Go to the people,
live among them,
learn from them,
plan with them,
work with them.
Start with what they know,
build on what they have.
But with the best leaders,
when the work is done,
the task accomplished,
the people will say,
"We have done this
for Rural Reconstruction
GUIDELINES FOR PLANNING
Revised Edition Prepared
University of California,
Helen L. Vukasin
CODEL, Inc. (Coordination in
VITA (Volunteers in Technical Assistance)
Environment and Development
475 Riverside Drive,
New York, New York 10115,
Order books from:
1600 Wilson Boulevard,
703/276-1800 * Fax:
Permission received to
reprint as follows.
(See Appendix A for
International Council for Research on
Agroforestry, page 129-134
Company, page 76
Mujeres en Desarrollo,
VITA, page 34,
Drawings by Linda
Diagrams by Linda
Cover Design by Susann Foster Brown
TABLE OF CONTENTS
Chapter 1 -
USERS AND USES
of the Manual
Use This Manual
Chapter 2 -
THE RELATION OF AGRICULTURE
What Is Meant
By Ecology and Environment
Agriculture and Environment Are Related
Ecological Concepts Are Important for Agricultural Development
Ecosystems Are and Why They Are Important
When Natural Systems Are Altered
The Food Web
Relates to Diversity
of Environmental Concepts and Impacts
Can Be Used to Ensure More Successful
Chapter 3 -
THE PLANNING PROCESS
The End is
Identify and Assess Needs and
Community Profile and Natural Resource
Natural Resource Profile or Inventory
Learning from Local Agricultural
Define Goals and Objectives
Design Project with Consideration of
Implement the Activity
Monitor the Project
Evaluate the Project
Chapter 4 -
OTHER CONSIDERATIONS FOR PLANNING
BACKGROUND FOR PLANNING
Chapter 5 -
SOIL MANAGEMENT THROUGH
What Is It?
and Why It Is Important for Control of Erosion
Can Be Controlled
Residues Combat Erosion
Tillage Methods for Erosion Control
and Erosion Control
Practices for Erosion Control
Contour Strip Cropping
of Soil Management/Erosion Control
Erosion Control Practices
Chapter 6 -
WATER SUPPLY AND MANAGEMENT
Sources of Water
Balance in Croplands
Moves and the Effects
Importance of Irrigated Agriculture
Why It Is
Necessary to Plan Irrigation
Water for Irrigation
Effect on the Aquatic Environment
Effect on Farmland
Salinization and Alkalinization
Groundwater for Irrigation
Return Flows and Their Effects
and Human Health
the Effects of Water Supply and Management Projects
Chapter 7 -
SOIL NUTRIENT MANAGEMENT
Natural Soil Fertility
The Significance of the C/N Ratio
Precipitation and Run-on Water
the Source of Nutrients
of Fertilizers on the Environment
of Movement or Loss of Soil Nutrients
Plowing-Under Green Legumes
Controlling Surface Applications
of Nutrient Management
for Nutrient Control
Chapter 8 -
Sound Pest Management Practices
Crop Management Practices
Destruction of Alternate Host Plants
Mechanical and Traditional Control
Biological Control Methods
Pest Management: What Is It?
Effects on People
Effects on Soil Fertility
Effects of Pesticides on the Balance of
Some Other Effects of Pesticides
Effects on the Aquatic Environment
Pesticides Move About the Environment
Distribution in Soil
Distribution in Water
That Should Be Considered Before Applying Pesticides
Alternative Pest Control Measures
Timing of Application
Projecting the Impacts of Chemical
Pesticide Use and the Potential For
Chapter 9 -
Ecologic or Climatic
Socio-Economic Scale and Level of
Advantages of Agroforestry Systems
Economic and Socio-Economic Advantages
Constraints of Agroforestry Systems
Role of Women
The Role and
Effect of Trees
Traditional Agroforestry Systems
Alley Cropping in High Potential Areas
Fodder Bank - Cut and Carry
4. Fodder Bank - Grazing
Multistorey Planting of Domestic/Industrial Tree Crops
Tree Planting Around Water Places and Dams
Woodlot Planting for Fuelwood and Poles
Chapter 10 -
CONCLUSION: A CHECKLIST FOR
DEVELOPMENT, EXAMPLES OF
SYSTEMS, AND LONG TERM
for Developing Sustainable Agricultural Projects
Traditional Resource Management Systems
Evaluation of Local Agro-Ecosystems
Assistance or Information
Appendix A -
Appendix B -
Appendix C -
original manuscript for this manual was a creative idea that
during a conference in 1977, sponsored by the Mohonk
that brought together the US environmental nongovernmental
(NGOs) with those groups that work with
assistance in the Third World. Peter
Ann LaBastille created a document that provided the
basis for the
original edition. Paul and Marilyn
Chakroff worked on
draft and Laurel Drubin, formerly with VITA, and
edited the manuscript for publication in 1979.
CODEL has published four additional volumes on forestry,
energy, and livestock. Each volume has
relied heavily on
technical experts and potential users in the field.
The revised edition of the agriculture
manual is indebted to
for constructive and helpful comments on a review
prepared by Miguel Altieri. CODEL
acknowledges with thanks
from the following:
Ms. Becky Andrews, Rodale Press,
Mr. William R. Austin, Van Wingerden
Mr. Fabio Bedini, Undugu Society of
Ms. Joan Brinch, Kenya Institute of
Organic Farming, Kenya
Mr. Richard Carpenter, East-West Center,
Policy Institute, Hawaii
Professor Gordon R. Conway,
International Institute for Environment
and Development, England
Ms. Margaret Crouch, Volunteers in
Professor Peter F. Ffolliott, University
of Arizona, Arizona
Mr. Peter Freeman, Development Ecology
Washington, D. C.
Mr. George Gerardi, Hermandad, Dominican
Mr. Terry Gips, International Alliance
for Sustainable Agriculture,
Mr. Matthias Quepin, Kenya Institute of
Mr. Lawrence Hamilton, East-West Center,
Policy Institute, Hawaii
Ms. Susanna B. Hecht, University of
California at Los Angeles,
Mr. John Michael Kramer, CARE, New York
Dr. Bede N. Okigbo, International
Institute of Tropical Agriculture,
Rev. John Ostdiek, OFM, Franciscan
Mr. W.J. Pape, Swaziland Farmer
Ms. Caroline Pezzullo, Pezzullo
Associates, New York
Mr. Coen Reijntjes, Information centre
for Low External Input
Agriculture, The Netherlands
Mr. Raniari Sabatucci, Kenya Freedom
from Hunger Council,
Rev. Kenneth F. Thesing, MM, Maryknoll,
Dr. Norman Ulsaker, Institute for
Mr. Napoleon T. Vergara, Participatory
Through Extension, FAO Thailand
Mr. Peter von der Lippe, Christian
Children's Fund, Virginia
Mr. Fred R. Weber, International
Resources Development and
Conservation Services, Idaho
Bro. Andrew Winka, Christian Brothers
Conference, New York
Mr. Ben Wisner, Hamshire College,
Dr. Timothy Wood, Wright State
Mr. Charles S. Wortmann, CIAT Regional
Bean Programme of
Eastern Africa, Uganda
Miguel Altieri, with assistance from Helen
L. Vukasin, CODEL
and Development Program, spent many hours integrating
technical and user suggestions in order to make the
useful to the field staff to which it is addressed.
In addition to the above named persons
there are some special
that should be mentioned. International
in a forestry
class at the University of Arizona each wrote extensive
the Agroforestry chapter that provided useful local
perspectives. Terry Gips, author of the
Breaking the Pesticide Habit, commented helpfully on the
Management chapter. The candid comments
of colleagues in
helped to reduce the Northern perspective of the text.
Finally, a special word of gratitude is
due to Debra Decker who
her talents to the preparation of the text for printing
dedication - from the initial draft of the author through all the
We welcome comments from readers of the
book. A questionnaire
for your convenience. Please share your
Rev. Boyd Lowry, Executive Director
Sr. Mary Ann Smith, Environment &
in Development (CODEL) is a private, not-for-profit
forty Christian-related development agencies working
countries. CODEL funds community
locally initiated and implemented.
agriculture, water, forestry, health, appropriate technology,
Environment and Development Program of CODEL serves the
voluntary development community by providing workshops,
and materials designed to document the urgency,
and potential of an approach to small-scale development
the interdependence with human and natural resources.
is one of several materials developed under the Program
development workers in taking the physical environment
during project planning, implementation, and
For more information, contact CODEL,
Program at 475 Riverside Drive, Room 1842, New York,
Technical Assistance (VITA) is a private non-profit
development organization. It makes
and groups in developing countries a variety of information
resources aimed at fostering self-sufficiency:
and program development support; by-mail and on-site
services; information systems training; and management of
projects. VITA promotes the use of
especially in the area of renewable energy.
documentation center and worldwide roster of volunteer
experts enable it to respond to thousands of technical
each year. It also publishes a
quarterly magazine and a
technical manuals and bulletins. For
at 1815 N. Lynn Street, Suite 200, Arlington, Virginia
USERS AND USES
THE PURPOSES OF THE MANUAL
This manual is designed to assist those
who plan and implement
agricultural projects. By promoting
concerns, the manual can increase the development
ability to design projects that are both environmentally
potentially more sustainable.
This manual has two objectives:
To promote well-planned and environmentally sound small-scale
To introduce environmental concepts into technology development
and alternative management techniques,
the transfer into training programs.
Environmentally sound planning requires
more than finding the
technology and a source of funds.
Planning involves consideration
social, cultural, economic, and natural environments in
project occurs. The challenge is to
that have reasonable production but do not degrade the
and upset the ecological balance.
are in a
position to pass on awareness of environmental concerns to
groups, government planners, village residents, farmers,
students. For example, a development
worker may use this
manual in a
training course to increase students' awareness of erosion
methods and alternatives. As a project
planner or implementor,
worker may wish to use the book for planning
training of project workers or for technical training
and local residents.
By providing guidelines to planning, this
manual can assist
workers to view projects as part of larger environmental
It offers a perspective that can assist
users to ask the
questions and to look for and find information about local
availability and use, traditional methods, weather patterns,
Many issues of importance to small-scale
that need to
be considered are beyond the scope of this manual.
include: land use patterns; inability of small landless farmers
risks; lack of credit and money; and access to technical
appropriate agricultural expertise.
address all of the environmental conditions or implications
with individual project sites. The use
concepts and principles outlined here should enable development
recognize environmental issues and to consider
them in the
WHO SHOULD USE THIS MANUAL
This manual has been prepared for those
who are actively
planning and implementing small-scale agricultural
It will be most useful for those who wish
- learn more about environmental
considerations and their
relationship to small-scale agricultural
- approach agricultural projects, even
though small, from an
environmentally aware perspective
through the promotion of
technologies appropriate to the
- integrate environmental and
socio-economic factors into
agricultural planning activities, so
that recommended technologies
fit the resource base, perceptions, and
needs of local
WHAT THE MANUAL PROVIDES
The manual covers the following subjects:
* Introduction to important ecological
concepts relevant to the
development of agricultural projects.
* Technical information related to
* Some suggestions for planning
* Guidelines for using knowledge of
environmental effects to
determine positive (benefits) and
negative (costs) factors in a
given small-scale agricultural effort.
Consideration of these factors can lead to
alternative project designs. In
addition, this background
can be used as the basis for planning environmentally
projects in the areas of water supply and management, nutrient
soil conservation, pest management, and related
THE RELATION OF AGRICULTURE
Agriculture is defined as the science,
business, and art of growing
rearing animals in order to produce food, fodder, fiber,
products useful to people. A customary
goal of agricultural
to enhance food production for growing populations.
should also be concerned with the farm as a
system that includes animals and plants other than food
However, this manual emphasizes crop
the series deal with livestock, forestry, water, and energy.
Crop production can be increased by one or
more of the following:
- expanding the area planted to crops
- increasing the yield per unit area of
- growing more crops per year (in time
and/or space) on the
same unit of land
OF THE NATURAL SYSTEM RELATED TO ENERGY SUBSIDY AND STABILITY>
is essentially an environmental activity.
It is a process
the natural ecosystem in order to channel energy to
people in the
form of food. The process works by
by the addition of energy and resources.
the degree of
modification of the natural system, the more energy
channeled to humans. At the same time,
the stability and sustainability of the system.
Agricultural systems that have greatly
modified the natural
thus dependent on high energy and resource inputs to
maintain a desired level of yield. In
the tropics commercial
(monocultures) and tree-based plantations require
intervention than annual multi-crops (polycultures) and
of ground and tree crops (agroforestry systems).
OF MODIFYING THE NATURAL ECOSYSTEM>
Systems that require more input and
intervention are usually
with higher resource depletion and negative social impacts
low-input, diversified agricultural systems.
the possibility of enhancing the environment for
addition to the negative impact on the environment
from altering the natural system. The
agricultural development should be to balance these two
in the search for environmentally sound and socially
agricultural production techniques.
Environmental problems in some areas have
misapplication of temperate-zone technologies to the tropics.
yields in these areas will only be achieved through
methods unique to the ecological and socio-economic conditions
tropics. (Dover and Talbot 2.5)
WHAT IS MEANT BY ECOLOGY AND
Many environmental concepts have their
basis in the science of
Ecology is defined as the study of the
structure and function
of nature, or
the interactions among and between the living and
components of the place being studied.
aspects of the sciences of biology, physiology, geology,
and others in the study of natural systems
In agriculture, the appropriate level of
organization to be
managed is the agroecosystem and the corresponding
agroecology. All that ecologists
study--such as the
abundance, and interactions between organisms and
physical environment, succession, and the flows of energy
materials--are important for an understanding of agroecosystems.
ecological processes can shed light on the development of
agricultural technologies. In
agricultural studies, the
sciences also are critical in understanding the relation between
social systems. (Altieri 2.1, King 2.6)
Environment, on the other hand, defines
the natural, social,
economic surroundings of a project.
influence and are influenced by environmental factors.
AGRICULTURE AND ENVIRONMENT ARE RELATED
Each agricultural project takes place
within a complex system
attitudes, cultural framework and practices, economic
and physical, chemical, and biological factors.
system is the
environment in which a project occurs, and every
project, no matter what its size or scope, affects and is
these factors, i.e., by its environment.
The many forms
agriculture found throughout the world are the result of variations
climate, soil, economics, social structure, and history.
solar radiation, temperature, and soil conditions are the
determinants of the physical ability of crops to grow and
systems to exist. Human factors that
play dominant roles
social, economic, and political considerations.
traditional and religious practices; cost and ease of transport;
marketing channels; inflationary tendencies; availability
and credit; and stability of the government, accompanied
and consistency in policies, programs, and commitment.
words the environment of any one area consists of the
the area, including the time, customs, and practices of
people. (Briggs and Courtney 2.2)
Farming systems also depend heavily on the
i.e., whether the crops are produced in a subsistence or a
economy. The subsistence farmer
produces crops primarily
consumption. Consequently, there may be
production methods because livelihood and survival are
the changes turn out to be unproductive.
subject to market conditions, may also resist change because
they are not
willing to take the risk or because they are not willing
The way crops are grown further depends on
and level of
technology, the availability of suitable land area, and
resources. High levels of technology
and large land units are
accompanied by a high degree of mechanization, and
land, soil fertility, and genotype. On
the other hand
low levels of
technology and small parcels of land are usually associated
soils, intensive cropping systems, and less
BETWEEN AGROECOSYSTEMS AND SOCIAL FACTORS>
All agricultural development projects,
whether they involve
pest control, fertilization, or the introduction of new
crops and cropping methods, have positive and negative
Some of the interactions between parts of
the total environment
can be easily
forecast. For example, it is clear that
rainfall, the money available for the project, and the
in the project of local people are factors that can affect
of an agricultural project. Other
factors, however, such
as the effect
of using certain pesticides over a long period of time are
Environment in the agricultural setting
has been defined here
the people of the region, the animals, the plants, soil,
nutrients, the weather, ways of planting and cultivating, and
Those planning and implementing small-scale
of these influences. Interactions
systems involve exchanges of energy, materials, and
between both systems. The decisions
that farmers make
in using a
cropping system or technology depend not only on the
and local resources available but numerous aspects of the
social system as well.
WHY ECOLOGICAL CONCEPTS ARE
FOR AGRICULTURAL DEVELOPMENT
Agricultural development implies
continuing change in the
an improved system. Therefore, in order
to occur as a
result of agricultural project activities, the alterations
made as a result of the project must have more
effects than negative. Because they are
ecosystems function, ecological concepts can provide assistance
how the natural environment may be affected by
projects. Moreover, understanding the
that underlie basic processes in natural ecosystems
nutrient cycling, succession, and others), can provide important
for developing appropriate low input alternatives for
management, pest and disease management, development of
for various activities from planting to post-harvest
WHAT ECOSYSTEMS ARE AND
WHY THEY ARE IMPORTANT
A planner viewing a potential project site
is looking at an
natural system--an ecosystem. An
ecosystem is defined
complex of organisms interacting among themselves and with
non-living environment in processes such as competition, predation,
feeding, habitat, and so on. The
structure of the
related to species diversity. The more
greater the diversity of species. The
function of the
related to the flow of energy and the cycling of materials
structure. The relative amount of
energy needed to
system depends upon its structure. The
and mature it
is, the less energy it needs to maintain the structure.
agricultural project interferes with the flow of energy
materials through the natural system or ecosystem by adding
or eradicating pests, ecological patterns may be changed.
Whether an area is farmland under rice
cultivation for many
years, or a
virgin forest, it is a functioning system.
introduce change, such as replacing the rice with a new crop
down the forest for agriculture, should be made with an
the characteristics of the existing system and of the
effects such a decision would have.
A good example is the substitution of
tractor for buffalo power
fields of Sri Lanka. At first sight,
the substitution of tractor
seems to involve a straightforward trade-off between more
planting and labor saving, on the one hand, and the provision
of milk and
manure, on the other. But associated
with buffaloes are
wallows and these in turn provide a surprising number of
In the dry season these mud holes are a
refuge for fish
who then move
back to the rice fields in the rainy season.
caught and eaten by the farmers and by the landless,
valuable protein; other fish eat the larvae of mosquitoes
malaria. The thickets harbor snakes
that eat rats that
eat rice, and
lizards that eat the crabs that make destructive holes
ricebunds. The wallows are also used by
the villagers to soak
fronds in preparation for thatching. If
the wallows are lost
mechanization, so are these benefits.
consequences may not stop there. If
pesticides are brought
in to kill
the rats, crabs or mosquito larvae, then pollution or pesticide
both can become a problem. Similarly if
for the thatch this may hasten forest destruction since
required to bake the tiles.
In forest ecosystems there are also
components. Trees protect forest soils
by serving as
by breaking and cushioning the beating action of
that rainwater can be absorbed slowly and prevent
Trees also provide shade and cooler
canopy. This protection of the soil
allows dead organic
decompose, releasing important nutrients used for growth
by the forest
plants. Forests also provide habitat
for wildlife and
produce valuable fuelwood, construction materials, and
substances--all resources used by local farmers.
worker makes the decision to assist the farmer to
yields by substituting another crop for rice or cutting down
all or part
of the forest, it is also a decision about interacting with
ecosystem. For that reason the
taken into account.
WHAT HAPPENS WHEN NATURAL SYSTEMS
A look at the forest ecosystem will show
what can happen
protection of the trees is taken away and not replaced by
* Wind can pick up the organic matter and
dry out the soil so
that it is not good for cultivation.
* Nutrient-rich soil particles may be dislodged
during rain storms.
Both soil particles and nutrients in
solution may be carried away.
* Protection against flooding may
disappear. Forests maintain
soil porosity, aid the infiltration of
rain, and retard the
surface movement of water, thereby
protecting villages from
floods and retaining moisture in the
* Sources of firewood, lumber, and tree
crops for domestic
needs are no longer available.
* Diversity of plant and animal life is
affected. Many birds,
mammals, reptiles, amphibians, and
insects that prey upon
agricultural pests disappear with the
loss of the forest
The Food Web
Plants, plant-eating animals, predators,
scavengers and decomposers
what is commonly called a "food web."
the food web,
food energy moves in one direction:
from producers to
With a knowledge of the dynamics of the
food web, the quantity
available to us can be increased by:
- reducing the number of organisms that
compete for the same
- converting forests and rangelands into
- increasing the efficiency of food use by
livestock by improving
animal husbandry practices
- growing crops that put more
photosynthetic energy into
- eating less meat and more fruits,
vegetables, and cereals
All these efforts are limited by the
energy inefficiencies that are
food webs, since there is energy lost at each transfer
trophic level to another trophic level.
HOW STABILITY RELATES TO
When land is cleared for agricultural
crops, usually the numbers
and kinds of
plants and animals living there are greatly reduced.
It is often best
to design projects that will maintain the diversity
of the plants
and animals insofar as possible.
diversity is often related to stability, implying that ecosystems
many different kinds of species are more stable
containing only one (as in monoculture).
It is clear, however, from recent evidence
cannot be made more stable by simply increasing complexity.
biological interactions with potential stabilizing
be encouraged. For example, it is known
vegetational component of agroecosystems with
associations often significantly lowers pest population,
economic thresholds and result in agronomic benefits.
is to evaluate which crop assemblages will result in
For example, forest ecosystems tend to be
very diverse and
stable. Severe stress on the physical
environment (e.g., by
less likely to adversely affect such a system because
alternatives exist for the transfer of energy and nutrients
system. Similarly, internal biological
or biotic controls
predator-prey relationships) prevent destructive shifts in
population numbers. Hence, the system
is capable of adjusting
continuing to function with little if any detectable disruption.
Agricultural ecosystems, on the other
hand, (particularly those
the use of monoculture cropping systems) are likely to
stable because a single species represents a high proportion
of the total
number of plants on the site. Such
high yields, carry with them the disadvantages characteristic
young, and developing ecosystems. Particularly,
are unable to
perform protective functions such as soil conservation,
cycling, and population regulation. The
functioning of the
depends on continued human intervention in the form of
inputs, mechanization, and irrigation.
be easier to plant and less time-consuming to
also lend themselves more readily to mechanization, use of
inputs, manipulation in various ways, and the advantages
of scale. On the other hand, some
small farmers throughout the Third World may also
effort to tend. For example, corn,
bean, and cassava
combinations in Costa Rica have been found to be less labor
because of reduced weed growth in the multi-crop fields.
COMPARED WITH POLYCULTURES>
One of the major reasons that small
farmers choose to use
systems (polycultures) is that frequently more yield can be
a given area sown in polyculture than from an
area sown in separate patches of a single crop (monoculture).
Over the long
term, single crop systems tend to be more
to major crop failure than a multi-crop farm.
look at a
multi-crop farm containing equal numbers of pea,
and bean plants compared with a monoculture maize
If both farms were attacked by a disease or
per cent of the corn, the multi-crop farmer would still
have a 73 per
These considerations must be evaluated in
view of local situations,
small-scale experimentation is recommended whenever
considering changing present crops or cropping
SUCCESSION AND AGROECOSYSTEMS
Ecosystems tend toward complexity as they
ecosystems are less diverse and have a high energy in-flow
per unit of
biomass. In mature ecosystems that are
there is less
accumulation of energy because the energy flows
diverse channels. This flow or change
is called succession.
refers to the process in which plant and animal
a site, change the site, and are later replaced by other
plants and animals. The repeated
invasion and replacement
until the site is dominated by types of plants and animals
themselves and are not forced out by other species.
is known as the "climax community" for the site.
will remain relatively unchanged until the site is disturbed
changes in climate or water table, or by human
such as clearing land by logging or for farming.
The succession process can take hundreds
of years, but the
can be seen much more quickly. If a
field is left fallow
growing season, weeds, legumes, grasses, and wildflowers will
field, along with various insects, rodents, and birds.
many years, the field will eventually become a forest or
climax community, but not necessarily similar to the
that previously existed on the site.
Succession may be
under different conditions than previously and produce a
climax. This makes conservation of
The observation and study of succession in
local natural ecosystems
apparently guided many traditional farmers in the design
structuring of their agricultural systems.
For example, farmers
in West Java
follow a system comprised of three stages--kebun, a
annual crops; kebun-campuran incorporates some perennials;
talun, a climax dominated by perennials, closely
successional sequence of neighboring tropical rainforests.
FARMING SYSTEM IN WEST JAVA>
Succession tends to restore agricultural
sites to the original
not prevented from doing so by the farmer.
succession, the farmer has to interfere with the process
by weeding (manually or by applying herbicides), or by
flooding. In many cases, succession
would return a site
secondary bush, woodland, or thicket vegetation within
even years, thereby reversing negative effects of certain
and induced changes in the environment.
Thus the impact
reversible. However, if a project has
had major impacts on the
site, such as
altering the water table or resulting in massive erosion
natural succession can take centuries or may never return
the site to
its previous condition. The impact may
sites exist where humans cleared out forests centuries
ago only to
have the unprotected site remain as a barren desert.
development worker should consider seriously the magnitude of
and whether its effects are reversible or irreversible by
In the well-known traditional practice of
slash and burn
farmers clear a patch of forest and burn the biomass to
nutrients before planting their crops.
Once the soil fertility
built up over many years is exhausted by continuous
farmer moves to a new site and begins the cycle again.
uncropped (fallow) land, succession takes over.
allowed to elapse the land may again take on the characteristics
original community and nutrients will be restored to the
Population growth and land tenure problems
to be reduced or eliminated in many areas, thus, over
decreasing the soil fertility. Because
the decision to cultivate a
requires a continuous supply of nutrients, organic or
fertilizers will have to be added to the site.
supply necessary chemical nutrients, but do not supply
matter to the soil or contribute to the maintenance or improvement
structure over the long term. The use
fertilizer should be considered in the planning process
beginning. Care should be taken that
sufficient nitrogen is
which may have to be supplied by chemical sources.
In areas of Nigeria where the fallow
period has become progressively
improved fallow system was developed by the
Institute for Tropical Agriculture.
(See Appendix B for
Leguminous shrubs and trees (e.g., Leucaena
in association with food crops to restore soil nutrients.
"alley cropping systems" food crops are grown in rows (2-4
between strips of Leucaena which are pruned during
The prunings provide green manure and mulch
crops, erosion control, fodder, firewood, and staking
In a trial, Leucaena rows averaged 100-162
kg. of soil
meter, increasing maize yields about 23 per cent.
observed that Leucaena prunings are a more effective
source when incorporated in the soil than when applied as
Agricultural projects are undertaken in
all kinds of environments--forest,
mountainside, or coastal plain. In each
factors that will determine crop distribution and performance.
agricultural projects, crop production can be improved
or decreasing one factor. For example,
area, climate, nutrient availability, and soil type may
for the growth of rice. However, there
is not enough
rice plants to grow. In another field,
conditions may be
good for corn
but there is so much water the corn will drown.
water availability is the limiting factor:
it dictates both
the type and
the quantity of growth on the site.
The physical environmental conditions of
amount, timing, and intensity of rainfall, soil characteristics,
availability of nutrients--dictate the variety and density of plant
species that can live in an ecosystem.
SYSTEMS FOR SINGLE ANNUAL RAINFALL>
In rainfed areas, the distribution and
amount of rainfall are
most critical determinants of the types of cropping
can be adopted. In some areas where
rainfall is limited,
not feasible. Crops that require less
water are the
choice for such areas. Water-conserving
measures such as
fallowing, and terracing can often conserve enough water
to make the
difference between profit and loss. In
rainfall is over 600 mm, cropping systems are generally based
maize. In areas where rainfall is over
1,500 mm per year, cropping
often based on rice. Other crops grown
rainfall pattern are roots, cocoyams, tubers, plantains, and
others. For example in Southeast Asia,
the rainfall pattern, which is a single annual rainy
Since rice needs more water than other
cereal crops, and
because it is
the only major crop that tolerates flooding, only rice is
grown at the
peak of the rains. Upland crops can be
planted at the
and/or end of the rains to utilize residual moisture and
intensities during the dry season (System I).
systems, such as, maize and groundnuts, are often best
until the end of the rainy season (System II).
Natural sites are able to support a number
of plants and
The limits of this support are determined by
elements needed for life. This limit is
known as the site's
potential or carrying capacity.
Obviously, the biological
a fertile flood plain is much greater than that of arid
lands of the
same size because more water, better soil, and more
available to organisms living there.
Biological potential can be increased by
adjusting the limiting
Crop production can be increased by adding
be fertilizer, organic matter, water, or some
form of pest
control. Improved technology can also
When considering limiting factors,
* Satisfying the most obvious limiting
factor may not solve the
In fact, satisfying one limiting factor may reveal
For example, when nitrogen is lacking in a
corn field, the farmer may add a
nitrogenous fertilizer. He
may then find that nitrogen-induced crop
growth attracts a
greater pest attack, thus revealing a
new limiting factor.
* There are upper and lower limits to the
amounts of nutrients
plants can use.
* Changing present conditions by adding
limiting factors may
harm currently adapted organisms.
Understanding the concept of limiting
factors and knowledge of
ecosystems function constitute a basis for drawing up appropriate
ecologically sound guidelines for planning agricultural projects
that are more
HOW KNOWLEDGE OF ENVIRONMENTAL CONCEPTS
IMPACTS CAN BE USED TO ENSURE
MORE SUCCESSFUL PROJECTS
A feasibility study of a project should
consider potential ecological
well as economic, social, and cultural factors that may
project. If this process indicates a
number of possible
bad effects, the development worker then looks for
alternatives or makes what seem to be acceptable
compromises based on the situation. For
starving and increased crop production seems to require
use of a
pesticide that may be harmful, the decision will depend on
of the situation, but the planners and the community
need to be
aware of the implications of pesticide use and take
In order for small-scale agricultural
efforts to benefit from an
sound approach, planners should be aware of the
factors impinging on the type of agricultural project
considered, and then utilize this information to design management
limit environmental impacts.
PLANNING FOR SUSTAINABLE
THE PLANNING PROCESS
This book contends that all development
activities must have a
basis of local participation in planning, decision making,
implementation. Planning is often
described as a linear process
identifying needs, proceeding to project objectives, and designing a
meet those objectives. In reality the
process is and should
complex. Effective planning of a
project is a dynamic
involving the beneficiaries, the implementors, and any outsiders
assisting. The initiator may be the
or it may be
an outside development assistance agent or organization.
case the partnership relations between the community
assistance must be balanced if the development
to belong to the community.
Planning can be done on an international,
national, regional, or
level. It may be initiated by the local
community people on
initiative, by nongovernmental organizations, by regional
officers, or personnel of national universities or ministries.
level or whoever the initiators, the sustainability
activities will be depend on the involvement in the planning
making of those the project is intended to benefit.
THE END IS THE BEGINNING
Meeting the needs of beneficiaries is both
the beginning and
the end goal
of development activities. If the
initiator is a community
members need to sit together and explore their
needs and the
resources available to meet those needs.
are external to the community, they need to sit with the
identify needs and resources from the local perspective.
A local group organizing a project must
establish a clear
itself and the natural resource base.
gather a profile of the community and a profile of the
bases of the activity.
The next step is for the community to
define the goals and
the activity being undertaken to meet identified needs.
If there is
an external agency involved the process should be collaborative.
Plans for the
activity can be made based on the ultimate
goal and the
specific objectives. This part of the
needs to be
done with conscious recognition of the tradeoffs involved
needs with limited resources and the realities of politics,
values, and preservation of the natural resource base.
The project may need input of a technical
nature in design,
monitoring, and redesigning. If there
the evaluation should not be external but participatory.
Various quantitative techniques may be
used to help complete
phases of the planning process. Such
techniques will help
baseline against which to measure accomplishments.
Some of these
quantitative techniques can be quite detailed, requiring
the use of
computer programs and simulation techniques.
worker will not have ready access to computer
simulation techniques. In that case, it
to have a
checklist for a guide as planning proceeds.
that may be
useful can be found later in this chapter.
outlining this planning process is on the following page.
Flexible planning is the ability to use a
framework and the
and perspective provided by it creatively in designing a
A planning framework/methodology presents
a logical, step-by--step
defining and integrating project variables and for
among project opportunities. Because
the steps in the
process have been lifted out of a "real context," they may
appear neat and
well ordered. In reality, the steps to
be taken in a
are not likely to be clear-cut (at least initially) and the
components may be difficult to categorize.
helps the user work through the mass of information
structure steps that are possible and feasible.
planner can use this methodology to determine priority
number of possible projects and to decide when a project
perhaps because of a likely imbalance in benefits/costs terms,
The key to good planning is applying a
within pre-determined boundaries. The
guidelines, are things that should not be changed--except for very
reasons. Certain aspects of a project
can be altered easily
represent different methods of accomplishing the project
same boundaries. Alterations that do
change the boundaries
must be made
only with great caution. These
set, can provide
the basis for an environmentally sound, small-scale
project in various local situations and with alternative
1. IDENTIFY AND ASSESS NEEDS AND
When community members participate in all
phases of project
execution, and evaluation, they will be more committed to
and have a sense of ownership. Arousing
participation is a challenging task. It
communicate with one or two leaders or a small group.
involving the whole community and helping them to realize
what can be
achieved is more difficult. Some
references on the
included in Appendix A.
Planners and community members may not
always agree on
needs of a community. Each is looking
at the problem
own point of view. If planners begin a
project that addresses
are not identified by the community, there will be
support from the community. With the
planners can learn which issues are critical to the
Communities are groups of individuals that
may have conflicting
If the project satisfies only the goals of
community, planners should make sure that the project does
no harm to
those who are not participating. A
project that satisfies
the needs of
several different groups within the community will be
Where commercial sales of agricultural
products are involved,
retailers, and transporters should be included in planning.
are experienced with marketing problems and
successes and failures. If all related
groups are included
development process, they can explore the reasons why projects
so that mistakes are not repeated.
2. COMMUNITY PROFILE AND NATURAL
A community profile can be an important
tool for the development
outside the community as well as a community
planning a project. The profile should
be structured so that it
easy-to-use data on key social, economic, cultural, and
characteristics of the community or region.
The profile does
not have to
be prepared in great detail, nor should it take weeks and
complete. The topics suggested here for
activities. The user will want to gear
the profile so
data relevant to the primary area of concern.
* Determine the social structure and
kinship relationships of
Note these particularly as they pertain to
agricultural activities such as
cultivating, harvesting, marketing,
* Understand the traditional roles of men
and women in relation
to the agricultural system.
Include all related activities
such as land preparation, planning,
harvesting, storage, sale
and other aspects of crop management.
* Note the cultural traditions and
folkways of the community
associated with food production.
* Identify community leaders, their
spheres of influence, and
how these may or may not affect
* Analyze the economy of the community and
the area, especially
as it relates to phases of agricultural production, such
as cultivation, harvest and post-harvest
* Consider marketing opportunities or lack
* Note land use and ownership patterns.
* Note availability of such services, as
agricultural extension, and agricultural
* Determine people's ability to put more
time into crop production
or to take risks.
* Include a range of perspectives among
on agricultural and personal needs and
the priority of each
* Verify all of the above with the
The planner will also want to be sure that
encompasses all the information that is relevant to the community
Resource Profile or Inventory
A survey of the natural environment
(climate, soil, topography,
soil fertility, pests, etc.) provides information necessary for
project feasibility and for determining potential benefits
and costs as
well as required modification. For
need not be turned into an intensive study, but rather
a rapid rural
appraisal method. It can be a useful
tool providing a
which to refer after the project is underway.
There are at least two levels at which
inventories should be
The first consists of creating an overview
picture of the area
As part of this inventory, the planner
should look at
as watershed characteristics, significant topographical
general rainfall distribution patterns, general climatic
This information may be available through
observation, or discussion with local people.
The second inventory is a localized
biophysical and socio-economic
The biophysical evaluation entails an
cropping systems, farming systems determinants, and the
among farm components. The
resources needed for the farming systems (human
land, credit, capital, etc.) on a seasonal basis.
Local Agricultural Experience. Learning
experience is important because agricultural practices in
countries are already well-adapted to prevailing environmental
Over many years of trial and error, farmers
work. As more research is conducted,
practices, once regarded as primitive or misguided are now
sophisticated and appropriate.
Confronted with specific
slope, flooding, droughts, pests and diseases, and low soil
small farmers throughout the world have developed unique
systems aimed at overcoming these constraints.
By learning about local practices, it is
possible to obtain further
on (Chambers 3.5):
- local crop varieties that have shown
particular resistance to
disease and pests
- cropping methods, such as intercropping
and multiple cropping,
that are designed to get the most out of
- availability and use of organic
fertilizers (e.g., manure and
compost) that do not have to be
- agricultural methods that conserve
water, soil, and nutrients
- agricultural methods that may require
less time, money, and
labor than some other alternatives
- agricultural tools which are made
locally and are suited to
All this information can serve as a
starting point to develop
agricultural systems and technologies adapted to local
This inventory should also cover the
following among other
* What crops are grown and why?
* Who is growing which crops (men or
* Are crops grown for consumption, cash,
medicine or other?
* What local resources are available for
food production? Are
they used efficiently?
* Are there food shortages or surpluses?
* What are the major causes of crop loss?
* Are pests a serious problem?
control methods are in use?
* Do current crops provide adequate
nutrition for human diet?
* Do current cropping systems improve or
lessen the nutrient
content of the soil?
* Do local agricultural practices promote
or otherwise enhance
watershed management and soil
* What types of soils dominate?
* What is the organic and nutrient content
of the soil?
* Are there signs of degradation, such as
light colored soils?
* Is wind erosion a problem?
* What is the topography and how does it
affect soil quality
and water/soil relations?
* What kinds of organisms does the soil
contain? Are earthworms,
protozoa, grubs present?
* What fertilizing practices are used, if
any? What ingredients
are available for composting?
* What are the major local sources of
water? Is the same
water source used by both animals and
* Is the water of good quality?
* What water-carrying methods are used to
bring water to
* Is the water table relatively stable?
* What kind of vegetation exists around
the water source?
* Is the supply of water steady year
* Is there much fluctuation in water
supply due to heavy
flooding or drought?
* What type of watershed management is
* What are the rainfall/sunshine patterns?
* Do floods and droughts present serious
* Is altitude an important factor?
* Is wind a predominant feature?
* Who owns the land in the community?
* How many are landless and engage in
day-labor on other's
* What are the characteristics of the land
available for farming,
for example size, existence of or
potential for irrigation,
topography, land cover?
* Is the land titled or registered?
* Can additional land be acquired?
* Who owns or controls water sources and
* Is land being priced out of the
The above checklists of questions should
help to meet the
objectives of the survey which are to:
* Define the productive potential of each
* Delineate the limiting factors (i.e.,
zones of moisture surplus
or deficit) so that appropriate
techniques of resource conservation
* Identify other areas with similar
ecological environments and
social contexts, so that technology
developed in one environment
can be transferred.
* Facilitate the choice of appropriate
agricultural inputs and
technologies and quantify the levels of
risks associated with
* Promote development of sustainable
farming systems with
well defined inputs, calendars, and
DEFINE GOALS AND OBJECTIVES
After the community has identified needs
with the highest
goals and objectives that address these needs can be
the group. A goal is an overall purpose
project. The objectives help direct
action toward this
Objectives are the more specific targets
that will be achieved
project. Objectives should be clearly
defined, measurable, and
An objective should indicate what is to be
it will be
completed, and how success will be measured.
actual numbers, such as, the number of hectares
kind of crops to be produced, the number of wells to be
and so forth.
If the objective states when achievements
are expected, it
time line for achieving the objective.
A valuable outcome
formulating objectives is that information needs become
Once project objectives have been
established, the ways to
objectives can be considered. It may
assist in developing
for the community to answer the following questions.
* What is the overall purpose or long
range goal? (example:
increase income, improve nutrition)
* Who will be responsible for achieving
* How do the relations between and
responsibilities of both
men and women affect that achievement?
* Who will benefit from the project?
Are they the same people
who are responsible for achieving the
* How can progress toward achievement of
the goal be measured?
* What results would indicate that the
goal was reached?
* In what time frame can these results be
* Over what geographical area will the
Answers to these questions can be combined
PROJECT WITH CONSIDERATION
Once objectives are defined, members of
the community in
with development workers and technical personnel can
to achieve the objectives. Informed and
be helpful in reaching decisions. Some
of the key
designing agricultural activities are listed in the box on
KEY ELEMENTS FOR DESIGNING
- start small
- include local participation at every stage
- start with knowledge and information from
enhanced with technical information
- seek technical information on soil, water,
crops and seeds
- include training in the basic plan
- consider integration of conflicting land
uses (agriculture, forestry,
livestock) to maximize productivity of the
- consider alternatives to chemical
pesticides and fertilizers
- where tree planting is involved plan for
harvesting of the trees
- benefit the whole community
- build evaluation into the dynamic of
implementing the planned
In preparing alternative courses of action
predictions should be
probable impacts, both negative and positive, of the proposed
Choices often involve trade-offs.
A choice that has strong
benefits may also have negative effects.
For this reason, the
benefits of each alternative are often compared with each
a standardized format. This is called a
References that can provide methodology for
and cost benefit analysis can be found in Appendix A.
IMPLEMENT THE ACTIVITY
After alternative designs have been
examined, the sequential
to put the plan into action can be finalized and a
timeline established. Meeting the
objectives of the project
continuous community participation, development of
leadership, and consideration of community dynamics.
adapted to the local environment should utilize local materials
expertise. It also should include
training in new
methods and other skills needed for project realization,
advantage of local knowledge of the environment.
Case studies have shown that farmers and
their families have
understanding of their immediate environment.
the world have developed traditional calendars to time
activities. Thus many farmers sow
according to the
phase of the
moon, believing that there are lunar phases of rainfall.
cope with climatic seasonality by utilizing weather
based on the vegetative stages of local vegetation.
Training is almost always needed when
innovation is being
It is essential when larger or more complex
new crops or trees are to be introduced, or when new
to be adopted. It may be necessary to
are willing to risk being innovative.
likely to achieve increased yields and are often easily
If such people are given special training,
support, they can often help in the training of other
the community and can demonstrate project benefits.
Funding of projects is not always
necessary but sometimes it is
Small farmers usually have few resources and
or time to
risk in a new enterprise. They may be
reluctant to enter
agreement in an untried venture.
However, the more sustainable
those in which the beneficiaries have made
sacrifice of time or have contributed resources.
sometimes may be needed from the local community,
or other organizations in the form of loans and/or
MONITOR THE PROJECT
Plans for monitoring the project should be
part of the original
Systematic monitoring often detects
unexpected positive or
impacts and modifications of project design can be made.
Because environmental and human interactions
effects cannot be predicted and changes may not be immediately
Therefore, it is important to continue to
in operation to observe both expected and unexpected
Planners may want to monitor effects on
fertility, land use, diet and cultural practices.
help to identify maintenance procedures that will ensure
EVALUATE THE PROJECT
The project plan should outline the
evaluation methods to be
ensure that the evaluation is carried out.
Too often this
ignored, especially when the project may not appear to be
objectives. However, project evaluation
is important for
all who were
involved in a project. Every project
involves a certain
risk for project participants. In the
event of project
these participants must not be abandoned by planners or
hesitate to try any future projects.
Evaluation must be a joint effort of
planners and community
Outside evaluators may add fresh insight or
overlooked by those close to the project.
judge the project from their own value system that may not
purposes. The point is to observe and
measure how well
have been achieved and to determine if there have been
expected or unexpected results.
Investigation of the causes of
failure will help future planners to improve project
Evaluations are especially helpful if the
project methods have
experimental, with no past history of success or failure in a
environment. Planners and project
managers should exchange
with those in nearby regions in order to compare
A SUMMARY CHECKLIST
* Are project objectives measurable and
* Are they compatible with community
* Were community members involved in
establishment of project
* Was a cost-benefit analysis which
includes an environmental
analysis used to help select the best
project design to achieve
* Is an effective technical assistance and
integrated into the project design?
* What assistance can be provided by
and other institutions or groups?
* Is there a reasonable plan to monitor
and evaluate the
This chapter has outlined a planning
process. Chapter 4 contains
suggestions about the broad framework of understanding
planning. The chapters following
explore some of the
issues that might be encountered in planning an agricultural
Chapter 10 concludes with a checklist for
examples of traditional systems, and a look at long term
OTHER CONSIDERATIONS FOR
Chapter 3 reviewed the process of
planning. The suggestions
chapter, however, are not a prescription.
They need to be
the local situation. In addition, there
are some other
that affect planning a project. There
are some natural
involving biological and physical relationships.
discussed in the chapters providing technical background for
This chapter will discuss legal constraints
considerations; and related to these, the
considerations of women's activities in agriculture.
CONSIDERATIONS FOR PLANNING>
Legal limitations, unlike natural
limitations, are established by
meet specific conditions and, therefore, can be modified by
response to changes in legal, social, and economic situations.
conditions have been established over time by
use. Considerations concerning women in
not new but their
importance is newly recognized.
Among the important institutional
considerations in planning
agricultural projects are the laws that affect the use of
Often in the rural areas of developing
countries the legal
land ownership is ambiguous. Vast areas
of farm land
low-income farmers is unregistered, with usage passing from
generation without legal protection.
These lands are
marginal, lacking fertility and irrigation, and otherwise
for agricultural production. Where
statutes are clear
to land ownership and distribution, for example, in a
program, enforcement is always mixed.
There may be a
between the level of poverty of the low-income farmer and
the issue of
security of land titles. Political
considerations color the
process producing uneven results. Also
land prices can
difficult for governments to acquire land for distribution.
As regards laws that address ownership,
use, and the sale of
of natural resources, the development worker may be
dual legal systems in some jurisdictions:
a common law
inherited from the colonial period and customary law deriving
indigenous concepts of ownership and usage.
In parts of Africa,
land ownership may reside in the person of the tribal
Accordingly the use of the land and
distribution of products
will be subject
to his regulation. At the national
level a price
established by the government to hold down the cost of
food in the
urban areas may make a small-scale commercial agricultural
unprofitable. Law always affects
level, too often with negative results.
A development worker should consult with
local authorities to
be sure that
a small-scale agricultural project can be implemented
existing land tenure jurisdiction and patterns of land
Legal considerations, as discussed above,
are formal rules that
conduct. Less explicit, but equally
derived from other cultural practices of a society--from
religion, and folklore. As with laws,
these social considerations
reflected in the decision-making process.
Failure to do
so can lead
to adverse reactions that can severely affect the project.
Cultural considerations determine, in
part, the options available
to a planner
of environmentally sound small-scale agricultural
From the flood plains of the Mekong River
Basin to the
desert environments of northwestern Africa, situations can be
which social patterns affect implementation of particular
Social constraints are often difficult to
assess. They are not
susceptible to easy solution and are often ignored.
to do so is
folly. To increase the possibility of
management in agriculture, it is essential to include local
planning objectives of the project.
Training and public
Other socio-cultural factors such as
labor between men and women, and decision making in
agricultural activities are sometimes critical to project
should not be overlooked. Some projects
women by increasing their responsibilities and working
involved, when the objective of the project is to reduce the
WOMEN AND AGRICULTURE
In many areas of the developing world,
more of the agricultural labor force and may be responsible
as much as 90 per cent of the food. It
this in those regions where women traditionally are
producing food crops, managing small livestock, and
cultivating cash crops. Women need to
have a role in
about agricultural innovations and development
They need to have access to training,
are sympathetic to their traditional role, and they
In the past, when new options existed,
they have been more
available to men rather than women. For
a large majority of
especially in rural areas, innovation, training, and development
have not improved their quality of life.
just the opposite effect has been the result.
DIVISION OF RURAL LABOR BY
Labor in Hours
Cuts down the
forest; stakes out fields 95
seeds and cuttings 50
Hoes and weeds
crops home from the field
food crops 10
water and the fuel 10
Cares for the
domestic animals 50
cares for the family
UN Economic Commission for Africa, 1975, Women in
If there is to be a shift to a better
understanding, the following
are some of
the constraints that need to be addressed:
* Most of the power is in the hands of
men; therefore men
have access to new opportunities.
* Women tend to be viewed as consumers
rather than as producers.
* Women's chores such as food processing,
fetching water and
fuelwood, child care, and cooking are
generally not considered
to be productive contributions to the
* When these chores offer income-producing
potential, they are
usually undertaken by men.
The preceding table demonstrates the
division of labor between
men and women
in Africa, where women traditionally play a dominant
The local people and the development
worker must select from
plans of action. Choosing among
considerations. Economics involves
sometimes referred to as benefit/cost analysis.
To make an economic analysis of
alternative courses of action,
objectives form a basis of choice. The
objectives are to:
- provide the greatest possible benefits
for the costs incurred
- bring the best possible rate of return
- achieve a specified "production
goal" at the least cost
Analysis of these objectives can give the
local people and the
worker a better understanding of the economic implications
a particular course of action.
To analyze the first two objectives,
likely consequences of
courses of action and costs of implementation must be
the extent possible. Some information
can be obtained
local experience. If the course of
action is newly
development worker can seek available prediction
To satisfy the third objective, goals
should be established for
levels of production. These goals are
most effective if set
values of local residents, coupled with long-range goals
through the political process.
Benefits/costs analysis has often been
viewed as a purely
approach rather than as a tool to use in a more
development process. This view can be
for at least
two reasons: 1) it can cause the
planner to overlook the
economic effects; 2) it can lead to a failure to recognize
cultural, social, and ecological factors also can (and should) be
benefits and costs terms. Planners must
be able to
benefits/costs approach to all facets of the planning process if
they are to
be able to judge project feasibility in terms of impact on
BACKGROUND FOR PLANNING
THROUGH REDUCTION OF
Soil contains the nutrients and water that
plants need for
serves as the medium or substrate in which they grow.
purpose of soil management is to provide a continuously
and productive soil for plant growth through proper
water and nutrients and soil conservation practices.
When the soil is left without vegetative
cover, erosion may
Since erosion is the most serious
farmers around the world, this chapter provides background
agricultural projects in areas that are prone or
erosion, and need controls to reduce erosion.
project, it is necessary to understand the process of
its effects both upon the project and the environment.
MANAGEMENT THROUGH REDUCTION OF EROSION>
WHAT IS IT?
Erosion is movement of soil by water,
wind, ice, or other
processes. It is a function of climate,
vegetation, and human actions, such as cropping methods,
practices, and equipment use. Usually
necessary as the slope of the land increases because
helps the soil to move.
There are three stages of water-caused
erosion: sheet erosion,
and gully erosion.
Intense rainfall or large rain drops
displace particles of soil.
dislodged by this impact. As water
accumulates, it begins
soil more or less uniformly over a bare sloping surface.
the slope, the water follows the path of least resistance,
channels formed by tillage marks, stock trails, or
in the land surface. Sheet erosion is
the first stage of
damage and as
such can be hard to identify. Those
piece of land should check carefully for signs.
assessing erosion problems is to observe from the low end
of the field
what is happening during a heavy rainstorm; i.e., is the
dark with accumulated soil?
Concentrated runoff may remove enough soil
to form small
tiny gullies, or rills in a field.
While rills are often the
sign of erosion, they can be covered up by tillage practices.
recognize the signs of rill erosion and watch for
Under continued rainfall, rill erosion
longer slopes increase the depth of the rill.
flowing water increases as depth, velocity and turbulence
Sheet and rill erosion together account for
most of the soil
As water accumulates in narrow channels,
it continues to move
This is the most severe case of erosion and
can remove soil to
depths of 1
to 2 feet, or up to several hundred feet in extreme cases.
There is a widespread belief that tropical
soils, once cleared,
irreversibly transformed into hardened plinthite or laterite.
only a small proportion of tropical soils (for example, only 4
per cent of
the land in the Amazon) is subject to laterite formation.
is soft plinthite in the subsoil, and when the topsoil has
by erosion, hardening to laterite can take place.
laterization is more likely to occur in soils where erosion is
The main factors that affect erodability
of a soil are the physical
chemical composition of the soil, the slope of the
land and the
management (how is it used) of the land.
Soil loss is
directly related to the following:
- intensity and amount of rainfall
- quality of the soil and how much it is
subject to erosion
- length of slope
- degree of gradient (steepness) of the
- quantity of vegetation cover
- kind of crop system (monoculture or crop
- system of soil management (especially
related to soil cover)
- erosion control practices (discussed later
in this chapter)
determine how much water enters the soil, how much
runs off, and
the potential impact for erosion. It is
present and potential erosion in planning a project.
EROSION BY WIND ACTION
In arid and semi-arid regions, wind
erosion can be extremely
Topsoil blown away from the land can leave
and increase the number of particles in the atmosphere,
affecting local climate. Wind erosion
- cover and kill plants
- disturb organisms living in the area
- increase labor and cost of cleaning
those areas which are
covered by soil
- reduce amount of solar energy (sunlight)
available to plants
- increase evaporation, surface drying
Extreme wind erosion, coupled with
climatic changes and
activities, can contribute to the formation of deserts.
people contribute to increased wind erosion and hasten
by cutting woody species for firewood, overcultivation,
practices such as improper cattle management that leads
overgrazing. In many cases, such
practices are the result of
population pressures, but also because impoverished farmers
are pushed to
adopt these practices by social, political, and
SOIL COVER AND WHY IT IS
FOR CONTROL OF EROSION
A good soil cover is the most important
control of both wind
erosion. A cover directly on the soil
or close to it is the
effective. Soil cover serves the
- interrupts rainfall so that the velocity
is slowed down before
it hits soil particles thereby reducing
splash and dislodging
effects of rain
- decreases runoff velocity by physically
restraining water and
- increases ability of the soil to store
water by providing
shade, humus, and plant mulch
- improves surface soil porosity by root
systems that help
break up the soil and facilitate water infiltration
The leaves and branches of a crop provide
a canopy or cover
over the soil
and protect the soil from heavy rainfall and wind.
forms a canopy several feet above the ground.
leaves soil bare before seed germination and during
establishment. Shorter crops, such as
some grasses or
(beans, vetch), and crops such as sweet potatoes and squash,
closer to the ground surface and have an even better
reduce erosion. Soil loss from a grass
substantially lower than in a cornfield.
TREES AND CROPS>
Ideally, projects should be designed so
that some kind of
cover remains in place at all times.
This may not be
all ecosystems. If an area is cleared,
plan to cover the
with vegetation as soon as possible. If
this is not
least take time to check, and encourage weeds to grow
the fallow field. This is helpful in
* The cover reduces the possibility of
* The weeds can be plowed under to provide
manure) for later crops and improved
* The balance of the ecosystem may be
ensure that the disturbance will not
have lasting, negative
HOW EROSION CAN BE
Erosion can be controlled by reducing the
mechanical forces of
wind, by increasing the soil's resistance to erosion, or by
both. Water erosion can be controlled
by preventing splash
providing crop cover or a layer of mulch (crop residue or
materials) through which the rainfall then trickles
into the soil.
Another means of preventing erosion by
water is to constrain
that continues to exceed the rate of infiltration.
be done with
physical barriers such as contour-bunds, tied-ridges,
reinforced by rocks, ridges, or living barriers composed of
planted grasses or shrubs. Strip
cropping with furrows in
sprinkler irrigation or trickle irrigation can also help
erosion. Mulches and cover crops
sometimes deter both
wind erosion. Wind erosion can also be
trees and/or shrubs as a windbreak.
(See figure below) A
addition can provide other benefits (firewood, fodder,
poles) if multiple-use trees are planted.
is also used
in some areas to control wind erosion.
There are several ways to control erosion
caused by water. The
of each of these control measures may be a project in
the measures may be included in agricultural projects.
- increasing vegetation cover
- using plant residues to protect soil
- using improved tillage techniques such
- rotating crops and planting cover crops
- reducing erodability of soil, for
example, by adding organic
- planting deep rooted trees for slope
- using mechanical support carefully
- and other practices such as terracing,
using diversion channels,
contour plowing and planting, strip
strip cropping, tie-ridging, and
reducing of field lengths
HOW PLANT RESIDUES COMBAT
Plant residues are, for example, corn
stalks, wheat chaff,
similar remains left in the field after crops have been
They can provide effective erosion control
by reducing the
impact on the soil and reducing runoff.
The practice of leaving plant residues on
the field is called
Mulching is particularly useful for
high soil temperatures, retaining soil moisture, and
to soil fertility as the residues decompose.
Mulch can be left on the surface, or it
can worked into the
plowing, discing, or harrowing. When
this latter practice
the amount of organic matter in the soil increases and
structure or composition and water infiltration improve as
well as does
the water-holding capacity of soil. On
the other hand,
into the soil reduces the percentage of surface cover
soil so that it is somewhat more susceptible to wind and
erosion. Some pests as well as
disease-causing fungus and
thrive in the mulch and can be difficult to control.
The decision to plow plant residues into
the soil or to leave
them on the
surface depends upon the erodability of the soil in the
kind of organic materials, the amount of runoff expected,
tillage practices used. The cost and availability
of the labor
to do the
plowing are also factors. Greatest
protection from erosion
provided by not plowing mulch into the soil.
Yet, even when
worked into the soil, more soil can be saved than would be
mulch were not used at all.
Some crop residues may have negative
effects as a mulch.
can be a good source of information on this point.
TILLAGE METHODS FOR EROSION CONTROL
As farmers are well aware, conventional tillage
a bare soil
surface and expose soils to erosion until the crop is
Tillage methods can affect the runoff
velocity of water, the rate
infiltration of water into soil, and the degree of soil compaction.
which occurs naturally in soils with a high clay content,
root and plant development, can be worsened by the
use of heavy
field machinery, thus further increasing the chances of
Following are three tillage techniques
that can reduce erosion:
tillage, conservation tillage, and no-till.
Soil is tilled as little as possible to
produce crops under existing
climatic conditions. Fields may be
plowed or harrowed,
chisel plow rather than with moldboard plow.
Plant residues are usually left on the
surface as a mulch to
and to conserve soil and water. Plowing
are done in
one operation with crop residues mixed into the soil
Crops are planted directly into the field
or plot left untilled
last harvest. No-till is done by
planting in narrow rows
previous crop residues. The surface
mulch of weed and crop
vital to the sustained success of 'no-till' and reduced
systems. In the tropics, in addition to
protecting the surface
the impact of raindrops, the mulch helps develop and
soil surface and ensure rapid infiltration of water.
In some regions no-till needs to be
supplemented by carefully
chemical weed control programs and increases in the rate of
application. Such additions require
more capital and also
management and planning.
Studies indicate that erosion associated
be reduced 50-90 per cent by a switch to any of the above
Most development workers who work with
farmers in rural
and plan projects should become familiar with these
and new advances in this area. For
practices have been hampered in many areas by lack of
efficient tools for planting through the plant residue.
implements have been designed and tested to overcome
limitation such as the stick, the punch planter and the
rolling injection planter (RIP), developed by the International
Tropical Agriculture in Ibadan, Nigeria.
CROP ROTATION AND EROSION
Crop rotation is one way to reduce soil
erosion. Since the use
crops in rotation reduces the amount of time a field is
an adequate vegetative cover, erosion is reduced.
legume forage crops with non-forage crops, erosion can be
per cent over continuous cropping. The
supply nitrogen for the crops that follow.
In addition, if the
planned wisely, certain crops can be chosen for their
assist the resistance of soil to erosion under succeeding
The greatest of these residual effects is
derived from grass
meadows. Because they are sod-farming
and help build up the soil even when they are later
conventional tillage. There may also be
rotations using non-sod-forming crops.
For example, corn
less erodible than soybeans, but more erodible than small
In addition to planting crops with different
crops can be
planted between rows of permanent plant barriers such
broomstraw, elephant grass, or tree crops such as Leucaena.
called "alley cropping," will be discussed in Chapter 9.
SOME SUPPORT PRACTICES FOR EROSION
Support practices for erosion control may
require moving the
sometimes using machinery. The most
planting, and terracing--are practiced on long and
slopes. These practices reduce erosion
by slowing down the
water and its soil transporting capacity.
these practices or variations of them can be used for conserving
Crops are planted horizontally on the
contour of the slope,
up and down the slope. This practice
has the effect of
ridges across the land which reduce the rate of runoff.
barriers are provided by the rows the water moves
erosion is reduced, and the soil is able to absorb more
Average rates of erosion on contour-farmed
land are about 61
per cent less
than on similar cropland planted without contours.
However, contour planting needs to be
planned carefully. On a
slope or in areas of heavy rainfall and easily eroded soils,
build up in each contour, spill over, and break across
lines. The volume of water can build up
with each broken
row, and the
result can be more erosion, not less.
Contoured strips of crops are alternated to
reduce the effect of
breakage. For example, when sod and
crops are planted in
strips, the sod reduces water flow and serves as a filter
to catch much
of the soil washed from a strip crop row.
close to land contours give good erosion control.
Terracing is a very old practice,
especially in mountainous
Terraces are costly in terms of the labor
needed to build
require constant maintenance. When used
practices, terraces are more effective for erosion control than
cropping alone. Terraces reduce
effective slope length and
of the soil moved between terraces.
They can trap up
to 85 per
cent of the sediment eroded from a field.
Terraces are also
semi-arid regions for conserving both water and soil.
climates where topsoil is thin, poor soil is sometimes
the surface. Raised beds also help
OF SOIL MANAGEMENT/EROSION CONTROL
It is important to understand the
relationship among soil,
methods for erosion prevention and control, in order to
alternative land management techniques.
provided as a starting point for considering projects in
susceptibility of the soil to erosion is a significant limiting
* Would improved tillage practices provide
If so, would there be obstacles--money, customs--or
other constraints to changing practices?
* Is the site subject to wind or surface
water erosion or land-slipping?
For example, does the site have a steep
it a windy area without protective
windbreaks? Is there
evidence of past landslides?
* Are there periods during the year when
the soil of the
project site is unprotected by
vegetative cover and subject to
sheet, rill, or gully erosion?
* Will erosion cause silt to form in
downstream water bodies
such as streams, lakes, and reservoirs?
* Will use of mechanical equipment on the
project site damage
the soil structure and leave the soil
more susceptible to
* What is the major factor limiting
agricultural production in
Is erosion a major constraint to increased agricultural
* What are the social, cultural, physical
and economic costs of
* Can the project be set up to include a
training course for
local project participants?
* How have farmers traditionally adapted
to erosion problems?
* What other soil management practices may
Other tillage methods can be undertaken to
protect soil from
- improving soil fertility
- timing of field operations
- plow-plant systems
- grassed outlets and grass waterways
- ridge planting with tie-ridges
- construction of ponds for runoff
- changes in land use
- long low bunds, e.g., in the Sahel
These practices are described in the
following table, which is
material from the U.S. Department of Agriculture and the
Environmental Protection Agency. The
left-hand column gives
the name of
the practice; the right-hand column describes the advantages
disadvantages of each as an erosion control method
the potential effects of such a practice.
SUMMARY OF EROSION CONTROL PRACTICES
Highlights of Practices
Most effective for grasses,
small grains, and with
crop residues; reduces
labor and time required for
year-round control. Not
effective when soil is
too hard to allow root development.
tillage Includes a variety of no-plow
systems to retain
some crop residues on
surface; more adaptable
than no-till but less
Good meadows lose almost no soil and reduce
erosion of the next
crop; total soil loss is greatly
reduced but is unequally
distributed over rotation
cycle; may aid in
disease and pest control.
rotation Much less effective
than above; can provide more
soil protection than a
one-crop system; aids in
disease and pest
soil Reduces soil loss as well
as increasing production
systems Rough, cloddy surface
increases the infiltration
rate and reduces
erosion; seedlings may be poor
unless moisture is
sufficient; mulch effect is lost
Can reduce soil loss up to 50 per
cent on moderate
slopes, less on steep
slopes; less effective if
rows break; cannot use
large farming equipment
on steep slopes; must be
supported with terraces
on long slopes.
rows Similar to contouring but
less likely to have
breaks in rows.
strip Rowcrops and hay in
rotation in alternate 15 to
30 meter strips reduce soil loss
to about 50 percent
of that with the same
rotation that is only
contoured; area used
must be suitable for across-slope
Reduce erosion and conserve
more intensive cropping;
some terraces have high
initial costs and
maintenance costs; cannot use
large machines; support contouring and agronomic
practices by reducing
effective slope length
concentration. In tropical climates
where the topsoil is
usually very shallow, terracing
often leads to bringing
to the surface, soil
which is very poor.
This can have worse effects
terracing A technique for
terracing by creating bunds along
contours, then planting
seedlings on the bunds to
create a terrace.
This technique is used to replace
terracing in Kenya and is
called Fanya Juu (does
cropping Rotations of crops are
grown in between hedgerows
leguminous shrubs or non-leguminous
fallow shrubs planted
along the contour
with the hedgerows
pruned from time to
time to provide mulch
and organic residues.
system Where crops are grown in rows
on ground covered
by leguminous cover
crops that are killed by
an herbicide along the rows where the crops such
as maize are
planted. Can minimize erosion on
steep slopes; most
suitable where there is adequate
outlets Facilitate drainage of
graded rows and terrace
channels with little
erosion; are costly to build
planting Reduces erosion by
concentrating runoff in mulch-covered
rows; most effective
when rows are across
slope; earlier drying
and warming of root zones.
listing Minimizes row breakover;
can reduce yearly soil
loss by 50 per cent;
disadvantages same as contouring.
land May be the only solution in
some cases. Where
other control practices
fail, may be better to
change to permanent
grass or forest; lost acreage
can be supplanted by
intensive use of less erodible
Leaving the land to fallow is a common
practice in some areas.
practices May use contour furrows,
drainage, closer row
spacing, intercropping, and
(*) A simple
means of finding the contour is with the "A" frame technique.
is described in a brochure by World Neighbors
(see list of
agencies in Appendix B). World
Neighbors also has slides
about the technique.
WATER SUPPLY AND
An understanding of the relationship
between water and
is key to planning environmentally sound projects.
knowledge a development worker can judge a proposed water
control practice in terms of its impact on the environment
in which the
agricultural project is taking place.
As the primary transport medium on
agricultural lands, water
can be both
friend and enemy. Water carries or
soil to plants and within the plants themselves.
particles by the process of erosion. It
chemicals from the fields into the surrounding environment
can cause serious problems. An
moves and what its effects are on agricultural lands is
the key to
knowing how, when, and where a given project may
with these processes.
THE MAJOR SOURCES OF WATER
Lakes, ponds, streams, and rivers provide
water to plants
indirectly through evaporation and later condensation over
lands as rain, or directly, by tapping and channeling for
Rainfall is the climatic factor that most
in the tropics. Rain falls directly on
plants and moves
percolates, through the soil to the roots and on to groundwater
The important characteristics of rainfall
that affect agricultural
the amount, intensity, variability, and lengths of dry
spells and of
rainy seasons. The amount of rain
varies greatly from
season and from area to area. In many places,
amount of rainfall can be used to identify patterns in
of water available and to identify both flooding and
cycles. It is helpful to establish the
amount of rainfall and
the amount of
evaporation/transpiration (see glossary).
In a climate
well-defined wet and dry season, the growing season will
rainfall exceeds evaporation/ transpiration and continue
soil water reserve is exhausted.
Understanding the moisture
any changes in the patterns is of crucial importance
developing cropping systems adapted to local rainfall
Water accumulates in the soil at various
upon soil and
geologic structures. These groundwater
permanent. Groundwater can move up
through the soil by
action to become available to plants at times when there is
rain. Under drought conditions,
however, this source
help. Water held in deep pockets, called
aquifers, can be
available by digging wells.
THE WATER BALANCE IN CROPLANDS
The water balance or amount available to
the farming system
specific period of time reflects factors affecting sources of
What water is left in the soil around the
root zone of the
crops can be
calculated by balancing the following:
- what is left of the water from the
rainfall after runoff (water
moving below the surface soil, for
example, on top of an
impermeable layer of clay, towards a
- percolation below the root zone (water
seeping down through
the soil to the water table or the
- evaporation (from the soil)
- transpiration (moisture given off by the
The balance between rainfall and
the amount of water available for crop growth.
exceeds evapotranspiration the root zone is charged with
As evapotranspiration begins to exceed
rainfall, water available
growth decreases. Runoff and
percolation also will affect
the amount of
water remaining in the root zone.
The objective of water management in
agriculture is to minimize
the runoff, percolation, and evapotranspiration.
such as mulching and no-tillage can reduce evapotranspiration,
terracing can reduce runoff.
HOW WATER MOVES AND THE EFFECTS
Regardless of the source, water moves
materials to and from
site physically and chemically.
Raindrops falling on unprotected soil
dislodge soil particles and
over the surface of the land. This
surface water runoff
can be a
major cause of erosion. Erosion has
three negative effects:
- loss of valuable topsoil, making land
less productive where
runoff takes place (however, nutrient
laden sediment may
enrich soil in lowland areas)
- pollution of streams and lakes
downstream from the project
site by soil particles that accumulate
and become sediment
- washing of fine particles into spaces
between larger soil
particles creating a physical block
which reduces water
Sediment from this process chokes streams,
light that can penetrate the water, and clogs the gills of
shellfish. Nutrients and pesticide
chemicals adhering to
particles increase their polluting effects in the water.
On the other hand, physical movement of
the soil can have
effects. For example, in flood plains
fertile top soil as a result of annual floods that transport
Many minerals, nutrients, and pesticides or
chemicals are dissolved and carried in water (or leached) out of
soil. This occurs by surface and
sub-surface runoff, and also by
down through the soil (percolation).
up chemicals, nutrients, and sediment, and deposits
surface waters. A number of negative
effects can result
chemical transport. For example,
pesticides can kill
organisms and fertilizers promote growth of algae that may
water. The extent of the impact depends
runoff, the chemicals carried, and their concentration in
water. Through percolation, water may
chemicals directly to wells or to surface streams as part
groundwater. Percolation may move
nutrients beyond the root
plants. The amount and frequency of
the water storage capacity of the soil, the vegetative
amount of runoff and rainfall, and the type of soil and
conditions below the root zone.
Percolation has beneficial effects as
well. One of these is moving
salts deeper into the soil. When this
does not occur,
accumulate in the topsoil and eventually become toxic to
THE IMPORTANCE OF IRRIGATED AGRICULTURE
Water management seeks to ensure the best
use of available
In many areas and in many small-scale
problem, at least initially, is inadequate water supply.
is irrigated agriculture, although water conserving
systems and drought tolerant crops might also be appropriate.
Before a decision is made about irrigation
it is important to
amount and timing of rainfall that can be expected during
season and how rapidly this water will be depleted.
even though rainfall appears to be adequate, its monthly
should be considered in relation to potential evapotranspiration.
although total annual rainfall as shown in
below, is adequate for crop growth, moisture is in excess
September to May but inadequate from May through August, so
recommended during the period of peak evapotranspiration.
Agricultural lands are irrigated in many
ways. The best
method to use
- supply of water available
- quality of water
- slope of the site
- infiltration and percolation rates of
- water-holding capacity of the soil
- chemical characteristics of the soil
(salinity, alkalinity, and
- moisture requirements of the crop
- weather conditions of the area
- economic resources of the farmers,
especially for moving
water to the field
- techniques for moving water to the field
PHASES OF THE WATER BALANCE IN A UNI-MODAL RAINFALL CLIMATE>
WHY IT IS NECESSARY TO PLAN
IRRIGATION PROJECTS CAREFULLY
Irrigation projects can have far-reaching
effects on the environment
of a vast
area. Irrigation can affect the
quality, soil characteristics, crop productivity, human health
of diseases such as malaria and schistosomiasis), family
and mobility patterns, economic status of farmers, water
land ownership patterns. The land
ownership issue is
important because once land is irrigated its value is increased
and what was once marginal land, now becomes quite
and desirable. If the land title is not
secure in the hands
low-income farmers, they could lose the land to an unknown
owner. These possibilities should be
Irrigation projects also can be affected
by other factors. Control
sources needs to be considered. For
that will be providing water for the project should be
determine if the watershed is protected adequately to
of the quality and quantity needed for proposed crops.
development upstream from the project site could alter
supply drastically, causing flooding, drought, fluctuations
flow, or water contamination. Other
uses of water closer
to the source
can affect the supplies and possibly pollute the water.
USING SURFACE WATER FOR
Using surface water for irrigation can
have far-reaching effects.
water usually is diverted via canals, ditches, and channels
Effect on the
* Removal of water for irrigation can
result in reduced flow
* Reduced flow can cause the death of
aquatic plants and
* Water returned to the stream after
irrigation is often of
poorer quality than the original water,
and may cause death
of plants and animals.
Water carried to irrigated fields is also
subject to evaporation
canals or seepage from canals in areas where the soils are
On the other hand, when irrigation from
over the land surface, the water percolates downward
accumulate underground. Over a period
of time accumulated
water can raise the water table until it is within a
meter or even
a few centimeters of the soil surface.
inhibit the growth of plant roots by waterlogging the soil.
may also change the wet-dry cycle and increase pest
incidence of certain diseases. Many
die back to
low levels during the dry season. With
to breed throughout the year.
Improper irrigation can have various
negative impacts on the
will affect crops. Among these are
salinization and alkalinization.
contain more or fewer salts are better for different
crops. The measure for whether soil is
alkaline or acid is
pH. The normal pH balance in soils is
around 7. If the soil
normal acidity the pH reading will be higher than 7.
soil is below
normal or alkaline, the pH reading will be less than 7.
In soils with drainage problems and improper
surface can become very salty as water evaporates from
deposited salts in the upper layers of the soil (salinization).
is the concentration of salts--sodium, calcium, magnesium,
potassium--in the upper soil layers or on the surface in the
form of a
white crust or powder. Salinization if
reduce crop productivity. When drainage
present no problems. Salts can be
washed out of the
applying water in excess of the rate of evapotranspiration of
Where drainage is poor, concentration of
mineral salts can
surplus water accumulates and raises the water table to
meter or less of the surface so that increased evaporation
Inadequate drainage and elevated water
tables are the underlying
salinization problems in irrigation projects.
of the nature
of this problem and its causes is another planning tool.
workers must check drainage and water table characteristics
developing an agricultural project using surface
irrigation. The saline problem can be
which could cause saline contamination of groundwater and
waters elsewhere. An alternative to
transporting the saline
water elsewhere would be to use it on-site for irrigation of
crops such as barley, cotton, sugar beet, wild rye.
crops are beans, onions, and most fruit trees.
Salinization can also be caused by small
amounts of water if
the water is
of poor quality. It is a common problem
limited and there is a need to save it.
Another possible consequence of improper
alkalinization which is of particular concern in arid and semi-arid
Alkaline soils are those with a high content
whether or not in combination with substantial quantities of
Alkalinization is more serious than
salinization because it is
remedy. Salinization can be remedied by
alkaline soils may worsen their condition.
salts, does not leach away because it is adsorbed (clings
surface of soil particles and combines with water in a chemical
clay and organic matter. While salts
may be leached
runoff or irrigation water, the sodium remains in the form
hydroxide or sodium carbonate. The
presence of the
hydroxide causes the organic matter in the soil to dissolve
the soil structure, making it difficult to till and almost
by water. Expert technical assistance
is needed to
Technical assistance is required to
determine whether or not
conditions exist and how serious they are.
One easy way to
get help is
to take a soil sample to a government office.
a pamphlet describing "How to Take a Soil Sample."
B for the address.
USING GROUNDWATER FOR
When water for large-scale irrigation is
drawn from groundwater
sinking wells and pumping, the water table is often
This has several possible effects that must
be considered by
* Local vegetation may no longer be able
to draw on the water
* Marshes, springs, and wet places may dry
* River and stream flow may be reduced.
* The land may sink, or subside, if too
much water has been
pumped out too quickly from natural
storage areas, or aquifers.
This phenomenon is irreversible
(that is, it cannot be restored to its
former state by natural
* Heavy withdrawal of groundwater can also
lead to saltwater
contamination of the fresh water in the
* If too much water is applied,
waterlogging may occur in
IRRIGATION RETURN FLOWS AND THEIR EFFECTS
Water used for irrigation flows back to
water sources through
This return flow from irrigation can be a
polluter of surface waters, groundwater, and soil.
usually do not exert excessive withdrawal of water,
discharge of groundwater may occur through springs,
seepage along the sides of streams.
availability forces areas with marginal water supplies
groundwater, which increases water mining and costs of the
to high energy requirements. Dissolved
salts, for example,
carried to the subsoil or groundwater.
ground carries with it the salts accumulated in the
root zone and
moves them up or down in the soil profile.
into drainage systems and are returned to main streams.
When irrigation water returns to main
streams it may have
* Because of leaching and evaporation in
the fields and canals,
the salt content of the irrigation
return flow may be much
greater than that of the initial water used.
Too much salt
can kill fish and other aquatic
organisms downstream from
the point of return.
* Return flows can carry pesticides, which
can be lethal to
beneficial aquatic organisms that
provide food for higher
organisms in the food web, including
* Irrigation flows can carry sediment or
silt, which raises the
beds of irrigation canals, changes the
direction of canals
(causing them to meander), clogs drains,
and fills the
streambeds of reservoirs and lakes
IRRIGATION AND HUMAN HEALTH
The human health implications of
irrigation can be extremely
can include the following:
* Irrigation canals can carry chemical
pollution from one place
* Canals and ditches can provide new
places for the growth,
breeding, and reproduction of various
disease organisms, or
their vectors, and can be instrumental
in spreading these
diseases, especially if water is used
for drinking and/or
* Slow-flowing or stagnant storage ponds,
supply canals, or
deeper drainage ditches are ideal
habitats for disease organisms.
This occurs particularly when canals
with aquatic weeds, which slow-the flow
of water and offer a
feeding ground for mosquitoes and other
that transmit disease.
Many of the most serious human
diseases (for example, malaria, yellow
fever, and schistosomiasis)
are carried by organisms such as snails
* Although snails and mosquitoes that
spread disease can be
controlled by pesticides, these
pesticides may also kill the
eggs, larvae, and adults of many other
species of aquatic
Control of disease organisms with chemicals can
also harm fish-raising efforts in
irrigation canals and reservoirs.
Mosquitoes that transmit malaria can
to specific insecticides over time.
accumulate in the food web and can cause
harm to humans
who use the water or eat fish grown in
Alternatives to pesticides for mosquito control include
pathogens (i.e., Bacillus turringiensis var.
fish (Gambusia, the mosquito fish), birds and other
(See Chapter 8 for information on biological pest control
DETERMINING THE EFFECTS OF WATER SUPPLY
AND MANAGEMENT PROJECTS
By formulating and answering a series of
questions like those
for each project and site, development workers may be
anticipate a few of the potential effects of irrigation projects:
* Is there adequate water for the project,
either from precipitation
(rainfall), surface water, groundwater,
* Are cycles of floods and droughts
accounted for in the project
What would be their impacts on the project when
* Does the project design minimize surface
runoff that might
carry away valuable nutrients and
topsoil and cause pollution
* Do upstream resource uses (construction
activities) affect the quality of the
water to be used by the
* Will the project involve
irrigation? If so, the planner should
be particularly careful to assess the
impact of the project
downstream and the possibility for
increasing habitat for
aquatic pest insects including vectors
of waterborne diseases,
and abundance and quality of the project
* Will the project affect water-flow
patterns of the area?
Would these alterations affect the water
supply needed by
* Are malaria, yellow fever,
schistosomiasis, or other waterborne
diseases carried by organisms associated
prevalent in the region?
And will the project in any way
result in increased incidence of the
* Will the project reduce downstream water
flows and thus
affect fisheries, aquaculture projects,
the growth of aquatic
weeds, the habitat for mosquitoes and
other vectors of
disease-causing insect pests?
* If habitat is increased for disease
vectors, could this result in
increased use of insecticides or
molluscicides with the possible
result of chemical poisoning of fish and
* Could irrigation cause waterlogging of
* Is the soil susceptible to salinization?
* Does the soil have a characteristically
high pH and could
irrigation result in soil
* Does the site have lateritic soil or is
laterization a potential
(See Chapter 5).
* Will new wells be sunk?
If so, could this affect the water
* If the water table is affected how will
stream levels and
wetlands be affected?
* Is the project site near the sea?
If so, could lowering the
water table allow salt water to intrude,
* Could downstream water or groundwater
quality be affected
by high salinity in the return flows
from the project site?
* What other water supply and management
options should be
* What alternative designs could minimize
Other appropriate questions may be
added. By considering
questions, the trade-offs necessary to minimize the negative
the project can be evaluated.
WHAT ALTERNATIVES EXIST
A number of practices are available to
reduce the amount of
for irrigation (and thus decrease possible negative impacts)
conserve water. These management
methods can be
lessen water loss from runoff, evaporation, deep percolation,
and stored soil water. Practices are
also available to
efficiency of irrigation and the use of stored soil water:
- control of runoff losses through contour
tillage, terracing, use
of crop residues, and water spreading
(the diversion of
surface runoff to sites where the water
infiltrates and is
stored in the soil)
- control of evaporation losses through
reduction of deep percolation through the use of horizontal
barriers (i.e., asphalt)
- conservation irrigation such as drip
irrigation (See Appendix
A for references)
- water harvesting (i.e., through
construction of small ponds to
capture excessive water during rainy
- use of drought tolerant crops
- no-tillage agriculture (see Chapter 5)
- relying on summer fallows for dryland
farming areas currently
There are also several ways to avoid or
irrigation on human health. When canals
are used, people
extra care to draw water from uncontaminated stretches of
the canal, or
from safer sources such as deep wells if such possibilities
If alternative waste disposal methods are
cycles can be interrupted, preventing the spread of
More research on the natural enemies of
snails and mosquitoes
possible predators such as ducks, geese, or fish.
also be local plants that serve as molluscicides, such as
(berry of the dodecandra plant in Ethiopia).
method may be
to deprive disease vectors of a suitable habitat by
water in pipes or tile aqueducts and by using buried tiles
excess water from fields. On a small
scale, the use of
systems for irrigation would not only protect humans from
would also prevent seepage and evaporation of water
irrigation. However, these solutions
may be costly or
control of small-scale project operators.
SOIL NUTRIENT MANAGEMENT
Nutrients, such as Nitrogen (N),
phosphorus (P), potassium (K)
are essential to plant growth. Planners
should have an understanding of the dynamics and cycles of
the natural environment in order to devise wise soil
management plans. Understanding the
inputs and outputs
in a crop field will help in devising techniques that keep
balance of nutrients in the soil. For
example, the figure
illustrates how nitrogen is added and withdrawn from the soil
SOURCES OF PLANT NUTRIENTS
In crop lands there are six primary
sources of nutrients:
fertility, plant residues, animal waste, legumes, water,
All cropland has a degree of natural soil
fertility. Soil fertility
refers to the
inherent capacity of a soil to supply nutrients to plants
amounts. Some soils, such as the flood
plains of rivers,
very fertile. On the other hand, loose
sandy soils, which
little or no organic matter, and usually not very fertile.
PRODUCTION FROM CROP RESIDUES>
Significance of the C/N Ratio. There is
a close relationship
organic matter and nitrogen content of soils, expressed
as the ratio
of Carbon to Nitrogen or C/N. C/N is
the available N and the rate of organic decay in soils.
of these two elements in organic material added to the
crucial for two reasons: a) Keen
competition among micro-organisms
N results when added crop residues have a
ratio (more carbon in relation to nitrogen).
This means the
decomposition will be faster and the availability of nitrate to
plant will be
depressed until the activity of decay organisms slows
b) Because the C/N ratio is relatively
constant in the soil, the
matter content of the soil depends largely on the nitrogen
The figure above shows the trend to be
with high and low C/N ratio are added to the soil.
Residues. Leaves, roots, and other
plant debris build up the
structure by providing organic matter.
As these materials
nutrients are released. The amounts of
depending upon the type of plant, temperature, rainfall, and
material is plowed into the topsoil or not.
Wastes. Animal wastes such as manure
are organic matter
decompose to provide nutrients to the soil.
been used as
fertilizer for centuries and is useful and environmentally
excessive amounts are not used.
The nutrient content of manure depends
upon the animal, the
type of feed
given, and the amount of water consumed by the animal.
organisms that affect humans can be carried in animal
therefore, only manure from healthy animals should be
Extra precaution is necessary when using
animal manures if
diseases are a problem in the area.
Local authorities usually
are aware of
these problems and can provide information.
as discussed below, can kill the pathogenic bacteria, eggs
found in animal manures. Other
by-products that may
be used for
fertilizer are bone meal, blood meal, and fish meal.
Cover new manure as soon as possible and
mix it with the soil.
As much as
1/4 of the nitrogen content can be lost in one day due to
volatilization if the manure is not handled properly.
Temperature and moisture affect
decomposition of manures.
timing of the application of manure may vary with climatic
In a semi-arid area, for instance, where
high temperatures are
high aeration of the soil, manure applied too early
onset of rains, can lose a large part of its nutrients from
oxidation of the organic matter.
NUTRIENT CONTENT OF ANIMAL
% of Dry Weight
Legumes, including peas, beans, groundnuts,
nitrogen-fixing bacteria in their root systems.
from the air into proteins that become available to the
the bacteria die. Bacteria can fix
enough nitrogen to
grass and legume meadow if no other nitrogen source is
The nitrogen usually is produced as the
plant needs it.
poor growth will not fix much nitrogen.
If there is a
high level of
nitrogen available in the soil, the bacteria fix less.
is not a limiting factor.
Legumes are often grown in association
with other crops in
crop rotation systems to provide nitrogen for other
For example, peas or beans are often grown
with maize in a
beneficial system. Such multi-cropping,
reduce or eliminate the need for chemical fertilizers.
to exploit the ability of the cropping system to reuse its
nutrients. In complex crop mixtures,
closed canopies and
areas usually promote nutrient conservation and cycling.
In addition to their compatibility in the
field, maize and
combinations complement each other nutritionally.
beings can receive nearly their complete protein requirements--without
or dairy products. Other plants
relationships, both symbiotic and nutritional.
crop patterns adapted by local farmers turn out to be the
best use of
the land as well as the best combination for providing
proteins for human diets. Development
new species should consider the potential of indigenous
as a starting point for the design of soil management
In combination with other crops grown
can provide adequate nutrition and even improve local
and Run-on Water
Rainfall can provide nitrogen and
phosphorus to cropland, but
in very low
amounts compared to other sources. The
precipitation is influenced by the weather, and by the
industry, cities, disposal sites, power plants, feedlots, etc.
phosphates, that may be present in dust, ash or smoke,
available to plants when dissolved in rain.
Nutrients in soil and organic matter that
are suspended in
water, that is, eroded and carried from elsewhere, may be a
input in certain situations. For
to inundation or flooding from silt-laden rivers or
cropping systems that involve planting on previously inundated
have sufficient nutrients from this source when the
river flow declines.
Inorganic fertilizers consist of chemicals
with little or no
matter. Chemical fertilizers supply
nutrients that are
after application, in amounts and ratios that are
Inorganic fertilizers are expensive, often
little to improve the structure of the soil.
difficulty calculating how much chemical fertilizer to apply.
This can lead
to under-fertilization or over-fertilization either of
which do not
produce desired results. Many tropical
chemical nutrients long enough for the plants to use them.
first rain washes them out of the soil.
However, in some
fertilizers are not available or not in sufficient quantities.
In that case,
correct application of inorganic fertilizers is
EVALUATING THE SOURCE OF NUTRIENTS
The choice of nutrient source depends on
the situation. Even
are naturally very fertile may be depleted of nutrients by
The need for fertilizer, i.e., anything
added to the field to
natural fertility of the soil, depends on:
- ability of the soil itself to provide
essential nutrients to
crops (soil fertility)
- nutrient demands of the crops
The choice of
fertilizers depends on availability, costs, and the
effect on the soil. Whether nutrients
are organic or
does not matter to the plant. Plants
can use fertilizers
source. However, other effects of
inorganic fertilizers are
unknown. In the long-term perspective
they can reduce the
diversity of microbes
in the soil. They may also be hard to
expensive. Wherever possible it is best
to use organic fertilizer.
organic fertilizers exist wherever there are animal
wastes. They are relatively cheap
although they require
of labor. They have the added advantage
matter to the soil. In the warmth and
moisture of the
most soils are very highly weathered, sandy, and
textured. In such highly weathered
soils, organic matter, in
adding nutrients to the soil, plays a very dynamic role in
complex that holds nutrients and retards leaching.
organic matter decomposes rapidly so that its nutrients
quite quickly. One of the best
practices for fertilizing
materials is composting.
OF A COMPOST PILE>
Composting is a natural process whereby
organic wastes are
decomposed. It has the following
- uses waste material and is of low cost
- can yield organic matter for fertilizer
within several weeks,
depending upon the ingredients used, the
climate, and so
- generates heat sufficient to kill insect
eggs, larvae, weed
seeds, bacteria, and other pathogens
that may cause human
- stabilizes the volatile nitrogen
fraction of manure by fixing it
into organic forms
- the final product is easy to store and
Composting also has some disadvantages:
- is labor intensive to produce
- requires space to store
- requires water
- is bulky and less convenient to
transport and handle than
solid inorganic fertilizers
- is dependent on supplies of manure and
- is more feasible for smaller areas, such
as, kitchen gardens
or small plots
In many countries, composting in some form
or another is
traditionally. Examination of local
methods can provide
guidelines for project planning in terms of available ingredients,
preparation time, receptivity of residents to the practice,
and so on.
CHEMICAL COMPOSITION OF SOME
& Bedding 15-25:1
THE EFFECTS OF FERTILIZERS ON THE
Both fertilizers and naturally occurring
nutrients are subject to
natural processes that tend to reduce nutrient levels--leaching,
erosion. In addition, other sources of nutrient loss
agricultural systems are:
- nutrients in the crop material that
leaves the farm
- nutrients in stock or stock products
that leave the farm
- leaching of nutrients below the root
- loss of nitrogen to the atmosphere
(escaping as a gas) or through burning
of vegetation or crop
- losses through run-off water (erosion)
If these processes can be halted or
slowed, the chances are
the nutrients present in the soil and those applied in
the form of
fertilizers will remain available for plant growth.
nutrients remain in the soil for crop use lessens the likelihood
nutrients entering the larger environment and thus
Leaching is the process by which soluble
chemicals move downward
soil in water that is percolating through the soil.
the most easily leached nutrients and are commonly
drainage waters. Leaching from cropland
depends upon the
type of crop
grown, as well as the soil type and its drainage characteristics,
and on the
amount of available water passing through the
zone. Leaching effects are particularly
important early in
season in the humid and subhumid tropics, when the main
mineralization of soil organic matter occurs.
permanent, deep root systems, leaching is of minor
Runoff occurs when it rains so hard and
fast that the ground
the moisture fast enough. When
fertilizers are left on
surface, the first rainfall can carry away a substantial
the nutrients. Fertilizers during
periods of light rains
move into the
soil dissolved in the available water.
The loss of
may be much less if the fertilizer is incorporated into the
inches of the soil before rains begin.
Being soluble, nitrates
leached into the soil. The
concentration of nutrients in
will vary greatly from field to field, depending upon soil
slope, crops grown, type of manure or fertilizer used,
conditions. Organic fertilizers mixed
with the soil can
soil's capacity to absorb water.
Although sediment transport through
erosion depends upon the
velocity of water flow, it can be the major transport
phosphorus and organic nitrogen clinging to or adsorbed
particles. When the velocity of water
is reduced, the
particles of sediment fall out of solution.
usually finer and has a higher capacity (more surface
area to which
to adhere) to adsorb phosphorus, so that transported
richer in phosphorus and nitrogen than the original soil.
Organic matter is often transported along
with sediment, causing
nutrient losses from the fields.
Nutrient losses from
be controlled by proper management practices such as
described in Chapter 5 for sound erosion control.
For example, leaving plant residues on a
field can reduce
of 25-65 tons/hectare/year to 12.5 tons/hectare/year, and
at the same
time provide nutrients to the field and thereby reduce
the need for
inorganic fertilizer. Other soil
methods, such as crop rotations with sod, contouring, and
can reduce nutrient losses as well.
THE EFFECTS OF MOVEMENT OR LOSS
OF SOIL, NUTRIENTS
Nutrients, including fertilizers, in
solution or suspension in the
or surface water bodies, can result in two problems:
* Nutrients may reach toxic levels and
become a health hazard
to humans and animals.
* When added to water systems (i.e.,
ponds, small lakes),
nutrients may accelerate the
eutrophication rate to the
extent that it becomes harmful to the
Eutrophication is the enrichment of a body
of water by nutrients
resulting increases in growth of aquatic plants.
phosphorus enter the water in high levels as a result of
other transport methods from agricultural lands, over-fertilization
of the water
systems stimulates an exploding growth of algae
- cause taste and odor problems
- create obnoxious conditions in
impounded water such as
- block passage of the sun's rays and
interfere with photosynthesis
of bottom vegetation
- clog the screens of water treatment
massive algae populations suddenly die off, their decomposition
gaseous substances and depletes oxygen levels in
with harmful effects to fish and other aquatic organisms.
Fertilizers usually contain nitrogen,
phosphorus, and potassium.
nitrogen in particular has been associated with
problems. Nitrogen, which occurs as
nitrites, nitrates, and/or
be converted to another form by chemical reactions
naturally in the environment.
The nitrite form of nitrogen is very toxic;
if taken by
drinking water or in food, it enters the bloodstream
interferes with the ability of the blood to carry oxygen.
also combine in compounds that may cause cancer in
Nitrates are much less toxic than
animals with single stomachs are able to expel nitrates in
urine. However, cattle, young animals,
and children can
nitrates to nitrites in their stomachs, a condition that
Both nitrites and nitrates occur naturally
in foods and water,
but only in
small amounts. Only small amounts can
be tolerated by
The World Health Organization has fixed the
Standard for nitrates at 0 to 50 parts per million (ppm) as
levels, and 50 to 100 ppm as acceptable.
countries, however, these levels are exceeded, especially
drinking water supplies are contaminated by nearby concentrations
such as manure piles in farm barnyards.
Obviously project plans must include
consideration of fertilizing
terms of the location of compost piles, manure accumulations,
and slope of
fertilized fields in relation to housing and water
Ammonia, like nitrate, can be converted by
toxic nitrite. Ammonia occurs
naturally. It is generated
micro-organisms as they break down organic matter on the
stagnant lakes. Dissolved ammonia can
occur at levels
toxic to fish. Another problem with
nitrogenous fertilizers is
addition of a common fertilizer, sulfate of ammonia, may
already acid soil. However, this may
benefit a basic soil.
Phosphorus usually enters water as a soluble
is completely available for algae growth.
enter the water adsorbed on sediment or on particles of
matter. The phosphates are then slowly
then contribute to problems associated with eutrophication.
MANAGEMENT OF NUTRIENT-RELATED FACTORS
Erosion control practices may be an that
is needed to control
the loss of
phosphorus and nitrogen. If nutrient
other nutrient management practices may be necessary
fertilizer management, crop rotation, legume cropping etc.
One must be careful that solving one
problem does not create
an example, in certain areas of the state of Texas, USA,
built to retain moisture. While the
terraces did hold
moisture control caused nitrate leaching, which contaminated
groundwater supplies of the area.
To prevent the build up of nutrients in
soil and their subsequent
leaching, farmers should apply only the needed
fertilizer to croplands. Failure to
accurately leads many people to over-fertilize.
prevent overfertilization and the leaching that results is to
need for fertilizers and apply only that which will be
used by the
crop. The table below provides general
requirements of selected crops. It
should be kept in
however, that most of these generalizations must be evaluated
GENERAL CROP NITROGEN
Kilos of nitrogen
per hectare per
times as a top dressing) 100-150
Symptoms of lack of fertilizer will emerge
when the seedlings
are a few
inches tall. Fertilizer can be applied
at this time in
rows. At this point, when the soil is
deficient in a
nutrient, the crop plants will develop
and yellowing of leaves is typical of nitrogen deficiency,
purpling of leaves signals phosphorus deficiency.
elements are greatest when fertilizer is applied near the
fastest vegetative growth, that is, several weeks after the
from the soil. This is not true for
needs to be
applied early for root development.
With late application,
fertilizer is used and it is used more efficiently.
application can set back development of the crop.
is to put
half the fertilizer on the field at one time early in the
season and the rest later.
Soil fertility and physical conditions may
be estimated by
certain biological indicators such as the prevalence of
weeds. Although weed growth may be
determined by more
just soil conditions, at times the dominance of one
species can be well correlated with salinity, drainage,
levels, or soil texture characteristics.
advised to consult local farmers, extensionists, or technical
interpret the indicators.
Project planners who are not agricultural
experts will probably
consult others for advice on actually choosing fertilizers and
using them in
crop production. Local farmers,
experts have experience in determining what kind and
fertilizer is needed.
The average amount of fertilizer needed on
fields often can be
rotating crops. Crops that require high
maize, sorghum, and cotton, can be rotated with legumes
soybeans, beans, or alfalfa, or with crops that require
amounts of nitrogen such as small grains.
Crops can be
growing season to reduce the need for other fertilizers.
particular cropping sequence appropriate in a rotation will vary
climate, soil, tradition, and economic factors.
affected by the previous crop. For
example, yields of
crop after barley are usually lower than after corn,
Animal manures can be good fertilizers,
but there are problems
with them. If manure is applied as it
be released slowly before planting.
This is not always
Storing manure, however, is difficult and
costly. It is also
determine how much nitrogen is being applied when
are used, especially since the nitrogen amount varies
animal and its diet. The best way to
use animal manures
nitrogen loss to volatilization is to plow it into the soil
add it as a slurry, so that it soaks into the soil.
advantages of animal wastes as fertilizers is that they release
slowly enough that little is lost through leaching.
Before chemical fertilizers were
developed, many farmers would
grow a legume
on a field and then plow it into the soil to serve as a
source for later crops. The main
disadvantage is an economic
can be harvested from the field that season.
compared with the cost of using chemical fertilizers and
potential impacts upon the environment, this practice is useful
when a farmer
has enough land to leave fields fallow.
chemical fertilizers or animal wastes are not available, this is
one way to
add nitrogen and organic matter to the soil.
benefits from incorporation are only observed with young
manures. Most other residues have high
ratio, see beginning of this chapter for explanation)
"tie-up" nitrogen during a period of time.
The type of fertilizer must be chosen
carefully, and it must be
the right time. For example, nitrogen,
through the soil, should be applied just before or during the
season. Phosphorus and potassium
fertilizers can be applied
growing season or sometime before the next one.
to mix fertilizers into the soil right after application to
of nutrients to erosion.
THE EFFECTS OF NUTRIENT MANAGEMENT
By answering questions such as those below
for each project
and site, the
development worker can estimate the potential effects
fertilization projects on the environment.
If the answers are not
apparent, go back and think about the project site again.
experts in the field if the answers point out major
Use the questions as guidelines to plan
projects that will
environmentally sound and successful.
* Is manure available for use as a
fertilizer in the project? If
used, would this practice result in the
spread of weeds
and/or disease through human contact
with the manure?
* Will plant residues be used for
fertilizers and soil structure
What is the C/N ratio of these materials?
* Will new plant species or varieties be
introduced? This could
have long-term environmental
repercussions and the potential
effects should be carefully reviewed.
* Could the new species out-compete
traditional crops in the
* Do the new varieties need more
fertilizer than traditional
* Will the new varieties require more
pesticides, and/or the
use of heavy farm machinery, which could
lead to other
* Could new pest species be attracted into
the region along
with the new crop?
* Will the project involve the use of
* Could this practice lead to nitrite
toxicity for people or animals?
* Are precautions being taken to avoid
* Could the project enhance loss of
nutrients via runoff,
erosion, or leaching?
* Could nutrient transport cause
* Are there other nutrient management
* Does the success of the project depend
on inorganic fertilizers?
If so, do farmers have a reliable
source? Have they
been trained in its use?
What are the projected costs of
* What alternative project designs could
be used at the site to
minimize nutrient loss?
ALTERNATIVES FOR NUTRIENT CONTROL
The following table lists ways to manage
nutrients in agricultural
The left-hand column names the practice; the
column describes the advantages, disadvantages, and
effects of each as a nutrient control method.
CONTROL OF NUTRIENT
nitrogen application Reduces nitrate
leaching; increases efficiency
use. However, may
crops Reduces fertilizer
need for pesticides. But may
production of saleable crops.
excessive Reduces cost of
fertilizers; can cut nitrate
wastes Enables slow release
of nutrients; economic
gain for small farms; improves soil
extends the period of residual
applied nutrients on subsequent
However, there are labor costs and
green Reduces need for
nitrogen fertilizer; not
crops always feasible;
amounts of nitrogen difficult
ties up available land.
fertilizer May decrease nitrate
leaching; not yet
surface Decreases nutrients in
runoff; may add
costs; not always possible;
no effect on
fertilizer plow-down Reduces erosion
and nutrient loss; may
U. S. Department of Agriculture, 1975.
Control of Water from Cropland, Vol. I, A Manual for
"Pest" is a human-oriented
term. It has been defined as "an
reduces the availability, quality, or value of some
resource. This resource may be a plant
or animal grown for
or pleasure (or) a person's health, well-being, or peace of
(Gips 8.8, Flint 8.7)
What is considered a "pest" then
human needs and values and thus can change from situation
situation. Most organisms and animals
are not pests and are
The use of chemicals that control pests
and herbs developed in
the 1940s and
accelerated in the following decades.
The use of
and herbicides has now spread throughout the world.
only in the
past twenty-five years that the horrors of using pesticides
known and documented. Balancing against
pesticides and herbicides offer is the negative impact of
contact in applying the chemicals, and of secondary effects on
through the water, food, and meat that we eat, as well as
damage to the
Pests, however, are a particular problem
in farming systems.
cropping systems often lead to changes in the numbers
or kinds of
pests and associated natural enemies (predators and
the agricultural ecosystem. Planning
agricultural projects requires looking beyond the types of pests
present and considering how measures used to control
affect the total ecosystem. Too often
failure to take this
approach has resulted in damage to the environment and in
In many agricultural projects, pests are
controlled only by the
chemical pesticides. Some chemical
pesticides, however, cause
problems as a result of their toxic or residual effects
and are a
cause of sickness and death to humans.
In a small-scale
may be possible to control pests by using less damaging
such as promoting biological control, planting different
mixtures, using less persistent and less toxic pesticides, finding
species-specific pesticides, or growing resistant crop varieties.
It should be
recognized, however, that some alternative methods
POTENTIAL RELATED TO CROPS>
Some birds and rodents if they reach pest
damage and losses in agricultural systems and thereby
reduce the amount of food available for people and
Various methods can be used to control
to trapping and killing them individually.
however, to poison these animals, even though poisoning
potentially a far more dangerous practice to people and other
organisms. Whenever possible, trapping
and other mechanical
practices should be used to control larger pests.
managed, the pests that are edible can provide an
source of protein and income to local people.
ENVIRONMENTALLY SOUND PEST
The best way to lessen or avoid unwanted
pesticide use is to minimize their use.
often exist and should be investigated by the
worker. For example, there may be
that can control pests. In some areas,
the use of resistant
delayed or early planting can reduce crop damage
pests. It is important for the
development worker to understand
how to use
alternative control methods. In the
long run, it may be
protect and enhance the natural predators and parasites of
than to use chemical pesticides. Insect
pests can become
certain pesticides and may do so after only a few applications.
species, on the other hand, may have longer
and may be more sensitive to repeated pesticide applications.
Find out what
kinds of pests are a problem before using a
try to use pesticides that are both species-specific and
Broad spectrum pesticides kill beneficial as
well as pest
are not recommended. Also find out what
are being used locally to control disease vectors or other
If pesticides are already in use some
resistance may already
If possible consult local specialists and
authorities before deciding
particular pesticide for use on agricultural lands.
have very specific laws governing the use of particular
and these should be taken into account before any time or
spent obtaining or using chemical pesticides.
certain pesticides and export them to other countries.
government agencies and local universities or the regional
office of the
Pesticide Action Network (PAN) for information on local
and alternative control practices. A
list of regional
the Pesticide Action Network (PAN) that can provide
information or answer specific questions is in Appendix B.
Because of the potentially harmful effects
of chemical pesticides,
workers should take care to investigate alternative
use them wherever possible.
ALTERNATIVES TO PESTICIDES
Many farmers know the plant species in
their area that have
properties. There are about 1,600 plant
species known to
pest-control properties. Try to find
indigenous plant materials
and use them
rather than chemical pesticides. Two
insecticidal properties are tobacco and pyrethrum (derived from
Both are now widely distributed throughout
Another plant used is the derris root.
It produces a chemical
rotenone which is used as a poison especially for ridding
fish ponds of
trash fish. Some plants, like the neem
types of pest-control action. When a
local plant which has
properties is pointed out, try making a solution from
leaves or stems and spray it on a small test area.
successful, it may be cheaper to use than commercial pesticides,
get, and environmentally safer. Even if
the test is
successful there may be other ways of utilizing the tree or plant
pest-control. Local farmers often have
Crops usually are rotated for economic and
reasons. Crop rotation also can be used
as a method to
insects, weeds, and plant diseases.
Many traditional agricultural
rely upon crop rotations to provide weed, disease and
control. Crop rotations, including
non-host crops, have proven
against soil-borne pathogens (cabbage black rot, bean bacterial
corn rootworms and should be explored with local
with local farmers who rotate their crops.
Varieties. There are also crop
varieties that are resistant
to attack by
disease or insects. These varieties
sometimes need the
pesticides, but in greatly reduced quantities.
Intercropping and polyculture can also
pests and disease organisms. By
with host plants in the same field, the spread of the
disease organisms among susceptible crops can be considerably
Moreover, the intercrop may also provide a
habitat for the growth and reproduction of pest and disease
than the primary crop. It may also
provide habitat for
insects and other organisms. For
example, alfalfa strips
among cotton rows attract lygus bugs away from cotton,
damage. Surrounding melon or squash
fields with a few
rows of corn,
acts as a trap crop for melon flies.
Time. Another crop management practice
is to change
times to prevent attack by insects and disease.
cycles are often attuned to the growth of plants.
crops can be
planted a few weeks before or after the normal time,
be able to by-pass the stage of the insect that causes
damage to the crop. Early maturing
varieties may escape
Early planting can be effective in
avoiding the egg-laying
period of a
pest by allowing crop maturation before pest attack
However, because it requires knowledge of
insect species and
cycles, the advice of entomologists or other scientists from
universities and government agencies may be needed.
Spacing. Modifying the spacing of crop
plants by decreasing or
plant densities may provide a measure of pest control by
micro-environment of the pest, the vigor of the plant,
duration of crop growth. For example,
grain crops suffer less from chinch bug attack, whereas
planting of cotton can discourage boll weevil infestations.
of Alternate Host Plants. It may be
found that the crop
breeding or spending part of their life cycle on another
species. If the alternate host is
another crop, it may be best
not to grow
both in the same area. If the alternate
host is a weed,
it may be
possible to control it and thus reduce the pest population.
the sugar beet curlytop virus involves destruction of the
thistle, the alternate host of the insect vector, the beet
Many weeds, however, especially flowering
family) and Umbelliferae (carrot family), can provide
food (pollen, nectar) to a number of important parasites
predators. For example, biological
control of crickets in Puerto
on the presence of two weeds that provided nectar to
wasps. In this case, it was desirable
to have more
weeds of this
type. On the other hand, if a certain
type of crop is
a pest, one way to control the pest is to plant that crop
the desired crop and sacrifice the alternate crop that
serves as a
trap to the pest. Pests and diseases
can also be controlled
in sequence or rotation, crop plants that are not
or do not constitute alternative hosts.
and Traditional Control Practices
Sometimes the easiest, least costly, and
of controlling pests on agricultural lands is by using
and traditional control methods. Some
of these methods
control, for example, involve:
- pulling weeds by hand or cutting them
- covering weeds with mulch to prevent
- burning a field prior to planting
- flooding the field
- normal tillage practices such as plowing
Mechanical and traditional practices can
be very effective in
countries where labor is available and money and pesticides
For example, insects can be killed by
trapping; rats can be
trapped or clubbed; and birds can be shot or trapped in
removed from the field. Hunting and/or
birds or game animals can also be effective.
Pests can be effectively controlled by
supporting the resident or
natural enemies of pests. Many of these
as far as research is concerned.
However, in agricultural
retain a diversified environment, biological control is an
Birds eat insects, cats eat birds, and so
has its prey and helps control the population of that
In practice, biological control is the use
or encouragement of
enemies for the reduction of pest organisms as well as
crop varieties that are resistant to pests discussed
Natural enemies act as mortality agents
that directly respond
to the size
of the population. Thus natural enemies
act as density-dependent
This relationship between pest density and
of attack by natural enemies is called a functional
For density-dependence to happen in
agroecosystems it is
let the insect pest population build up sufficiently to
corresponding build-up of the beneficial predator or
population. This will not happen if
pesticides are used on
the pest as
soon as it appears. Thus, a certain
amount of injury to
the crop may
occur. A small test plot may
demonstrate the effectiveness
negative possibilities before introducing the technique
Observation and discussion with farmers can
help to determine
pest population that can be tolerated at a
time without crop damage becoming too serious before
controls are sought. Natural controls
may take over before
Research into the use of biological
suppression controls has
include other methods, including the use of sex attractants,
regulators, sterilized male insects, repellants,
or aggregating chemicals (pheramones) that influence
of insect colonies. These methods have
worked well in
small-scale applications but may or may not work in other
They should be considered as alternatives
that may be
used alone or
in combination with other pest control practices.
INTEGRATED PEST MANAGEMENT:
WHAT IS IT?
The best way to control pests on
agricultural lands may be a
of the chemical, biological, cultural, and mechanical
techniques described here. Using a
combination of these pest
practices has the following advantages:
- prevention of adverse impacts upon the
the continuous use of pesticides
- prevention of the development of
resistance to particular
pesticides in pest species
- provision of a backup pest control
system in the event that
any one method fails
Ideally integrated pest management
requires well-trained pest
understand the complex factors of ecosystem interrelations.
without such resource persons there are merits
introducing and experimenting with some alternative means of
described in the previous sections, when the results of
are sickness and death to people.
Some of the most characteristic features
and goals of the integrated
management Approach are:
* The focus is on the entire pest
population and their natural
enemies operating within an
ecosystem. The agroecosystem
is the management unit.
* The objective is to maintain pest levels
pre-established economic threshold.
The goal is to manage
rather than eradicate the pest
THRESHOLD OF PEST MANAGEMENT>
* Control methods are chosen to supplement
the effects of
natural control agents (parasites,
predators, weather, etc.).
* Alleviation of the problem is long-term
and regional, rather
than localized and temporary, and the
harmful side effects
on the environment are minimized.
Thus, integrated pest
management should be part of government
* Monitoring is essential.
Pest population numbers need to be
regularly monitored, and also the
influencing pest abundance in order to
determine when to
apply control actions.
How monitoring is conducted depends
on the crop, the pest species, the
climate, the human skills,
and economic resources.
Simple monitoring procedures that
involve no special equipment or expenses
have been designed
for farmers with limited resources.
For example, with rice, a
system based on plant tapping can be
used to sample for the
Each week a farmer randomly picks 20
hills across the paddy.
He slaps the plants with force
several times with the palm of the
hand. He then counts
both adults and nymphs that fall on the
water. Finally, he
calculates the average green leafhopper
numbers per hill,
and based on this data makes decisions
whether or not the
pest needs to be controlled.
BY PLANT TAPPING>
DEFINITION OF A PESTICIDE
"Pesticide is an umbrella term used
to describe any chemical
or kills a pest, be it insect, weed, disease, or animal.
are generally classed by the type of pest they control:
(insects), herbicide (weeds), fungicide (fungus), rodenticide
nematicide (nematodes), acaricide (mites, ticks and spiders).
are also defined by their method of dispersal
mode of action, such as an ovicide, which kills the eggs
pests. Although they do not
specifically kill pests, insect growth
are considered pesticides because they modify the insect's
such a way as to halt its deleterious effects."
Pesticides used today belong to three
principal groups of
* Organochlorides are derivatives of
chlorobenzene that are
highly toxic and have long-lasting
effects. Included in this
type of chemicals are DDT, chlordane,
endrin, toxaphene, lindane, heptachlor,
* Organophosphates are highly toxic to men
Examples are phosdrin, parathion,
methyl parathion, azodrin or nuvacron,
* Carbamates are derived from carbonic
acid. Like organophosphates,
they have inhibitive or disruptive
effects on the
central nervous system, which controls
all bodily functions,
they are very poisonous and take
immediate effect. Examples
are temik, furadan, lannate, sevin,
Secretariat for Ecologically Sound
EFFECTS OF PESTICIDE USE
The use of pesticides should be limited to
in which all
other measures fail to provide control.
should seek to reduce both the frequency of application
dosage. Following are some of the
common effects of
Pesticides can be inhaled by humans or
taken into the body
skin. Body contact is a particular
problem during the
of pesticides. Failure to take safety
precautions and to
certain pesticides carefully may even result in death.
individuals suffer from pesticide poisoning every year.
annually. Fatalities have mainly
occurred among people
pesticides--farmers, crop dusters, farm workers, and
pesticide manufacturing factories. More
and more concern
focussed on the issue of poisonings attributed to eating
and meat containing pesticide residues.
Each square meter of fertile agricultural
soil contains millions
forms--insects, earthworms, oligochaete worms, nematodes,
algae, fungi, bacteria, and yeast cells.
All these organisms
absolutely necessary for soil fertility maintenance.
in: the conversion of bound nutrients
available to plants; the break up of organic matter; the fixation
and the aeration of the soil. Their
balance or equilibrium is maintained.
that do not decompose rapidly can alter this soil organism
and, ultimately, may reduce soil fertility.
earthworms, critical to some ecosystems, may be drastically
chlordane, endrin, parathion, carbametes and most
Some fungicides and herbicides seem to
microflora, thus upsetting the dynamics of most nutrients in the
Pesticides on the Balance of Nature
Most organisms in nature are regulated by
in a state of balance with their environment.
or misuse of
pesticides can interfere with this natural control system.
happens, pest problems can actually be worsened.
During the last three decades, despite a
tenfold increase in
use, crop losses to insect pests have nearly doubled.
account for this near doubling of crop losses:
- more than 300 species of insects, mites
and ticks have developed
genetic resistance to pesticides
- pesticides have inadvertently destroyed
natural enemies of
certain insect pests, resulting in pest
secondary pest outbreaks
Effects of Pesticides
Certain pesticides can also alter the
chemical makeup of
Some organochlorines can increase amounts of
elements in corn and beans. Herbicides,
accumulation of nitrates in plants, with possible toxic
livestock and other animals. These
changes in plant
can alter the physiology of certain crop plants, such as
them more susceptible to insect or pathogen attack.
2,4-D can render some crops more susceptible to pests
the Aquatic Environment
Pesticides transported from treated fields
into the aquatic
by runoff and erosion are distributed throughout water,
mud, and the
organisms living in both. The buildup
of pesticides in
a given body
of water depends on:
- how much pesticide is entering the
- the persistence of the pesticide
- the tendency of the pesticide to
bioaccumulate, or build up
within an organism and food chains
- the sites or organisms in which the
pesticide concentration is
Pesticide persistence is the length of
time a pesticide remains
active, or toxic, to target pests. Most
pesticides are rated
their persistence, as indicated in the table below.
PERSISTENCE OF CHEMICALS
Persistent 1-12 weeks
phorous com- methyl para-
pounds; thion, para-
Carbamates thion carbaryl
arsenic or lead lead
(1) A number
of organochlorine compounds are in the "non-persistent"
"moderately persistent" classifications, e.g., methoxychlor, dicofol,
In general, persistent pesticides (those
which remain biologically
longer periods) are less soluble and volatile but have a
tendency to become adsorbed (attached to particles of soil).
known of the persistent pesticides are the organochlorine
(DDT, Aldrin, Endrin, Heptachlor, etc.), the herbicide
the fungicide benomyl. These can remain
up to 14-17
years in the
soil. The longer the pesticide
persists, the greater the
that it will move from the target area via soil, water, air,
and influence adjoining ecosystems.
HOW PESTICIDES MOVE ABOUT THE ENVIRONMENT
Pesticides are applied in either liquid or
powder form. Both
forms can be
sprayed on the soil or plants. During
pesticide is lost to the air through drifting or volatilization.
application, the pesticides can travel in various ways in the
- biological degradation by soil
degradation on the soil surface, or
as a result of sunlight
- absorption by plants (which may be eaten
by animals and/or
- adsorption onto soil particles
(especially clay and organic
matter) that may move with erosion
- dissolution in water (rain or
irrigation) that becomes surface
runoff or that infiltrates into the soil,
later appearing in
surface water or groundwater supplies.
Pesticides take one pathway rather than
another depending on
a number of
factors. Principal among these
are: characteristics of
itself; the soil type; the strength and amount of rainfall;
the type of
erosion control measures being used; and the temperature.
pesticide compounds that are more water-soluble
persistent will move primarily in runoff water.
firmly adhered or adsorbed to soil particles will generally
Organic content and texture are the most
influencing how pesticides move in the soil.
properties--pH, moisture content, temperature, mineral content--may
influence pesticide persistence and movement.
greatest persistence of organochlorines is found in soils
organic matter, with high clay content and with acid pH.
pesticides compete for adsorption sites on soil particles;
moisture in the soil decreases, the amount of pesticide
increase. Some pesticides in the soil
are subject to
Leaching of pesticides is influenced by the
rate of water
flow, and the formulation, concentration, and rate of
of the pesticide. Pesticides may move
soil as well,
appearing in surface or sub-surface runoff.
of the soil
can also enhance loss of volatile pesticides.
Pesticides enter lakes, ponds, rivers, and
other waterways from
treated areas, from drift, or from direct pesticide (mainly
applications. The quantity of a
pesticide that moves into a
from treated areas depends upon topography, intensity
of rainfall, soil erodability, and land management
Improved erosion control practices can be
pesticides from entering the larger environment.
requires consideration of the methods for erosion
light of their applicability for pesticide control.
If pesticides enter a body of water in a
dissolved state, the
solution will move as the water moves.
remain in solution in the water; precipitate
out of the water
and end up in
bottom silt; be taken up by aquatic organisms; be
or chemically degraded; or more commonly become
live or dead particulate matter which eventually
the bottom as sediment. Pesticides
adsorbed on sediment
with the sediment. The finest particles
concentration of pesticide) will be transported the
will typically be the last to settle out of the water to
the bottom in
lakes or quiet water. Systems with
away pesticide pollutants tend to be more resilient
where water is static.
Until they chemically degrade, pesticides
will not disappear.
system is dynamic, even those deposited in bottom muds
may be later
churned up and carried downstream.
separate from muds and remain in the water.
the pesticides may reach the surface and volatilize
gaseous) or be degraded by sunlight. On
the bottom of a
there is often a lot of microbial activity in the organic
At the bottom, biological decomposition
creating anaerobic (without oxygen) conditions that favor the
of many pesticides.
If pesticides must be used, try to use
those that will degrade
water in order to protect nearby aquatic environments.
Also, keep in
mind that the products of pesticide degradation may be
Information appropriate for your region is
available by writing
Pesticides Action Network (PAN).
Addresses of the regional
PAN are in Appendix B.
SOME FACTORS THAT SHOULD BE CONSIDERED
BEFORE APPLYING PESTICIDES
Check with local farmers or extension
agency personnel to see
experience has been with given pesticides.
There is no
for the persistence and potency of pesticides.
depending upon local conditions.
Pest Control Measures
Check the variety of alternative
non-chemical control measures
that may meet
project needs. Become familiar with
the pesticides you may be considering.
Some of these
are described elsewhere in this chapter.
Consider the possibility of relationships
between two or more
used in the same area before applying more than one to a
When two or more pesticides are applied at
the same time,
combined toxicity may actually be greater than the sum of their
toxicities. This is called synergism.
If possible, apply pesticides well before
heavy rains if they are
to do the
most good in controlling target organisms.
The rate at
pesticides are washed off the land is usually high at first.
This rate of
loss, however, decreases reaching a steady rate, unless
weather, soil, temperature, soil moisture level, acidity, or
practices. Some pesticides have greater
losses if they are
wet soil rather than dry, especially if runoff occurs soon
application. When pesticides are
incorporated into the soil, the
runoff is not as great as when they are just left on the soil
Explore the ways in which pesticides might
move through the
to help design projects that will contribute less to
Runoff travelling from cropland to open
water can carry
As the water crosses other lands, some
pesticide is left
While the total amount entering the water is
may also be contaminated by pesticides.
damaging impacts on animals and humans.
you are going to introduce pesticides it is important to
training to those who will be applying them.
bodily exposure of those applying chemicals and
others in the area. At the very least,
read the directions
on the label
carefully. These will instruct on the
way in which the
be safely applied, the time that needs to elapse following
before the area is safe, and the relation of using the
the maturing of the crop. Also, read
the precautions on
the label and
understand the steps to take in case of emergencies
swallowing some, or coming in physical contact with the
Never reuse pesticide or herbicide
CHECKLIST FOR PROJECTING THE IMPACTS OF
CHEMICAL PESTICIDE USE AND THE
POTENTIAL FOR ALTERNATIVES
Addressing questions such as the following
will provide the
planner with a background for making informed judgments
environmentally sound pest control.
* Are chemical pesticides suggested for
* Have all pest management options been
* Are alternative pesticides available
that are relatively safer
* Are there plants with pesticidal
properties which could be
Are they locally available?
* Are the pesticides to be used in the
project recommended for
use on these particular crops by the
manufacturers? By the
* Are similar pesticides being used
locally for health purposes,
such as malaria control?
* Can a species-specific pesticide be
* Does the project design recognize the
possibility that target
species will develop resistance to the
pesticide and larger
quantities may be required each year to
control the pest?
* Is it possible to change pesticides to
reduce the likelihood of
target species developing resistance to
an important pesticide?
If so, can a schedule for implementation
* Is the pesticide persistent in
soil? Will it tend to accumulate
in the soil?
* Might the pesticide suggested for use
kill beneficial soil
* Does the pesticide tend to bioaccumulate
or biomagnify (biologically grow) in
so, which organisms would it affect in
the immediate area, if
* Is there a body of water nearby?
If so, are people downstream
highly dependent upon aquatic resources
fisheries, aquaculture, and drinking
water which might be
contaminated by an accidental discharge
of pesticides because
of the project?
What effect would contamination of the
water have on health, finances, and other?
* Is it likely that erosion will carry
pesticides into downstream
If so, could such pesticides affect fisheries,
aquaculture projects, and domestic water
* Have adequate precautions been taken to
from pesticide poisoning during
transport, storage, and
application of pesticides?
Are instructions available in local
languages with culturally sensitive
* Can pesticide applications be timed to
avoid rapid loss to
wind and rain?
* Is it possible to develop plans that can
be put into effect
easily and simply in case of an
emergency, such as accidental
pesticide pollution or physical contact?
* What alternative project designs could
be used at the site to
minimize environmental impacts from
Agroforestry systems are production
strategies designed to
more varied diet, new sources of income, stability of
minimization of risk, reduction of the incidence of insects
efficient use of labor, intensification of production with
resources, and maximum returns with low levels of technology.
Some form of
agroforestry has been practiced by many traditional
For a number of reasons such as commercial
development, cattle raising, deforestation, and population
these practices may have been abandoned.
the value of
combining trees with crops and livestock as a means of
soil, increasing the multiple uses of land, rehabilitating
sites, and diversifying to reduce risk is leading development
consider introducing or reintroducing agroforestry practices
improvements based on research and experience.
This recognition has grown out of a
combination of acknowledging
experience and scientific research.
shifting cultivation could be said to be a precursor of the
understanding of agroforestry. The
clearing of woody vegetation
for crops for
a period of years and reestablishment of forest in
period was a combination of agriculture and forest in
has been practiced in many regions.
Taungya is an
early form of
agroforestry that introduced tree seedlings planted by
combined with growing of crops in the cleared area until
canopy provided too much shade.
typically been a mixture of shrubs, food crops, and
plants in a multistoried arrangement.
For some species of
cacao interplanting with shade trees has been a necessity.
purposeful combinations of trees and crops practiced
introduction of fodder trees in fields; dispersing indigenous
fields for nutrients and fodder, as for example Acacia
millet fields; use of trees for shelter belts and hedgerows.
cropping is a recently introduced system that involves planting
management of relatively close-spaced rows of nitrogen-fixing
shrubs such as Leucaena and Gliricidia, with a crop
such as maize
in between. (Winterbottom 9.19)
DEFINITION AND CLASSIFICATION
Agroforestry denotes a "sustainable
land and crop management
strives to increase yields on a continuing basis, by
production of woody forest crops (including fruit and
crops) with arable or field crops and/or animals simultaneously
sequentially on the same unit of land, and applying management
that are compatible with the cultural practices of the
population." (International Council for Research in Agroforestry,
There are several ways to classify and
practices). The most commonly used
and arrangement of components); function (the use of
ecologic (ecosystem or climatic zone); and socio-economic scale
and level of
Agroforestry systems can be grouped as:
the use of land deliberately for the
or sequential production of agricultural
crops field and
tree crops) and forest crops (woody
- silvo-pastoral systems:
land management systems in which
forests are managed for the production
of wood, food and
fodder, as well as for the rearing of
- agro-silvo-pastoral systems:
systems in which land is managed
for the concurrent production of
agricultural (field and
tree crops) and forest crops (woody
forest plants)and for the
rearing of domesticated animals
- multipurpose forest tree production
systems: in which forest
tree species are regenerated and managed
for the ability to
produce not only wood, but leaves and/or
fruit that are
suitable for food and/or fodder
The functional basis for classifying
agroforestry systems refers
to the main
output and role of various trees, especially the woody
These would be productive functions
(production of "basic
such as food, fodder, fuelwood, and other products), or protective
conservation, soil fertility improvement, protection
windbreaks and shelterbelts, and so on).
discussed in detail later in this chapter.
On an ecological basis, systems can be
grouped for any defined
or climatic zone such as lowland humid tropics, arid
tropics, tropical highlands. They can
also be based on
zones defined by rainfall patterns or other groupings that
Scale and Level of Management
The socio-economic scale of production and
level of management
of the system
can be used as the criteria to designate systems as
intermediate, or subsistence.
Each of these ways of looking at
agroforestry systems is useful
applicable in specific situations, but for each there are limitations
so that no
single way of grouping is universally applicable.
depends upon the purpose for which it is intended.
SOME ADVANTAGES OF AGROFORESTRY SYSTEMS
By combining agriculture and forestry/tree
crop production, the
functions and objectives of forests and food crops production
can be better
achieved. There are advantages of such
agriculture and/or forestry monocultures.
* A more efficient use is made of the
natural resources. The
several vegetation layers provide for an
efficient utilization of
solar radiation, different kinds of
rooting systems at various
depths make good use of the soil and
plants can profit from the enriched
topsoil as a result of the
mineral cycling through treetops.
By a three dimensional
use of space, total growing capacity is
increased. By including
animals in the system, unused primary
also be utilized for secondary
production and nutrient recycling.
* The protective function of the trees in
relation to soil, hydrology,
and plant protection can be utilized to
hazards of environmental degradation.
It should be
kept in mind, however, that in many agroforestry
components may be competitive for light, moisture, and
trade-offs must be considered. Good
interference and enhance the complementary interactions.
* By ecological efficiency the total
production per unit of land
can be increased.
Although the production of any single
product might be less than in monocultures,
in some instances
production of the base crop may
example, in Java it has been
demonstrated that after introduction
of the tumpang-sari or taungya system,
production increased significantly.
* The various components or products of
the system might be
used as inputs for production of others
(for example, wooden
implement, green manure) and thus the
amount of commercial
inputs and investments can be decreased.
* In relation to pure forestry
plantations, the inclusion of
agricultural crops with trees, coupled
intensive agricultural practices, often
results in increased
tree production and less costs for tree
fertilization and weeding of agricultural crops may also
benefit tree growth), and provide a
wider array of products.
* Tree products can often be obtained
throughout the year
providing year-round labor opportunities
and regular income.
* Some tree products can be obtained in
off-season (e.g., dry season), when no
opportunities for other
kinds of plant production are present.
* Some tree products can be obtained
without much active
management, giving them a reserve
function for periods of
failing agricultural crops, or special
social necessities (e.g.,
building a house).
* By the production of various products a
spreading of risk is
obtained, as the various products will
be affected differently
by unfavorable conditions.
* Production can be directed towards
The dependency on the local market situation
can be adjusted according to the
farmer's need. If so desired,
the various products are entirely or
or delivered to the market, when
conditions are right.
SOME CONSTRAINTS OF AGROFORESTRY SYSTEMS
There are a number of limiting conditions
or constraints to
agroforestry systems. These constraints
and efforts made to overcome them, if agroforestry is to
* A major ecological constraint is that
agroforestry systems are
ecosystem-specific and on certain low
grade soils the choice
of suitable plant species might be
limiting, although many
trees are better adapted to poor soils
than annual crops.
* The competition between trees and food
crops, and the
priority that must be given to them to
meet basic needs,
may exclude poor farmers, who have very
little land, from
* In promoting tree planting, short term
benefits as well as
long term benefits are needed.
Economic or production
incentives need to be included.
* A common economic constraint is that
established agroforestry systems might
investment costs to get started (e.g.,
planting material, soil
For these investments, credit may
In most agroforestry systems one may need a
few years before the first yields are
obtained. In some cases,
financial support is needed to provide
for this waiting period.
* Size of plot may affect the kind of
inputs. In areas with a
high population pressure and poor soils,
the private landholdings
might be too small as viable production
this case some kind of cooperative
effort might be necessary.
* Availability of seeds and/or seedlings
is a critical variable for
Check with government offices, university
forestry or botanical departments, or
organizations involved in species
research for the best species
to meet your needs.
Then check on availability of seeds
In most cases, longer run planning includes
developing small nurseries along with
* Management of livestock sometimes can
conflict with agroforestry
ventures especially in areas where
cattle or goat
herding is being practiced.
* Wildlife is a problem in some
areas. Where elephant herds
still exist they have threatened
* Pests may also threaten agroforestry
projects--both tree and
Current infestation of locusts in some areas of
the Sahel in Africa are a problem.
* In areas with complex clan or communal
developing agroforestry systems may be
rights are a fundamental consideration
in agroforestry. They
may be a limiting factor.
* Tree tenure is also a possible
constraint. In many cases,
land on which trees may be planted and
protected is not
owned by those who planted them.
The planters, then, may
not be legally entitled to harvest the
trees or the produce of
Further, in some countries there are laws that
restrict the harvesting/cutting of trees
for any purpose
regardless of who owns the land on which
they are planted.
It is therefore necessary to check
before undertaking a tree
planting project to see:
- who owns the land
- what are the regulations about protecting
- what are regulations about harvesting
the trees and/or
produce of the trees
* Factors that may limit the participation
of people and affect
their motivation need to be
considered. In addition to land
and tree tenure these include other socio-political policies of
the government as well as some
traditional social mores.
* In all cases, it is essential that the
local population is
directly involved and traditional
farming knowledge taken
into account in the planning and design
of the system. (See
Chapter 3) Agroforestry is a complex
form of land-use and
requires adequate farming
knowledge. Local knowledge and
experience is still available about
For developing new agroforestry techniques,
traditional land use and farming systems and
education and/or extension work is essential.
ROLE OF WOMEN IN AGROFORESTRY
Women have traditionally been involved in both agriculture
and in the
use and management of trees. Most often
of trees. Yet women have often been
ignored in the
agroforestry projects. There are
significant examples of
the initiative to create possibilities for tree planting
trees to the farm system. Notable among
these are the
Movement of the National Council of Women, Kenya, The
and Ecological Education Project of Mujeres en Desarrollo
(MUDE) in the
Dominican Republic, and the Chipko movement in
Projects that involve participation of women
from the outset
more sustainable. (Fortmann and
HAVE MANY USES>
THE ROLE AND EFFECT OF TREES
Agroforestry systems are multiple use
systems in which the
components provide most of the multiple benefits.
of the tree
component can affect, directly or indirectly, the
ecosystem components, for example soil conservation, nutrient
the hydrological cycle, as well as bio-components (other
insect populations, micro-organisms).
trees these other components can to some extent be
Perhaps the most important ecological role
of trees in farmlands
effect on soil conservation.
Inclusion of trees usually increases
organic matter content, and
physical conditions of the soil.
Below is a schematic presentation of
nutrient relations and
ideal agroforestry systems in comparison with common
and forestry systems.
Hydrological Cycle and Erosion
Trees also influence hydrological
characteristics from the micro-climate
level up to
the farm and local levels.
HYDROLOGICAL CYCLE AND EROSION>
A summary of linkages between
agroforestry, land management,
conservation is found in the table on the following
EXAMPLES OF TRADITIONAL AGROFORESTRY SYSTEMS
Traditional agroforestry represents
centuries of accumulated
interaction with the environment by farmers without
scientific information, external inputs, capital, credit, and
markets. Shifting cultivation (swidden
agriculture and the
burn system) was among the earliest forms of agroforestry
These methods were sustainable under
conditions of low
pressures and long fallow periods.
LINKAGES BETWEEN AGROFORESTRY, LAND
MANAGEMENT, AND SOIL CONSERVATION
Moisture - Alley cropping, line
plantations - Use of compost,
cover- - Controlled grazing
- Incorporating organic matter into
and dispersed trees to
* Organic matter
- Crop-residue left in
fields - Rotational grazing
- Preparing micro-catchments,
contour ridges or other micro-site
* Shade to reduce
surface - Mulch
- Fire Management
Fertility - Nutrient cycling and
Nitrogen - Crop rotation
(including - Use of Animal
- Contour vegetation strips
Erosion - Surface Runoff
reduction - Contour
farming - Range
rotation - Berms, ditches,
* Establishment of
trees/ - Maintaining soil
tilth - "Grazing
reserves" - Benches or
- Waterway and gully control
features - Maintaining
maximum - Contract
grazing - Protection of stream
linked to vegetation
* Trees along
Erosion - Wind reduction
through: - Maintaining
maximum - Controlled lopping
cover for fodder
Trees - Natural
- Palisades, other physical
left when clearing new land
treatment in extreme cases
Trees - Minimum till
- Live fencing
- Stock driveways
left - Herding as opposed
- Layout of soil conservation
when laying out
fields. to letting animals
plantings to reinforce
fencelines and livestock trails.
- Alignment of livestock trails
- Borderline Trees
- Tethering or
Weber and Stoney 3.8
Throughout the tropics, traditional
agroforestry systems may
over 100 plant species per field. These
are used for
materials, firewood, tools, medicine, livestock feed, and
food. In Mexico, for example, Huastec
Indians manage a
agricultural and fallow fields, complex home gardens, and
totalling about 300 species. Small
areas around the
commonly average 80-125 useful plant species, mostly native
plants. Management of the noncrop
vegetation by the
these complex farm systems has influenced the evolution
plants and the distribution and composition of the total
noncrop communities. Similarly, the
West Java commonly contains about 100 or more plant
Of these plants, about 42% provide building
are fruit trees, 14% are vegetables, and the remainder
ornamentals, medicinal plants, spices, and cash crops.
Javanese agroforestry systems usually
consist of three
kebun-campuran and talun--each stage serving a
function (Christanty 9.1). The first
state, kebun, is usually
a mixture of annual crops. This stage
has a high
value since most of the crops are sold for cash.
seedlings have begun to grow into the field and there is
for annual crops. The kebun gradually
evolves into a
where annuals are mixed with half-grown perennials.
value of this stage is not as high, but it has a
biophysical value, as it promotes soil and water conservation.
harvesting the annuals, the field is usually abandoned for two
years to become dominated by perennials.
This stage is
talun, the climax stage in the talun-kebun system.
both economic and biophysical values.
To begin the process after clearing the
forest, the land can be
dryland rice (huma) or wet rice paddy (sawah), depending
irrigation water is available.
Alternatively, the land can
with a mixture of annual crops, the first stage (kebun).
In some areas
the first agroforestry stage (kebun) is developed after
the dryland rice (huma) by following the dryland rice with
crops. If the kebun is mixed with tree
crops or bamboo,
second stage (kebun campuran), a mixed garden.
perennials will dominate and create the third stage, a
crop garden (talun). (See figure on
Agroforestry systems are also widespread
among many tribal
example, in the Amazon region, the Himalayas, the
and the Sub-Saharan countries of Africa.
cultivators, the Bora in Brazil do not have a transition
cropping and fallow, but rather a continuum from a cropping
dominated by crops to an old fallow composed entirely of
vegetation. This process may take as
long as 35 years or
Given current population pressure trends and
rates in the
area, this system may not be sustainable in the future.
DESIGN OF AGROFORESTRY COMBINATIONS
Arrangement of component plant species in
space and time is
important but difficult factor in agroforestry because of the
variations in the types of agroforestry practices and the conditions
they are practiced. When attempting to
or to devise new ones, it is therefore necessary to know
the short-term productivity of the plants and the
sustainability of the system. Thus,
depending on whether
interaction is favorable or not, plant arrangements have
to be devised
to maximize the beneficial interactions and minimize
undesirable ones. There are also
several other factors to be
account, such as:
- growth habits and growth requirements of
species when grown near other species
- simplicity of management procedures for
the whole system
- realization of additional benefits such
as soil conservation
plant arrangement patterns in agroforestry are very
One way to develop agroforestry is to
imitate the structure and
natural communities. In the humid
can be particularly appropriate models for the design of
ecosystems. In Costa Rica, plant
spatial and temporal
replacements of wild species by botanically
structurally/ecologically similar plants.
the natural system such as Heliconia species, cucurbitaceous
Ipomoea species, legume vines, shrubs, grasses, and
were simulated by plantain, squash varieties, yams,
potatoes, local bean crops, Cajanus cajan, corn/sorghum/rice,
cashew, and Cassava species, respectively.
By years two
fast-growing tree crops (for example, Brazil nuts, peach,
rosewood) may form an additional stratum, thus maintaining a
crop cover, avoiding site degradation and nutrient leaching
crop yields throughout the year.
Some agroforestry systems are given below
based on materials
the International Council on Agroforestry (ICRAF),
(Spicer 9.12) Information about the choice
of species and
planting and management schedule needs to be sought locally
regionally. Some of the techniques
discussed below are described
Cropping in High Potential Areas
Alley cropping is appropriate for home
gardens and for cultivated
land. This system can be helpful in the
- providing green manure or mulch for
companion food crops;
in this way plant nutrients are recycled
from deeper soil
- providing prunings, applied as mulch,
and shade during the
- suppressing weeds
- providing favorable conditions for soil
macro- and micro-organisms;
when planted along the contours of
to provide a barrier to control soil
- providing prunings for browse, staking
material and firewood
- providing biologically fixed nitrogen to
the companion crop
Trees and shrubs suitable for alley cropping should meet most
- can be established easily
- grow rapidly
- have a deep root system
- produce heavy foliage
- regenerate readily after pruning
- have good coppicing ability
- are easy to eradicate
- provide useful by-products
species are generally preferable because they give the
cropping system flexibility. Leguminous
trees and shrubs,
their ability to fix atmospheric nitrogen, are preferred
Contour planting is useful where there are
- poor or easily depleted soils
- sloping (erodible) land as well as
- medium to high population density
planting can help in the following ways:
- to restore/improve soil nutrient and
increase organic material
- to reduce soil and water run-off
- to spread the risk of crop failure during
seasons by moderating the effects of
evaporation on exposed land
- to add wood products for home
consumption or sale
The appropriate farming systems in which
to utilize this
permanent crop cultivation, medium to small farm size,
and medium to
high labor input available per unit of land.
species can be established at the start of the growing season
them the opportunity to establish while livestock are
kept out of
the arable areas.
Fodder Bank - Cut and Carry
Establishment of fodder banks is useful
where there is high
density and nearby markets for livestock products.
can improve fodder availability and quality, particularly
late dry and early wet season. They
also seem to
soil nutrients and organic matter content.
Creating these banks of trees will
facilitate ease of fencing.
(blocks, strips, lines) of trees (mainly leafy fodder) can
near cattle kraals, in homestead gardens, in arable lands
areas, along watercourses and around the margins of
The appropriate farming system for fodder
banks is on the
where there is intensive land use, a kraal feeding system
labor input per animal.
Fodder Bank - Grazing
Fodder banks for grazing are usually
located in grazing
They may be on hills (especially pod
species), on uplands,
watercourses, and on borders of watering places.
Fodder banks for grazing will improve
fodder availability and
low to medium population density areas, and restore/improve
nutrients and level of organic materials.
A mixture of trees (pods and leaves) and
grasses (fenced) can
be planted in
blocks. Pod and foliar species should
be planted in
Scattered trees need to be protected by
thorns. The pod
provide a feed supplement for cattle during the early
Species selected must be adaptable to
local climate and soil as
having other attributes such as palatability, high protein
of establishment by direct seeding, transplanting or
setting. Pod trees for hills and
uplands seed from August
December. Self-seeding varieties in
watering places must be
up to 6 months waterlogging. They
should have a limited
rate in order not to have a detrimental effect on the
the area. Foliar species should be
maintained at the
In the homestead arable area and garden it
is useful to
fruit-producing trees. Scattered trees,
planted near the home
for protection from animals. Fruit
trees may also be
create boundaries around the homestead.
nutrition, produce fruit for sale, provide shade, and firewood.
Use of the system is limited by the
availability of improved
varieties. There needs to be adequate
extension support to help
of varieties and management, e.g., propagation, grafting
planting, mulching, watering, and control of weeds,
Hedges and living fences are useful in
areas with medium to
population density and where animals roam freely in the area.
or hedges provide an alternative to constructed fencing
* The demarcation of boundaries; for
schools, farms and fields (particularly
paddocks in grazing
* Protection from the ravages of
free-grazing livestock; for example
crop lands, orchards, nurseries,
protein banks (grazing schemes),
vegetable gardens and
hedges can offer secondary benefits, such as reducing the
influence of wind, and they provide not only organic material
soils but also multiple tree products (firewood, poles,
medicines, etc.) to the local community.
The appropriate farming system for living
fences is the small
sized farm with permanent crop cultivation.
Mixed intercropping is most useful in poor
or easily depleted
flat to gently sloping land, in areas of medium population
This system will serve to restore/improve
soil nutrients and
The appropriate farming system is that
with permanent crop
medium to small farm size using medium labor input per
unit of land
and no animal cultivation (at high tree densities).
Multistorey Planting of Domestic/Industrial
Multistorey tree crops are best suited to
home gardens and as
storey of productive trees in hedges or plantations.
planting fits well in areas with high population density
rainfall. It will contribute resources
for tree products, some
of which will
supply household requirements. This may
expenditures, and add to cash income.
Multistorey tree crop
appropriate for small sized farm systems with high labor
unit of area.
Tree Planting Around Watering Places and
Tree planting around watering places and
dams is appropriate
is a high population density or presence of animals in
Planting trees will reduce the damage to the
dams that is caused by livestock. It
will also provide
wood products for home consumption or sale.
can be laid
out in strips or planted in woodlots. A
mixture of trees
is helpful. Planting can also be spaced
and mixed with
species. The appropriate farm system is
a small to
farm with permanent crop cultivation.
Selective clearing is useful in areas with
substantial acreage of
woodlands. It is particularly useful in
is a low population density. Selective
functional indigenous vegetation, biodiversity, and help to
supplies of woodland products and germ plasm.
selected trees are left in croplands.
Strips of trees and
left around newly opened plots, between fields and along
and watercourses. The appropriate farm
system is the
medium to large
farm with low labor input per unit area.
Woodlot Planting for Fuelwood and Poles
Woodlot planting for fuelwood and poles is
areas, and for all areas with a market for poles and/or
Such woodlots can produce fuelwood/poles to
household industries requirements. They
may also add
to the cash
flow of the family. Woodlots should be
"live fences" should be established within the protection
the fence. Firebreaks are
recommended. The appropriate
is the medium to large farm with low to medium labor
unit area. The system is also
appropriate for tobacco
barn construction as well as curing) and small industries
works or small mines.
More detail about these systems is
available from the International
Research in Agroforestry, Nairobi, Kenya.
A CHECKLIST FOR SUSTAINABLE
DEVELOPMENT, EXAMPLES OF
SYSTEMS, AND LONG TERM
This manual has reviewed the relation
between the environment
agricultural projects. With a framework
for planning, the
technical information and other considerations have been
This is only a start.
Now you have to adapt the information
here to the
local situation and seek the specific technical assistance
information identified with the help of this manual.
The technical guidelines and information
are designed to give
development worker a better understanding and to indicate the
effects. In most cases the decisions to
be made involve
For example, should the community introduce
fertilizer that will produce quick results but is expensive
and does not
improve the quality of the soil; or alternatively, should
they try to
introduce techniques for organic fertilizing that will
soil but incur increased labor costs and sometimes
alternative uses of the local materials?
The ideals sometimes advocated here also
may not be possible.
about trade-offs should be made by those who will bear the
burden of the results. The enlightened
contribute to community understanding through consciousness
A CHECKLIST FOR DEVELOPING
This checklist of concepts helpful for
projects has been prepared to assist you in utilizing the
in this book.
* Use land according to its use
capabilities, thus avoid if
possible slopes prone to landslides.
Where these are in use,
maintain cover to conserve the soil.
* Ensure that, with the exception of
edible and useful products
harvested or taken out of the system
from time to time, as
much recycling of materials and wastes
as possible occurs.
* Control pests by biological and
mechanical methods insofar
* Utilize local resources, including human
and animal energy,
without increasing the level of
* Do not overlook local varieties of
crops, and conserve local
wild plants and animals that may be
important food sources,
as well as genetic resources.
* Satisfy local consumption first in
* Focus on species with multi-use
potentials in combining
nutritional needs (legumes, fruits,
vegetables, animals with
high protein yields per unit weight)
with other uses for
example, crafts, construction materials,
and drugs, especially
in densely populated areas).
* Combine a variety of species with
products, and contributions.
* Exploit the full range of ecosystems
which may differ in soil,
water, temperature, altitude, slope,
fertility, etc., within a
field or region.
* Involve community and farmers in the
management, and evaluation of the
* Involve women, as well as men, in
decision making and
* Include cultural values (religious or
other) and beliefs in the
development of plans for conservation of
species and undisturbed
* Build upon existing social organizations
and mutual assistance
customs for environmental rehabilitation
* Consider the non-quantifiable and
indirect benefits and costs
in any economic analysis for decision
* In all cases, focus on minimizing
negative impacts while
trying to introduce improvements.
* Check the land tenure problems of the
farmers and include
consideration of them in planning.
* Ensure the program has a sufficiently
To this checklist, however, the
development worker may want
others. Other guidelines may be based
on such things as: 1)
the goals or
philosophy of the the local residents and the sponsoring
individual, and 2) the realities of the context within
project will occur (limits of time, funding, scope).
For small-scale, community-based efforts
appropriate technology and/or appropriate development
some points that should be considered are:
- optimal use of locally available
material and human
- strong community involvement and support
- community-identified and/or community
- high potential for enhancing community
self-reliance in both
short and long-range terms
- technologies that can be taught from one
farmer to another
so that a multiplier effect is achieved
- availability and allocation of funds
- high priority on use and adaptation of
- necessity to complete activity during a
certain time frame
of principles developed by World Neighbors (Bunch
reproduced on the next page. These
principles can help
main goals of any agricultural program which are:
- that farmers develop the ability to
solve their own problems
- that they learn about and adapt
that build on traditional practices
- that the program achieves early but
As boundaries within which the project
must operate regardless
design aspect, these principles serve two major purposes:
provide a framework for designing projects; second, they
can be used
to enable the planner to make wise choices regarding
among possible project designs. For
example, the planner
these guidelines knows that any design he or she comes up
include a strong community participation and/or involvement
the planner judging a project against these guidelines
must take a
closer look at an effort which does not indicate
PRINCIPLES OF SMALL SCALE PROJECTS>
EXAMPLES OF TRADITIONAL RESOURCE
The following table provides examples of
followed by traditional farmers in developing countries, to
environmental constraints in a variety of circumstances.
that you consider the perspective of traditional systems
already solved some of the resource management questions
raised in the
earlier chapters. (Altieri 10.1)
SOME EXAMPLES OF SOIL,
AND VEGETATION MANAGEMENT
SYSTEMS USED BY
THROUGHOUT THE WORLD
space Maximum utilization
cropping, home gardens,
altitudinal crop zonation,
slopes Erosion control,
Terracing, contour farming,
and dead barriers, mulching,
diversification and/or fallow cover,
use (planting so
that each crop has
soil Sustain soil
fertility Natural and/or
crop rotations and
with legumes, litter
composting, manuring, green
grazing animals in
fields, night soil and household
refuse, mounding with
hills used as fertilizer
of alluvial deposits,
use of aquatic weeds and
cropping with legumes,
leaves, branches, and
other debris, burning
excess Utilization of
Raised field agriculture
water bodies in
chinampas, tablones), ditched
fields, diking, etc.
or Lowering of
Planting of appropriate
logging water table
water Optimum use of
Control of floodwater with
canals and checkdams.
fields dug down to ground
level. Splash irrigation.
fed from ponded
rainfall Best utilization
Use of drought tolerant crop
species and varieties,
use of weather
that best utilize end of
rainy season, use of crops
Shade reduction or
plant spacings, thinning,
use of shade tolerant crops, increased
fences, tree rows; weeding,
incidence Crop protection
Overplanting, allowing some
pest damage, scaring away
low pest popula-
pests, setting traps, hedging
and/or fencing, use of
direct picking, use of
repellents, planting in
low pest potential, etc.
EVALUATION OF LOCAL AGRO-ECOSYSTEMS
The long-term performance of local
agricultural systems can be
four properties: (See Conway 10.4)
Relates to the ability of an agricultural
system to maintain production through
time in the face of
long-term ecological and/or socio-economic
Sustainability of small-scale farming
systems depends on the
accessibility to resource poor farmers
of technologies and
Expresses the consistency of production of a
cropping system through time under a
given set of environmental,
economic, and management
trends can be expressed as yield by
area, season, or year.
Both stability and sustainability have
two dimensions--time and
disturbance. These terms
then have two connotations--persistence
Persistence is the tendency of the system
to look the same through time; resistance
is its capacity to
Relates to the ability of a system to recover from
disturbances of perturbations.
Perturbations can be salinity/acidity
problems, pests, flood/drought, etc.
Is a measure of how equitably the products of the
farm (income, productions, etc.) or
the inputs used (labor,
land, etc.) are distributed among the
local producers and
consumers and between men and women.
ADDITIONAL ASSISTANCE OR INFORMATION
At this or any point in the planning
process, there may be
seeking additional assistance. For
may show clearly that the area requires access to more
expertise, as in the case of working with a degraded
Consultation with specialists such as local
resource managers, ecologists, sociologists, resource economists
agricultural extension officers would be recommended before going
very far with
the planning process.
Second, even when and if the project
seems to be relatively
easily tackled, it is a good idea to seek an objective
The development worker can do this by
date, making recommendations based on those findings,
planned activities, and getting in touch with experts who
with community based projects. If
possible, the development
provide a community profile and natural environment
These can provide an excellent base from
offer assistance even from a distance.
There are a number of other ways to bring
insight to the planning process:
* Seek advice from local residents.
Their knowledge of local
conditions and past environmental
impacts is not usually
available elsewhere and is a resource that is much too
important to be overlooked.
* Contact local universities and
government agencies, and local
representatives of international
organizations as well as local
NGOs, churches and missionaries.
Often they have a great
deal of pertinent information on local
soils, climate, terrain,
and upon plants and animals native to
the region. Or they
may have insights and valuable
suggestions about other
* Using local resource people, organize
team to observe possible project
sites. The team can then
discuss the project from their
respective viewpoints. Collectively,
the team may be able to identify potential
will have to be accounted for in the
project design. Depending
upon the type of project, the team
might include representatives
from several of these fields:
soil science, entomology, and so on.
* As planning and investigation continues
locally, get in touch
with other organizations.
Network with nongovernmental
organizations in the area or region.
Through outside assistance the planner
can test the reality and
of the project. Some planners may
prefer to have the
reviewed only after the needs identification and assessment
complete. Other planners may choose to
have the material
several points. For those who wish to
use such services,
they may be
available locally, or through international non-governmental
A list of organizations that can help is
2: The Relation of Agriculture and
The Scientific Basis of
and F.M. Courtney.
Analysis for Research and
International Institute for
Cox, G.W. and M.P. Atkins.
Agricultural Ecology: An
Analysis of World Food Production
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LIST OF RESOURCE
Environment Network (ANEN)
Social Development Center
Corner Real Street
Education and Technology (CET)
Agronomico Tropical de Investigacion y Ensenanza (CATIE)
in Development, Inc.
Drive, Room 1842
New York, New
York 10115, USA
Liaison Centre (ELC)
and Development in the Third World
P.O. Box MP 83
Institute for Economic and Social Development
08 BP 8
Abidjan 08, IVORY COAST
P.O. Box 14022
Centre for Low External-Input Agriculture (ILEIA)
P.O. Box 64
Leusden, THE NETHERLANDS
Alternative Agriculture, Inc.
Road, Suyite 117
Consumer Policy Research
New York 10553, USA
Alliance for Sustainable Agriculture (IASA)
University Avenue, S.E., Room 202
Minnesota 55414, USA
Council for Research in Agroforestry (ICRAF)
Institute for Environment and Development (IIED)
Massachusetts Avenue, N.W.
D.C. 20036, USA
Institute of Tropical Agriculture (IITA)
Organizaton of Consumers Unions (IOCU)
P.O. Box 1045
Rice Research Institute (IRRI)
P.O. Box 933
Institute of Organic Farming (KIOF)
Action Network International (PAN)
Environment Liaison Centre
P.O. Box 72461
International Organization of Consumers
P.O. Box 1045
10830 Penang, MALAYSIA
22, rue des Bollandistes
1040 Brussels, BELGIUM
Pesticide Education and Action Project
P.O. Box 610
San Francisco, California
Malaysia (Friends of the Earth)
Technical Assistance (VITA)
Lynn Street, Suite 200
Virginia 22209, USA
absorb - To
suck in as in a blotter.
adsorb - To
adhere to the surface of as ions on molecules.
biomass - Total weight and molecules of living materials.
aquifer - An
underground layer of rock that is porous and permeable
store significant quantities of water.
- Mechanisms, techniques, and processes introduced
- Refers to substances that can readily be decomposed
- The critical multiplicity of species that creates and
biomass - The
total weight of all the living organisms in a given
Living or derived from living things.
action - The movement of water upward against the force
through small openings. The liquid is
pulled upward by
attractions between the water molecules and the sides of
capacity - The maximum number of individuals of a given
can be supported by a particular environment.
community - A natural system that represents the end, or
apex, of an
Made up of solid, liquid, or gaseous substances of very
- Reduction of nitrates to gaseous state by certain
that produces nitrogen.
- The process whereby lands that have been disturbed
phenomenon (e.g., drought, flooding) or people
processes (e.g., improper farming practices) are converted to
cropping - Growing two crops in the same year in sequence,
transplanting one after the harvest of the other (same
niche - The description of the unique functions and
an organism in an ecosystem.
ecosystem - A
group of plants and animals occurring together plus
that part of
the physical environment with which they interact.
defined to be nearly self-contained, so that the matter
and out of it is small compared to the quantities that
internally recycled in a continuous exchange of the essentials of
- The enrichment of a body of water by nutrients,
consequent deterioration of its quality for human purposes.
Vaporization of water from surfaces.
- The conversion of liquid water to water vapor
transpiration followed by evaporation from the leaf surface.
(economic) - The portion of the cost of a product that
accounted for by the manufacturer but is borne by some other
society. An example is the cost of
from a manufacturing operation.
system - The manner in which a particular set of farm
assembled within its environment, by means of technology,
production of primary agricultural products.
processing beyond that normally performed on the
farm for the
particular crop or animal product. It
used in marketing the product.
food chain -
An idealized pattern of flow of energy m a natural
In the classical food chain, plants are
eaten only by
consumers, primary consumers are eaten only by secondary
secondary consumers only by tertiary consumers, and so
See also food web.
food web -
The pattern of food consumption in a natural ecosystem.
organism may obtain nourishment from many different
levels and thus give rise to a complex, interwoven series of
revolution - The realization of increased crop yields in many
to the developing of new high-yielding
strains of wheat,
other grains in the 1960s. The second
green revolution is
use of the
techniques of genetic engineering to improve agricultural
Water that has accumulated in the ground and is
by infiltration of surface water.
season - Used in a general way to refer to the period of
the year when
(most) crops are grown, e.g. the rainy season.
- The period required for an annual crop to complete
cycle of establishment, growth and production of harvested
Place where plant or animal lives.
hectare - A
metric measure of surface area. One
hectare is equal to
10,000 sq. m.
or 2.47 acres.
herbicide - A
chemical used to control unwanted plants.
humus - The
complex mixture of decayed organic matter that is an
of healthy soil.
cycle (water cycle) - The way water moves in a
cycle in all
its forms, on the earth.
- The process whereby water filters or soaks into soil as
running off the surface.
- Two or more crops grown simultaneously in the
alternate, or paired rows in the same area.
laterite - A
soil type found in certain humid tropical regions that
large proportion of aluminum and iron oxides and only a
concentration of organic matter. Laterite
soils cannot support
The extraction, usually by water, of the soluble components
of a mass of
material. In soil chemistry, leaching
the loss of
surface nutrients by their percolation downward below the
legume - An
plant of the family Leguminosae, such as peas, beans,
alfalfa. Bacteria living on the roots
of legumes change atmospheric
[N.sub.2], to nitrogen-containing salts that can be readily
by most plants.
factors (law of) - A biological law that states that the
growth of an
organism (or a population of organisms) is limited by
that is least available in the ecosystem.
litter - The
intact and partially decayed organic matter lying on top
of the soil.
- The process of gradual oxidation of organic matter
soil that leaves just the gritty mineral components of the
cropping - Two or more crops are grown simultaneously in
field at the same time, but not in row arrangements.
called mixed intercropping.)
planting - Growing a single crop on the land at one
particularly the repetitive growing of the same crop on the
year after year.
Leaves, straw, peat moss, or other material spread around
prevent evaporation of water from soil and roots.
cropping - Growing more than one crop on the same land
year. Within this concept there are
many possible patterns of
arrangement in space and time.
selection - A series of events occurring in natural ecosystems
eliminates some members of a population and spares those
endowed with certain characteristics that are favorable
farming - A system of farming using no chemical fertilizers
outputs - The
products (for rainfed agriculture, crops), services (e.g.
recreational facilities) or other benefits (e.g. wildlife
resulting from the use of land.
The process of water seeping through cracks and
pores of soil
- The process by which chlorophyll-bearing plants
from the Sun to convert carbon dioxide and water to
The impairment of the quality of some portion of the
by the addition of harmful impurities.
The breeding group to which an organism belongs in
A population is generally very much smaller
than an entire
because all the members of a species are seldom in close
predator - An
animal that attacks, skills, and eats other animals;
an organism that eats other organisms.
consumer - An animal that eats plants.
farming - The growing of crops or animals under conditions
rainfall. Water may be stored in the
crop field by bunding,
lowland rainfed rice, but no water is available from
water storage areas.
- When irrigation water is applied to farmlands, much
evaporates, leaving the salts behind.
Salinization is the process
minerals accumulate until the fertility of the soil is
cultivation - Several crop years are followed by several
with the land not under management during the fallow.
cultivation may involve shifts around a permanent
village site, or the entire living area may shift location
as the fields
for cultivation are moved.
slash and burn
- A specific type of shifting cultivation in high
areas where bush or tree growth occurs during the fallow
The fallow growth is cleared by cutting and
belt - The layer of soil from which water can be
drawn to the
surface by capillary action.
structure - The manner in which soil particles are loosely stuck
form larger clumps and aggregates usually with considerable
air space in
cropping - Growing two or more crops in different strips
field wide enough for independent cultivation.
enough to give greater association among the crops in the
between the different crops.
diversity - A measure of the way in which the canopy
or soil cover
is organized in layers in a cropping or forestry system.
The foundation provided by the soil to support plant
The sequence of changes through which an ecosystem
the course of time. Primary succession
is a sequence
when the terrain is initially lifeless, or almost so.
succession is the series of community changes that takes
disturbed areas where some regrowth is taking place.
- Includes all bodies of water--lakes, rivers, ponds,
streams - on
the surface of the earth in contrast to ground water that
A measure of the constancy of agricultural production
in the long
use - Continuing use of land without severe or permanent
of the resources of the land.
The intimate association of two organisms that provides
benefit to both.
inversions - A meteorological condition in which the
cool air remain stagnant leading to concentration pollutants.
The level of population of insect pests beyond which any
level - The minimal dose of a toxic substance that causes
substance - Any substance whose physiological action is
- The passage of water through the tissues of plants,
through leaf surfaces.
- Level of nourishment. A plant that
directly from the sun occupies the first level and is called an
An organism that consumes the tissue of an
second trophic level, and an organism that eats the
had eaten autotrophs occupies the third trophic level.
vector - An
animal, such as an insect, that transmits a disease - producing
one host to another.
- Process of a liquid or solid becoming gaseous.
pollution - The deterioration of the quality of water that
the addition of impurities.
ABOUT THE AUTHOR
Altieri is an Associate Professor and Associate Entomologist
University of California, Berkeley. Dr.
Altieri, a native of
a Ph.D. in Entomology at the University of Florida in
studied agronomy and agroecology in Latin America.
research has centered on methods to enhance naturally
introduced biological control agents of pests, and
of plants and pests, in annual agricultural systems and
His research has been based in North, South,
has published extensively in the fields of agroecology,
agriculture, entomology, alternative agriculture, and pest
Among his publications are the following
The Scientific Basis of Alternative
Agroecosystems: Ecological Approaches,
ABOUT THE EDITOR
Helen Vukasin has been active in the field of environment
development. In 1979 she became
associated with CODEL
and helped to
develop the CODEL Environment and Development
Working with indigenous organizations in
the Program fosters natural resource management in
development projects particularly emphasizing people's
in the process.
to serving as a consultant to CODEL, Ms. Vukasin is
Program Associate with the Development Institute of the
California at Los Angeles. She is
actively interested in
in natural resource management and in contributing to
about ways to foster people's participation in development