Directions in Tropical Agroforestry Research: Adapted from selected papers presented to a symposium on Tropical Agroforestry organized in connection with the annual meetings of the American Society of Agronomy, 5 November 1996, Indianapolis, Indiana, USA

251 Pages·1998·5.21 MB·English

by  M. R. Rao

DIRECTIONS IN TROPICAL AGROFORESTRY RESEARCH
FORESTRY SCIENCES
Volume 53
The titles published in this series are listed at the end of this volume.
Directions in
Tropical Agroforestry Research
Adapted from selected papers presented to a symposium on Tropical Agro
forestry organized in connection with the annual meetings of the American
Society ofA gronomy, 5 November 1996, Indianapolis, Indiana, USA
Edited by
P. K. R. NAIR and C. R. LATT
University ofF lorida, Gainesville, Florida 32611, USA
In cooperation with CATIE (Centro Agron6mico Tropical de /nvestigacion y Enseflanza),
Turrialba, Costa Rica
Reprinted fromAgroforestry Systems, Volume 38, Nos. 1-3 (1997)
Springer-Science+Business Media, B.V.
Library of Congress Cataloging-in-Publication Data
A c.I.P. Catalogue record for this book is available from the Library of Congress.
ISBN 978-90-481-5025-0 ISBN 978-94-015-9008-2 (eBook)
DOI 10.1007/978-94-015-9008-2
Printed on acid-free paper
All Rights reserved
© 1998 Springer Science+Business Media Dordrecht
Original1y published by K1uwer Academic Publishers in 1998
Softcover reprint ofthe hardcover Ist edition 1998
No part of the material protected by this copyright notice may be reproduced or
utilized in any form or by any means, electronic or mechanical,
including photocopying, recording or by any information storage and
retrieval system, without written permis sion from the copyright owner.
Table of Contents
P.K.R. Nair and C.R. Latt: Preface 1
M.R. Rao, P.K.R. Nair and C.K. Ong: Biophysical interactions in tropical
agroforestry systems 3
R.J. Buresh and G. Tian: Soil improvement by trees in sub-Saharan Africa 51
P.L. Mafongoya, K.E. Giller and C.A. Palm: Decomposition and nitrogen
release patterns of tree prunings and litter 77
P.K. Khanna: Nutrient cycling under mixed-species tree systems in south-
east Asia 99
E.T. Craswell, A. Sa.ijapongse, D.J.B. Howlett and A.J. Dowling: Agro-
forestry in the management of sloping lands in Asia and the Pacific 121
J. Beer, R. Muschler, D. Kass and E. Somarriba: Shade management in
coffee and cacao plantations 139
R.R.B. Leaky and A.J. Simons: The domestication and commercialization
of indigenous trees in agroforestry for the alleviation of poverty 165
D.E. Mercer and R.P. Miller: Socioeconomic research in agroforestry:
progress, prospects, priorities 177
S.A. Vosti, J. Witcover, S. Oliveira and M. Faminow: Policy issues in agro
forestry: technology adoption and regional integration in the western
Brazilian Amazon 195
P.K.R. Nair: Directions in tropical agroforestry research: past, present, and
future 223
Agroforestry Systems 38: 1-2, 1998.
© 1998 Kluwer Academic Publishers.
Preface
In any long-term activity, periodic review and evaluation of progress and
setbacks is an essential part of program development and implementation. If
the establishment of ICRAF in 1977 is taken as the starting point of organized
research in agroforestry, we have just crossed its 20-year mark. It is appro
priate at this juncture that the agroforestry research community takes stock
of its accomplishments and failures. With this objective, a one-day sympo
sium on tropical agroforestry research was organized on the occasion of the
annual meetings of the tri-societies of American Society of Agronomy, Crop
Science Society of America, and Soil Science Society of America, at
Indianapolis, Indiana, USA, on 5 November 1996. Acknowledged world
leaders in various aspects of tropical agroforestry were invited to present state
of-the-art reviews of the developments in their respective research areas, and
subsequently were requested to submit the texts of their presentations for
publication. This volume represents 10 of the 13 papers; all have been peer
reviewed, updated and/or otherwise improved, and edited for style and con
sistency.
In accordance with the objective of the symposium, each paper synthe
sizes the results of research, summarizes the current state of knowledge, iden
tifies knowledge gaps, and outlines the directions that research should take
in the years ahead in the respective subject areas. Not all aspects of past or
current research in agroforestry are covered in the publication in deserving
detail, nor are all major geographical/ecological regions of the tropics repre
sented. In spite of these drawbacks, we believe that the volume makes a
significant contribution to the growing body of knowledge in tropical agro
forestry, and it complements well the several noteworthy books and publica
tions with which agroforestry literature has lately been blessed.
While organizing the symposium and putting together this publication, it
became quite clear to us that agroforestry research has been somewhat skewed
in favor of biophysical investigations. The apparent "neglect" of some impor
tant areas, as discussed in Chapter 10, is a serious deficiency in the context
of overall thrust and developments in agroforestry research today. We hope
that the research- and donor communities will accept the challenge of
addressing this glaring deficiency in the near future.
The generous financial support of CATIE (Centro Agronomico Tropical
de Investigacion y Ensefianza -: The Tropical Agricultural Center for Research
and Education), Turrialba, Costa Rica, in this endeavor was very timely and
appropriate. Without it, it would not have been possible to bring out this
publication so expeditiously. We express our sincere thanks to Dr Ruben
Guevara Moncada, Director-General of CATIE and the staff of its Agroforestry
Division, notably Dr John Beer, Head, for their splendid support. Our special
2
thanks go to all authors for their excellent cooperation in responding to the
various editorial requests in a timely manner, and to Kluwer Academic
Publishers, The Netherlands, for bringing out this publication as a special issue
of Agroforestry Systems. Finally, we thank the American Society of Agronomy
for granting permission to publish selected papers from one of its symposia
in this manner.
P. K. R. Nair and C. R. Latt
School of Forest Resources and Conservation
University of Florida
Gainesville, Florida 32611, USA
Agroforestry Systems 38: 3-50, 1998.
© 1998 Kluwer Academic Publishers.
Biophysical interactions in tropical agroforestry systems*
M. R. RAOl.*, P. K. R. NAIR2 and C. K. ONal
International Centre for Research in Agroforestry, P.O. Box 30677, Nairobi, Kenya; E-mail:
I
[email protected]; [email protected]; 2 School of Forest Resources and Conservation, IFAS,
University of Florida, Gainesville. Florida 32611. USA; E-mail: PKN@gnv.;fas.ufl.edu
(* Corresponding author)
Key words: boundary plantings, hedgerow intercropping, improved fallows, parkland systems,
sequential systems, simultaneous systems
Abstract. The rate and extent to which biophysical resources are captured and utilized by the
components of an agroforestry system are determined by the nature and intensity of interac
tions between the components. The net effect of these interactions is often determined by the
influence of the tree component on the other component(s) and/or on the overall system, and is
expressed in terms of such quantifiable responses as soil fertility changes, microclimate
modification, resource (water, nutrients, and light) availability and utilization, pest and disease
incidence, and allelopathy. The paper reviews such manifestations of biophysical interactions
in major simultaneous (e.g., hedgerow intercropping and trees on croplands) and sequential (e.g.,
planted tree fallows) agroforestry systems.
In hedgerow intercropping (HI), the hedge/crop interactions are dominated by soil fertility
improvement and competition for growth resources. Higher crop yields in HI than in sole
cropping are noted mostly in inherently fertile soils in humid and subhumid tropics, and are
caused by large fertility improvement relative to the effects of competition. But, yield increases
are rare in semiarid tropics and infertile acid soils because fertility improvement does not offset
the large competitive effect of hedgerows with crops for water and/or nutrients. Whereas
improved soil fertility and microclimate positively influence crop yields underneath the canopies
of scattered trees in semiarid climates, intense shading caused by large, evergreen trees nega
tively affects the yields. Trees in boundary plantings compete with crops for above- and below
ground resources, with belowground competition of trees often extending beyond their crown
areas. The major biophysical interactions in improved planted fallows are improvement of soil
nitrogen status and reduction of weeds in the fallow phase, and increased crop yields in the
subsequent cropping phase. In such systems, the negative effects of competition and micro
climate modification are avoided in the absence of direct tree-crop interactions.
Future research on biophysical interactions should concentrate on (I) exploiting the diver
sity that exists within and between species of trees, (2) determining interactions between systems
at different spatial (farm and landscape) and temporal scales, (3) improving understanding
of belowground interactions, (4) assessing the environmental implications of agroforestry,
particularly in the humid tropics, and (5) devising management schedules for agroforestry
components in order to maximize benefits.
Introduction
Exploitation of interactions between woody and nonwoody (annual crop) com
ponents is the key to the success of all agroforestry (AF) systems. Therefore,
a better understanding of the interactions provides a strong scientific basis
* Florida Agricultural Experiment Station Journal Series No. R-06063.
4
for improvement of traditional, as well as evolving, systems. Research on
interactions in AF systems, which was of a relatively low-key nature until
the early 1990s, is now receiving increasing attention. Anderson and Sinclair
(1993) and Nair et al. (1994) examined the topic from an ecological per
spective, whereas various chapters in the recent book on tree-crop interac
tions (Ong and Huxley, 1996) approached it from a more quantitative and
physiological perspective. Additionally, other recent reviews have examined
specific aspects of interactions, e.g., pest and disease relations in agroforestry
(Singh Rathore, 1995). Interactions in shade-tree/perennial-crop systems and
mixed-tree systems have been discussed separately in this volume by Beer et
al. (1997) and Khanna (1997), respectively. Thus, considerable progress has
been made lately in our understanding of biophysical interactions in AF
systems. But, so far, the efforts have been confined mostly to strategic
research, with little or no progress in translating this knowledge into man
agement options. The emphasis in this paper, therefore, is to synthesize the
available information and discuss the agronomic significance of biophysical
interactions in the major agroforestry systems, focusing on systems not
covered by other reviewers in this volume. By following this approach, the
paper complements the efforts of Sanchez (1995) and stresses the importance
of management implications.
In the study of biophysical interactions in AF, some efforts were made to
extrapolate from research on annual intercropping, on the assumption that
the principles of interactions between component species for growth resources
are common in all types of plant associations. Thus, early research (during
the 1980s) on resource 'capture' in agroforestry systems concentrated on the
interception and use of radiatio~, although radiation is seldom the most
limiting growth resource in the tropics (Ong and Black, 1994). Agroforestry
systems are much more complex than annual intercropping systems because
there are major differences in the nature and arrangement of components and,
therefore, in the nature and extent of interactions. Of considerable importance
is the fact that the components in AF systems are 'unequal,' the trees being
dominant and perennial. Thus, interactions in AF systems are continuous,
rather than seasonal as in annual systems, and the course and extent of inter
actions are largely determined by the system's tree component.
Interaction is defined as the effect of one component of a system on the
performance of another component and/or the overall system (Nair, 1993).
Furthermore, for this review, AF systems are broadly categorized into two
groups: 1) simultaneous systems, in which trees and crops are grown together
in different spatial arrangements; examples include trees on croplands,
hedgerow intercropping (HI), intercropping in perennial-tree-crop stands and
multistrata systems; and, 2)' sequential systems, in which trees and crops are
grown in rotation; examples include rotational bush fallow or planted tree
fallows followed by crops (Sanchez, 1995). Some systems, such as taungya,
rotational HI, and relay planted tree fallows in crops combine the features of
both simultaneous and sequential systems.