The purpose of this publication is to summarize the recent knowledge regarding the formation and significance of the great soil groups in the United States for the general reader. The treatment is in no sense complete or exhaustive. Attention is directed toward a discussion of those principles in broad implication. Should the reader require more specificity, the detailed reports of surveys and researches must be consulted.

This profusely illustrated book gives an exhaustive account of the principal types of soils of our planet. The "progressive descent of weathering fronts" model, recognized and used by eminent international scientists is the guiding principle of choice to link the observations and to give the reader a synthetic and coherent view of the differentiati

623435-28b.gifVolume B covers the ecological significance of the interactions among clay minerals, organic matter and soil biota. Soil is a dynamic system in which soil minerals constantly interact with organic matter and microorganisms. Close association among abiotic and biotic entities governs several chemical and biogeochemical processes and affects bioavailability, speciation, toxicity, transformations and transport of xenobiotics and organics in soil environments. This book elaborates critical research and an integrated view on basic aspects of mineral weathering reactions; formation and surface reactivity of soil minerals with respect to nutrients and environmental pollutants; dynamics and transformation of metals, metalloids, and natural and anthropogenic organics; effects of soil colloids on microorganisms and immobilization and activity of enzymes, and metabolic processes, growth and ecology of microbes. It offers up-to-date information on the impact of such a processes on soil development, agricultural production, environmental protection, and ecosystem integrity.