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FOREWORD

FAO has been concerned for many years with the development, manage- ment and conservation of land resources.

As part of its work in this field the Land and Water Division has, since 1965, produced a series of Soils Bulletins. These have been written with the intention of bringing knowledge to those interested and involved in the development of land resources. To do this, the Bulletins have been aimed at meeting particular requirements as understanding and experience of different aspects of this subject have become available.

In recent years there has been a growing interest in the semi-arid regions of the world. This interest has largely been brought about by the droughts and famines of the 1970s and 1980s that have affected huge areas, and millions of people, in the semi-arid areas of Africa.

What can be done to prevent calamities like these occurring again? There can be no simple answer to this question as a wide range of technical, economic, social and political problems must be examined and resolved.

However, we do know that droughts are very much a part of the natural events in the semi-arid regions - they have occurred often in the past and they will occur frequently again in the future. We also now realize that the terrible effects of these last droughts have been exacerbated by soil erosion and other forms of land degradation which have been allowed to develop over the years in semi-arid regions through mismanagement and poor land use. Degraded land and vegetation is just not capable of withstanding the added demands placed upon them by drought.

But soil erosion can be overcome and the land base restored to a healthy, productive state if sound management and appropriate techniques are applied.

All the answers to conservation in the semi-arid regions could not be given in a short publication such as this - even if they were all known. Exactly what is needed varies from place to place depending on the local climate, soils, vegetation and human requirements.

What has been done in this Bulletin, therefore, is to present methods and techniques which have been tested and proved effective in some part of the world where lack of rainfall is a problem because of amount, distribution or unreliability. Many of these methods and techniques, we believe, have potential for wider use in other parts of the world with similar problems. This Bulletin then is intended as a reference and a guide to those planners and technicians working in the semi-arid areas who are searching for ideas to develop and adapt in their efforts to control land, degradation and introduce sustainable systems of productive agriculture.

The reader is asked to note that owing to the differences in terminology in soil classification systems, the author has used the terms from the orginal works referred to. As different terms mean different things to different people, Annex 2 has been included. This consists of a table taken from Elsevier's Agricultural Compendium (1981), Table 2.7/7, entitled "Summary of FAO/Unesco system of soil classification, with analogues in the US system of taxonomy".