Drought Management on Farmland

371 Pages·2000·12.173 MB·English

by  J. S. Whitmore (auth.)

DROUGHT MANAGEMENT ON FARMLAND
Water Science and Technology Library
VOLUME 35
Editor-in-Chief
V. P. Singh, Louisiana State University, Baton Rouge, U.S.A.
Editorial Advisory Board
M. Anderson, Bristol, U.K.
L. Bengtsson, Lund, Sweden
J. F. Cruise, Huntsville, U.S.A.
U. C. Kothyari, Roorkee, India
B. M. Sahni, Aurangabad, India
D. Stephenson, Johannesburg, South Africa
The titles published in this series are listed at the end of this volume.
DROUGHT MANAGEMENT
ON FARMLAND
by
I.S. WHITMORE
Consultant in Applied Climatology and Hydrology,
Climatique Consultancy,
Pretoria, South Africa
Former Director,
Hydrological Research Institute,
Pretoria, South Africa
Former Lecturer,
University of Pretoria,
South Africa
Springer-Science+Business Media, B.Y.
A C.I.P. Catalogue record for this book is available from the Library of Congress.
ISBN 978-90-481-5333-6 ISBN 978-94-015-9562-9 (eBook)
DOl 10.1007/978-94-015-9562-9
Printed on acid-free paper
Cover picture: Fig. 1 from Geojoumal, Vol. 35, No.3, 1995, art. M. T. Jackson
"Protecting the Heritage of Rice Biodiversity".
All Rights Reserved
© 2000 Springer Science+Business Media Dordrecht
Originally published by Kluwer Academic Publishers in 2000.
Softcover reprint of the hardcover 1s t edition 2000
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 permission from the copyright owner.
To the Creator,
and all who labour
to make his works
bear good fruit.
TABLE OF CONTENTS
PREFACE .............................................................................................................................. ix
INIRODUCTION ................................................................................................................... I
CHAPTER I -DROUGHI CONCEPTS AND CHARACTERISTICS ...................................... 4
Drought Definitions and Criteria ...................................................................................... 4
Types of Drought ............................................................................................................ 7
Misconceptions ............................................................................................................... 9
Relationship between Drought and Sustainable Agriculture ............................................ II
CHAPTER 2 -PRINCIPLES OF DROUGHI RISK MANAGEMENT ................................... 13
Introduction .................................................................................................................. 13
Risk Assessment ............. " ............................................................................................ 14
The Law ofLirniting Factors as a Risk Assessment and Management Tool ..................... 16
Risk Management Planning ........................................................................................... 16
The Joseph Principle ..................................................................................................... 18
CHAPTER 3 -SOIL MANAGEMENT IN RELATION TO DROUGHI ................................ 21
Relevant Soil Physical Properties ................................................................................... 21
Water Relations of Soils ................................................................................................ 23
Soil, Water and Plant Interactions .................................................................................. 27
Curbing Evaporation of Soil Moisture ............................................................................ 31
CHAPTER 4 -SOIL CULTIVATION AND TILLAGE IN DROUGHI- PRONE AREAS ....... 36
Cultivation Methods ...................................................................................................... 36
Tillage Practices ............................................................................................................ 43
CHAPTER 5 -PLANT RESPONSES TO DROUGHI ........................................................... 49
Regulatory Functions of Leaves during Drought ............................................................. 49
The Regulatory Role of Roots ........................................................................................ 51
Attempts to Curb Moisture lost by Transpiration ............................................................ 53
Water Use Efficiency and the Harvest Index .................................................................. 56
Drought Evasion ........................................................................................................... 58
Drought Avoidance ....................................................................................................... 60
Drought Resistance ....................................................................................................... 61
Weed Competition ........................................................................................................ 62
CHAPTER 6 -CROPPING SYSTEMS FOR MOISTIJRE ECONOMY .................................. 64
Types of Cropping System ............................................................................................. 64
Planting Practices .......................................................................................................... 72
Integrated Cropping ....................................................................................................... 75
CHAPTER 7 -HARDY AND DROUGHI-EVASIVE CEREAL CROPS ............................... 79
Small Grain Cereals ...................................................................................................... 79
Coarse grained Cereal .................................................................................................... 90
CHAPTER 8 -EDlBLE LEGUMES FOR DROUGHI-PRONE REGIONS ............................ 98
CHAPTER 9 -VEGETABLES FOR DROUGHI-PRONE ARRAS ...................................... 106
CHAPTER 10 -DROUGHI-HARDY OIL-PRODUCING CROPS ...................................... 112
CHAPTER 11-ROOT, TIJBER AND FIBRE CROPS ......................................................... 120
Root and Tuber Crops ................................................................................................. 120
Fibre Crops ................................................................................................................. 124
CHAPTER 12 -DECIDUOUS AND BERRY FRUITS ........................................................ 128
Deciduous Fruit. .......................................................................................................... 128
Berry Fruits ................................................................................................................. 136
CHAPTER 13 -F AlRL Y DROUGHI-TOLERANT CI1RUS, SUBIROPICAL
AND IROPICAL FRUITS .......................................................................................... 140
vii
viii TABLE OF CONTENTS
CHAPTER 14 -NUTS ........................................................................................................ 151
CHAPTER 15 -:MISCELLANEOUS CROPS ...................................................................... 155
CHAPTER 16 -WATER STORAGE ON FARMS ............................................................... 167
Types of Reservoir ...................................................................................................... 167
Curbing Seepage Loss................................................................................................. 173
CHAPTER 17 -CURBING EVAPORATIVE LOSS OF STORED WATER ......................... 176
Methods ...................................................................................................................... 177
CHAPTER 18 -WATER HARVESTING ............................................................................ 186
CHAPTER 19 -IRRIGATION SCHEDULING .................................................................... 199
Crop Monitoring ......................................................................................................... 200
Monitoring Soil Moisture ............................................................................................ 201
Weather Monitoring .................................................................................................... 205
CHAPTER 20 -IRRIGATION SYSTEMS AND EFFICIENCy ........................................... 208
Irrigation Systems ....................................................................................................... 208
Irrigation Efficiency .................................................................................................... 216
CHAPTER 21 -IRRIGATION METHODS ......................................................................... 221
Mechanized Systems ................................................................................................... 230
CHAPTER 22 -TAPPING AUXILIARY GROUNDWATER. .............................................. 235
CHAPTER 23 -SALINITy ................................................................................................. 242
Introduction ................................................................................................................ 242
Methods of Irrigating with Saline Water.. ..................................................................... 248
Summary .................................................................................................................... 250
CHAPTER 24 -FORAGE GRASSES FOR DROUGHT-PRONE AREAS ............................ 252
CHAPTER 25 -FORAGE LEGUMES FOR DROUGHTY AREAS ..................................... 275
CHAPTER 26 -RANGELAND MANAGEMENT FOR GREATER STABILITy ................ 288
CHAPTE 27 -LIVESTOCK MANAGEMENT DURING DROUGHT ................................. 302
Phase I - Predrought Management ............................................................................... 302
Phase II - Short Drought, and the Early Stage of Long Drought... ................................. 304
Phase III - Progressive Drought ................................................................................... 306
Fodder Banks .............................................................................................................. 319
Stock Watering ........................................................................................................... 322
Other Useful Animals for Drought-prone Areas ............................................................ 326
CHAPTER 28 -SOME USEFUL HARDY TREES .............................................................. 328
CHAPTER 29 -SOME CARDINAL PRINCIPLES OF DROUGHT
MANAGEMENT ON FARMLAND ............................................................................ 339
CHAPTER 30 -SUMMARY:
SOME KEY DROUGHT MANAGEMENT STRATEGIES AND TACTICS ................ 341
Water. ......................................................................................................................... 341
Soil ............................................................................................................................. 342
Crops .......................................................................................................................... 343
Irrigation (see also Water) ........................................................................................... 344
Grazing Management .................................................................................................. 345
Livestock .................................................................................................................... 346
SELECTED BIBLIOGRAPHY ............................................................................................ 348
INDEX ................................................................................................................................ 354
PREFACE
Man has landed on the moon, probed deep space, and is transforming our lives by
countless technological feats - yet he cannot create a rain cloud at will. Nor can he
prevent droughts, or even predict them with certainty.
What's more, there is little evidence of concerted efforts to manage drought
effectively and thereby overcome it. This is remarkable, as drought occurs to a major or
minor degree on nearly every farm worldwide, and is a recurrent and inescapable
natural phenomenon. Drought is as much a part of the environment of farms as their
soils, vegetation, and other weather vicissitudes such as untimely frost.
Fortunately much can be done to mitigate the effects of drought, this being the
main thrust of this comprehensive book on drought management on farmland.
Proactive preparedness for drought is the key. It entails upgrading the drought
resistance of a farm systematically within cost constraints, and also having well-
formulated, auxiliary plans lined up for use during prolonged drought. This book
provides tools for these two complementary strategies as it covers not only the
management of water, soils, rangeland, crops, fodder and livestock but many additional
drought-related topics.
The book stresses the need for maximum self-reliance in dealing with drought on
farms, in the face of growing, competitive demands for scarce water and funding on the
part of other economic sectors. In line with this is the need to apply sound principles of
drought risk management to counteract the tendency to rely heavily on crisis and
disaster measures and relief payments which should be reserved for rare megadroughts.
Similarly apathy and defeatism in the face of drought demonstrate that problems
associated with drought can stem as much from attitudes and mindsets as from
meteorological realities.
This holistic book should prove useful not only to policy makers and
university/college staff, students and research workers in the agricultural sciences,
water and land use, environmental management, ecology, geography, and risk
management, but also to key practitioners such as farmers, agricultural advisors, land
developers and project managers.
So far from being something exceptional, drought is part and parcel of Earth' s
environment - but fortunately there is a host of ways to avoid, escape, dodge, bridge,
ameliorate, tolerate, mitigate, survive, surmount and triumph over the effects of
drought. Although this book describes many options, there is still vast scope for further
innovative and creative developments. The book provides a solid foundation on which
to build further.
As it is clearly impossible to deal with drought management at all levels of
sophistication in a single volume, the book focuses on core principles and practices.
These can be adapted to differing needs and circumstances.
The information contained in this book has been garnered over the years from so
many diverse sources that a curtailed, selected bibliography was the only practicable
option. Similarly the many people to whom I am indebted for the wealth of information
I gained along the path of life are also far too numerous for all to be acknowledged
individually - but I hope they will sense that they have been participants in what may
ix
x PREFACE
be viewed as an offering from workers in the second millennium to those who will
follow in the third.
However, there are a few people to whom lowe special thanks for their help while
I was compiling this book. Elisabeth Schroder assisted with data collection and
checking of the early drafts, and Peter Thomas checked the contents of the contract. I
am also grateful to Margo Lock for meticulous proof-reading and criticism. Thanks to
their rare insight and understanding of the unremitting work demands and stress, Lily
Gerdes and Liesel Eiselen in particular buoyed me up to the end with their enthusiasm
and encouragement which I shall cherish in memory. Dorothy Venter was a kingpin in
expertly preparing the camera-ready script, displaying not only a high level of
professionalism but a degree of interest and commitment that went beyond the bounds
of duty.
I also thank Kluwer Academic Publishers, specifically editor Petra van
Steenbergen, for accepting the book proposal, and for pleasant and fruitful
collaboration.
Finally I wish to record my sincere gratitude to Lettie Mabasa for her loyal,
competent and caring assistance over many years, which helped me to write this book.
Joan Whitmore
Pretoria
October 1999
INTRODUCTION
Although all except seasonal droughts are still largely unpredictable, they are a
perfectly normal, recurring feature of the climate of virtually all areas inhabited by
man.
It is vital to recognize this cardinal fact as it is fundamental to the core concept of
drought management -that of preparedness, of proactive development of an armoury of
strategies with which to cushion or bridge drought whenever it strikes. Naturally the
extent to which it is advisable to invest in precautionary measures depends on the level
of drought risk. To assess this, some insight into the characteristics of drought is
needed.
Firstly it should be emphasized that all farmed regions are subject to drought, for
nowhere is the rainfall absolutely constant. Everywhere there are spells, seasons or
years when the rainfall is subnormal. These constitute drought, even if only to a minor
degree. Moreover as droughts have recurred throughout recorded history, there is little
need to attribute them to global warming or a hole in the ozone layer. While the causes
of drought are still debatable, the scourge has been around for aeons of time.
Unlike other natural disasters such as floods, hurricanes, cyclones and hailstorms
which tend to start suddenly, and to be fairly localized and short-lived, drought is often
a creeping, insidious phenomenon whose onset may be difficult to pinpoint. From the
agricultural perspective drought does not necessarily start just after the last good rain,
as an ample reserve of soil moisture may have accumulated which can sustain crops
and pasture for a considerable time. In fact, there is much truth in the assertion that the
onset, duration, severity and termination of drought can only be identified
retrospectively. Again in contrast to most other natural disasters, major droughts often
affect vast areas but do not cause sudden, dramatic devastation and loss of life as in the
case of earthquakes, for example. However, over the time span of protracted droughts,
and with no proactive drought preparedness measures in place, the prolonged suffering
and deaths from famine, plus the vast and varied impact of a major drought on virtually
all sectors of the economy, can be devastating. These impacts depend not only on the
severity of the drought but on the way of life, water needs and acumen of people living
in drought-prone regions. Often the effects of a dry spell are aggravated by high
temperatures, low atmospheric humidity and strong (often scorching) wind. These
combine to heighten water loss by evaporation from soil and water surfaces, and
transpiration by plants. Moreover the effects of drought may persist long after it has
broken, as it may take several years for denuded grazing and browse to recover,
depleted reservoirs and aquifers to fill, and for herds to be built up again.
The lower the long-term average annual rainfall, the more wildly does the yearly
rainfall tend to fluctuate about that mean, and so the greater is the likelihood of
drought. However, as the farming options in the driest regions are few, the major
impact of drought is felt in semi-arid and subhumid regions where the incidence of
drought years is fairly high, but intensive, diversified farming is profitable in years of
good rainfall. However, such years are usually in the minority. The temptation to cash
in recklessly on the good years is understandable, but cannot long be sustained. It is no
use trying to wish away the poor years lying just around the comer. Instead, the
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