Land husbandry - Components and strategy

313 Pages·2007·4.13 MB·English

Land husbandry - Components and strategy http://www.fao.org/docrep/T1765E/t1765e00.htm#Contents
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Land husbandry - Components
and strategy
Table of contents
by
Eric Roose
70 FAO SOILS BULLETIN
Director of Soils Research
ORSTOM
Montpellier, France
Food and Agriculture Organization of the United Nations
Rome, 1996
Soil Resources Management and Conservation Service Land and Water Development Division, FAO
The designations employed and the presentation of material in this publication do not imply the
expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United
Nations concerning the legal status of any country, territory, city or area or of its authorities, or
concerning the delimitation of its frontiers or boundaries.
M-57
ISBN 92-5-103451-6
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or
transmitted in any form or by any means, electronic, mechanical, photocopying or otherwise, without the
prior permission of the copyright owner. Applications for such permission, with a statement of the purpose
and extent of the reproduction, should be addressed to the Director, Information Division, Food and
Agriculture Organization of the United Nations, Viale delle Terme di Caracalla, 00100 Rome, Italy.
© FAO 1996
Contents
Foreword
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Acronyms and abbreviations
Acknowledgements
Introduction
Part one: Erosion control strategies and the concept of land husbandry
Chapter 1. Definitions: words conceal a philosophy
Erosion
Soil loss tolerance
Erosion varies according to place: different agents, two perspectives
Erosion varies according to time
Soil degradation
Factors in the water balance
Chapter 2. History of erosion control strategies
Soil erosion and population density
Traditional erosion control strategies
Modern strategies for developing rural water infrastructures
Land husbandry
Chapter 3. Some social and economic aspects of erosion
Erosion crisis diversity
Who is concerned by erosion control?
The importance of exceptional rainstorms
Erosion effects in different regions
Effects of erosion on the eroded site: loss of productivity
Negative off-site effects of erosion
The economic rationale for land husbandry
Criteria for the success of soil conservation projects
Morroco case study: socio-economic study of erosion control in the Loukkos
Basin
Part two: Erosion control as a response to various erosion processes
Chapter 4. Dry mechanical erosion
Definition, forms, dynamics
Causative factors
Erosion control methods
Chapter 5. Sheet erosion: the initial phase of water erosion
Forms and symptoms of sheet erosion
Cause and dynamics of sheet erosion
Wischmeier and Smith's Empirical Soil Loss Model (USLE)
Soil erodibility
The topographical factor
Effects of plant cover
Influence of cropping techniques
Erosion control strategies
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Erosion control practices
The P factor in Wischmeier's equation
Erosion control structures as related to water management methods
Variability of erosion factors
Conclusions on the applicability of the USLE in Africa
Implementation of Wischmeier's erosion forecast model
Chapter 6. Linear erosion
Forms of linear erosion
The cause and processes of linear erosion
Factors in runoff
Controlling runoff and linear erosion
Cost effective gully treatment
Chapter 7. Mass movement
Forms of mass movement
Causes and processes of mass movements
Risk factors
Mass movement control
Chapter 8. Wind erosion
Processes
Forms of wind structures
Effects of wind erosion
Factors affecting the extent of wind erosion
Wind erosion control
Part three: Case studies
Chapter 9. The wide range of erosion control strategies in West Africa: from
subequatorial forest to Sudano-Sahelian savannah
Erosion control in the subequatorial forest zone of the Abidjan region of
southern Côte d'Ivoire
Erosion control in the humid, tropical, Sudanian savannah of Korhogo in
northern Côte d'Ivoire
Erosion control in the tropical savannah environment of the Koutiala region
of Mali: strictly rainfed farming
Erosion control in the Sudano-Sahelian savannah of the Ouahigouya region
of north-western Burkina Faso: runoff farming
Erosion control in the northern Sahelian zone around the Doti marches in
Burkina Faso: valley farming
Chapter 10. Development of the Bamiléké bocage
The situation
Diagnosis: relatively fragile environments
Effective traditional techniques
Hazards
Some suggested improvements
Chapter 11. Agroforestry, mineral fertilization and land husbandry in Rwanda
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The situation
Analysis of local conditions
Traditional techniques
Suggestions for managing surface water
Suggestions for managing soil fertility
Chapter 12. A new approach to erosion control in Haiti
The situation
Analysis of local conditions
Farmers' traditional strategies and their limitations
Control measures
Chapter 13. Agricultural erosion in the Ecuadorian Andes
The situation
Soil erosion: diagnosis and source
Hazards: the impact of erosion on the agricultural environment
Suggested improvements
Chapter 14. The Mediterranean Montane Region of Algeria
The situation
Diagnosis: trial conditions
Hazards
Suggested improvements: influence of the farming system
Chapter 15. Pays de Caux: a temperate, field-crop region in north-western France
The situation
Local conditions
Hazards: the erosion process and its negative effects
Solutions and measures adopted
Prospects and orientations
Land husbandry: a new philosophy
Land husbandry: a strategy for action
References
Further reading
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Foreword
Since the 1939 work of Bennett, the father of soil conservation, the world has seen a host of erosion
control manuals, most of them in English or Spanish and describing practical experience, technical
principles, mechanical (and sometimes biological) methods to be used, and a series of practical recipes that
have been adopted with varying degrees of success in specific regions. However, there have been few
authors who, having seen at first hand the relative ineffectiveness of the generally recommended
techniques, have been ready to re-examine the erosion control principles that Bennett developed for the
very specific environmental, social and economic conditions of the large-scale, mechanized cropping of
groundnut, cotton, tobacco and cereals, all providing little ground cover, that the European immigrants
introduced into the semi-arid Great Plains of the United States of America during the Great Depression of
the 1930s. Bennett's approach to soil conservation (based on draining runoff water from cultivated fields
along gently sloping channels to designated outlets) was then applied, with no prior testing, in totally
different circumstances (for example among small subsistence farmers in tropical upland areas)... with the
very indifferent results that have been seen by all.
Science has made giant strides since Bennett's day.
Firstly, it has been discovered that the kinetic energy of raindrops can lead to degradation of cultivated
soils. Risks of runoff and erosion can therefore be cut by introducing production systems that provide
better ground cover (Ellison 1944, Stallings 1953, Wischmeier and Smith 1960 and 1978, Hudson 1973,
Roose 1977a, etc.).
Secondly, people have realized that there are many different processes in soil degradation and erosion,
with a variety of causes - and a similar variety of sometimes contradictory factors involved in any action to
alter them. Treatment of sheet erosion has, for instance, sometimes increased the risk of landslides (as can
happen with marls).
Thirdly, differences in physical landscapes and in the social and economic conditions of effective
application of erosion control methods are better analysed today. The erosion crises facing large-scale,
modern landowners in temperate zones are no longer treated in the same way as the subsistence problems
of poor, densely-populated communities clinging to tropical hillsides.
Instead of simply describing schemes that have worked in one specific place, today one has to learn to
assess different conditions and work with, rather than against, the forces of nature; for example, by
progressively modifying the slope of a hillside by slowing down sheet runoff and using farming techniques
that will gradually terrace the land, instead of tearing at mountains with powerful bulldozers to produce
often unstable and expensive-to-maintain infrastructure.
The author would like to remind agricultural experts that erosion control is not the exclusive domain of
specialists working to rehabilitate land degraded because it has been more mined than farmed, but must
incorporate the viewpoints of the land-use planner responsible for water and soil fertility management in
the development of cropping systems that are profitable, sustainable, and safe for rural and urban
environments.
Since the 1980s there has been much criticism of the failure rate of most programmes incorporating
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erosion control.
It is now recognized that there are two spheres in erosion control:
• The State sphere, with the government responding to disasters and sending in engineers to
stop landslides, control torrents, replant mountains with trees, or harness watercourses that
threaten structural works, lines of communication, inhabited areas, irrigation schemes and
dams through siltation. In the public interest, representatives of the central authorities insist on
water control in the rural environment. It is expensive and upsets the farmers, but is the only
way of controlling the quality of water supplies (the off-site perspective), and only the State is
in a position to engage in such large-scale mechanical undertakings.
• The farming sphere of land protection (the on-site perspective), which can be assured only
by the rural community, so long as it is helped in making a correct diagnosis of the causes of
the erosion crisis and the best ways of improving environmental protection, biomass
production and living standards.
It is essentially on this latter sphere - that of water, soil fertility and biomass management (GCES), or land
husbandry - that this work would like to focus, taking stock especially of research by French-speaking
soil, agricultural and geographical experts (particularly from ORSTOM and CIRAD), who have worked
mainly in Africa, where problems develop much faster than in Europe. After all, the work of
English-speaking experts in this sphere is already well known (Wischmeier and Smith 1978, Hudson 1992).
The author presents a personal and intentionally confrontational point of view, offering a new and more
constructive approach to the problems small farmers face in their battle with the degradation of their land.
This is not a manual with clear-cut remedies for each and every erosion problem, but a work that should
allow research experts, teachers and agronomists in the field to appreciate differences in situations,
diagnose the causes of crises, and propose a range of technical solutions from which a small rural
community (a family, a ward, a village, a slope, a hillside or a micro-watershed) can choose the
technological package best suited to its particular needs. Rather more "instruction-oriented" material for
training extension agents (Dupriez and De Leener 1990, Inades 1989) and more technical manuals on
torrent control and landslides (Heusch 1988, CEMAGREF documentation) or improving soil fertility (Pieri
1989) are available elsewhere.
This document has been used for eight years as a basis for courses on "Land Husbandry as an Instrument in
Land Management" given to 700 agricultural or forestry engineers at CNEARC and ENGREF in
Montpellier, in France, and ANDAH in Haiti, as well as 50 senior water technicians at ETSHER in
Ouagadougou, in Burkina Faso. It is hoped that future editions will be enriched with readers' comments
and details of new experiences. It will have met its aim if it provides large numbers of land-use planners
and agronomists with pointers for developing intensive and sustainable farming systems suited to specific
environmental situations and social and economic contexts.
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Acronyms and abbreviations
ANDAH Association Nationale des Agronomes Haïtiens
AREAS Association Régionale pour l'Etude et l'Amélioration des Sols (France)
CEMAGREF Centre National du Machinisme Agricole, du Génie Rural, des Eaux et Forêts (France)
CIRAD International Cooperation Centre on Agrarian Research for Development
CNEARC Centre National d'Etudes en Agronomie des Régions Chaudes (France)
CTFT Centre Technique Forestier Tropical (CIRAD)
DRSPR Division de la Recherche sur les Systèmes de Production Rurale de l'Institut d'Economie
Rurale de Bamako (Mali)
EC European Community
ENGREF Ecole Nationale du Génie Rural et des Eaux et Forêts (France)
ESAT Ecole Supérieure d'Agronomie Tropicale (France)
ETSHER Ecole de Techniciens Supérieurs en Hydraulique Rurale (France)
ICRAF International Center for Research in Agroforestry
ICRISAT International Crops Research Institute for the Semi-Arid Tropics
IITA International Institute of Tropical Agriculture
INRA Institut National de la Recherche Agronomique (France)
INRF Institut National de Recherches Forestières (Algeria)
IRA Institut de Recherche Agronomique (Cameroon)
IRAZ Institut de Recherche Agronomique du Zaire
IRFA Institut Français de Recherche Fruitière Outre-mer (CIRAD)
IRHO Institut de Recherche sur les Huiles et Oléagineux (CIRAD)
ISAR Institut Supérieure Agronomique du Rwanda
ISCO International Soil Conservation Organisation
ITCF Institut Technique des Céréales et des Fourrages (France)
LH land husbandry
NGO non-governmental organization
ONTF Office Nationale du Travaux Forestière
ORSTOM Institut Français de Recherche Scientifique pour le Développement en Coopération
PRATIC Projet de Recherche appliquée à l'Aménagement intégré des Terroirs Insulaires Caraibes
RML rehabilitator of mountainous land
SPR soil protection and restoration
SWC soil and water conservation
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USDA United States Department of Agriculture
USLE Universal Soil Loss Equation
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Acknowledgements
First of all I should like to express my gratitude to ORSTOM, which encouraged me to put to good use the
knowledge French-speaking research experts have gained over the past thirty years in the field of soil
conservation, water management and fertilization.
Next, I should like to thank David Sanders and Jean Claude Griesbach of the FAO Soil Resources
Management and Conservation Service for their encouragement throughout the preparation of this work.
A dozen or so colleagues agreed to read the first draft, and I am particularly grateful to them for
encouraging me to revise it in order to complete, correct and expand it. They all provided me with major
ideas:
- Jacques Arrivets, CIRAD agricultural scientist, for his thoughts on the aim and presentation
of the work;
- Christophe De Jaegher, a young agricultural scientist working in Peru under an external aid
programme, for details of traditional Peruvian soil preparation methods;
- Georges De Noni and Marc Viennot, my colleagues at ORSTOM, for a whole chapter on
erosion in the Ecuadorian Andes;
- Jean-Marie Fotsing, a Cameroonian geographer, lecturer at Yaoundé University, for a
chapter on Bamiléké hedge systems (bocage);
- Bernard Heusch, agricultural scientist, for his vast experience of soil conservation problems
throughout the world;
- Charles Lilin, forestry expert at the French Ministry of the Environment, for a chapter on
sociological aspects of erosion crises;
- Raymond Mura, forestry expert with CEMAGREF, for his experience of rehabilitation
strategies for mountainous terrain;
- Jean François Ouvry, agricultural scientist and director of a regional association for land
improvement, for a summary of the work of a whole INRA team on large-scale agricultural
planning in northern France;
- Chris Reij, geographer at the Free University of Amsterdam, for many ideas on traditional
methods of water management and soil conservation;
- Bernard Smolikowski, agricultural expert working in Haiti under an external aid programme,
and Michel Brochet, Director of ESAT in Montpellier, for a whole chapter on Haiti;
- Christian Valentin, of ORSTOM, for details of soil surface structures;
- François Ségala, agricultural scientist, and Jean Claude Griesbach, geographer, technical
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officers in FAO's Soil Resources Management and Conservation Service, for constructive
criticism and invaluable support in completing the work.
I should also like to acknowledge my debt to the young research scientists who have carried out their
thesis work under my direction or verified certain land husbandry ideas in the field François Ndayizigiyé,
Vincent Nyamulinda and Leonard Sekayange in Rwanda, Vincent Ngarambé and Théodomir
Rishirumuhirwa in Burundi, Mourad Arabi, Morsli Boutkhil, Mohammed Mazour, Rachid Chebbani and
other colleagues from the INRF erosion team in Algeria, F.X. Masson, Djamel Boudjemline, Marie
Antoinette Raheliarisoa in France, and Zacheé Boli and Bep Aziem, IRA soil and agricultural scientists in
Cameroon.
I cannot close these acknowledgements without recalling all I owe to the "elders" who patiently initiated
and guided me throughout my career: in France, Bernard Heusch, Frederic Fournier, Claude Charreau and
Georges Aubert; in the English-speaking world, Norman Hudson, Walter Wischmeier, Donald Meyer and
William Moldenhauer.
Finally, my thanks go to Mme Rigollet and Chrissi Smith-Redfern for tirelessly typing, correcting and
editing the manuscript, and Mr Mazzei for drawing the figures so well.
Most of the photographs have been taken from my own collection. Other sources have been cited in the
text, and I am grateful for their assistance.
Ideas do not belong to any one person, but are the fruit of a long period of gestation and the encounter
between people and a range of environments and socio-economic conditions. May all those who have
played a part in this long labour be included in this expression of gratitude.
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