Conservation agriculture case studies in latin america and africa

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 ag

Case studies in Latin America and Africa

BULLETIN 78

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.

Rome, 2001

Case studies in Latin America

Land and Plant Nutrition Management Service

Land and Water Development Division

ISBN 92-5-104625-5

© FAO 2001

All rights reserved Reproduction and dissemination of material in this information product for educational or other non-commercial purposes are authorized without any prior written permission from the copyright holders provided the source is fully acknowledged Reproduction of material in this information product for resale or other commercial purposes is prohibited without written permission of the copyright holders Applications for such permission should be addressed to the Chief, Publishing and Multimedia Service, Information Division, FAO, Viale delle Terme di Caracalla, 00100 Rome, Italy or

by e-mail to copyright@fao.org

The purpose of this publication is to show how conservation agriculture can increase crop productionwhile reducing erosion and reversing soil fertility decline, improving rural livelihoods and restoring theenvironment 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 aset of conditions necessary for farming systems to be conservation-effective and sustainable in the longrun As described in the second chapter, these experiences have demonstrated that the development ofintensive production systems in the tropics is technically feasible and economically profitable, whileimproving the quality of the natural resources and protecting the environment These production systemsallow a more adequate land use, which in turn generate more nutrients in the soil and improve its waterretention capacity Additionally, agro-biodiversity and carbon sequestration are enhanced through theseconservation-effective systems

The farming systems represent a wide range of geographic and resource features and contrastingsociological conditions They include the reduction or elimination of slash and burn in Honduras, thedevelopment of minimum tillage and direct drilling practices on small farms in Brazil, the liberation ofareas through intensification of the livestock sector in Costa Rica, the mass adoption of zero tillagepractices in El Salvador, biomass transfer to increase soil fertility in Kenya, the use of stover for bothlivestock and conservation purposes in the United Republic of Tanzania, a historical perspective of soiland 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 cansell 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 newtechnology, have to be supported by institutions, extension services, research and policies All casesillustrate the importance of cover crop species in the farming system, but in general these species havenot been adequately studied Much research has been weak on socio-economic variables or even ignoredthem 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 ofgovernments 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 tomeet the demand for food, to reduce poverty, and to utilise resources in an environmentally, socially, andfinancially sustainable way They illustrate the importance of production systems that are capable ofcontinually adapting to changing social, economic and environmental conditions Additionally, the casesshow the importance of reliable support facilities to facilitate the transition of farms from subsistence tomore intensive systems of farming

This publication which was prepared by Alexandra Bot, FAO Consultant, and José Benites, TechnicalOfficer, 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 areinvolved in ongoing projects of international organizations, such as FAO and the World Bank, or of non-governmental 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); BillBerry (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); MarioChavez (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); ChristinaChoto (Centro de Tecnología Agrícola, Ministerio de Agricultura y Ganadería, El Salvador); EdwardChuma (Institute for Environmental Studies, Zimbabwe); William Critchley (Vrije Universiteit Amsterdam,The Netherlands); Diógenes Cubero (FAO, Costa Rica); Pieter Dercksen (FAO, Costa Rica); MichelleDeugd (FAO, Honduras); Hinton Estates (Agriway, Zimbabwe); Jim Findlay (Agrecon Consultants, SouthAfrica); German Flores (Lempirasur, Honduras); Valdemar Hercilio de Freitas (EPAGRI, Brazil); JorgeGaray (Lempirasur, Honduras); Amadu Hiang (ICRAF, Kenya); John Landers (Associação de PlantioDireto no Cerrado, Brazil); Wilfred Mariki (Selian Agricultural Research Institute, Tanzania); NicholausMassawe (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 (AgriculturalResearch Trust, Zimbabwe)

Several people contributed to the development of this publication The authors would like to acknowledgethe assistance of Francis Shaxson, Richard Fowler, Romualdo Hernández, Paul Mueller, Rob van Haarlemand Willem Hoogmoed The valuable comments provided by Robert Brinkman, Sally Bunning, RudyDudal, 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 andLynette Chalk-Contreras

Impact of management practices on soil fauna and soil fertility 14Mitigating climate changes and greenhouse gases 16Reduction of contamination and water pollution 17

3 RURAL COMMUNITIES ACTIVELY IMPLEMENTING CONSERVATION AGRICULTURE 21Organization: the role of farmers’ groups and non-governmental

Appropriate scenarios for conservation agriculture 34Designing community-based projects: tools and practices 34

Conservation agriculture linkages with international initiatives 46

4 Reasons for the slow research response to zero tillage in Brazil prior to 1995 9

10 Nutrients availability under various cover crops (southern Brazil) 16

12 Increase of protected areas through livestock management (Costa Rica) 18

21 Conservation agriculture based on minimum tillage and animal production

22 Crop selection for high residue production – Guaymango, El Salvador 30

23 Better management and use of crop residues (northern Tanzania) 31

26 Trash lines and banana mulching: farmers’ innovations (Uganda) 37

28 Conservation tillage – technology transfer in Kwa Zulu-Natal (South Africa) 39

30 Contribution of the Brazilian government to zero tillage promotion 40

32 Law 7779 “The use, management and conservation of soils” (Costa Rica) 42

List of boxes

1 Continuous cultivation damages the vital but fragile ecosystem of soil flora

3 Smallholder coffee farmers covering the soil with straw to preserve moisture,

4 The use of tied ridges to catch and guide run-off and prevent damage to the crops 10

5 Land preparation is by far the most time-consuming activity for the farmer

6 Only a small percentage of the total area is worked in reduced tillage systems 14

7 Flooding and sediment transport to the reiver increasing cost of water treatment 18

8 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

9 Maasai, traditionally herding cattle, are engaging in vegetable growing activities to

10 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 24

11 A Kenyan farmer in front of his Tithonia hedge, which is cut and used to fertilize

12 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 26

13 Implements have been adapted for resource-poor farmers: a herbicide spray, which

14 The knife-roller bends over or crushes the cover vegetation, preparing the land for

15 Simple seed drill, which can cope well with the enormous amount of crop residues

16 First introduction of an animal-drawn direct seeder in a Maasai village in northern

17 Stripping maize to separate palatable and non-palatable parts to be used respectively

19 Discussing and thinking about the future, and planning together 35

20 Farmer explaining to his neighbours the functioning of a new implement 36

21 Imitation of the erosive effect of rainfall on bare soil and on a soil covered

22 Banana mulching, a common practice to prevent soil moisture to evaporate and

23 Free-roaming cattle often lead to conflicts between pastoralists and agriculturalists 45

List of plates

List of tables

Page

2 Total area - in hectares - under no-tillage in different countries in the seventies,

3 Water, soil and plant nutrient losses under conventional agriculture and direct

Page

1 Production increase of maize and sorghum under the Quesungual system 12

5 Reduction in burning over the last three years in southern Lempira 43

List of figures

ABEAS Brazilian Association for Higher Education in Agriculture

ACT African Conservation Tillage network

ABHL Association for Better Land Husbandry

ARC South African Agricultural Research Council

CCD Convention to Combat Desertification

CGIAR Consultation Group for International Agricultural Research

CIDA Canadian International Development Agency

CIMMYT International Maize and Wheat Improvement Center

EPAGRI Empresa de Pesquisa Agropecuária e Difusão de Tecnologia de Santa CatarinaFAO Food and Agriculture Organization of the United Nations

FARMESA Farm-level Applied Research Methods Programme for East and Southern AfricaFEBRAPDP Brazilian Federation for Direct Planting into Crop Residues

GTZ German Agency for Technical Cooperation

ICRAF International Centre for Research in Agroforestry

IFDC International Fertilizer Development Center

IITA International Institute of Tropical Agriculture

MAFE Malawi Agroforestry Extension Project

NEAP National Environmental Action Plan

NGO Non-Governmental Organization

NSSD National Strategies for Sustainable Development

PTD Participatory Technology Development

SADC Southern African Development Community

SARI Selian Agricultural Research Institute

SFI Soil Fertility Initiative

ZTAT Zero Tillage Association for the Tropics

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 tothe management of land and water resources They include malnutrition, food insecurity, lowstandards of living, large-scale migration and sometimes violent competition for resources tosatisfy basic needs Environmental concerns include land degradation, destruction of terrestrialand aquatic habitats and loss of biodiversity

The human population, which doubled in the last forty years, is expected to double againwithin the coming half century The increase will occur mainly in poor countries with fewresources and unstable conditions for production Therefore, social and political repercussionswill be proportionately greater

While populations continue to increase, the availability of non-renewable resources per personwill clearly decline Another issue of increasing importance is the prevention of environmentalcontamination 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 andanimal 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 citysewage and landfills A crude calculation shows that the daily dietary requirements of phosphorusfor a world population of 5.5 billion people annually requires about 1.4 kg of phosphorus fromeach hectare of the 1.5 billion hectares of cropland in the world No soil, regardless of its initialmineral composition, can continue to have food products exported from it indefinitely withoutactive 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 frequentlyregarded 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

• if a soil becomes too compacted and water cannot penetrate the soil, implements such as achisel 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 problemsfor the human being and the environment (Table 1)

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 mechanicalimplements, particularly those drawn or driven by tractors (Plate 1), destroy the soil structure byreducing the aggregate size, and currently conventional tillage methods are a major cause of soilloss and desertification in many developing countries

Tillage-induced soil erosion in developing countries can entail soil losses exceeding 150 t/haannually and soil erosion, accelerated by wind and water, is responsible for 40 percent of landdegradation world-wide

The increased mineralisation of soil organic matter resulting from continuous cultivation maybring short-term yield increases, but in the long term the soil life and the soil structure aredamaged Deep tillage is harmful to earthworms and other soil organisms It can kill them

T ABLE 1

Common practices and consequences of conventional agriculture

Removal or burning of crop residues

Continuous ploughing and harrowing

Pest invasions Loss of biodiversity

P LATE 1 Continuous cultivation damages the vital but fragile ecosystem

of soil flora and fauna, Bolivia.

[R Jones/FAO/19376]

outright, disrupt their burrows, lower soil moisture, and reduce the amount and availability oftheir 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 inorganicfertilizers, especially ammonium sulphate, can also be harmful to soil life All these practicesresult in declining soil life and organic matter which are important for oxygen, water and nutrientcycles, including moisture retention, water infiltration and plant nutrition.

The soil then becomes vulnerable to compaction, which in turn reduces water infiltration rateand storage capacity One of the results is an increased water flow across bare soil inducingrun-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 farmhouseholds throughout the world The main causes include not only intensive soil preparation byhoeing or ploughing, but also deforestation, the removal or burning of crop residues, poor rangelandmanagement and inadequate crop rotations that do not maintain vegetative cover or allowappropriate 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 severalclimatic zones Many farmers have been induced to reconsider ploughing and its effects.Conservation tillage systems were developed to protect the soil and reduce erosion Economicpressures 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 Soiltillage 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 towind 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-) inputagriculture can be highly productive, provided farmers participate fully in all stages of technologydevelopment and extension This evidence indicates that the productivity of agricultural andpastoral lands is a function of human capacity and ingenuity as much as of biological and physicalprocesses

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

B OX 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 no- tillage 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.

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

A growing number of experiences of the

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 inexploiting the natural resources upon which they are based without degrading them, and in somecases allowing their restoration Each case brings out the interactions and complementarity thatexist between sound scientific and practical knowledge, market factors, social and politicalcontexts, and public policies and investments The cases discussed are examples of the widerange of circumstances found in Latin America (Plate 2) and Africa All are of rainfed farmingand cover a range of low-income and lower-middle income countries with contrasting physicaland economic conditions The set of cases covers only small-scale farm operations Some havedeveloped in response to macroeconomic and market changes, often changes in physical andsocial infrastructure have been important, but in all cases a necessary condition for change has

B OX 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

to maximise biological controls (i.e., more plant and crop diversity).

P LATE 2 Soybean grown under conservation agriculture in Brazil

[J.R Benites]

been that the underlying physical, chemical, and biological systems have been understood andrespected by the farmers.

Conservation agriculture has evolved from the zero tillage technique Zero tillage or tillage system is based on the use of crop residues or mulch as a surface cover, and theimprovement of the natural cycles in the soil With time, soil life takes over the functions oftraditional soil tillage, loosening the soil and mixing the soil components But in addition to thatthe increased biological soil activity creates a stable soil structure through accumulation oforganic matter

no-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)

Conservation agriculture based on zero tillage has proven especially useful for maintainingand building up soil organic matter and improving soil fertility, primarily through reducing soildisturbance, conservation of the soil structure and stimulating soil biota Information on the soilecosystem is provided in Annex 2

T ABLE 2

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

2000 (Derpsch, 1999 modified by Benites)

4 800 000 -

19 750 000

4 080 000 - - - -

8 640 000 -

Chapter 2 Concepts and impacts of conservation

Where topsoil has been eroded, and soil layers of poorer quality for root growth have becomeexposed, it is essential to rehabilitate and restore the soil to bring it up to good productive capacityfor the next crop or pasture Failing this, a spiral of degradation is set in motion as a result of thereduced vegetative cover and biomass production and reduced soil and water retention Thusthe quality of the soil that is left behind should be of even greater concern than the quantity andquality 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 waterdynamics, 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 term improvement of soil properties Moreover, incorporation implies tilling the soil, whichaccelerates organic matter breakdown and destroys soil structure and organisms

long-The primary need is to feed soil organisms (bacteria, fungi, earthworms, etc.) and to regulatetheir 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 oftenled 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 andsun, improves water infiltration, reduces soil moisture loss, and regulates the soil microclimate(Plate 3)

This practice should be accompanied by others related to conservation agriculture, whichintend 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

Pest management can also benefit from

conservation practices that enhance biological

activity and diversity, and hence competitors

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, whichstimulates 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

The current concept shift from soil being a thin layer of material at the outside of the lithosphereimmediately below the atmosphere to a living entity that has dynamics of root growth and soil

P LATE 3 Smallholder coffee farmers

covering the soil with straw

to preserve moisture,

Malawi

[A Conti/FAO/17732]

B OX 3: Agro-environmental features of conservation agriculture

• Soil loss does not exceed rates of soil formation;

• Soil fertility and soil structure are maintained or enhanced;

• Biodiversity is maintained or enhanced;

• Downstream effects of run-off or leaching do not impair water quality;

• Rainfall is managed to avoid excessive runoff;

• Emissions of greenhouse gases are reduced;

• Food production levels are maintained or enhanced;

• Environmental stewardship is engendered amongst rural communities and producers of all types, ensuring continuity of sound land management.

fauna, temperature, moisture and oxidation-reduction, has profound significance for ecologicalstudy and practical management Nutrients that are lost from the soil by crop production, erosionand leaching need to be replaced and the availability of all nutrients needs to be optimised Thebroader focus of conservation agriculture embraces not only the nutrient content of soils butalso 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 managementpractices, crop rotations and planting times, soil conservation measures, the strategic use oforganic 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 aparadigm centred on the user’s role and the significance of the soil’s biological and architecturaldynamics, 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 workmore closely with the biological world, they will often find ways to reduce purchases of externalinputs

With a new emphasis on conservation agriculture has come a reawakening of interest in soilorganic 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 pestinfestations, may be indirectly related to it Thus, the build-up and maintenance of the soil biotaand good levels of organic matter in soils are of critical importance

The adoption of conservation agriculture requires the opening up of dense and compactedsoils as well as an opening of minds and innovative thinking In fact, almost all of the pastlimitations 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 courseswere a great success and completely turned around the attitudes of extension services to zerotillage, paving the way for collaboration in more pilot projects with small farmers and leading toconsiderable 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

B OX 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

• Research was on-station

• Research generally not system-oriented

• Researchers not in close contact with farmers

• 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

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

The control of soil erosion and establishing permissible amounts of soil loss have long beenprincipal foci in addressing land degradation and aiming at increasing and stabilising agriculturalproduction

In contrast to this narrow approach to soil-related problems, it is being increasingly recognizedthat land and its soil components should be looked upon as a living resource to be nurtured andused in sustainable and responsible ways The definition of land is implicit in the followingquotation:

“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 cropyields Soil erosion has conventionally been perceived as one of the main causes of land degradationand 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

P LATE 4 The use of tied ridges to catch and guide run-off and prevent damage to the crops

[FAO]

production systems in the tropics while improving the quality of the natural resources and protectingthe environment This requires a focus on the management of biological resources together withrelated hydrological and nutrient cycling functions, complemented where necessary, with physicalworks (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 farmersthe management of rainwater as a productive resource rather than merely as a means of savingsoil Achieving better infiltration and in-soil storage of rainwater when these have been limitations,while favouring agricultural production, automatically also reduces soil and water movementand 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 thosewhich aim to control run-off – they are complementary in a sequence, and are not competingalternatives

In areas of high rainfall and tendency to soil water-logging, conservation of water and soilrequires careful management of soil structure and the vegetative cover to enhance infiltrationand maintain above-ground and internal drainage

Facilitating farmers to improve their land care – land husbandry – thus provides a moreeffective 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 providesopportunities for governments to harmonise certain national objectives (better management ofnatural resources and development of sustainable agriculture) with major objectives of farmfamilies (secure livelihoods) However, this approach requires many adjustments in common

thinking (Hinchcliffe et al., 1995).

B OX 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.

S OCIO - 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

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

80-100 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

F IGURE 1

Production increase of maize and sorghum under the Quesungual system (J Hellin, 1998)

B OX 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.

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

(Ellis-Jones 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)

The farmers’ point of view is a central consideration in an adoption process (Box 8); theywill not change their practices if they do not see any benefit In fact, the reductions in costs andtime required are usually the most compelling reasons for farmers to adopt conservation tillage

Experience has shown that conservation agriculture systems achieve yield levels as high ascomparable conventional agricultural systems but with less fluctuations due, for example, tonatural disasters such as drought, storms, floods and landslides Conservation agriculture thereforecontributes 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, lessemergency assistance)

P LATE 5

Land preparation is by far the

most time-consuming activity for

the farmer and family

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).

Conservation agriculture also contributes towider environmental benefits such as:

• improved management of soil and waterresources from farm to watershed levels: lessflooding, less erosion, less desertification, moreconstant flow in the rivers, better recharge ofgroundwater resources, improved water quality(less pollution) and reduced siltation effectsdownstream;

• increased carbon sequestration and less carbonrelease (less fuel used, less organic matterdegradation);

• increased biodiversity through diversification

Impact of management practices on soil fauna and soil fertility

The greater production of biomass in a system withcover crops and zero or reduced tillage compared

to monocrop cultures with conventional tillage,leaves a protective blanket of leaves, stems and

P LATE 6

Only a small percentage of the total area

is worked in reduced tillage systems

[J Kienzle]

Box 8 The farmers’ point of view – Lempira (Honduras)

Among the benefits farmers found in applying conservation agriculture practices within the Quesungual system, were:

• improved soil moisture conservation, which permits a good development of the crop, even in very bad conditions (such as El Niño in 1997);

• less soil erosion (even during the heavy rains of hurricane Mitch in 1998);

• reduced disease incidence in the bean crop due to the mulch;

• production of firewood and fruits from the trees and shrubs; timber trees can also be cut after about 7 years and used for construction or sold;

• the soil becomes more fertile and the effect of fertilizers on the production is higher;

• agricultural production is higher than in traditionally managed plots;

• plots can be cultivated for longer periods than in the slash and burn system;

• less labour involved in the establishment and maintenance of the system;

• improved soil workability, which implies less labour need during land preparation and sowing;

• harvested products, such as beans and maize, can be dried by hanging them over the tree trunks;

• cattle can feed on the residues after the harvests of maize and sorghum;

• trees and shrubs in the plot provide shade for the farmer and attract animals and insects, birds and butterflies.

The disadvantages mentioned by the same farmers were:

• equal or slightly lower grain production during the first year compared to the traditional system;

• higher incidence of slugs in the bean crop during the first years;

• sometimes too much soil cover impedes the germination of the seeds;

• the shade can result in higher disease incidence during periods of high rainfall because of higher humidity.

stalks from the previous crops on the

surface In this way organic matter can

be built up in the soil, which has great

influence on the activity and the

population of the micro-organisms This

results in a greater biological activity

(Box 9) , more humus formation, and

hence a darker coloured topsoil With

time, in reduced or zero tillage systems,

soil fauna take over the functions of

traditional soil tillage, which is loosening

the soil and mixing the soil components

In addition, the increased biological

activity creates a stable soil structure

through accumulation of organic matter

The vegetal cover on the soil surface

creates a more humid environment,

which is conducive to the activity of soil

organisms The greater numbers of

worms, termites, ants and millipedes

combined with a higher density of plant

roots result in more large pores, which in

turn increase water infiltration (Roth,

1985) Thus in an experiment in southern

Brazil rainwater infiltration increased

from 20 mm/h under conventional tillage

to 45 mm/h under no-tillage (Calegari

et al., 1998) As a result soil erosion may

be reduced to a level below the

regeneration rate of the soil and the

groundwater resources may be

maintained or even enhanced (Derpsch

1997) Leaching of plant nutrients or

other substances into the aquifer is also

reduced (Becker 1997) compared to conventional arable agriculture Soil moisture storage andavailability is also improved both by soil cover (less evaporation, more infiltration) and soil organicmatter All these phenomena are improving plant nutrition (Box 10)

Organic matter also plays an important role in the formation and stabilisation of soil aggregatesthrough connecting the organic polymers and the inorganic surface with polyvalent cations Thehyphae fungi and bacteria slime, even if formed and decaying again rapidly, also play an importantrole in connecting soil particles A strong relationship also exists between the soil carbon content

and an increase in aggregate size Castro Filho et al (1998) found an increase in soil carbon

content under zero tillage resulting in a 134 percent increase in aggregates of more than 2 mmand a 38 percent decrease in aggregates of less than 0.25 mm, compared to conventional tillage.Where conditions are suitable, increased residues and soil cover resulting from higher yieldscan generate an upward spiral in soil productivity The inclusion of leguminous green-manure orcover crops in small-farm systems has shown such effects by providing not only dense cover

B OX 9: Soil microbial communities and zero

tillage

A component of soil quality maintenance is favouring the activity of beneficial soil organisms Among the most important species are the root nodule bacteria involved

in biological nitrogen fixation Several studies have indicated that zero tillage systems increase soil microbial biomass and the size of the microbial population (Ferreira

et al 2000) For zero tillage systems in southern Brazil,

differences of about 50 percent in soil biomass and rhizobial populations compared to conventional tillage

were reported (Hungria, et al 1997) Evaluations have

demonstrated that some crop rotations and zero tillage favour bradyrhizobia populations (Figure 2), nodulation and thus nitrogen fixation and yield (Voss and Sidirias,

1985, Hungria, et al 1997, Ferreira, et al 2000).

F IGURE 2 Population size of root nodule bacteria under zero tillage (left) and conventional tillage (right) with different crop rotations [S=soya; W=wheat; M=maize] (Voss and Sidirias, 1985)

and large quantities of organic matter to the soil, but also significant quantities of microbiallyfixed nitrogen.

Castro (1991) compared water, soil and plant nutrient loss between conventional agriculture

and direct seeding in a wheat-maize rotation The losses were less under direct seeding due tothe soil cover, which reduced the rainfall impact on the soil surface (Table 3)

Mitigating climate changes and greenhouse gases

Emissions of the so-called greenhouse gases resulting from human activities are substantiallyincreasing the atmospheric concentration of carbon dioxide (CO2), methane (CH4) and nitrousoxide (N2O) Half of the increase in global warming since the industrial revolution is considered

to be the consequence of an increased level of carbon dioxide in the atmosphere (Lal, 1999).Sources of carbon dioxide emissions include burning of fossil fuels, industrial production,

B OX 10: Nutrient availability under various cover crops (southern Brazil)

Different cover crops and tillage systems may affect the availability of plant nutrients, especially nitrogen These effects are being evaluated in long-term soil management experiments in southern Brazil:

The reduction of tillage and the addition of nitrogen by legumes in the cropping system increased the total nitrogen in the soil The intensive system consisted in oats and clover as the cover crops and maize intercropped

afterwards with cowpea (Vigna unguiculata), under zero tillage After five years, the 0-17.5 cm soil layer

contained 490 kg/ha more total soil nitrogen than the traditional system oats-maize under conventional tillage After nine years, the system even resulted in a 24 percent increase in soil N compared to conventional tillage

(Amado et al., 1998).

Calegari and Alexander (1998) found that after nine years, the phosphorus content (both inorganic and total)

of the surface layer (0-5 cm) was higher in the plots with cover crops Depending on the cover crop the increase was between two and almost 30 percent This indicates that the different cover crops have an important P-recycling capacity and this was even improved when the residues were retained on the surface This was especially clear in the fallow plots, where the conventional tillage plots had a P-content 25 percent less than the zero tillage plots.

According to Burle et al (1997), many studies report soil acidification in legume-based systems caused by

intense nitrification followed by NO3- leaching, H3O + excretion by legume roots, and the export of animal and plant products In general, legume-based systems did not increase soil acidification in the surface layer, where the greatest soil organic matter accumulation occurred.

The highest soil cation exchange capacity (CEC) is found in legume-based cropping systems with the highest

organic matter content Especially systems with pigeon peas (Cajanus cajan) resulted in a 70 percent

increase of the CEC compared to a fallow-maize system.

The highest levels of exchangeable K, Ca and Mg were found in systems containing pigeon peas and lablab

(Dolichos lablab) and lowest in systems containing clover It is possible that clover systems had increased

NO3- leaching, which may be accompanied by increased leaching of exchangeable Ca and Mg (Burle et al.,

Water

m 3 /ha Soil t/ha kg/ha

Conventional agriculture 700 29 56 3 36 83 18 Conservation agriculture

using zero tillage

deforestation and agriculture Although estimates of the total CO2 emissions vary widely, thecontribution of forestry and agricultural activities to the emission of carbon dioxide is estimated

at only five percent of the global total (Benites et al., 1999).

Conversely, the potential of agriculture and forestry for sequestering carbon (the absorption

of carbon in biomass) is significant (Box 11) For example, systems based on high crop residueaddition and no-tillage tend to accumulate more carbon in the soil than is released into theatmosphere (Greenland and Adams, 1992) Bayer (1996) found that crop rotation systemsaccumulated about 11 t/ha of carbon in the topsoil (0-17.5 cm) after nine years Under conventionalagriculture and with monoculture systems the carbon liberation into the atmosphere was about1.8 t/ha per year of CO2 (Reicosky et al., 1995).

Reduction of contamination and water pollution

The change in land use and management associated with conservation-effective practices leads

to a significant reduction in erosion, and thus to a reduction in water pollution and contamination(Plate 7)

Indicators that can be used to measure this reduction of water pollution include:

• Water turbidity and the concentration of sediments in suspension;

• Total sediment loss and associated loss of nutrients;

• Reduction of water treatment costs

Bassi (2000) found significant reductions of water turbidity and concentration of sedimentsover a period of ten years (1988-1997) in different catchment areas in southern Brazil Thereductions varied between 50 and 80 percent, depending on soil types predominating in theareas These reductions are due to increased perennial crops (banana and pasture) on hillsides,thus reducing the erosion process Total sediment loss decreased by 16 percent and the cost of

B OX 11: Carbon sequestration (southern Brazil)

The emission of carbon dioxide to the atmosphere is related to the mineralisation and decomposition processes

of soil organic matter by micro-organisms (Lal, 1999) The CO2 emission from the soil is increased by ploughing, mixing crop residues and other biomass into the soil surface and burning of biomass.

Studies in southern Brazil show an increase in organic carbon in the soil under conservation agriculture The different cover crops showed significant effects on the organic carbon level for two depths (0-5 cm and 5-

15 cm) The means of all winter cover crops presented greater values for soil organic carbon than fallow at both depths (Calegari and Alexander, 1998).

During the initial years until establishment of the cropping system the increase in total organic carbon content

was restricted to only the surface layers of the soil (0-2.5 cm) (Testa et al., 1992) With time, this effect reached deeper soil layers (2.5-7.5 cm) Castro Filho et al (1998) found a 29 percent increase of soil organic

carbon in no-tillage compared to conventional tillage in the surface 0-10 cm of the soil, irrespective of the cropping system.

Compared to the cropping system fallow-maize, which was taken as a reference, soil carbon content

increased by 47 percent in the system maize-lablab (Dolichos lablab) and by 116 percent in the maize-castor (Ricinus communis) cropping system In systems where nitrogen was applied as a fertilizer the carbon contents increased even more (Testa et al., 1992).

Bayer and Mielniczuk (1997) found that five years after the introduction of intensive cropping systems containing leguminous crops (especially the cropping systems oats+clover-maize and oats+clover- maize+cowpea), soil organic carbon contents were restored, after the loss of 8.3 tons of organic carbon per hectare under previous cropping systems.

plant nutrients by 21 percent Reduced sediment loss and less soil particles in suspension alsoreduced the cost of water treatment Data obtained in Chapecó indicated that the quantity ofaluminium sulfate used for flocculating suspended solids fell by 46 percent over a period of fiveyears.

Enhancement of biodiversity

The result of increasing soil cover, through

living crops and crop residues, is an

increase in the variety and variability of

animals, plants and micro-organisms, which

are necessary to sustain key functions of

the agro-ecosystem

Conservation agriculture provides more

habitats for birds, small mammals, reptiles

and earthworms, amongst others, and more

food, including insects and seeds, which in

turn leads to an increase in species and

population The increased production from

conservation-based agriculture also makes

it possible to set aside areas for natural

regeneration (Box 12)

Less vulnerability to natural disasters

The improved soil conditions make the land

and the agricultural system more resilient

to extreme events This effect has been

studied in the Quesungual system (Lempira,

Honduras – Plate 8) during the Canicula,

El Niño, and excessive rainfall during

P LATE 7 Flooding and sediment transport to the river increasing cost of water treatment

[WOCAT, FAO, 2000]

B OX 12: Increase of protected areas through livestock management (Costa Rica)

Traditionally, livestock was produced in hilly areas, in

an extensive form, without any management of the resources, leading to erosion and environmental problems After the hurricane Cesar in 1996, a rehabilitation programme was launched to reinitiate agricultural production in a sustainable way The solution for livestock production was to change towards a more intensified production system, with the objective to reduce degradation risk, improve the nutrition status of the cattle and liberate areas which can be used for other activities, including the natural regeneration of the vegetation.

The intensified system is based on semi-stall-fed production of livestock and was initiated through a farm planning in order to define land use capacity and to select the areas most suitable for livestock raising Part

of these areas was then sown with improved pastures and the rest with fodder crops The improved pastures were divided into smaller parcels to permit rotational grazing The fodder crop area is fertilized with manure produced in small stables.

The intensification of the livestock system has resulted

in spectacular increases in the production of meat and milk The relocation of livestock activities has led to the natural regeneration of severely eroded land and areas unsuitable for agricultural production, which is having

a positive effect on the biodiversity and allows the government to “trade” the area in international treaties dealing with forest protection or carbon sequestration.

hurricanes, such as Mitch in 1998.

Compared to farmers who did not

change their cropping system from the

traditional slash and burn, the

Quesungual farmers did not

experience a major loss in maize

production during the dry period of El

Niño in 1997, as is shown in Figure 3

Even the following year, when

hurricane Mitch passed over Central

America resulting in excessive

rainfall, and many farmers lost their

crop for the second time, the

Quesungual farmers obtained similar

yields as in the year before El Niño

The Quesungual system is an

indigenous agroforestry system characterised by the combination of naturally regenerated and

pruned trees and shrubs with more traditional agroforestry components, such as high-valuetimber and fruit trees The traditional staple crops, i.e maize, sorghum and beans, are grownbetween the trees

P LATE 8

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,

roghum and beans are grown

[A.J Bot]

F IGURE 3 Maize production under the Quesungual system

(Alvarez and Flores, 1998)

* Data from only one of the farmers (Bot, personal observation)

Chapter 3 Rural communities actively implementing conservation

agriculture

“In the past we relied on natural regeneration to improve our soil fertility, then we relied on fertilizer Now that the population has increased and the cost of fertilizer has gone up, we have to rely on our own efforts to regenerate our soils.”

The traditional slash and burn system has been used for generations in many countries, to clearthe land before sowing the crops It consists of slashing part of the forest vegetation and burningthe debris Depending on population pressures and other factors the cleared plot may be usedfor cultivation for only one to three years, and may then be left fallow while another plot will becleared This system is only sustainable where there is land in abundance

With high population pressures, however, there is less land available, fallow periods areshorter and the plot will be cultivated for more years Reduction of the fallow period, biomassburning and over-use of the natural resources lead to a loss of organic matter and plant nutrients,increasing erosion and lower yields

Farmers have the ability to make development sustainable – to ensure that it meets the needs

of the present without compromising the ability of future generations to meet their own needs.Usually their decisions about change are strongly influenced by their assessment of the risksattached to an innovation including its possible side effects Their seemingly reactionary orconservative attitudes may be in fact an essential caution in weighing the possible benefits andhazards that could follow change

Where new conservation-effective technologies or practices have met farmer requirementsfor risk aversion, create no major conflicts and have an assured beneficial effect, adoption hasbeen shown to be very rapid, e.g zero tillage in the Brazilian cerrado, use of shade trees forcoffee production in parts of Costa Rica, agroforestry in Kenya and Nepal

Farmers have multiple objectives, hence a need for multi-disciplinary analysis of the problemsthey face in specific situations, and for multi-purpose solutions But they often do not havecontact with people and information that can help them work out appropriate solutions to theproblems which they really face, and which are not always those in fashion among policy makers,technicians and scientists (Box 13)

The challenge is for would-be advisers to develop a sense of partnership with farmers,participating with them in defining and solving problems rather than only expecting them toparticipate in implementing projects prepared from outside

Farmers have latent skills and enthusiasm,

which are tapped when they are involved in doing

things that concern and interest them For

instance, experiences with small resource-poor

farmers in Kenya, Costa Rica, El Salvador and

Honduras show that in cases where

conservation-effective farming can increase their

cash incomes, they are keen to adapt and adopt

such techniques, even if this may lead ultimately

to a complete change in farming system (Plate 9)

For example, the Quesungual system

(Box 14) offers an alternative land use practice

for farmers as land becomes scarcer in this area,

due to continued inequality in land distribution and

population increases It has proved to be a

sustainable system surviving with minimal damage

the El Niño period in 1997 and excessive rainfall

after hurricane Mitch in 1998

Successful improvement of land husbandry in a catchment depends not just on the motivations,skills and knowledge of individual farmers, but also on actions taken by groups, communities orregions as a whole Simple extension of the message, even coupled with demonstration, usuallywill not suffice Community-based action through local institutions and users’ groups will also berequired

The development of common-interest groups around the concepts and practices of conservationagriculture has already served to provide encouragement and mutual support to members asthey make the changeover These groups have become very effective in farmer-to-farmerspread of the beneficial ideas and practical technologies They have also begun to develop intosignificant local pressure-groups for improvements in the policy and institutional environment so

as for political and legal support to their initiatives.

B OX 13: Indigenous knowledge and empowerment in Africa

African farmers developed forms of conservation agriculture centuries ago To a large extent the advent of colonialism, Western- trained agriculturalists and the moldboard plough slowed the further development and adoption

of these practices What is now required is to re-empower the farmers by making them aware of:

the importance to themselves (not just to future generations) of the soil entrusted to them; the value of the experience they have inherited and the expertise they have developed.

And then providing:

methods whereby s/he can determine for her/ himself the major constraints in her/his production system;

a “basket” of options which have proved successful elsewhere to select from and test under their own conditions as to the suitability for their requirements.

(Fowler, 2000)

P LATE 9 Maasai, traditionally herding cattle, are engaging in vegetable growing activities to increase their income and spread the risks

[A.J Bot]

For example, zero tillage in Brazil is a story

of farmer-led technological evolution and

integration Farmers and technicians who

adopted this technology have, so far, consistently

resolved all the challenges to its sustainability in

the humid sub-tropics and humid wet-dry tropics

of Brazil, and obtained results in the humid

tropics This successful experience was initiated

and supported by the Brazilian Zero Tillage

Association for the Tropics, ZTAT (Box 15),

which helped to disseminate the technology in

the tropical region of the country

Zero tillage was attractive to farmers for

several reasons: lower production costs, a longer

period available for planting, a simpler operation

to manage, greater drought tolerance, reduced

investment and replacement costs for farm machinery and generally higher yields The farmersthemselves have been extremely active in promoting the new technology The adoptionmechanisms are based on the large-scale continuing substitution of conventional tillage by zerotillage technology The area under zero tillage in Brazil is estimated at over 13 million ha in 1999/

2000, about 30 percent of the area of annual summer crops The tropical region represents onethird of Brazil’s zero tillage area

From the farmer’s point of view, the main obstacles to adoption of zero tillage were the lack

of knowledge, information and technical support Considerations of erosion losses, lack of research,crop insurance and opinions of agronomists were not as important when deciding whether toadopt zero tillage or not

The obstacles were overcome through the activities of Clubes Amigos da Terra (Box 16).The operational basis of the CATs is farmer-to-farmer exchanges of experiences on a monthlybasis Organization of promotional events, such as field days and debates, to assist the spread ofzero tillage is common during the learning phase (Landers, 2000) CATs also organise on-farmresearch and pilot projects with the support of other organizations An important factor for

B OX 14: The Quesungual agroforestry system – Lempira (Honduras)

The Quesungual system is an indigenous agroforestry system Its 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 It is mainly practised by smallholder farmers (1-3 ha).

Prior to sowing, vegetation is cleared by hand – not burnt, and in addition some farmers use a herbicide Still

in the dry season, the trees and shrubs are pollarded at a height of 1.5 - 2 m, in order to eliminate the branches and regrowth and provide light for the future crop The pollarded material is used as a surface cover The branches and trunks, which can be used as firewood and poles, are removed from the plot In general, high- value timber trees and fruit trees are not pruned Farmers achieve an ideal density through the management

of the natural regeneration A typical plot consists of numerous pollarded trees and shrubs and about 15-20 large trees: timber and fruit species The diversity of species in the system is high.

Farmers usually use zero tillage for crop sowing or minimum tillage in very specific situations The major production system of the region is subsistence agriculture (maize, beans and sorghum) characterised by its low productivity Maize is the first crop, intercropped with (both) sorghum and beans Before sowing the second crop (often beans) the field is cleared a second time but trees and shrubs are not necessarily pollarded Mineral fertilizers are expensive and thus only used when maize and sorghum are both grown as first crop Only once during the cropping season, weeds are cleared either manually or by using a herbicide The crops are harvested in the traditional way.

B OX 15: The Zero Tillage Association for the Tropics (ZTAT) – (Brazil)

ZTAT was born from the recognition by nearly fifty farmers and technicians that they could help fill the gap which existed from lack of adequate research information on the nascent tropical zero tillage technology.

By the creation of a network of local farmers’ clubs (CATs: BOX 16), with the objective of disseminating and improving zero tillage technology, it only took eight years to become a significant and representative force in the region.

By that time, ZTAT had forged fruitful partnerships with government and private sectors and achieved

a reputation for technical leadership in tropical zero tillage.

(Landers, 2000)

success has been the assistance which medium and

large farmers, through individual CATs and ZTAT

(now FEBRAPDP, the Brazilian Federation for

Direct Planting into Crop Residues), have provided

to small farmers wishing to adopt zero tillage Private

sector support and ZTAT integration with farmers

was fundamental to the expansion of zero tillage

Once large farmers have developed the

technology, the research and development effort

required to adapt the system to small farmers is

relatively small Thanks to a FEBRAPDP-initiated

pilot project in south Brazil, where zero tillage by

small farmers is well developed, there are more than

ten manufacturers specialising in zero tillage

machinery for small farmers Both in south Brazil

and in Paraguay, zero tillage systems for small

farmers that eliminate the need for herbicides have

been developed

Recently the LandCare movement in South Africa adopted a similar approach as CAT inBrazil, advocating the establishment of local Landcare Groups which would conduct situationanalyses, broaden their strategic understanding with a visioning process, then undertake aparticipatory land use planning, ideally initially at a micro-catchment level (Auerbach, 2000).Another example is the Association for Better Land Husbandry in Kenya (Box 17) ThisNGO aims to identify and promote low-cost methods of better land husbandry that effectivelycombat poverty and improve the livelihood of rural people

Before introducing conservation agriculture, it may be necessary to eliminate or alleviate somemajor effects of degradation, such as compacted soil layers, plant nutrient deficiencies or toxicity,heavy weed infestation

P LATE 10

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

1993 with farmers and technicians interested in zero tillage in the region of Brasilia.

The main objective of the CAT network is the promotion of zero tillage CATs are non- profit, non-commercial and non-political, open to anyone interested and self- managed, interacting with ZTAT as a central support agency After 2-3 years, when farmers have solved most of the immediate problems, support by outside specialists becomes more frequent At this point CAT leadership becomes more important in order

to facilitate a change from a pioneer context

to a sustainable one.

Depending on their depth, compacted layers in the soil may need to be broken by subsoiling.Subsoiling of compacted and degraded soils can bring spectacular effects due to higher waterinfiltration and result in immediate yield increases of up to 30 percent.

However, subsoiling is a very energy demanding operation In degraded soils it can easilylead to a recompaction of the soil which could be even more severe than the original compaction.Therefore subsoiling should only be undertaken in combination with other structure buildingoperations and much care should be taken not to compact the loosened soil Sandy soils areparticularly prone to compaction, and subsoiling may have to be repeated after some years evenunder a zero tillage system

In case of shallower compaction horizons deep chiselling of the entire plot might be requiredduring the first and possibly, the second year before changing to a true minimum or zero tillagesystem Care should be taken to select tools that loosen the soil with a minimum of surfacedisturbance Particularly the transport of clods to the soil surface should be avoided

Biological chiselling, using different species of deep rooting plants, such as pigeon pea (Cajanus

cajan) and castor bean (Ricinus communis) to break hardpans may be a cheaper and more

sustainable, albeit slower, option as the structuring elements of the “chiselling” remain in the soil

in form of root channels and additional organic matter is applied to the soil

Before converting a field to zero tillage, care should be taken that the soil surface is assmooth (level or sloping) as possible Plough furrows, tracks of machines and tractors or anyother irregularities should be levelled, as this will not be practical any more under zero tillage.Severe nutrient deficiencies should be corrected by incorporating mineral fertilizers (especiallyrelatively immobile elements such as phosphorus) into the soil in order to encourage deep rooting.Aluminium toxicity, salinity or other severe soil chemical or physical anomalies might requirechemical remedies However, these actions should be well planned and the reclamation operation,defined on a case by case basis, should be carefully implemented

Weed management is critical for a successful transition Weed growth must be controllednot only during but also between cropping seasons to prevent multiplication of weed seeds andthe unnecessary utilisation of soil moisture This can be achieved by using cover crops or bychemical weed control

B OX 17: The Association for Better Land Husbandry (ABLH) – (Kenya)

ABHL works on the premise that systems of productive and sustainable land use can be built on existing skills, knowledge and organizations of rural people It is designed to encourage groups of farmers to develop productive conservation practices for themselves with a minimum of inputs and subsidies It concentrates mainly on organic based farming practices and those that require a minimum of cash investments.

Besides the technical aspects the association aims at stimulating a conservation for business approach that brings the products of conservation farming to the market place, often in the form of processed products with value added It operates by providing support to participatory research and development programmes working with small scale farming groups.

One of the practices promoted by ABLH is double digging of vegetable beds: a system of deep digging and incorporating compost into the soil, mainly practised in kitchen gardens and maize fields The cash income from the sale of the vegetables not only allows purchases of maize and other foods but also meets other essential household needs, such as school fees.

Surveys indicate that self-sufficiency in maize is increased from 22 percent to 48 percent of the farmers; hunger experience is reduced from 57 to 24 percent; the proportion of farmers buying vegetables is reduced from 85 to 11 percent and the proportion of those selling vegetables is increased to 77 percent.

The need for purchased inputs, especially mineralfertilizers and herbicides, may increase in some cases

in the early phase of adoption of conservation agriculture,but only until a higher level of soil fertility and biologicalactivity are established and a new balance betweencrops and other plants (weeds) and between pests andbeneficial organisms is reached

The long term experience with conservationagriculture shows that in commercial farming operationsthe need for purchased farm inputs decreases, as theunderstanding of the systems grows with themanagement capacity of the farmer (Derpsch, 1997)

On severely degraded soils, it might be necessary togrow heavy crops of green manure and incorporate themdeeply into the topsoil during the first year But this should

be only a first step: later, the biomass should be managed

without its incorporation into the soil In this way organic

matter can be built up in the soil, which has greatinfluence on the activity and the population of the micro-organisms Green manure and other vegetation can beused as a soil cover with mechanical methods (kniferollers or in special cases, mowers or choppers) or bydesiccation with herbicides

Within the framework of the Soil Fertility Initiative

(SFI), the International Centre for Research in

Agroforestry (ICRAF) has been identifying and

evaluating options for soil fertility replenishment in East

and Southern Africa Two years after introducing

identified options in farmers’ fields, 8 700 smallholder

farmers in western Kenya had adopted two of them:

• biomass transfer with the use of the wild sunflower

Tithonia as a green manure (Plates 11 and 12);

• improved fallows with Crotalaria sp., Tephrosia

vogelii and Sesbania sesban

The practice of applying Tithonia as a green manure

consists of cutting and chopping leaves and soft twigs

into small pieces, before the flowering, and then spreading

them evenly over the surface and incorporating them

into the soil As applying Tithonia to a maize crop is not

profitable, farmers are applying Tithonia to high-value

crops such as sukumawiki (Brassica sp.), french beans,

tomatoes and napier grass Profits were substantially

increased, ranging from US$91 to US$1 665 per ha, but

the practice is very labour intensive, even if Tithonia is

now grown on internal and external borders and

boundaries, as well as on contour ridges close to the

P LATE 11

A Kenyan farmer in front of his Tithonia

hedge, which is cut and used to fertilize

his sukumawiki crop (Brassica sp.)

[A.J Bot]

P LATE 12

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

[A.J Bot]

fields, in order to reduce the time required to

collect and carry the material into the field

The other practice adopted by farmers is

the improved fallow (Box 18) Surveys have

indicated that an average of 23-30 percent of

the farmers in western Kenya leave their land

fallow for a period of three to six months,

and some of them up to one or two years

The reasons for leaving land under natural

fallow according to farmers, are the

availability of land and labour, erratic rainfall

and the soil fertility status of the land

The limitations of these techniques are the

nematode problem and the fact that the soil

is still being tilled, which is not an improvement

of the soil management under tropical

conditions Conservation or zero tillage should

be introduced and the residues produced could

then be used as soil cover, which would be

more effective for the soil fertility and less

labour demanding than incorporating them

Crop rotation, which is an important

practice in conservation agriculture, allows the

cultivation of more than one crop, so that

farmers can spread the risk of fluctuating

prices Also, in addition to the positive effects

on soil organic matter and nutrient cycling,

rotations can help break disease, weed, and

insect-pest cycles (Box 19) When crops are

grown in a rotation, they usually do better than

when the same crop is grown in the same

field year after year Rotations can also

spread labour needs more evenly during the

year

The presence of crop residues on the soil

surface require changes in the seeding and

planting techniques used by farmers Cover

crops and crop residues can be managed by

desiccation with herbicides, or mechanically

by means of cutting, crushing or bending the

plants

Any use of herbicides should be with full

regard for health and safety of the operator

and for the environment (Plate 13) The use

of herbicides should be considered only one

of the options in an integrated approach to

B OX 18: Improved fallow with legumes

In order to restore the soil fertility in a shorter period than traditional fallow, several fast growing leguminous species are introduced into the farming system During the long rains (March-July) when maize is grown, the leguminous species are undersown after or during the second weeding After harvesting the maize crop, the fast growing species take over, using the remaining soil moisture and the short rains, which start in September Depending on their density and growth habit the legumes will suppress the emerging weeds In February the legumes are cut and left to dry for a few days Then the woody stems and twigs are removed, which will be used for fuel, and the leaves are incorporated into the soil by tillage With the onset of the long rains maize is sown.

After three years of maize production the improved fallow is repeated and maize can be grown for another three years, before yields start to decline The difference with the traditional way of preparation is that fallow lands are no longer burned prior to sowing Although farmers derive major advantages from the improved fallow (increased

maize yields, fuel, less Striga infestation after a Sesbania fallow), root-knot nematodes are a problem both for Tephrosia and Sesbania, and

susceptible crops, such as tobacco, tomato, and beans, which are planted following these fallows, will also be affected and yield poorly.

Box 19: Improving conservation agriculture

of toxic pesticides.

It is not sufficient, therefore, to merely maintain soil cover and use tillage systems that cause minimum soil disturbance Direct sowing is a system and not just a method of land preparation For the system

to be successful, it is necessary to introduce crop rotations (not just cover crops), i.e the use of a sequence of different species in time and space within the farm (FAO, 2000).

Crop rotation is the basis for the sustainability of direct-sowing systems A production system including green manure, crop rotation and zero tillage, can be regionally adapted and therefore can contribute to the sustainability of soil management

in the region.

weed and cover crop management This is especially important in cases where farmers do notyet have experience in the use of chemicals, or lack financial resources to afford them.

A good alternative for using herbicides is

bending and crushing with a knife-roller

(Plate 14) This consists of a roller on which

knives are mounted transversally and a

support, traction and protection structure

When the roller is pulled, the knives bend over

and crush or chop off the plants Part of the

plant biomass comes into close contact with

the soil, where the interaction with the soil

fauna can start In case of the establishment

of subsequent crops, the bending over should

be done in the beginning of the reproductive

stage, when the seeds are not yet viable

Leguminous species therefore should be

managed at the full flowering stage, and

cereals and grasses at the milky stage

For example in Northern Brazil, the

traditional shifting cultivation system consists

of a two-year cropping period followed by a

fallow period of several years The land is

prepared by burning the slashed fallow

vegetation Intensification of land use with

continuation of the traditional agricultural

practices leads to a decrease of the system’s

productivity A prototype chopper encouraged

the farmers to change to a conservation

agriculture system (Box 20)

Seed drills and planters have been

developed that can plant through increased amounts of crop residues and into soil that has notbeen tilled at all (Plates 15 and 16) The development of this planting and seeding technology aswell as the existence of effective mechanical as well as chemical residue management andweed control technologies, make it possible to grow a crop without any tillage In these systems

P LATE 13 Implements have been adapted for resource-poor farmers: a herbicide spray, which can be drawn either manually or by animals

• to cut the secondary forest vegetation close the ground, facilitating weeding as no stumps;

• not to damage the root systems with the chopper

or with the tractor to assure a vital re-growth of the fallow vegetation by re-sprouting;

• to chop the plant material while moving and cutting, spreading the chips homogeneously over the field;

• to be simple and robust, and to work with a conventional tractor.

The prototype machine constructed on the basis of these specifications found immediate interest, encouraging the small farmers to adopt the mulch farming system without burning.

(Block et al., 1999)