An Introduction to Agroforestry - World Agroforestry Centre

489 Pages·2006·7.63 MB·English

P.K. Ramachandran Nair
An Introduction
to Agroforestry
KLGWER ACADEMIC PUBLISHERS
An Introduction to Agroforestry
P.K. Ramachandran Nair
Department of Forestry,
University of Florida,
Gainesville, Florida, U.S.A.
Kluwer Academic Publishers
DORDRECHT / BOSTON / LONDON
IN COOPERATION WITH
International Centre for Research in Agroforestry
ICRAF
Library of Congress Cataloging-in-Publication Data
Nair, P. K. R.
An introduction to agroforestry / P.K. Ramachandran Na1r.
p. cm.
Includes bibliographical references and index.
ISBN 0-7923-2134-0 (alk. paper)
1. Agroforestry . I. Title.
S494.5.A45N3543 1993
634.9'9—dc20 92-46550
ISBN 0-7923-2134-0
Published by Kluwer Academic Publishers,
P.O. Box 17, 3300 AA Dordrecht, The Netherlands.
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Printed in The Netherlands
Contents
Preface xi
Acknowledgements xiii
Section I. INTRODUCTION
1. The history of agroforestry 3
References 11
2. Definition and concepts of agroforestry 13
Community forestry, farm forestry, and social forestry 16
References 17
Section II. AGROFORESTRY SYSTEMS AND PRACTICES
3. Classification of agroforestry systems 21
3.1. Structural classification of systems 24
3.2. Classification based on function of systems 26
3.3. Ecological classification 28
3.4. Classification based on socioeconomic criteria 30
3.5. A framework for classification 31
3.6. Agroforestry systems and practices 32
References 35
4. Distribution of agroforestry systems in the tropics 39
4.1. The tropical environment 39
4.2. Distribution of tropical agroforestry systems 41
4.3. Agroecological spread of tropical agroforestry systems 48
References 53
v
vi Contents
5. Shifting cultivation and improved fallows 55
5.1. System overview 55
5.2. Soil management and shifting cultivation 60
5.3. The evolution of planted fallows 63
5.4. Improved tree fallows 68
References 71
6. Taungya 75
6.1. Soil management 78
6.2. Alternatives and improvements to Taungya 79
References 83
7. Homegardens 85
7.1. Types of homegardens 85
7.2. Structure of homegardens 91
7.3. Food production from homegardens 94
7.4. Research on homegarden systems 95
References 96
8. Plantation crop combinations 99
8.1. Integrated land-use systems with plantation crops 100
8.2. Smallholder systems with coconuts: a notable example of
integrated land-use 103
8.3. Crop combinations with other plantation crops 115
8.4. Multistory tree gardens 117
References 121
9. Alley cropping 123
9.1. Nutrient yield 125
9.2. Effect on soil properties and soil conservation 127
9.3. Effect on crop yields 130
9.4. Future directions 134
References 137
10. Other agroforestry systems and practices 141
10.1. Tree fodder and silvopastoral systems 141
10.2. Agroforestry for firewood production 144
10.3. Intercropping under scattered or regularly planted trees 146
10.4. Agroforestry for reclamation of problem soils 150
10.5. Underexploited trees in indigenous agroforestry systems 152
10.6. Buffer-zone agroforestry 153
References 155
Contents vii
Section III. AGROFORESTRY SPECIES
11. General principles of plant productivity 161
11.1. Photosynthesis 161
11.2. Plant productivity 165
11.3. Manipulation of photosynthesis in agroforestry 167
References 170
12. Agroforestry species: the multipurpose trees 171
12.1. Multipurpose trees (MPTs) 172
12.2. Herbaceous species 182
References 183
Appendix: short descriptions of multipurpose trees and shrubs
(MPTs) commonly used in agroforestry systems 201
13. Component interactions 243
13.1. Positive (production-enhancing) interactions 245
13.2. Negative (production-decreasing) interactions 249
13.3. Component management 254
References 255
Section IV. SOIL PRODUCTIVITY AND PROTECTION
14. Tropical soils 261
14.1. Soil classification: the U.S. soil taxonomy and
the FAO legend 261
14.2. Tropical soils 263
References 266
15. Effects of trees on soils 269
15.1. Beneficial effects 271
15.2. Adverse effects 273
References 274
16. Nutrient cycling and soil organic matter 277
16.1. Nutrient cycling in tropical forest ecosystems 277
16.2. Nutrient cycling in agroforestry systems 279
16.3. Improving nutrient cycling efficiency through management 283
16.4. Soil organic matter 289
16.5. Litter quality and decomposition 291
16.6. Trees and biomass production 296
16.7. Role of roots 297
16.8. Conclusions 301
References 303
viii Contents
17. Nitrogen fixation 307
17.1. Rhizobial plants 308
17.2. Actinorhizal plants 311
17.3. Estimation of nitrogen fixation 312
17.4. Technology for exploiting nitrogen-fixing trees
in agroforestry 315
17.5. Future trends in N fixation research in agroforestry 319
2
References 319
18. Soil conservation 325
18.1. Changing concepts and trends 327
18.2. Measurement of soil erosion 328
18.3. Effect of agroforestry on erosion factors 328
18.4. Erosion rates under agroforestry 331
18.5. Trees as windbreaks and shelterbelts 333
18.6. Erosion control through agroforestry in practice 338
References 343
Section V. DESIGN AND EVALUATION OF AGROFORESTRY SYSTEMS
19. The diagnosis and design (D & D) methodology 347
19.1. The genesis of D & D 347
19.2. Concepts and procedures of D & D 348
19.3. Key features of D & D 351
19.4. Variable scale D & D procedures 352
19.5. Comparison of D & D with similar methodologies 355
References 356
20. Field experiments in agroforestry 357
20.1. Agroforestry research: different perspectives 358
20.2. Principles of field experimentation 361
20.3. Special considerations in agroforestry experiments 362
20.4. The current state of agroforestry field experimentation 368
20.5. Prognosis of the directions in agroforestry research 370
References 372
21. On-farm research 375
21.1. General considerations 375
21.2. Modified stability analysis of on-farm trial data 377
21.3. On-farm research in agroforestry 379
21.4. Methodologies for on-farm research in agroforestry 380
21.5. Conclusions 382
References 382
Contents ix
22. Economic considerations 385
22.1. General principles of economic analysis 385
22.2. Financial and economic analyses 389
22.3. Project analysis 391
22.4. Past and recent economic studies of agroforestry 406
22.5. Conclusions 408
References 408
23. Sociocultural considerations 413
23.1. Agroforestry as a social science 413
23.2. Important sociocultural factors in agroforestry 414
23.3. Farmer's perception of tree planting 418
23.4. Government policies and agroforestry implementation 421
23.5. Social acceptability of agroforestry 423
References 425
24. Evaluation of agroforestry systems 429
24.1. Productivity evaluation 429
24.2. Sustainability evaluation 432
24.3. Adoptability evaluation 434
24.4. Towards development of a methodology for evaluating
agroforestry systems 435
References 438
Section VI. AGROFORESTRY IN THE TEMPERATE ZONE
25. Agroforestry in the temperate zone 443
25.1. Characteristics of temperate-zone agroforestry 443
25.2. Historical perspective 445
25.3. Current temperate-zone agroforestry systems 446
25.4. Opportunities and constraints 462
References 465
Glossary 469
List of acronyms and abbreviations 483
SI units and conversion factors 485
Subject index 491
Preface
Agroforestry has come of age during the past fifteen years. During this period,
activities and interest in agroforestry education and training have increased
tremendously, as in other aspects of agroforestry development. Today,
agroforestry is taught at the senior undergraduate and postgraduate levels in
many institutions around the world, either as a separate subject or as a part of
the regular curricula of agriculture, forestry, ecology, and other related
programs. Although several books on the subject have been published during
the past few years, there is still no single publication that is recognized as a
textbook. This book is an effort to make up for this deficiency.
The need for such a book became obvious to me when I was faced with the
task of teaching a graduate-level course in agroforestry at the University of
Florida five years ago. Subsequently, the Second International Workshop on
Professional Education and Training held here at the University of Florida in
December 1988 recommended that the preparation of an introductory textbook
be undertaken as a priority activity for supporting agroforestry education
world-wide. The various educational and training courses that I have been
involved in, and my interactions with several instructors and students of
agroforestry in different parts of the world, further motivated me into this
venture.
Agroforestry is a very complex subject; indeed, it is an amalgam of many
subjects. For centuries, agroforestry has been artfully practiced throughout the
world, especially in the developing countries of the tropics. Lately, the
underlying principles of these time-tested practices, as well as the scope for
applying scientific principles to improve them, are being explored vigorously. It
has now become obvious that the science of agroforestry does, or ought to,
involve a harmonious blending of both biophysical and social sciences. While
it is important that an introductory-level textbook should cover all these
aspects, it is quite a difficult task to integrate these seemingly disparate subjects
under one cover. Nevertheless, an attempt has been made in this book to
include elements of most, if not all, of the major areas of current interest in the
subject.
The 25 chapters of the book are organized into six sections. After an
xi
xii Preface
introductory section that traces the brief history of the development of
agroforestry and the underlying concepts and principles of the subject, the
major agroforestry systems in the tropics and the recent developments in each
of them are discussed in Section II (Chapters 3-10). Three chapters (11-13) that
constitute Section III deal with the plant aspects; brief notes on about 50 of the
commonly-used multipurpose trees and shrubs in agroforestry and illustrations
of several of them are included in this section. Section IV (Chapters 14-18) is
on soil productivity aspects. The level of discussion in this section is more
detailed than in others, partly because this topic has attracted more research
attention, and also because soil-productivity improvement is often considered
to be one of the most important advantages of agroforestry. Section V, called
Design and Analysis of Agroforestry Systems, deals with the diagnosis & design
(D & D) methodology, on-station field experiments, on-farm research,
economic and social considerations; and system-evaluation criteria. The main
focus of these 24 chapters (Sections I-V) is on the tropics and developing
countries, where the practice of and potential for agroforestry are most
conspicuous. However, significant developments in agroforestry are occurring
in the temperate zone too; these are the subject of the last chapter, which forms
Section VI.
Given the breadth of subjects covered in the book, it was important and even
essential to draw heavily from the available literature on the different topics. In
some cases, I thought it appropriate and important to present the subject in the
respective authors' own words, to retain the authenticity of the subject and the
arguments. A basic understanding of the elements of various biophysical (plant
and soil) and social sciences is essential for the scientific study of agroforestry.
However, many students have been found to be weak or out-of-touch with these
basics. Therefore some of these basic principles are explained in separate
chapters; relevant references to standard textbooks on these subjects are also
made to enable the readers to update themselves.
The students of agroforestry have varied backgrounds and interests. Their
expectations of agroforestry and hence of a textbook on the subject are
divergent. Because of this, as well as the complexity of the subject, one single
book may not be completely satisfying to all. However, I hope that students,
professional trainees, researchers, and other professionals in agroforestry will
find the book a useful introduction to this complex subject.
Gainesville, Florida, USA P.K.R. Nair
November 1992