Soil is one of our most important natural resources. It is at the heart of terrestrial ecology, and an understanding of the soil system is key to the success and environmental harmony of any human use of the land. This book is designed to help make your study of soils a fascinating and intellectually satisfying undertaking. We are confident that much of what you learn will be of enormous practical value in equipping you to meet the many natural-resource challenges of the 21st century. You will soon find that the soil provides many opportunities to see practical applications for principles from the basic sciences of biology, chemistry, and physics. Our priority in this newest edition ofThe Nature and Properties of Soilsis to explain the fundamental principles of soil science in a manner that you will find relevant to your interests. Throughout, the text emphasizes the soil as a natural resource and highlights the many interactions between the soil and other components of forest, range, agricultural, wetland, and constructed ecosystems. We have sought to craft a book that will serve your needs well, whether you expect this to be your only formal exposure to soil science or you are embarking on a comprehensive soil science education. This new book is meant to provide both an exciting, accessible introduction to the fascinating world of soil science and a reliable, comprehensive reference for your professional bookshelf. Readers who have used earlier editions will notice that in order to serve these two functions, the number of pages in the book has increased with the last few editions. Most of this increase (nearly 80%) is attributable to the new photographs, diagrams, and special "boxes" that have made the text so much more engaging to use. About 20% of the increased length has been in the form of additional text, mainly devoted to expanded coverage of topics critically important to the future role of soils in natural-resource sciences, such as wetlands, septic drain fields, salt-affected soils, bioremediation, soil ecology, nutrient and irrigation management, soil hydrology, and new orders inSoil Taxonomy.In a few areas, we have had to reduce the detail to make room for new topics and information. In doing so we have carefully maintained the level of rigor and thoroughness so valued in previous editions. This edition includes new sections on the pedosphere concept, subaqueous soils, ethnopedology, x-ray diffraction, nonsilicate colloids, inner- and outer-sphere complexes, nuclear contamination, effective CEC, the proton-balance approach to soil acidity, acid and nonacid cation saturation, human-influenced acidity, Ca and Mg in plants and soils, irrigation water quality, biomolecule binding, soil food-web ecology, forest nutrient management, the phosphorus site index, lead contamination, indicators of soil quality, and many other topics of current interest in soil science. In response to their popularity in the previous two editions, we have also added many new boxes that present either fascinating examples and applications or technical details and calculations. These boxes bothhighlightmaterial of special interest and allow the logical thread of the regular text to flow smoothly without digression or interruption. Examples include the stories of hypoxia or oxygen depletion in nutrient-laden water bodies and of the amelioration of selenium pollution in wetlands. In addition to updating many references, we have added a new feature to this edition, a set of World Wide Web universal resource locators (URLs) set in the margins of the relevant chapter sections. These Web sites, developed by colleagues and organizations around the world, expand and elaborate on certain topics in ways that would not be possible in a printed book. We could not have done all this without the many valuable suggestions, ideas, and corrections sent to us by soil scientists, instructors, and studentBrady, Nyle C. is the author of 'Nature and Properties of Soils', published 2001 under ISBN 9780130167637 and ISBN 0130167630.