming classes could lead to de-
creased political unrest and greater stability of
governments in arid lands. Foreign policy ef-
forts to strengthen the peace by buildup of mil-
itary hardware systems has proven futile in
Ethiopia, Iran, and Iraq. Development of arid
land plant production systems is a viable alter-
native to enhancing peace in politically volatile
arid land countries.


This document was prepared at the request
of the Office of Technology Assessment (OTA)
of the U.S. Congress to provide guidance in de-
velopment of low energy, nitrogen, and ma-
chinery requiring agricultural systems for semi-
arid developing countries. The format closely

follows OTA's specific issues and questions.
For the convenience of the reader, these re-
quests are reproduced in appendix A.

Identifying plant physiological, morpholog-
ical, and ecological characters that lend them-

selves to a minimal machinery, capital, and
fossil fuel input is the subject of a paper by
Felker and Bandurski (14) in which orchards
of leguminous trees were suggested to most
closely approximate an ideal system for mini-
mizing industrial inputs. Other closely related
shrub ecosystems have been suggested to
achieve similar objectives (32). Identification
of arid land plant species that would lead to
more stable and productive ecosystems has

been intensively investigated by Felger (11). Re-
cent review volumes (42) and symposia (27,6)
have dealt at length with arid land plant re-
sources. This document attempts to synthesize
the knowledge of arid land plant species, focus-
ing on minimal energy input agriculture and
a pragmatic commodity-oriented approach de-
signed to provide major needs such as fuel, for-
age, and food staples required for arid land


Development of leguminous trees (14) and
associated semiarid ecosystem plant compo-
nents such as saltbush (Atriplex spp.) (19), leu-
caena (Leucaena leucocephala) (15), cactus
(Opuntia and Cereus spp.) (33,52), jojoba (Sim-
mondsia chinensis) (23), and guayule (Par-
thenium argentatum) (50) can make a significant
contribution to meeting the major commodity
needs of people in semiarid developing coun-
tries. Some of the main biological needs and
appropriate approaches to supplying them are
as follows:
1. Need: increased availability of inexpen-
sive fuelwood.
Approach: use of leguminous tree biomass
farms with Prosopis, Leucaena, and
Acacia species.
2. Need: increased soil fertility to triple or
quadruple water use efficiencies of food
staples so that productivity is water-limited
and not fertility-limited.
Approach: use locally respected, drought-
adapted, nitrogen-fixing legume tree such
as Acacia albida and Prosopis cineraria,
use shrubby legumes such as Dalea spe-
cies, and use perennial arid-adapted her-
baceous legume such as Zornia and
3. Need: production of cash crops for
farmers and for foreign exchange.

Approach: use perennial arid-adapted
plants, such as jojoba, guayule and high
value, drought-adapted annuals, and ephem-
erals, such as sesame when grown in con-
junction or rotation with arid-adapted ni-
trogen fixers.
4. Need: production of livestock food and
Approach: use arid-adapted, salt-tolerant
shrubs, such as saltbush (Atriplex species)
in conjunction with high water to dry mat-
ter conversion plant specialists, such as
spineless cactus (Opuntia ficus-indica) and
high protein and/or sugar content pods of
leguminous tree species of Acacia tortilis,
Acacia albida, and Prosopis spp.
5. Need: sustained production of traditional
food staples, such as millet, sorghum,
groundnuts, and cowpeas.
Approach: intercrop the annual staples
with nitrogen fixing trees previously dem-
onstrated to stimulate annual legume
yields such as the association with Acacia
albida and peanuts.
6. Need: slow the spread of desertification.
Approach: when intensive management
of forage, fuelwood, and staple products
are carried out as outlined above, desertifi-
cation will slow.


Development of Tree Legumes
for Fuelwood
Areas of use: Prosopis alba and P. nigra were
reported to have fired industrial boilers and
steam locomotives during World War II in
Argentina (10). In Chile, the leguminous trees
chanar (Geoffrea decorticans) and espino
(Acacia caven) have been widely harvested by
Indians and present day subsistence farmers
for fuel (2). Mesquite wood and charcoal (Pro-
sopis species) is highly esteemed and widely
used in the Southwestern United States in
steakhouses for barbecues and home heating.
From 1956 to 1965, 78,000 metric tons of mes-
quite charcoal and 200,000 m3 of mesquite
firewood were recorded as items of commerce
in Mexico (29). In the Jodphur state of India,
Prosopis was declared the "royal plant" be-
cause it provided the bulk of the fuel to the local
population (20). Acacia forests are harvested
along the Nile 400 km upstream from Khar-
toum, Sudan, and brought to Khartoum for
brick making and other industrial uses (24). In
the Sahelian zones of Africa, many of the
Acacia species such as A. tortilis, A. seyal, and
A. senegal are consumed for woody biofuel.
Research organizations: The Central Arid
Zone Research Institute in Jodphur has been
conducting research on leguminous trees as
sources of biofuels since the early 1940s (1).
Their work is meagerly documented in the
scientific literature and, from the lack of recent
papers in the literature, their current research
on tree legumes does not appear to be very
The Forestry Research Institute in Khartoum,
Sudan, has received about $200,000 from the
International Development Research Center
(Ottawa) to evaluate Prosopis species under
200, 300, and 400 mm annual rainfall regimes.
Much of the seed material for this experiment
was supplied by the University of California-
Riverside mesquite project. The United Na-
tions Development Program (UNDP) provided
support for Felker to supply seeds, mesquite

rhizobia, plants, containers, and consultation
to conduct varietal trials with 30 selections of
leguminous trees (most Prosopis) in the Sudan
at the Forestry Research Institute. Over 400
acres of Prosopis have been planted along ir-
rigation canals in the Sudan courtesy of the Su-
dan Council of Churches to prevent sand from
blowing into and filling the canals (26).
Dr. J. Brewbaker at the University of Hawaii
has been conducting extensive research in Ha-
waii, Colombia, and the Philippines, on the de-
velopment of leucaena as a biofuel crop. In the
United States, the U.S. Department of Energy
has funded research on Prosopis under Felker
at the University of California-Riverside to de-
velop an arid-adapted germplasm collection;
to evaluate the collections in field conditions
under drought, heat, and frost stress; to study
nitrogen fixation and salt tolerance; and to
clonally propagate outstanding single trees.

Use of Nitrogen Fixing Trees to
Increase Soil Fertility
Areas of use: Prosopis cineraria has been
used on a subsistence level by farmers in the
India-Pakistan region to increase the yields of
their pearl millet crops. Soil chemistry studies
(46) corroborated increased nutrient contents
and forage yields under P. cineraria trees
versus other trees and open control areas.
Acacia albida is widely used on a subsistence
level in the West African countries of Senegal,
Upper Volta, Mali, Niger, and Chad to increase
the yields of sorghum, millet, and peanuts
grown beneath the tree canopies (12). Parkia
biglobosa was observed by this author grow-
ing in sorghum fields in a 400 mm annual rain-
fall regime where farmers stated the Parkia also
increased the yields of their crops.
Yields of grasses and forbs grown in a growth
chamber on soil from beneath mesquite can-
opies were four times greater than herbage
yields grown on soils from outside mesquite
canopy cover (49). The stimulation of forage
yields after mesquite removal in the Southwest-

ern United States is probably due to increases
in soil fertility supported by nitrogen fixation
and reduction in competition for water. Mes-
quite nitrogen fixation and soil fertility in-
creases on the 72 million acres (38) presently
occupied by mesquite in the Southwestern
United States is an unrecognized resource.
Leucaena (Leucaena leucocephala) has been
widely used in the Philippines in rotation with
other crops, as a companion crop, and as a
green manure with other crops to increase soil
Research organizations: Dr. Y. Dommergue,
working for ORSTOM in Dakar, Senegal, West
Africa, has conducted rhizobial inoculation
trials with many African Acacias including
Acacia albida and at this writing is actively in-
volved in nitrogen fixation aspects of semiarid
soils. Dr. Habish at the University of Khartoum,
Sudan, published excellent papers on char-
acterization of Acacia-rhizobia symbioses (21),
but is now a dean at the University and no
longer actively involved in research. A Univer-
sity of Arizona group, funded by the National
Science Foundation (NSF), with Dr. Pepper as
principal investigator, is collecting and char-
acterizing rhizobia strains from many arid-
adapted legumes.
A three-year $650,000 NSF grant has been
awarded to study nitrogen cycling in a mes-
quite dominated desert ecosystem in southern
California. This project involves: 1) an ecology
group headed by Dr. Philip Rundel at the
University of California, Irvine, that is conduct-
ing dry matter productivity analyses; 2) a
University of California-Riverside soils group
headed by Dr. Wesley Jarrell, that is convert-
ing the dry matter productivity measurements
of the Irvine group into nitrogen productivity
and conducting soil moisture profile measure-
ments with 20 ft deep neutron probes, quan-
titating soil chemical characteristics on and
around the site, quantitating denitrification,
and developing in situ acetylene assays; and
3) a Washington University (St. Louis) group
headed by Dr. D. H. Kohl that is correlating the
above-mentioned findings with natural abun-
dance lN14N measurements to develop quali-

tative and perhaps semiquantitative assays of
nitrogen fixation from dried plant samples.
The Department of Energy has funded studies
on cross-inoculation of 13 Prosopis species (15),
has conducted greenhouse studies of the effect
of heat and drought stress on Prosopis nitro-
gen fixation, and has developed models com-
paring efficiencies of water and nitrogen in-
puts to increasing productivity of semiarid
rangelands (16). USDA scientists have demon-
strated that fertility can dramatically increase
water use efficiency of rangeland species in a
10-year study on Montana rangelands (51). The
USAID-supported Niftal group at the Univer-
sity of Hawaii maintains large stocks of
rhizobia. Basak and Goyal (3) at the Central
Arid Zone Research Institute at Jodphur have
published cross-inoculation data and temper-
ature and salinity tolerance characteristics for
rhizobia for semiarid adapted leguminous trees
in India.

Development of Cash Crops on
Semiarid Lands
Areas of use: Jojoba (Simmondsia chinensis),
a non-legume, is one of the most promising
cash crops for arid lands. Jojoba seeds contain
a rancidity-resistant, non-allergenic, liquid wax
with lubricating properties equivalent to an oil
obtained from the endangered sperm whale. Jo-
joba is under development in southern Califor-
nia, Arizona, Mexico, and many of the
semiarid less developed countries (53). Mature
jojoba plantations should yield over 1,000 kg/
ha-' at over $1 per kg. This yield could earn
a gross return of over $1,000 per hectare.
Guayule (Parthenium argentatum) a plant
native to the Chihuahuan deserts, contains nat-
ural rubber and is under extensive develop-
ment by both the United States and Mexican
governments (50). There is no reason guayule
could not be cultivated in other semiarid re-
gions of the world as a cash crop.
Hydrocarbon bearing plants such as Euphor-
bia lathyris have been suggested as raw mate-
rials for oil and gasoline production (7). The

drought-adapted legume trees Acacia senegal
exudes a gum from wounds of the trunk known
as gum arabic that has many industrial and
food uses (18). Eighty-five percent of the
world's annual supply of gum arabic, about
50,000 to 60,000 metric tons, is harvested and
exported from the Sudan at prices of about $1
per kg (18). Other Acacia and legume trees,
such as Prosopis, exude gums that could be de-
veloped for cash crops. Seeds of the fast-
growing, drought-tolerant, annual sesame sell
for $1 to $2 per kg and show potential for an
arid zone cash crop (53). The fruits of the
cactus Opuntia ficus-indica can produce
dessert or table quality fruits. This author was
served an excellent cactus fruit with a meal on
a Chilean airline. Commercial (5 ha and larger)
Opuntia ficus-indica orchards are currently
operating in southern California to supply
these fruits to supermarket chains. There are
several little-known species of cactus that
possess fruits equal or superior in quality to
Opuntia ficus-indica that could also be devel-
oped (11). Because cactus use water very effi-
ciently, they should support fruit and cash crop
production in semiarid areas.
The pods of carob (Ceratonia siliqua) are bro-
ken into pieces, kibbled, and separated into
seed and pod fractions. The pod fractions are
sold for livestock food in Europe and are im-
ported into the United States where they are
manufactured into chocolate substitutes (34).
Industrial quality gums are extracted from the
seeds. In 1970, the world production of carob
seed gum was 15,000 tons. Prices ranged from
$0.62 to $1.10 per kg (43). The pods of Parkia
biglobosa and P. clappertoniana, and a fer-
mented product of the seeds known as dawa-
dawa, are sold for human food on the sub-
sistence levels in markets in Senegal and other
parts of West Africa.
Research organizations: The most extensive
germplasm collections, plantings, and cytoge-
netic studies of jojoba are being made at the Uni-
versity of California-Riverside under Dr. D. M.
Yermanos. This has been funded by the United
Nations Development Programme (UNDP),
NSF, and the California State Legislature.
Another large-scale jojoba research operation

is being carried out at the University of Arizona
under Dr. L. Hogan. There are numerous com-
mercial jojoba developers, some of whom are
less than scrupulous. Donor agencies should con-
tact Yermanos or Hogan before dealing with
private jojoba developers. Dr. Yermanos has
also developed nonshattering sesame types and
mechanical harvesting devices with UNDP
support. The USDA has a multi-million-dollar
budget to develop guayule in the Southwest-
ern United States.
The Diamond Shamrock Co. is supporting a
multi-million-dollar project at the University of
Arizona Office of Arid Land Studies to develop
potential of hydrocarbon producing plants
such as Euphorbia lathyris.
The Canadian International Development
Research Center (IDRC) is supporting a re-
search program to develop gum arabic for West
Africa through the "Eaux et Foret" in Dakar,
Senegal. The University of Chapingo, Mexico,
has a program to develop spineless cactus (52).
Dr. Richard Felger at the Arizona/Sonora Des-
ert Museum has identified numerous arid land
crops with potential including several out-
standing cactus varieties.

Production of Livestock Food
and Forage
Areas of use: In Mexico, Prosopis glandulosa
var. glandulosa, and Prosopis laevigata are
harvested from wild trees and sold to whole-
sale dealers who incorporate it into livestock
rations. In 1965, 40,000 tons of mesquite pods
were sold in commercial operations in Mex-
ico (29). Undoubtedly, many more pods were
used or bartered locally that were never
entered into the agricultural statistics. One
thousand ha of P. juliflora has been established
in the Peruvian coastal desert under partial ir-
rigation. By providing 250 mm of irrigation the
first year and 160 mm thereafter, pod produc-
tion of 6 to 7 t/ha-1 have been obtained from
the Peruvian plantings (39). In nearby Chile,
30-year-old P. tamarugo trees growing in the
Atacama salt desert have produced 6,000
kg/ha-' of leaves and pods that are used to
support a sheep-raising industry (44). Twenty-

38-846 0 85 4

two thousand hectares of P. tamarugo have
been planted by the Chilean corporation CORFO
(54). Felker has visited these areas to assist
CORFO with vegetative propagation, selection
techniques, and nitrogen fixing inoculants.
In the Southwestern United States, mesquite
pods were the staple for Indians in southern
California and Arizona deserts (13), but today
are only marginally important in supporting
wildlife. In West and East Africa the pods of
A. albida and A. tortilis are highly regarded as
a supplemental livestock feed (12,34). Some A.
albida pods are collected and stored for later
rationing to cattle on a subsistence level, but
no organized or commercial use of pods has
been attempted (12). The forage of Acacia xan-
thophlea and A. hockii supplies much of the
diet of giraffes in the Serengetti National Park
in East Africa. Pellew (41) has suggested that
the Acacia-giraffe ecosystem be managed for
meat production.
Forage systems based around the spineless
cactus (Opuntia ficus-indica) have been widely
used in Mexico and North Africa where the
spineless pads are fed to cattle. Selections of
saltbush (Atriplex species) are high in protein
and carotenoids and constitute a useful live-
stock forage. The Chilean corporation CORFO
has planted thousands of hectares of saltbush
in contour ridges along the Chilean coast for
use as cattle food (Felker, personal observa-
tion). In Tunisia, commercial-scale, govern-
ment-supported plantings of saltbush provide
forage for grazing animals (22).
In Mexico, cattle rations have been formu-
lated from high energy, sweet, highly palatable
mesquite pods; high protein, high carotenoid
and low palatability saltbush foliage; and high-
energy containing cactus pads (29). These three
plants possess the complimentary physiologi-
cal characters of high salt tolerance in saltbush,
high water to dry matter conversion
efficiencies of cactus, and nitrogen fixing prop-
erties of mesquite.
Research organizations: Surprisingly little
research is being done about these forage
plants. The Tunisian and Chilean governments
support the largest developments of forage-pro-

during plants. The Chilean company CORFO
has planted thousands of hectares of Atriplex.
CORFO has investigated plant spacing, canopy
closure, and pod productivity as a function of
age for 36-year-old Prosopis tamarugo planta-
tions (44). They are just beginning to become
involved with selection work, nitrogen fixation,
and vegetative propagation.
The Tunisian government has employed
large earth-moving equipment and water trans-
port vehicles to establish saltbush and cactus
plantings (22). The Algerian government also
has initiated some Opuntia plantings (33). Dr.
Henri LeHouerou, formerly of the Interna-
tional Livestock Center (ILCA) in Addis Ababa,
has been a key figure in North African devel-
opments of Atriplex and Opuntia. The Chap-
ingo Agricultural Experiment Station outside
of Mexico City has made selection of Opuntia
with promising economic characters (52).
Lopez, et al. (28), at the Antonio Narro Agri-
cultural University in Saltillo, Mexico, has con-
ducted a thorough analysis of the productivity
and ecosystem characteristics of economically
important aspects of Opuntia production in
Mexico. The International Development Re-
search Center, Ottawa, is supporting a Prosopis
juliflora forage production project in Peru.
In the United States, Dr. C. M. McKell, Plant
Resources, Inc., Salt Lake City, and Dr. J.
Goodin of Texas Tech University have con-
ducted extensive research on saltbush as an
economically important forage crop. Felker,
while at University of California-Riverside,
made Prosopis selections for pod producing
characteristics in cooperation with Becker and
Saunders at the USDA Western Regional Re-
search Center. They also have conducted pro-
ximate analyses and feeding trials on the pods.

Intercropping Traditional Food
Staples With Arid Adapted Legumes
To Sustain High Food Staple Yields
Areas of use: Prosopis cineraria has been
widely used in the Indian-Pakistan region on
a subsistence level to increase yields of pearl
millet and other forage crops grown beneath
its canopy (31). Acacia albida has been used