Tillage systems i for soil and water conservation F000 ANO AOMCULTuNt ONGANUADON OF TNE watt()NATIONS FOREWORD The Food and Agriculture Organiaation of the United Nations (FAO) has been concerned with the need for soil and water conservation since its establishment in 1945. Since that time, FAO has supported numerous projects, sponsored or participated in various con- ferences and seminars, and published various bulletins, reports, proceedings, etc. to focus attention on the nature of this worldwide problem and to provide information regarding remedial action to be taken to alleviate the problem. However, the problem remains, and the increasing world population is resulting in intensified cropping of the limited areas of arable land to provide the necessary food in some countries. Unless effective conservation practices are used, such intensive cropping tends to increase the loss of soil and water resources. This trend must be reversed. The objectives of this Soils Bulletin are to present the principles and practices of tillage systems for sustained food production and to create an awareness of the need to conserve the world’s soil water and energy resources for future generations. Although energy is an integral part of tillage systems, the emphasis is on soil and water conservation. However, effects of the systems on energy are discussed where appropriate. This Bulletin emphasizes tillage systems for developing countries, but relies heavily on principles that have been developed throughout the world. It is intended mainly for the training of and use by extension workers for improving crop production through use of improved tillage systems for conserving the soil and water resources in developing countries. Since not all the solutions to particular soil conditions are yet known, the need for more research on conservation tillage in developing countries is stressed. ACKNOWLEDGEMENTS The Food and Agriculture Organization of the United Nations is greatly indebted to the Agricultural Research Service of the US Department of Agriculture and in particular to its Conservation and Production Research Laboratory at Bushland for permitting Dr. Paul W. Unger to research and write this bulletin over a period of time. FAO is most grateful for his assistance. The author is a noted Soil Scientist with years of experience in conservation tillage research under a range of conditions. He has published about a hundred papers, many dealing with conservation tillage, and is one of the most renowned experts in this field. Though material for this publication has been drawn in large part from the USA where most of the experience on conservation tillage exists, results from developing countries have been taken into due consideration and cited. The author has used illustrations from many sources and acknowledges with thanks permission to use copyright material. In all cases credits are given under the appropriate illustration or with the table. The author wishes to express his sincere gratitude to FAO for the invitation to prepare this bulletin, to the USDA Agricultural Research Station for permitting him to accept the invitation, and to the many people who helped in numerous ways to make this bulletin possible. Special thanks go to Drs. M.D. HIeilman and B.A. Stewart of the USDA Agricultural Research Service and to Dr. D.M. Van Doren Jr., of the Ohio Research and Development Center for reviewing and offering suggestions for improvement, and to Mrs. Lynette Lott for typing the original and several Revised versions of the manuscript for the bulletin. CONTENTS Page Foreword iii 1. INTRODUCTION 1 1.1 Opening Statements 1 1.2 Objective 9 1.3 Intended Audience 9 1.4 Summary and Conclusions 9 2. LAND DEGRADATION 13 2.1 Types 13 2.1.1 Erosion 13 2.1.2 Silt deposition 25 2.1.3 Desertification and dune creep 27 2.1.4 Salinization and alkalization 28 2.2 Potentials for Controlling Land Degradation 29 2.2.1 Introduction of appropriate land use measures 29 2.2.2 Tillage 30 2.2.3 Practices related to tillage 31 2.2.4 Alternate practices 31 3. TILLAGE SYSTEMS 33 3.1 Selection of Tillage System 33 3.1.1 Climatic zone 33 3.1.2 Crop to be grown 36 3.1.3 Soil factors 37 3.1.4 Economic level of the farmer 45 3.1.5 Preference of the farmer 47 3.1.6 Social influences 47 3.1.7 Government policies 48 3.2 Cultivation Systems 50 3.2.1 Traditional shifting cultivation 50 3.2.2 Labour intensive continuous cultivation 63 3.2.3 Animal-draught and small tractor cultivation 80 3.2.4 Modern high-technology cultivation 3.2.5 Dust mulches 168 3.3 Cost Comparisons of Different Tillage Systems 170 4. CROP MANAGEMENT SYSTEMS IN RELATION TO TILLAGE 179 4.1 Continuous Cropping 179 4.2 Crop Rotations 182 4.3 Multiple Cropping 186 5. SUPPORTING PRACTICES 193 5.1 Land Smoothing 193 5.2 Contour Tillage 193 5.3 Strip Cropping 195 5.4 Graded Furrows 196 5.5 Basin Listing 196 5.6 Terracing 5.7 Diversion Terraces, Waterways and Gully Control 204 5.8 Land Levelling 206 5.9 Water Harvesting, Runoff Farming and Water Spreading 206 5.10 Microwatersheds and Vertical Mulches 209 5.11 Mulching 210 5.12 Cover Crops and Catch Crops 211 5.13 Land Imprinting 211 5.14 Irrigation 212 5.15 Drainage 215 5.16 Control of Drifting Sand and Sand Dunes 216 6. TYPES AND USES OF CROP PRODUCTION EQUIPMENT 219 6.1 Equipment for Clean Tillage Systems 219 6.1.1 Hand powered system 219 6.1.2 Animal powered system 221 6.1.3 Tractor powered system 222 6.2 Equipment for Conservation Tillage Systems 229 6.2.1 Stubble mulch tillage 229 6.2.2 Minimum or reduced tillage 232 6.2.3 No-tillage 233 REFERENCES 241 APPENDIX 1 Glossary 271 APPENDIX 2 Common names and scientific names of crops mentioned in the report 273 APPENDIX 3 Common and chemical names of herbicides mentioned in the report 275 APPENDIX 4 Classification of soil series mentioned in the report (US Classification System) 276 APPENDIX 5 Pest organisms other than weeds mentioned in the report 277 APPENDIX 6 Common and scientific names of weeds mentioned in the report 278 LIST OF FIGURES Page l. A farmer in Ethiopia digging potatoes with a primitive tool 2 2. “Ploughing” by hand in Upper Volta 2 3. Workers preparing land for planting in Jordan 3 4. Hand tillage equipment in Bangladesh 3 5. Primitive plough (goose-foot cultivator) in Chile 4 6. Preparing a seedbed for millet in Nigeria 4 7. Disk plough in Libya 5 8. Chisel plough 5 9. Shifting cultivation in Indonesia 6 10. Intensive grazing by sheep contributes to soil erosion 7 11. Women of Togo carrying crop products from the fields 7 12. Soil erosion and silt deposition in clean-tilled maize field with rows up and down the slope in Illinois 8 13. Slope steepness and length affect soil erosion 8 14. Sand dunes in Pakistan 15 15. Sand dunes of the Namib desert, Namibia 15 16. Disk ploughs or harrows which often result in a relatively smooth soil surface usually are less effective for soil and water conservation than some other implements 16 17. A heavy-duty cultivator leaves a residue-covered, cloddy surface which reduces soil and water losses 16 18. Falling drop of water impacts soil surface 18 19. Intense rain loosens and lifts soil particles 18 20. Intense rainfall on bare soil causes aggregate dispersion, surface sealing, and high runoff and low infiltration of water 19 21. Rill erosion on wheatland in the Palouse region of Washington, USA 19 22. Gully erosion in the Oued Lallouf hills of Tunisia 20 23. Maximum potential annual soil loss due to sheet and rill erosion in Morocco 22 24. Extensive erosion caused by deforestation in Colombia 22 25. Food distribution in Bangladesh in 1977 24 26. Women and children awaiting emergency feeding in Ethiopia 24 27. Silt deposited in low area of maize field in the USA 26 28. Workers removing silt from Solo River in Java, Indonesia 26 29. Complex pattern of saline (dark) and non-saline (light) areas in Iraq 28 30. Farmer in Brazil amid plants that are badly in need of water 34 31. Straw left on the surface by non-inversion tillage increases water absorption and helps control wind and water erosion 34 32. Terraced rice field, Luzon 37 33. Terraced land north of Taipei, Taiwan 38 34. Relatively smooth surface (left) resulted from disk tillage and rough surface (right) from chisel tillage 38 35. Clean tillage on the contour with a lister plough in Israel 40 36. Lister ploughing a field after wheat harvest 40 37. Basin lister in Uganda 41 38. Water from precipitation in basin-listed furrows on the contour 41 39. Stubble mulch tillage with sweep equipment 42 40. One-way disk plough 42 41. Effect of soil random roughness and pore space on cumulative infiltration 43 42. Burning crop residues releases plant nutrients and minimizes tillage problems, but destroys residues that effectively conserve soil and water 49 43. Homes of the Ovambos in Namibia 53 44. Plants intercept raindrops, thus protecting the soil surface against erosion 57 45. Erosion removed soil from unprotected areas, leaving behind soil pedestals capped by rocks 58 46. Equipment used for jungle clearing in the Gal Oya valley of Sri Lanka 60 47. Shifting cultivation in Indonesia: land cleared by felling trees and burning 60 48. Small fields of Sherpa villagers in Nepal 68 49. Land fragmentation in Ghana 68 50. Land fragmentation in Uganda 70 51.