In writing this book I have tried to show how soils fit into both the natural and the man-made, largely agricultural world. More specifically, my intention has been to help the interested layman and the student understand the behaviour of soils: (i) in supporting the growth of crops, trees and grassland; (ii) in maintaining a clean environment; and (iii) as a source and sink for atmospheric gases. These topics, which have relevance for a wide range of students in earth, biological and environmental sciences, are dealt with in Part B. They are described in simple terms, but knowledge of scientific principles is required if they are to be properly understood; some topics, for example the acidification of soils (Chapter 9), necessarily include an account of chemical reactions. An understanding of soil properties and processes is also needed and the chapters in Part A are intended as an introduction; the serious student is advised to put some effort into reading these chapters. Chapter 1 serves as a general introduction to the text.

Before reading this book two particular points should be noted. First, there are big differences in soil properties between regions of the world, within regions, and often within individual fields. Generalizations about soils can therefore be misleading, as can be the transfer of information between sites or regions unless the relevant soil properties are known and other environmental factors are taken into account. Secondly, environmental issues are often emotive, sometimes being treated unscientifically, or they receive publicity from those who disregard the evidence.