Asked at the 20th anniversary College on Soil Physics, 'what soil physics means', Professor Edward L. Skidmore, a research leader at the USDA-ARS Wind Erosion Unit, Manhattan, Kansas, USA, defined it in simple terms as 'the study of the physical charactersitics of soil' or 'as the study of the physical laws of nature governing the behaviour of soil'. The study and potential applications of soil physics involve an understanding not only of physics, but of biology, chemistry, hydrology, engineering and land use management. And Prof. Donald R. Nielsen, a former dean of the University of California, Davis, USA, added that soil physics is not just an academic exercise. It involves implications for understanding present critical issues as food security, drinking water, pollution of waters, contamination of soils, natural disasters as flooding and landslides. Soil physisists need to examine complex processes as water flow in soils, erosion and runoff, solute transport and oxygen diffusion. Soil physicists belong to a big family and former participants of ICTP Colleges on Soil Physics take new initiatives to draw attention to the importance of soil physics for our environment. Reference is made to the symposia 'AgroEnviron' co-organized by former ICTP participants in Faisalabad, Pakistan (1998), Tekirdag, Turkey (2000), Cairo, Egypt (2002) and scheduled to be organised in 2004 in Udine, Italy. The present book is a partial compilation of contributions from selected former participants of the College on Soil Physics invited to make presentations related to their achievments as a result of attending the College. It also serves as a testimony of the existing links between soil physicists throughout the world strengthened by the support and programs of the International Centre for Theoretical Physics originally envisioned by Abdus Salam to foster the growth of advanced studies and physics research in developing countries. (ISBN 92-95003-26-8)