Soil management: compost production i and use in tropical and subtropical environments I P000 ANO AGWULTURE ORGANIZAMDN OF THE Dktomoirs PREFACE This Soils Bulletin provides training material on composting for extension workers and teachers in countries in the tropics and subtropics. The objective is to promote the use of locally available organic materials to increase soil organic matter content for the improvement of soil fertility, and as sources of plant nutrients in conjunction with mineral fertilizers. This manual is written for all those concerned with the maintenance and improvement of soil fertility, especially under tropical and sub- tropical conditions. It is hoped that it will be of value to staff in Government Agricultural Advisory Services and in non-government agencies both at the policy making level and in various levels in extension services. It contains material for use in farmer training. Those involved in planning safe waste disposal systems will also find it useful and it should stimulate thinking among elected officials in local government bodies throughout the tropics. Schoolteachers in rural areas will be able to base science lessons on it. The manual has been written in simple language without detracting from the scientific basis or level of technology involved. This has been done deliberately to enable those whose mother tongue is not English to use it and also to form a bridge between scientific knowledge and practical compost production. The severe drought and famine in parts of Africa in 1985 have shown the necessity for adequate soil organic matter to prevent hillside erosion and to retain moisture in the soil for crop growth. The cost of mineral fertilizers and their relative scarcity in some areas has increased the need to recycle waste organic materials as sources of crop nutrients. This Bulletin explains the basic composting process, suitable organic wastes, practical composting methods, use of the product in a variety of situations and a consideration of economic and social benefits. It also deals with approaches to practical extension work with farmers on the subject. The book has been written by Howard Dalzell, Director of the Medak Agricultural Centre, India, in conjunction with Ken Gray, Joe Biddlestone and Kamala Thurairajan of the Compost Studies Group at the University of Birmingham, England. The latter group was formed in 1965 in the Department of Chemical Engineering and has been studying the composting process and its application to the treatment of organic wastes from garden, farm and municipal sources. During his 16 years experience of agricultural development in India, Dalzell has carried out the practice of composting with support from the university group in England. This manual is the result of their joint experiences. It is sincerely hoped that the information given in this Soils Bulletin will provide help and encouragement to the many people involved with increasing the food supply in developing countries. ACKNOWLEDGEMENTS The authors are grateful to Dr. C.S. Ofori (FAO) for advice on preparing the book and to Miss F. Botts (FAO) for help with the photographs which were taken from FAO filmstrips. We thank the following for permission to use Plates 7, 8, 14, 15, 20 and 27 - Dr. G.F. Wilson and Dr. B.T. Kang, Butterworths, Faber & Faber, Farmers Weekly, Oxford University Press and the World Health Organization. Intermediate Technology Transport Ltd kindly supplied Figures 28 and 29. Rev. J.W. Barya, on rural development in Uganda, supplied information on conditions in Africa. Mr. L.D. Hills gave helpful advice on several aspects of composting. Sincere appreciation is expressed to Mrs. P. Saul for typing the manuscript. Financial assistance from several sources, particularly the Methodist Church Overseas Division in London and the Wolfson Foundation, is gratefully acknowledged. Finally, the authors thank the many enthusiastic composters, worldwide, whose knowledge has helped lay the foundations for this book. SUMMARY The manual combines a comprehensive description of raw materials, composting theory, all scales of composting practice and the use of the compost product in soil management. Economic and social aspects of composting are considered and attention is given to methods of extension education. Chapter 1 outlines reasons for the widely occurring lowering of soil fertility in many parts of the tropical world which is leading to decreases in food production levels. These decreases are taking place despite the rapidly increasing food needs of expanding populations. The chapter provides an analysis of the sort of farming systems required for stable production increases and describes the way in which soil fertility is maintained under naturally occurring tropical vegetation systems. The need for composting is highlighted and a historical description is given of the worldwide development of composting. Chapter 2 describes the microbiology, biochemistry and process factors such as aeration, moisture and temperature which must be controlled to achieve a satisfactory compost product. Chapter 3 is a description of organic waste materials which can be composted. Consideration is given to quantities available, probable compositions and precautions to prevent loss of nutrients during storage prior to composting. The preparation of waste for composting is also described. Chapter 4 describes practical composting processes for small heaps containing less than half a tonne of wastes and for large heaps suitable for farms and villages. Partly mechanized and fully mechanized units for composting urban wastes in towns and cities are also covered. Chapter 5 considers the composition of the compost product and discusses the importance of soil organic matter in managing soil fertility. Attention is given to ways of using compost to maximum efficiency in kitchen gardens, market gardens, field crop farming, tree planting and fish farming. It is concluded that compost will in many cases enhance the efficiency of use of mineral fertilizers. The merits of green manuring and direct incorporation of straw and dung are described. Chapter 6 deals with the relevance of composting to minimizing environmental pollution risks normally associated with organic wastes. These include disease-causing organisms, flies and vermin, odours, weeds, heavy metals and pollution of drinking water. Chapter 7 examines the economic and social potential and difficulties involved in composting. Comparisons are made of mineral fertilizers and composts on a nutrient basis and costs are calculated in terms of labour. The cost of composting is considered in the context of connected factors at village level such as night soil disposal, fodder and fuel systems and the maintenance of community irrigation facilities. Chapter 8 looks at the requirements of extension systems which aim to develop the practice of composting. Stress is laid on the need to co-ordinate the work of researchers, extension agents and farmers. Practical suggestions are given on time schedules and the training of extension workers and farmers. Possible trials to enable farmers to test the effectiveness of the compost product are outlined. These trials can be used to define any problems clearly and indicate areas for further research and extension effort. Chapter 9 summarizes the findings of the earlier chapters and builds arguments for local bodies, agricultural and public health extension agencies and farmers throughout the tropics to take up composting. While the different agencies will have to consider different aspects of composting, there is a great underlying need for co-ordination to complement each other’s work and to integrate organic recycling with fodder and fuel management. The Appendixes provide a glossary of terms and abbreviations, notes on plant nutrient calculations, a review of the complementary nature of composting and biogas production, suggestions for further reading and information on FAO filmstrips about composting. For those who start composting or attempt to refine their systems a wide choice of possibilities exists. The authors will be happy to deal with specific difficulties and to provide further suggestions so that existing local advisory services may be fully utilized. CONTENTS Page Preface iii Acknowledgements iv Summary v Contents vii List of Tables xi List of Figures xiii List of Plates xv CHAPTER l. INTRODUCTION 1 1.1 Composting 1 1.2 Objective 1 1.3 Food production in less developed countries 2 1.4 Agricultural systems 2 1.5 Soil and its structure 5 1.5.1 Soil formation 5 1.5.2 Soil minerals 6 1.5.3 Soil organic matter 6 1.5.4 Living organisms 6 1.5.5 Air 8 1.5.6 Water 8 1.5.7 Soil structure 8 1.6 Tropical vegetation systems and soil fertility 9 1.7 The need for composting 13 1.8 Historical background of composting 14 CHAPTER 2. PRINCIPLES OF COMPOSTING 17 2.1 General 17 2.2 Microbiology 18 2.3 Biochemistry 20 2.4 Process factors 22 2.4.1 General 22 2.4.2 Separation 22 2.4.3 Particle size 22 2.4.4 Nutrients 22 2.4.5 Moisture 23 2.4.6 Aeration 24 2.4.7 Agitation 24 2.4.8 Temperature 25 2.4.9 Additives 26 2.4.10 Heap reaction, acidity or pH 27 2.4.11 Optimum process conditions 27 CHAPTER 3. MATERIALS FOR COMPOSTING 29 3.1 General 29 3.2 Materials 29 3.2.1 Unwanted materials 30 3.2.2 Useful organic waste materials 30 3.2.3 Home 30 3.2.4 Garden 30 3.2.5 Crop wastes 34 3.2.6 Livestock wastes 34 3.2.7 Forests 37 3.2.8 Rivers and the sea 37 3.2.9 Urban wastes 38 3.2.10 Agro-industrial wastes 41 3.3 Chemical compositions 42 3.4 Quantities 42 3.5 Collection, storage and preparation 45 3.5.1 Collection 46 3.5.2 Storage 47 3.5.3 Preparation 47 3.6 Additives 49 3.6.1 Activators 49 3.6.2 Inoculants 49 3.6.3 Other materials 50 3.6.4 Compost product enrichment 51 CHAPTER 4.