Soil survey investigations for irrigation [antikvár]

FOHEWORD The pressing need for increased agrioultiu-al production in the years ahead can only "be met by more efficient use of our land and water resources including more widespread and better irrigation in those regions where rainfall is inadequate. It has been estimated that some $2 million hectares of land are irrigated in the developing countries, of which half urgently need improvement, and that irrigation of an addition 22 million hectares is projected by 1990. Production gains will be shortlived iinless the attendant hazards of salinization, waterlogging and lowered fertility are kept in check by effective planning and management based on a thorough understanding of the soil conditions. Soil survey and land classification are generally accepted essential preliminaries to investment in irrigation development. The classical techniques developed in temperate regions for rainfed agriculture may be less suitable for assessing the potential for irrigation in tropical and arid regions. This publication aims to describe the special requirements of soil survey for irrigation development, and assumes that the reader is familiar Vfith basic soil science and soil survey techniques. It does not deal with other aspects of soil studies such as soil conservation or soil fertility maintenance on irrigated lands. Ho book can substitute for experience gained in the field but this one attempts to highlight soil characteristics which are significant under irrigation and tó suggest ways of recognizing and mapping them. The opening chapter emphasizes the breadth of cohsidei^ ations for evaluating land for irrigation and the role of the soil surveyor in the requii>-ed team of specialists. The next two chapters discuss the significant characteristics of soils and topography. Chapter Pour describes the assessment of drainage and reclamation and Chapter Five water quality and climate. Chapter Six describes field methods of soil survey and Chapter Seven interpretation of the.data and land evaluation for different conditions. The appendices give examples of land classification and specifications for various environments and procedures for measurement of permeability and infiltration rates. Acknowledgment is due to the Bureau of Reclamation of the U.S. Department of the Interior for its generous help in the preparation of this document. Appreciation is also expressed for the contributions made by several authors. Preliminary drafts were prepared by Dr, Claude L, Fly and Ir, W.F, van Beers and consolidated by Dr. R.B, Miller, Within the Bureau of Reclamation the principal contributors were Mr, Harold Parkinson and lir, William B. Peters, under the leadership of the late Dr, John T. Haletio, Within FAO, the document has been the responsibility of the Soil Resources Development and Conservation Service of the Land and Water Development Division, and in particular of Mr, A.J. Smyth who largely contributed those sections for which FAG was responsible and edited the draft edition issued in 1974. Acknowledgment is due to those who sent valuable caranents on that draft, which have been utilized by I4r. M.F. Pumell and lir. A. Ashby when editing the present issue. In preparing this document the aim has been to present guidance that is as factual and unambiguous as possible. Other recent PAD publications dealing with crop water requirements, water quality, drainage testing, salinity and alkalinity and land evaluation, have obviated the need for much detailed consideration in this document. Nevertheless, there are sections in which the advice is less clear cut than the authors would wish and FAO would welcome comments and suggestions which may serve to improve future publications on this subject. R. Dudal Director Land and Water Development Division