Why a mechanistic theory of soils is crucially important: Another line of supportive argument exists, seldom invoked in soil science

Abstract. In the last few decades, the effort that has been devoted to the mechanistic, quantitative description of soil processes has been justified on the grounds that theories and models help us understand how soils function, and also predict how, e.g., they are likely to adjust in the future to environmental change. The argument, familiar to physicists, that theories uniquely determine what should be measured, has rarely if ever been invoked in the soil science literature. On the contrary, to enable the classification and mapping of soils, enormous amounts of “theory-free” data have been and continue to be amassed by soil scientists. In this general context, the key objective of the present Forum article is to argue that the accumulation of more “theory-free” data, in particular to allow the application of artificial intelligence methods, does not make practical sense at this stage, and that the development of improved theories of soil processes is crucial to provide guidance about the type of measurements that should be collected. Hopefully, this Forum article will stimulate a debate on this issue, and will lead to a much-needed intensification of theoretical research and modelling in soil science.