Manual on integrated soil management and conservation practices iii Foreword The processes of land erosion in various regions of Latin America and Africa have their origin in social, economic and cultural factors that translate into the over-exploitation of the natural resources and the application of inadequate practices for the management of soils and water. The consequences of this are damage to much of the agricultural land, with detrimental effects on food production for the growing population in these continents. Over the last few decades, many efforts have been made to stop the degradation of agricultural land but the process of adoption of new conservationist technologies by the farmers is still slow. Furthermore, the availability of technical personnel trained for this change is limited. The technological strategies that have been developed for the management and conservation of soil and water sometimes are not adapted for the beneficiaries, because they could not participate in the processes of the diagnosis, planning and execution of the actions. In addition, the promotion of conservation tillage systems and practices that were not adapted to specific regional requirements has created credibility problems with the farmers probably since they had been developed in other places and introduced without a correct diagnosis of the local situation. The development of technologies that guarantee the maintenance of agricultural land productivity in Latin America and Africa is a challenge that both technicians and farmers must face through collaborative research and field work in the farmers’ own environments and conditions. This includes identification of the problems of management and conservation of soils and water and a greater emphasis on the evaluation of the potential for systems of conservation tillage adapted to the specific conditions of each region. This Manual has been put together with the objective of assisting actions by the diverse groups of human beings who intervene in the conservation of the natural resources, particularly soil and water resources and in the context of each continent, country, region or zone. The Manual brings together a collection of concepts, experiences and practical suggestions that can be of immediate use for identifying problems and for formulating, executing and evaluating actions so as to benefit and to improve the productivity and conservation of soil and water resources. This Manual is based on the Training Course for Soil Management and Conservation, focused particularly on efficient tillage methods for soil conservation, held at the International Institute of Tropical Agriculture (IITA) in Ibadan, Nigeria from 21 April to 1 May 1997. It was jointly organized by IITA and FAO with the participation of specialists from both national and international organizations. The publication serves as a guide that will allow technicians and farmers to jointly discover ways to solve the problems and the limitations posed by land degradation in Latin America and Africa. Participatory action by technicians and farmers will be the basis for success in benefiting these regions. It is hoped that the Manual will help to attain the ultimate objective, which is to improve the productivity of the soils and water in a rapid and efficient manner. iv Acknowledgements The present Manual is based on the Training Course on Soil Management and Conservation with Special Emphasis on Conservation Effective Tillage Methods jointly organized by José Benites, Land and Plant Nutrition Management Service (AGLL) and Theodor Friedrich, Agricultural Engineering Branch (AGSE), FAO and the International Institute of Tropical Agriculture (IITA) in Ibadan, Nigeria. The training course would not have been possible without the active support of the Director General of IITA, Lucas Brader, as well as his staff, in particular R. Booth, J. Gulley, R. Zachmann, R. Carsky, Y. Osinubi, B. Akisinde, G. Kirchof and G. Tian and we would like to express our gratitude for this support. We would further like to thank the authors of the different papers for their collaboration in this publication, particularly Elvio Giasson, Leandro do Prado Wildner, José Barbosa dos Anjos, Valdemar Hercilio de Freitas and Richard Barber, as well as Cadmo Rosell, John Ashburner, Robert Brinkman and R. Dudal for assisting with the editing of the different language versions. Special thanks are due to Lynette Chalk for her efficient preparation of the text and formatting of this document and Riccardo Libori for his elaboration of the graphics. Manual on integrated soil management and conservation practices v Table of contents Page FOREWORD iii ACKNOWLEDGEMENTS iv 1. INTRODUCTION 1 Objectives 2 Structure and content 2 2. KEY ENVIRONMENTAL AND SOIL FACTORS INFLUENCING PRODUCTIVITY AND MANAGEMENT 5 Topography 5 Rainfall 5 Soil limitations 6 Soil conditions 8 Productivity 12 3. GENERAL PRINCIPLES FOR THE DEVELOPMENT OF SOIL MANAGEMENT STRATEGIES 13 Objectives of soil management for agriculture 13 Principles for the development of soil management practices 14 4. CONCEPTS AND OBJECTIVES OF TILLAGE IN CONSERVATION FARMING 27 Why conserve the soil? 27 The concept of integrated management – conservation farming 28 Technical tillage parameters 32 5. TILLAGE IMPLEMENTS 37 Moldboard plough 37 Disc implements 38 Chisels 40 Spike-toothed tines – levellers and harrows 42 Rotary cultivators (rotavators) 42 Rollers 42 Direct drilling - zero tillage 43 6. IMPLEMENTS AND METHODS FOR THE PREPARATION OF AGRICULTURAL SOIL 45 Objectives of soil preparation 46 Implements for soil preparation 47 7. EFFECT OF TILLAGE ON SOIL PHYSICAL PROPERTIES 51 Causes of physical soil degradation 51 Stages in the physical degradation of soil 52 Principal physical characteristics affected by tillage 52 8. PRINCIPAL TILLAGE METHODS 55 Terminology, definitions and classification of tillage systems 55 Principal types of tillage system 57 vi Page Strip tillage or zonal tillage 69 Ridge tillage 70 Combined tillage and seeding systems 75 Subsoiling 76 9. LAND USE ACCORDING TO ITS CAPABILITY 81 Land evaluation 81 10. SOIL COVER 87 11. CONTOUR FARMING 91 12 GREEN MANURE 93 Concept 93 Functions of green manure 93 Characteristics to consider when selecting types of green manure 94 Characteristics of green manure 95 Management of green manure 99 Effects of green manure on the soil properties 102 13. PHYSICAL BARRIERS FOR THE CONTROL OF RUNOFF 113 Terracing 113 Safe waterways 120 14. GULLY CONTROL 125 Concept 125 Gully dimensions 125 Measures for control and stabilization 126 15. RAINWATER CAPTURE AND IRRIGATION 131 Principal factors affecting the establishment of systems for rainwater capture 131 Methods for in situ rainfall capture 132 Irrigation aspects 137 16. SELECTION OF ALTERNATIVE TECHNOLOGIES 143 Information sources concerning alternative technologies 143 Technology selection on the basis of farmers’ circumstances 143 Technology selection on the basis of environmental considerations 145 Technology selection on the basis of “Problem – Solution” relationships 146 Reflections concerning the selection of soil management technologies 166 17. PARTICIPATORY PLANNING IN THE EXECUTION OF SOIL MANAGEMENT PROGRAMMES 169 Micro-catchment areas as planning units 170 Implementation of programmes and projects 171 Objectives of a programme and project 171 Enthusiasm as the driving force for development 172 Success – the source of enthusiasm 172 Participation - the road to follow 173 Destructive participation 173 How to improve constructive participation 174 How to increase participation 174 Some criteria for selecting an appropriate technology 178 Manual on integrated soil management and conservation practices vii Page Participating with the rural families in planning the soil management practices 179 Community planning 180 Making thematic maps 181 Establishing priorities for the actions to be undertaken in the micro- catchment basin 182 Formulation of projects 182 Conservation farm planning 183 Community mapping 183 Implementation of soil management plans 184 BIBLIOGRAPHY 187 ANNEXES 197 1. Comparison of field work rates with tillage implements 197 2. Purchase and maintenance costs for tillage implements 199 3. Notebook for participatory planning in our community 201 viii List of tables Page 1. Training course on “Methods of soil management and conservation: efficient tillage methods for soil conservation” 4 2. Mulch cover and soil loss from two simulated rainfalls 15 3. Average effect of the nature and orientation of crop residues on the erosion of a sandy loam soil by wind at a uniform velocity 15 4. Effects of mulch cover and the type of tillage on the amount of moisture (mm) stored in 120 cm soil depth. Faizabad, India 17 5. Types of tillage and their effect on the moisture, temperature and rate of emergence for cowpea and soybean. 17 6 Application of mulch and the quantity of earthworm casts 18 7 Effects of cover crops on infiltration rates with and without earthworm activity 19 8. Straw production and the relationships of C/N and of the grain/straw weight for annual crops, Santa Cruz, Bolivia 21 9. Effects of deep tillage on some physical properties and on root development in a compacted soil 24 10. Work rates per unit area needed to carry out a selection of agricultural tasks on the farm 46 11. Effect of tillage systems on the soil density and porosity 53 12. Quantity of residues remaining on the soil after different tillage treatments 56 13. Tillage systems classified according to the degree of disturbance