Mechanistic Simulation Models for a Better Understanding of Nutrient Uptake from Soil
Norbert Claassen, Bernd Steingrobe
Abstract
Nutrient uptake includes desorption, nutrient transport in soil toward the root, transport across root membranes and transport to the shoot; it is a complex process influenced by many parameters. The use of models can improve understanding of this process. Two general categories of models are available. The first category is empirical models that describe facts by statistical means and regressions (Chanter, 1981; Ross, 1981). These models are often called black-box models, since they only describe the relation between input and output, without taking the underlying mechanisms into account. Models of this kind are often used successfully for practical purposes because they usually work with a low number of easily obtainable parameters, and results are sufficient for practical use. The other category includes mechanistic models aimed at explaining a phenomenon by means of basic biophysical, biochemical, and physiological mechanisms (Nye and Tinker, 1977; Claassen, Syring, and Jungk, 1986; Barber. 1995; review by Rengel, 1993). These models are mainly built to understand processes and, thus, are more suitable for scientific use. Most models are in between the two types mentioned, using partly empirical and partly mechanistic approaches. Obviously, there are different ways to describe a given phenomenon; models are therefore seldom right or wrong, but, depending on the purpose, only more or less suitable.