Simulation of accumulation and leaching in soils [antikvár]

1 Introduction The contents of this book may be seen as an extension of those simulations described by de Wit and van Keulen in their book 'Simulation of transport processes in soils' (Pudoc, 1972). They dealt with transport of heat, salts, ions and water in the unsaturated phase in a general way. In this book, besides transport, adsorption and desorption phenomena play an important role. Most of the simulations could be applied to the field or to laboratory experiments. Comparisons between results obtained with the simulations and experimental results form an important part of this book. In contrast to the work of de Wit and van Keulen the water movement in soils is considered to be known from other sources, either actual measurements or other simulation programs. This different approach is based on the enormous amount of computer time necessary for a detailed simulation of water movement in soils over a long period, say 10 years. In addition, the small time-intervals required for the integration for simulating water movement are unnecessary for the simulation of other processes. Often the effort and computer time invested in a detailed simulation of water movement, hardly improve the model, as the determining part may be formed by the adsorption and desorption phenomena and not by water movement. For writing the simulation programs use was made of the modern simulation language CSMP-III. With this choice the authors do not in any way deny the advantages of analytical methods or methods in which certain parts of the calculations are done by a numerical method. Analytical approaches, if they can be realised, are exact; the calculation can be done with tables or a simple desk calculator. The only problem is that an analytical method can only be applied in simple situations. For somewhat more complex systems it is worthwhile to consider a numerical method for integrating the differential equations that describe the system. A computer is usually required, with a program written in FORTRAN, ALGOL or another programming language, although sometimes monograms can be used.