In keeping with the spirit of an Advanced Series in the Agricultural Sciences, we have attempted to address herein most of the current research areas being used to characterize, describe and manage salt-affected soils. Because of a certain amount of personal bias inherent in our individual viewpoints and backgrounds, some areas have been accorded more emphasis than others. It has been our goal, however, to provide either detail about, or at least a recent reference to, each major area of current soil salinity research. This information, coupled with what we hope to be a rather logical progression from descriptive material on equilibrium or near-equilibrium soil chemistry, through transport processes, to eventual management practices including some elementary economic decisions, should enable the reader to bridge the gap from introductory soil chemistry or soil physics texts to the basic literature of this area. The text will be perceived by the astute reader as somewhat uneven in its treatment of respective sections. We feel that this is to a certain extent appropriate, for it thus portrays the unevenness of progress to date in the corresponding areas of research. The management of saline and sodic soils remains largely an empirical semi-science or even art, whereas transport phenomena are normally dealt with in a much more theoretical (and also a much more highly mathematical) vein. Equilibrium soil chemistry has historically occupied an intermediate position with respect to its mix of empiricism and theoretical rigor.

The world population in 1950 was 2. 5 billion and is more than 5 billion today. The agriculture community, however, has responded remarkably well to meeting the increased need for food and fiber. While the population growth during this period averaged almost 2% annually, the production of grain increased at an even faster rate. From 1950 to 1973, grain production increased 3. 1% annually, but slowed to about 2% from 1973 to 1984. There fore, as a whole, the world has more grain per capita available today than ever before. Several countries that were food importers just a few years ago are food exporters today. The world carry-over stocks today are the highest in years. While the major concern just a few years ago was whether the world could produce adequate food, the problem for many countries today is how to export their surpluses. Although the world as a whole has surplus food supplies, there are millions of people without adequate food to exist, and there are additional millions who have a bare subsistence diet at best. The average daily calorie supply for the developed countries is more than 3,300 per person, while the average for the developing countries is only about 2,200. The major global food produc tion problems have shifted from Asia to Africa, where malnutrition, poverty, and starvation are attracting world attention."