Conservation agriculture case studies in latin america and africa

ISSN 0253-2050

Conservation agriculture
Case studies in Latin America
and Africa

Empirical evidence has been accumulating that sustainable intensification of crop
production is technically feasible and economically profitable. Added benefits are the
improvement of the quality of the natural resources and protection of the environment in
currently unimproved or degraded areas, provided farmers participate fully in all stages of
technology development and extension. This has led to what is called “conservation
agriculture”. Three criteria, i.e. no mechanical soil disturbance, permanent soil cover and
crop rotations, distinguish conservation agriculture from a conventional agricultural
system. This publication demonstrates how conservation agriculture can increase crop
production while reducing erosion and reversing soil fertility decline, thus improving rural
livelihoods and restoring the environment in developing countries. The document is based
on testimonies and experiences of farmers and extensionists in Latin America and Africa.

FAO
SOILS
BULLETIN

78


Cover photograph by FAO. Zero tillage, Argentina.


Conservation agriculture
Case studies in Latin America
and Africa

FAO
SOILS
BULLETIN

78

Land and Plant Nutrition Management Service
Land and Water Development Division

Rome, 2001


The designations employed and the presentation of the material in
this information product do not imply the expression of any opinion
whatsoever on the part of the Food and Agriculture Organization
of the United Nations concerning the legal status of any country,
territory, city or area or of its authorities, or concerning the
delimitation of its frontiers or boundaries.

ISBN 92-5-104625-5

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by e-mail to

© FAO

2001


Conservation agriculture – case studies in Latin America and Africa

iii

Preface

The purpose of this publication is to show how conservation agriculture can increase crop production
while reducing erosion and reversing soil fertility decline, improving rural livelihoods and restoring the
environment in developing countries. Soil organic matter and biological activity in the rooting zone,
stimulated by continual additions of fresh organic material (crop residues and cover crops) are the basis
of conservation agriculture, as described in the first chapter.
A review of conservation-effective systems of land use in Africa and Latin America is used to present a
set of conditions necessary for farming systems to be conservation-effective and sustainable in the long
run. As described in the second chapter, these experiences have demonstrated that the development of
intensive production systems in the tropics is technically feasible and economically profitable, while
improving the quality of the natural resources and protecting the environment. These production systems
allow a more adequate land use, which in turn generate more nutrients in the soil and improve its water
retention capacity. Additionally, agro-biodiversity and carbon sequestration are enhanced through these
conservation-effective systems.
The farming systems represent a wide range of geographic and resource features and contrasting
sociological conditions. They include the reduction or elimination of slash and burn in Honduras, the
development of minimum tillage and direct drilling practices on small farms in Brazil, the liberation of
areas through intensification of the livestock sector in Costa Rica, the mass adoption of zero tillage

practices in El Salvador, biomass transfer to increase soil fertility in Kenya, the use of stover for both
livestock and conservation purposes in the United Republic of Tanzania, a historical perspective of soil
and water conservation in Malawi and the gradual improvement of poor agricultural lands in Ethiopia.
Farmers have responded rapidly to market opportunities where they have been confident that they can
sell their entire produce that is surplus to family requirements.
As shown in the third chapter, adaptations by farmers, either in their farming system or in the new
technology, have to be supported by institutions, extension services, research and policies. All cases
illustrate the importance of cover crop species in the farming system, but in general these species have
not been adequately studied. Much research has been weak on socio-economic variables or even ignored
them. This has often resulted in inappropriate promotional strategies or messages and a poor understanding
by policymakers of possibilities for improved use of natural resources. In all cases the role and policies of
governments have been of crucial importance, particularly with regard to creation of farmers’ groups,
land rights, input supply and credit schemes, incentives and penalties, and availability of and accessibility
to information.
The cases demonstrate the need for policy environments, institutions, and practices to be integrated to
meet the demand for food, to reduce poverty, and to utilise resources in an environmentally, socially, and
financially sustainable way. They illustrate the importance of production systems that are capable of
continually adapting to changing social, economic and environmental conditions. Additionally, the cases
show the importance of reliable support facilities to facilitate the transition of farms from subsistence to
more intensive systems of farming.


iv

Acknowledgements

This publication which was prepared by Alexandra Bot, FAO Consultant, and José Benites, Technical
Officer, Land and Plant Nutrition Management Service, is based on interviews with many farmers,
scientists, and senior managers of public and private institutions visited in Brazil, Costa Rica, El Salvador,
Honduras, Kenya, Malawi, United Republic of Tanzania, Zimbabwe and South Africa. These people are

involved in ongoing projects of international organizations, such as FAO and the World Bank, or of nongovernmental and governmental organizations in the mentioned countries.
The authors would particularly like to acknowledge the invaluable help provided by the main collaborators
in the countries covered:
Telmo Amado (Federal University of Santa Maria, Brazil); Roberto Azofeifa, (FAO, Costa Rica); Bill
Berry (KwaZulu-Natal Department of Agriculture and Environmental Affairs, South Africa); Brian Birch
(KwaZulu-Natal Department of Agriculture and Environmental Affairs, South Africa); Andreas Böhringer
(ICRAF, Malawi); Trent Bunderson (Washington State University, USA); Brian Burgess (Malawi); Mario
Chavez (Ministry of Agriculture and Livestock, Costa Rica); Rodney Cheatle (Farmers Own Ltd, Kenya);
Ian Cherret (FAO, Honduras); Horacio Chi (Ministry of Agriculture and Livestock, Costa Rica); Christina
Choto (Centro de Tecnología Agrícola, Ministerio de Agricultura y Ganadería, El Salvador); Edward
Chuma (Institute for Environmental Studies, Zimbabwe); William Critchley (Vrije Universiteit Amsterdam,
The Netherlands); Diógenes Cubero (FAO, Costa Rica); Pieter Dercksen (FAO, Costa Rica); Michelle
Deugd (FAO, Honduras); Hinton Estates (Agriway, Zimbabwe); Jim Findlay (Agrecon Consultants, South
Africa); German Flores (Lempirasur, Honduras); Valdemar Hercilio de Freitas (EPAGRI, Brazil); Jorge
Garay (Lempirasur, Honduras); Amadu Hiang (ICRAF, Kenya); John Landers (Associação de Plantio
Direto no Cerrado, Brazil); Wilfred Mariki (Selian Agricultural Research Institute, Tanzania); Nicholaus
Massawe (Selian Agricultural Research Institute, Tanzania); João Mielniczuk (University of Porto Alegre,
Brazil); Vincent Mkandawire (Ministry of Agriculture and Irrigation, Malawi); Osmar de Moraes (EPAGRI,
Brazil); Ant Muirhead (No Till Club, South Africa); Qureish Noordin (ICRAF, Kenya); Alan Norton
(Agriway, Zimbabwe); Brian Oldreive (Agriway, Zimbabwe); José Miguel Reichert (Federal University
of Santa Maria, Brazil); Bill Russell (No Till Club, South Africa); Gustavo Sain (CIMMYT, Costa Rica);
Milton da Veiga (EPAGRI, Brazil); Jan van Wambeke (FAO, El Salvador); Richard Winkfield (Agricultural
Research Trust, Zimbabwe).
Several people contributed to the development of this publication. The authors would like to acknowledge
the assistance of Francis Shaxson, Richard Fowler, Romualdo Hernández, Paul Mueller, Rob van Haarlem
and Willem Hoogmoed. The valuable comments provided by Robert Brinkman, Sally Bunning, Rudy
Dudal, Theodor Friedrich and Petra van de Kop on draft versions of the document are highly appreciated.
In the production of this publication, the authors have been effectively assisted by Sandrine Vaneph and
Lynette Chalk-Contreras.

Conservation agriculture – case studies in Latin America and Africa

v

Contents
PREFACE

III

ACKNOWLEDGEMENTS

IV

ACRONYMS

VI

1. INTRODUCTION

1

2. CONCEPTS AND IMPACTS OF CONSERVATION AGRICULTURE
Concepts
Changing mentalities
Combating land degradation and improvement of land productivity
Socio-economic advantages
Impacts on the environment
Impact of management practices on soil fauna and soil fertility
Mitigating climate changes and greenhouse gases

Reduction of contamination and water pollution
Enhancement of biodiversity
Less vulnerability to natural disasters

7
7
8
10
12
13
14
16
17
18
18

3. RURAL COMMUNITIES ACTIVELY IMPLEMENTING CONSERVATION AGRICULTURE
Organization: the role of farmers’ groups and non-governmental
organizations
Implementing conservation agriculture practices

21

4. ENABLING COMMUNITY-BASED PROJECTS
Appropriate scenarios for conservation agriculture
Designing community-based projects: tools and practices
Involvement of all stakeholders
Institutional and policy considerations
Laws and regulations
Incentives and restrictions

Land tenure
Conservation agriculture linkages with international initiatives

33
34
34
37
39
41
42
44
46

5. CONCLUSIONS

49

REFERENCES

51

ANNEX 1 KEY CONCEPTS AND DEFINITIONS

55

ANNEX 2 THE SOIL ECOSYSTEM

63

22

24


vi

List of boxes

Page
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19
20.
21.

Principles of conservation agriculture
Key features of conservation agriculture systems
Agro-environmental features of conservation agriculture
Reasons for the slow research response to zero tillage in Brazil prior to 1995
Conservation structures and practices in southern Brazil
Farmers’ benefits – Lempira (Honduras)
Conservation of time and energy
The farmers’ point of view – Lempira (Honduras)
Soil microbial communities and zero tillage
Nutrients availability under various cover crops (southern Brazil)
Carbon sequestration (southern Brazil)
Increase of protected areas through livestock management (Costa Rica)
Indigenous knowledge and empowerment in Africa
The Quesungual agroforestry system – Lempira (Honduras)
The Zero Tillage Association for the Tropics (ZTAT), Brazil
Clubes amigos de Terra (CAT), Brazil
The Association for Better Land Husbandry (ABLH), Kenya
Improved fallow with legumes
Improving conservation agriculture (southern Brazil)
The shifting cultivation system (northern Brazil)
Conservation agriculture based on minimum tillage and animal production
in east Africa
22. Crop selection for high residue production – Guaymango, El Salvador
23. Better management and use of crop residues (northern Tanzania)
24. Improving soil fertility (southern Ethiopia)
25. Supporting farmers’ land literacy (Zimbabwe)
26. Trash lines and banana mulching: farmers’ innovations (Uganda)
27. The SADC-ICRAF Zambezi basin agroforestry project
28. Conservation tillage – technology transfer in Kwa Zulu-Natal (South Africa)
29. The Malawi agroforestry extension project (MAFE)

30. Contribution of the Brazilian government to zero tillage promotion
31. History of a soil conservation law (Malawi)
32. Law 7779 “The use, management and conservation of soils” (Costa Rica)
33. The adoption process – Guaymango (El Salvador)
34. Sustainability through incentives: Paraná 12 meses, Brazil
35. The benefits of communal tenure
36. The African Conservation Tillage network (ACT)

3
4
8
9
11
12
13
14
15
16
17
18
22
23
23
24
25
27
27
28
30
30

31
31
36
37
38
39
40
40
41
42
44
44
46
47


Conservation agriculture – case studies in Latin America and Africa

vii

List of plates

Page
1.
2.
3.
4.
5.
6.
7.

8.

9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.

Continuous cultivation damages the vital but fragile ecosystem of soil flora
and fauna
Soybean grown under conservation agriculture in Brazil
Smallholder coffee farmers covering the soil with straw to preserve moisture,
Malawi
The use of tied ridges to catch and guide run-off and prevent damage to the crops
Land preparation is by far the most time-consuming activity for the farmer
and family
Only a small percentage of the total area is worked in reduced tillage systems
Flooding and sediment transport to the reiver increasing cost of water treatment
The Quesungual system is an indigenous agroforestry system which most distinct
characteristic is the combination of naturally regenerated and pruned trees and

shrubs with more traditional agroforestry components, such as high value timber
and fruit trees. In between the trees the traditional staple crops, i.e. maize, sorghum
and beans are grown
Maasai, traditionally herding cattle, are engaging in vegetable growing activities to
increase their income and spread the risks
A historic moment: this meeting of farmers, technicians, and municipal leaders
from Agrolandia, micro-catchment Ribeirao das Pedras, first discussed how to
convert traditional animal traction equiment to direct-sowing equipment
A Kenyan farmer in front of his Tithonia hedge, which is cut and used to fertilize
his sukumawiki crop
Flowering wild sunflower, Tithonia, now a roadside weed in Kenya and the
United Republic of Tanzania, which is used as green manure in western Kenya
Implements have been adapted for resource-poor farmers: a herbicide spray, which
can be drawn either manually or by animals
The knife-roller bends over or crushes the cover vegetation, preparing the land for
the succeeding crop, which will be sown through the residues
Simple seed drill, which can cope well with the enormous amount of crop residues
left in the field
First introduction of an animal-drawn direct seeder in a Maasai village in northern
United Republic of Tanzania
Stripping maize to separate palatable and non-palatable parts to be used respectively
for animal fodder and soil improvement
Drawings explaining box baling of maize stover
Discussing and thinking about the future, and planning together
Farmer explaining to his neighbours the functioning of a new implement
Imitation of the erosive effect of rainfall on bare soil and on a soil covered
with residues
Banana mulching, a common practice to prevent soil moisture to evaporate and
keeping the bananas productive for a longer period
Free-roaming cattle often lead to conflicts between pastoralists and agriculturalists

2
4
8
10
13
14
18

19
22
24
26
26
28
29
29
29
30
31
35
36
37
38
45


viii

List of tables

Page
1. Common practices and consequences of conventional agriculture

2

2. Total area - in hectares - under no-tillage in different countries in the seventies,
eighties and in1999/2000

5

3. Water, soil and plant nutrient losses under conventional agriculture and direct
seeding in a wheat-maize rotation

16

List of figures
Page
1. Production increase of maize and sorghum under the Quesungual system

12

2. Population size of root nodule bacteria under zero tillage

15

3. Maize production under the Quesungual system

19

4. Yield of maize-sorghum system in Guaymango, 1963 - 1989

34

5. Reduction in burning over the last three years in southern Lempira

43


Conservation agriculture – case studies in Latin America and Africa

ix

Acronyms
ABEAS
ACT
ABHL
ARC
CAT
CCD
CGIAR
CIDA
CIMMYT
EPAGRI
FAO
FARMESA
FEBRAPDP
GO
GTZ
ICRAF

IFDC
IITA
MAFE
NAP
NEAP
NGO
NSSD
PTD
SADC
SARI
SFI
ZFU
ZTAT

Brazilian Association for Higher Education in Agriculture
African Conservation Tillage network
Association for Better Land Husbandry
South African Agricultural Research Council
Clube Amigos da Terra
Convention to Combat Desertification
Consultation Group for International Agricultural Research
Canadian International Development Agency
International Maize and Wheat Improvement Center
Empresa de Pesquisa Agropecuária e Difusão de Tecnologia de Santa Catarina
Food and Agriculture Organization of the United Nations
Farm-level Applied Research Methods Programme for East and Southern Africa
Brazilian Federation for Direct Planting into Crop Residues
Governmental Organization
German Agency for Technical Cooperation
International Centre for Research in Agroforestry

International Fertilizer Development Center
International Institute of Tropical Agriculture
Malawi Agroforestry Extension Project
National Action Plan
National Environmental Action Plan
Non-Governmental Organization
National Strategies for Sustainable Development
Participatory Technology Development
Southern African Development Community
Selian Agricultural Research Institute
Soil Fertility Initiative
Zimbabwe Farmers Union
Zero Tillage Association for the Tropics


x


Conservation agriculture – case studies in Latin America and Africa

1

Chapter 1
Introduction

“It was only when we stopped using fertilizer that we realized something bad was
happening to our soils.” Several small-scale Malawi farmers during a 1997 survey1.”
Many of today’s most pressing problems for rural people and their environments are related to
the management of land and water resources. They include malnutrition, food insecurity, low
standards of living, large-scale migration and sometimes violent competition for resources to

satisfy basic needs. Environmental concerns include land degradation, destruction of terrestrial
and aquatic habitats and loss of biodiversity.
The human population, which doubled in the last forty years, is expected to double again
within the coming half century. The increase will occur mainly in poor countries with few
resources and unstable conditions for production. Therefore, social and political repercussions
will be proportionately greater.
While populations continue to increase, the availability of non-renewable resources per person
will clearly decline. Another issue of increasing importance is the prevention of environmental
contamination by minimising waste from production and marketing processes, and safe disposal
or reuse of waste products.
The primary source of food for humans and animals is based upon plants. Except for carbon,
which enters plants through the leaves, all the elements necessary for plant growth, human and
animal nutrition are obtained from the soil via the plant root system: nitrogen, oxygen, phosphorus,
potassium, calcium, etc.
Due to population concentration and pressure, these elements are drained from soils into city
sewage and landfills. A crude calculation shows that the daily dietary requirements of phosphorus
for a world population of 5.5 billion people annually requires about 1.4 kg of phosphorus from
each hectare of the 1.5 billion hectares of cropland in the world. No soil, regardless of its initial
mineral composition, can continue to have food products exported from it indefinitely without
active support.
Many agricultural systems are found around the world, such as intensive cropping systems,
shifting cultivation, agroforestry, etc. (Annex 1). In conventional agriculture, the soil is frequently
regarded only as a substrate that provides physical support, water and nutrients to plants, and it
is assumed that farmers must supplement all plant needs (such as nutrients, protection, water)
with external inputs:

• if a soil is deficient in some nutrient, fertilizer is applied;
• if a soil does not store enough rainfall, irrigation is provided;
1

Evans et al., 1999


Introduction

2

• if a soil becomes too compacted and water cannot penetrate the soil, implements such as a
chisel are used to rip it open;
• if a plant disease or insect infestation occurs, pesticides are applied.
Some of these practices may be necessary, under specific conditions and appropriate planning,
monitoring and management. However, some common practices may lead to serious problems
for the human being and the environment (Table 1).
TABLE 1
Common practices and consequences of conventional agriculture

Common practices

Consequences

Removal or burning of crop residues
Continuous ploughing and harrowing
Overgrazing
Deforestation
Mono-cropping
Excessive use of fertilizers
Misuse of pesticides
Misuse of water

Loss of soil fertility and decreasing yields

Erosion
Increased drought and flood risks
Food insecurity and health risks
Contamination of ground and surface water
Contamination and degradation of soils
Greenhouse gas release
Pest invasions
Loss of biodiversity

In conventional agriculture, soil tillage is considered as one of the most important operations
to create a favourable soil structure, prepare the seedbed and control weeds. But mechanical
implements, particularly those drawn or driven by tractors (Plate 1), destroy the soil structure by
reducing the aggregate size, and currently conventional tillage methods are a major cause of soil
loss and desertification in many developing countries.
Tillage-induced soil erosion in developing countries can entail soil losses exceeding 150 t/ha
annually and soil erosion, accelerated by wind and water, is responsible for 40 percent of land
degradation world-wide.
The increased mineralisation of soil organic matter resulting from continuous cultivation may
bring short-term yield increases, but in the long term the soil life and the soil structure are
damaged. Deep tillage is harmful to earthworms and other soil organisms. It can kill them

PLATE 1
Continuous cultivation damages
the vital but fragile ecosystem
of soil flora and fauna, Bolivia.
[R. Jones/FAO/19376]


Conservation agriculture – case studies in Latin America and Africa

3

outright, disrupt their burrows, lower soil moisture, and reduce the amount and availability of
their food. Other inappropriate land management practices, such as the use of certain pesticides
(for example aldicarb, carbaryl, carbofuran, benomyl, and most soil fumigants) and some inorganic
fertilizers, especially ammonium sulphate, can also be harmful to soil life. All these practices
result in declining soil life and organic matter which are important for oxygen, water and nutrient
cycles, including moisture retention, water infiltration and plant nutrition.
The soil then becomes vulnerable to compaction, which in turn reduces water infiltration rate
and storage capacity. One of the results is an increased water flow across bare soil inducing
run-off and water-borne soil loss and further loss of potential productivity.
Continuing soil degradation is threatening food security and the livelihood of millions of farm
households throughout the world. The main causes include not only intensive soil preparation by
hoeing or ploughing, but also deforestation, the removal or burning of crop residues, poor rangeland
management and inadequate crop rotations that do not maintain vegetative cover or allow
appropriate restitution of organic matter and plant nutrients. These practices leave the soil exposed
to climatic hazards such as wind, rain and sun.
Thus, the intensive and continued use of the plough has proven to be unsustainable in several
climatic zones. Many farmers have been induced to reconsider ploughing and its effects.
Conservation tillage systems were developed to protect the soil and reduce erosion. Economic
pressures in some countries also led to the development of minimum or reduced tillage systems.
A common feature of these systems is the elimination or the minimal use of the plough. Soil
tillage may still be used to loosen the soil and to mix soil components, but chisel tines are preferred,
leaving most of the crop residues on or close to the soil surface and not exposing the bare soil to
wind and rain.
Sustainable intensification of crop production is possible in currently unimproved or degraded
areas. Empirical evidence has been accumulating that low (but not necessarily zero-) input
agriculture can be highly productive, provided farmers participate fully in all stages of technology
development and extension. This evidence indicates that the productivity of agricultural and
pastoral lands is a function of human capacity and ingenuity as much as of biological and physical

processes.
This has led to what is called “conservation agriculture” (Box 1). Three criteria, which are
interrelated, distinguish conservation agriculture from a conventional agricultural system: reduced

BOX 1: Principles of conservation agriculture
The goal of conservation agriculture is to maintain and improve crop yields and resilience against drought and
other hazards, while at the same time protecting and stimulating the biological functioning of the soil.
Two essential features of conservation agriculture (Box 2) are no-tillage and the maintenance of a cover (live
or dead vegetal material) on the soil surface. Crops are seeded or planted through this cover with special
equipment. However, although no-tillage is an essential feature of conservation agriculture, the use of notillage by itself does not qualify for conservation agriculture. As long as a farmer ploughs for at least one crop
within the rotation or does not maintain a permanent soil cover, he does not practise conservation agriculture.
The soil cover also inhibits the germination of many weed seeds, minimising weed competition with the crop.
In the first few years, however, herbicide may still need to be applied, making a location-specific knowledge
of weeds and herbicide application important. Conservation agriculture also involves planning crop sequences
over several seasons, to minimise the build-up of pests or diseases and to optimise plant nutrient use by
synergy between different crop types and by alternating shallow-rooting crops with deep-rooting ones. The
continuous use of the cropland is allowed.


Introduction

4

PLATE 2
Soybean grown under
conservation agriculture in
Brazil
[J.R. Benites]

or zero tillage, permanent soil cover and crop

rotation. The biomass produced in the system is
kept on the soil surface rather than incorporated
and serves as a physical protection of the soil and
as substrate for the soil fauna. In this way
mineralisation is reduced and soil organic matter
is built up and maintained. Mechanical tillage is
avoided in order to maintain the existing
interactions between soil flora and fauna, which
are necessary to liberate plant nutrients. A varied
crop rotation is important to avoid pest and disease
problems and improve soil conditions.
Key features of conservation agriculture
systems are listed in Box 2.

BOX 2: Key features of
conservation agriculture
systems
•

No ploughing, disking or soil cultivation
(i.e., no turning over of the soil);

•

Crop and cover crop residues stay on
the surface;

•

No burning of crop residues;

•

Permanent crop and weed residue
mulch protects the soil;

•

The closed-nutrient recycling of the
forest is replicated;

•

Lime and sometimes fertilizers are
surface-applied;

•

Specialised equipment;

•

Continuous cropland use;

•

Crop rotations and cover crops are used

A growing number of experiences of the
to maximise biological controls (i.e.,

more plant and crop diversity).
benefits of conservation agriculture in both
mechanised and non-mechanised agriculture, on
tens of millions of hectares of small and large
farms in both temperate and tropical zones, suggest
that further significant improvements in conservation-effective agriculture are indeed possible.
These will be acceptable to farmers if they are cost-effective in the short term.
The conservation agriculture systems discussed in this report have proven to be effective in
exploiting the natural resources upon which they are based without degrading them, and in some
cases allowing their restoration. Each case brings out the interactions and complementarity that
exist between sound scientific and practical knowledge, market factors, social and political
contexts, and public policies and investments. The cases discussed are examples of the wide
range of circumstances found in Latin America (Plate 2) and Africa. All are of rainfed farming
and cover a range of low-income and lower-middle income countries with contrasting physical
and economic conditions. The set of cases covers only small-scale farm operations. Some have
developed in response to macroeconomic and market changes, often changes in physical and
social infrastructure have been important, but in all cases a necessary condition for change has


Conservation agriculture – case studies in Latin America and Africa

5

been that the underlying physical, chemical, and biological systems have been understood and
respected by the farmers.
Conservation agriculture has evolved from the zero tillage technique. Zero tillage or notillage system is based on the use of crop residues or mulch as a surface cover, and the
improvement of the natural cycles in the soil. With time, soil life takes over the functions of
traditional soil tillage, loosening the soil and mixing the soil components. But in addition to that
the increased biological soil activity creates a stable soil structure through accumulation of
organic matter.

The pioneers started to practise zero tillage as a form of conservation tillage on their farms
in the early sixties and seventies in the USA and Brazil respectively. Initial adoption was slow,
but since the mid-1980s its spread has been rapid, especially in the Americas and Australia.
(Table 2).
TABLE 2
Total area - in hectares - under no-tillage in different countries in the seventies, eighties and in1999/
2000 (Derpsch, 1999 modified by Benites)

Country
U.S.A.
Canada
United Kingdom
France
Netherlands
Japan, Malaysia, Sri Lanka
Australia
New Zealand
Brazil
Argentina
Mexico
Paraguay
Uruguay+Chile+Bolivia

1973/74

1983/84

1999/2000

2 200 000

200 000
50 000
2 000
200 000
100 000
75 000
1 000
-

4 800 000
275 000
50 000
5 000
250 000
400 000
75 000
400 000
-

19 750 000
4 080 000
8 640 000
13 470 000
9 250 000
650 000
800 000
350 000

Conservation agriculture based on zero tillage has proven especially useful for maintaining
and building up soil organic matter and improving soil fertility, primarily through reducing soil

disturbance, conservation of the soil structure and stimulating soil biota. Information on the soil
ecosystem is provided in Annex 2.


6

Introduction


Conservation agriculture – case studies in Latin America and Africa

7

Chapter 2
Concepts and impacts of conservation
agriculture

“Leaving crop residues on the soil surface is like using a sombrero; it conserves the
sweat, and keeps the head cool.” A small-scale farmer, Costa Rica.
CONCEPTS
Under forest, the great production and cycling of foliage results in much biological activity,
humus formation, and hence a dark coloured topsoil. Because of the great numbers of insects
and worms there are large pores, which allow water infiltration. In contrast, under annual crops,
leaf production is much less, the biomass is largely removed, the soil is tilled several times each
year and so is much drier. Consequently, less food and moisture are available for earthworms
and other insects, and their habitat is repeatedly disturbed or destroyed.
Where topsoil has been eroded, and soil layers of poorer quality for root growth have become
exposed, it is essential to rehabilitate and restore the soil to bring it up to good productive capacity
for the next crop or pasture. Failing this, a spiral of degradation is set in motion as a result of the
reduced vegetative cover and biomass production and reduced soil and water retention. Thus

the quality of the soil that is left behind should be of even greater concern than the quantity and
quality of that which has been lost.
Farmers need to create favourable conditions for soil life and should manage organic matter
so as to create a fertile soil in which healthy plants can develop. In tropical rainfed agriculture,
in which poor farmers generally suffer from decreasing soil fertility and declining soil water
dynamics, the restoration of soil organic matter is essential for the stabilisation of production.
However, this cannot be accomplished by merely incorporating organic matter into the soil,
as under tropical conditions, the degradation process is too fast to allow any medium or longterm improvement of soil properties. Moreover, incorporation implies tilling the soil, which
accelerates organic matter breakdown and destroys soil structure and organisms.
The primary need is to feed soil organisms (bacteria, fungi, earthworms, etc.) and to regulate
their living conditions, while protecting them from chemical and mechanical impacts. For example,
shallow tillage, ridge-tillage, or zero-tillage and surface management of crop residues has often
led to increases in earthworm activity compared to areas where deep tillage is practised.
Providing a permanent or semi-permanent soil cover (growing crops, crop residues or mulch)
provides food for soil organisms, protects the soil from the destructive forces of rain, wind and
sun, improves water infiltration, reduces soil moisture loss, and regulates the soil microclimate
(Plate 3).


Concepts and impacts of conservation agriculture

8

PLATE 3
Smallholder coffee farmers
covering the soil with straw
to preserve moisture,
Malawi
[A. Conti/FAO/17732]

This practice should be accompanied by others related to conservation agriculture, which
intend to minimise soil disturbance and protect and nourish the soil life, such as:

•
•
•
•

reducing or eliminating tillage operations;
practising crop rotations;
using fertilizers as appropriate;
relying on integrated pest and weed management.

The benefits of conservation agriculture
include agro-environmental features (Box 3).
Nutrient losses may be minimised through the
appropriate use of deep-rooting cover crops
that recycle nutrients leached from the topsoil,
moisture management, and improved
collection, storage and application of wastes
from crops, livestock and the household (food
wastes). Nutrients that are harvested and
removed may be replaced through symbiotic
nitrogen fixation, organic matter from
elsewhere, or the complementary use of
fertilizers and feed supplements.

BOX 3: Agro-environmental features of
conservation agriculture

•
•

Soil loss does not exceed rates of soil formation;

•
•

Biodiversity is maintained or enhanced;

•
•
•

Rainfall is managed to avoid excessive runoff;

Soil fertility and soil structure are maintained or
enhanced;
Downstream effects of run-off or leaching do
not impair water quality;
Emissions of greenhouse gases are reduced;
Food production levels are maintained or
enhanced;

• Environmental stewardship is engendered
Pest management can also benefit from
amongst rural communities and producers of all
conservation practices that enhance biological
types, ensuring continuity of sound land
activity and diversity, and hence competitors

management.
and predators, as well as alternative sources
of food. For instance, most nematode species
(especially the pathogens) can be significantly reduced by application of organic matter, which
stimulates the action of several species of fungi attacking nematodes and their eggs.
Several key concepts and terms used in this report are described in Annex 1.
CHANGING MENTALITIES
The current concept shift from soil being a thin layer of material at the outside of the lithosphere
immediately below the atmosphere to a living entity that has dynamics of root growth and soil


Conservation agriculture – case studies in Latin America and Africa

9

fauna, temperature, moisture and oxidation-reduction, has profound significance for ecological
study and practical management. Nutrients that are lost from the soil by crop production, erosion
and leaching need to be replaced and the availability of all nutrients needs to be optimised. The
broader focus of conservation agriculture embraces not only the nutrient content of soils but
also their structure and biological status, which are determinants of sustained productivity.
In many cases this may require a combination of changes in tillage and soil management
practices, crop rotations and planting times, soil conservation measures, the strategic use of
organic materials and the appropriate use of inorganic fertilizers to match farmers’ combinations
of crops, land, availability of organic materials and market opportunities.
An improved approach to the integrated and sustainable use of natural resources requires a
paradigm centred on the user’s role and the significance of the soil’s biological and architectural
dynamics, both at and below the surface, as much as on the increased synergy between local,
internal and external forces. As farmers use management skills and better knowledge to work
more closely with the biological world, they will often find ways to reduce purchases of external
inputs.

With a new emphasis on conservation agriculture has come a reawakening of interest in soil
organic matter. Some issues, such as soil fertility (thus food security), water storage, compaction,
and erosion are directly related to soil organic matter. Others, such as disease and insect pest
infestations, may be indirectly related to it. Thus, the build-up and maintenance of the soil biota
and good levels of organic matter in soils are of critical importance.
The adoption of conservation agriculture requires the opening up of dense and compacted
soils as well as an opening of minds and innovative thinking. In fact, almost all of the past
limitations to change in Brazil have been overcome with positive and creative thinking. During
1998 and 1999, 140 extensionists were trained from seven different states. The training courses
were a great success and completely turned around the attitudes of extension services to zero
tillage, paving the way for collaboration in more pilot projects with small farmers and leading to
considerable benefits to the small farm sector.
Agricultural science generally has poorly
understood, overlooked or ignored indigenous
knowledge and traditional approaches. Soil
conservation staff commonly have focused on
what they have seen as technically desirable
solutions to problems of erosion and runoff.
Extension agencies often find it difficult to learn
from farmers and rural people. Few systemic
processes exist for enhanced two-way feedback
on performance. An examination of the situation
in tropical Brazil identified several reasons for
the delay in research attention to farmers’
practices (Box 4).
In this case, the resistance to change of
researchers, academics and advisers was much
greater than that of farmers. The farmer saw
immediate benefits over and above the cost of
change, while the professionals saw a significant

cost in the effort of change but failed to foresee

BOX 4: Reasons for the slow research
response to zero tillage in Brazil prior to
1995

•

Rejection of farmer-based experience
(practices not proven statistically)

•
•
•
•

Resistance to the costs and effort of change

•

Rewards to researchers depended on
publications rather than on farmer impact

•

Little or no farmer control over research
priorities

•

Priority to feed urban populations makes
decision-makers risk-averse.

•

Misapprehension that zero tillage would only
be appropriate for large farmers

Research was on-station
Research generally not system-oriented
Researchers not in close contact with
farmers


Concepts and impacts of conservation agriculture

10

the economic benefits accruing to this extra effort. Farmers, they felt, needed to be motivated
by non-financial stimuli, which they believed would take much longer.

COMBATING LAND DEGRADATION AND IMPROVEMENT OF LAND PRODUCTIVITY
The control of soil erosion and establishing permissible amounts of soil loss have long been
principal foci in addressing land degradation and aiming at increasing and stabilising agricultural
production.
In contrast to this narrow approach to soil-related problems, it is being increasingly recognized
that land and its soil components should be looked upon as a living resource to be nurtured and
used in sustainable and responsible ways. The definition of land is implicit in the following
quotation:
“For a land use system to be sustainable requires, first, that it should meet the

needs of farmers and other land users; and, secondly, that it should achieve
conservation of the whole range of natural resources, including climate, water,
soils, landforms, forests and pastures.” (Young, 1998)
In the past, soil conservation has been advocated as a necessary starting point to raise crop
yields. Soil erosion has conventionally been perceived as one of the main causes of land degradation
and the main reason for declining yields in tropical regions. Based on these assumptions,
conservation measures were directed at three main components:

• physical works to catch, guide and prevent
damage by run-off (Plate 4);

• pressures to stop people from deforesting the
area and to reduce the number of grazing
animals;

• planning of different land uses according to Land
Use Capability Classifications, based on the
assessment of different degrees of erosion
hazards.
Experience has shown that none of the
recommended physical and institutional anti-erosion
methods was widely adopted by the smallholder
farmers of tropical regions. Since conserving soil
does not by itself raise yields, and is not the farmers’
overriding concern (while improving productivity
may be), it is advisable to emphasise those practices
of good soil and crop management that have,
positive effects on conservation. This insight has
led to a switch from stopping erosion to assisting
farmers to achieve a more conservation-effective,

higher and more stable production.
Case studies where these insights have been
applied show that it is technically feasible and
economically profitable to develop intensive

PLATE 4
The use of tied ridges to catch and guide
run-off and prevent damage to the crops
[FAO]


Conservation agriculture – case studies in Latin America and Africa

11

BOX 5: Conservation structures and practices in Southern Brazil
Large areas of arable land in Southern Brazil suffered from erosion to such an extent that the very livelihood
of the farmers was being endangered. Initial efforts to contain the damage by the implementation of conservation
works such as terracing did not prove effective.
As research studies developed, scientists confirmed that the erosion problem was due to the way the land
between terrace banks was managed. Even if the terraces were well constructed, the rate of rainwater
infiltration was progressively reduced due to excessive soil movement and compaction. The technique
presented as a solution when used as an isolated practice, i.e. the construction of terraces, accentuated
rather than alleviated the problem (Mielniczuk, personal comm.).
This resulted in the revival of the ancient practice of green manuring. Firstly with the clear objective of
erosion control, which later developed into what could be defined as good soil management. More important
than using physical barriers to control runoff, which is responsible for only 5 percent of erosion, research
showed that the ideal solution is to maintain soils covered as much of the time as possible with growing
plants or crop residues. By avoiding the detachment of soil particles by raindrop impact, which accounts for
95 percent of erosion, soil losses are avoided and at the same time the soil can be cultivated in conditions

similar to those found in forests (FAO, 2000).
This was accompanied by the emergence of new systems of land preparation such as minimum tillage and
direct sowing techniques as alternatives to the conventional practices introduced from temperate climates.
Depending on the crop to be sown, the area of soil to be disturbed is limited to a narrow strip, between 10 and
50 cm wide. In this strip, the vegetative cover is partially incorporated and the soil surface is still 60-80
percent protected from raindrop impact and the sun’s rays. Direct sowing consists of the elimination of
ploughing or soil disturbance using traditional equipment such as the plough or cultivator. Direct sowing is
practised through a cover of crop residues or in a narrow partially cleared strip.

production systems in the tropics while improving the quality of the natural resources and protecting
the environment. This requires a focus on the management of biological resources together with
related hydrological and nutrient cycling functions, complemented where necessary, with physical
works (contour ridging, conservation banks or terracing) as appropriate on steep slopes (Box 5).
Similarly, especially in the arid and semi-arid tropics, it is opportune to emphasise with farmers
the management of rainwater as a productive resource rather than merely as a means of saving
soil. Achieving better infiltration and in-soil storage of rainwater when these have been limitations,
while favouring agricultural production, automatically also reduces soil and water movement
and transport. In this regard, to enhance water availability and retain soil productivity it is important
to consider those practices which promote rainfall capture in the soil before considering those
which aim to control run-off – they are complementary in a sequence, and are not competing
alternatives.
In areas of high rainfall and tendency to soil water-logging, conservation of water and soil
requires careful management of soil structure and the vegetative cover to enhance infiltration
and maintain above-ground and internal drainage.
Facilitating farmers to improve their land care – land husbandry – thus provides a more
effective response than efforts to combat erosion alone. It specifically recognizes farmers’
desire to raise yields and incomes as they stabilise or reverse resource depletion. It also provides
opportunities for governments to harmonise certain national objectives (better management of
natural resources and development of sustainable agriculture) with major objectives of farm
families (secure livelihoods). However, this approach requires many adjustments in common

thinking (Hinchcliffe et al., 1995).


12

Concepts and impacts of conservation agriculture

SOCIO-ECONOMIC ADVANTAGES
The adoption of conservation agriculture practices by farmers often shows increased yields
(double or even triple sometimes), which can be seen by farmers and measured, as for example
in Figure 1 and Box 6.
FIGURE 1
Production increase of maize and sorghum under the Quesungual system (J. Hellin, 1998)

Other benefits quickly appreciated by farmers
include the reduction of the amount and costs of
labour and energy required for land preparation
and sowing, due to the fact that the soil becomes
soft and easy to work. Ploughing the soil is by
far the most energy- and time-consuming
operation for the farmer. In many farming
systems, it constitutes an important bottleneck,
often due to the necessity to hire equipment
which does not arrive in time and therefore delays
planting (Plate 5 and Box 7).
Of the total energy used in crop production in
North Africa in 1987, 69 percent was derived
from people, 17 percent from animals, and 14
percent from tractors (Twomlow et al., 1999).
In sub-Saharan Africa this ratio was 89:10:1.

Findlay and Hutchinson (1999) estimated that 80100 person-days/ha would be needed to prepare
a land for planting with hand hoes. Animal-drawn
mouldboard ploughing may take two or three
days, whereas tractor ploughing may require only
two or three hours.

BOX 6: Farmers’ benefits – Lempira
(Honduras)
In Lempira (Honduras), farmers moved from a
traditional slash and burn system to the
Quesungual system: conservation agriculture
with an agroforestry component.
An economic analysis of this transition showed
that during the first two years maize and
sorghum yields are about equal to those obtained
with the traditional slash and burn system. From
the third year, however, their yields increase, in
addition to which the plot provides the farmer
with firewood and posts, which give an extra
value to the production.
Because of the increased production of maize,
the quantity of stover increased as well; this
can be sold as livestock fodder. Additionally,
from the first year onwards the farmer can rent
out the land for livestock grazing, because of
the increased biomass production. Usually this
is done for two months.
The application of the Quesungual system not
only meets the household subsistence needs
for fruit, timber, firewood and grains, but

generates a surplus, which generates an extra
income when sold in the market.


Conservation agriculture – case studies in Latin America and Africa

13

PLATE 5
Land preparation is by far the
most time-consuming activity for
the farmer and family
[J.R. Benites]

Although it is often recommended that farmers
should plough immediately after harvest, most farmers
wait until the first rains before commencing seedbed
preparation. Because the majority of African farmers
have no direct access to animal or motorised traction,
seedbeds are often prepared too late, the cropping
season shortened, and crop yields reduced (EllisJones and Mudhara, 1997).
Under conservation agriculture, in most systems
only a small proportion of the land is worked instead
of ploughing or hoeing the whole area to be planted
(Plate 6). Cultivation is also usually shallower than
conventional tillage. Herbicides may be used in some
systems (Findlay and Hutchinson, 1999), hand hoes
in others, and farmers who have animal-drawn
ploughs can fit simple and inexpensive tines or
subsoilers (Bwalya, 1999). Farmers using

conservation tillage reduced the production costs of
soybeans per hectare by US$67 in Argentina, by
US$35 in the USA and by US$27 in Brazil (FAO,
1998a).

BOX 7: Conservation of time and
energy
Weeding accounts for more than 60
percent of the time a peasant farmer
spends on the land. Conservation
tillage reduces the energy (for example
fuel for machines and calories for
humans and animals) and time
required. Thus a large-scale trial at the
IITA in Nigeria found zero tillage
required 52 MJ energy and 2.3 hours
labour per hectare compared to 235
MJ and 5.4 hours on conventional
tillage (Wijewardene, 1979). Use of
pre- and post-plant herbicides in no till
in Ghana required only 15 percent of
the time required for seedbed
preparation and weed control with a
handhoe, while the reduction in labour
days required in rice in Senegal was
53-60 percent (Findlay and
Hutchinson, 1999).

The farmers’ point of view is a central consideration in an adoption process (Box 8); they
will not change their practices if they do not see any benefit. In fact, the reductions in costs and

time required are usually the most compelling reasons for farmers to adopt conservation tillage.
IMPACTS ON THE ENVIRONMENT
Experience has shown that conservation agriculture systems achieve yield levels as high as
comparable conventional agricultural systems but with less fluctuations due, for example, to
natural disasters such as drought, storms, floods and landslides. Conservation agriculture therefore
contributes to food security and reduces risks for the communities (health, conditions of living,
water supply), and also reduces costs for the State (less road and waterway maintenance, less
emergency assistance).