Soil degradation is clearly one of the most pressing problems facing man kind. A continuation of soil degradation will eventually lead to a loss in crop productivity even though fertilizers and other inputs often result in increased yields in the short term. Soil degradation also leads to environ mental pollution. A decrease in soil quality invariably leads to a decrease in water quality, and often in air quality. While there is a clear consensus that soil degradation is a major problem, the literature on this subject leaves numerous baffling questions. If statis tics on land degradation are correct, there is a definite cause for concern, and present a mammoth challenge for agricultural scientists. There are those that say the scientific community has over dramatized this issue, and created a credibility problem. Consequently; Volume 11 of Advances in Soil Science was organized by Dr. Rattan Lal who is recognized as a lead ing authority on the subject. The objective of Volume 11 was to assess the types and processes of soil degradation and establish some of the major cause-effect relationships. Volume II documented the seriousness of soil degradation in many parts of the world. Therefore, it seemed immediately important to devote a volume to the principles and technologies for restor ing degraded soils to a productive status. While the land resources are limited, world population is rapidly increasing, particularly in developing countries. Dr."

The purpose of Advances in Soil Science is to provide a forum for leading scientists to analyze and summarize the available scientific information on a subject, assessing its importance and identifying additional research needs. A wide array of subjects has been addressed by authors from many countries in the initial ten volumes of the series. The quick acceptance of the series by both authors and readers has been very gratifying and confirms our perception that a need did exist for a medium to fill the gap between the scientific journals and the comprehensive reference books. This volume is the first of the series devoted entirely to a single topic soil degradation. Future volumes will include both single-topic volumes as well as volumes containing reviews of different topics of soil science, as in the case of the first ten volumes. There are increasing concern and attention about managing natural re sources, particularly soil and water. Soil degradation is clearly one of the most pressing problems facing mankind. Although the spotlight regarding soil degradation in recent years has focused on Africa, concern about the degradation of soil and water resources is worldwide. The widespread con cern about global environmental change is also being linked to severe problems of soil degradation. Therefore, we are indeed pleased that the first volume of the series devoted to a single topic addresses such an impor tant issue. The current volume is also the first of the series involving a guest editor."