ABSTRACT
The rhizosphere is a highly complex environment where almost every process involves multiple interactions between the soil-root-microbe triumvirate, as other chapters in this volume document. Understanding rhizospheric processes is therefore extremely challenging, especially as many of the questions to be studied require quantitative answers. For example, the rate of nitrogen influx into the root system is an important determinant of plant productivity, and yet explaining why this flux differs between different experimental treatments requires a very detailed knowledge of plant physiology, soil physics, chemistry, and biology as it relates to the N cycle (1). The value of mathematical models is that they do generate quantitative answers and allow the integration of many individual plant and soil processes to predict a single outcome. However, such models require parameters to run the simulations and the experiments to measure them may be extremely difficult to do.
