SOIL BEHAVIOR UNDER FIELD CONDITIONS - DIFFERENCES IN PERCEPTION AND THEIR EFFECTS ON RESEARCH

Soil behavior can be considered from different levels of perception: b y the user, by experts and by specialists. The most comprehensive and effective characterization of soil behavior is likely obtained when th ese three levels are considered together as is illustrated in six case studies. Soil behavior is determined by interacting physical, chemica l and biological processes of natural and man-induced origin. Three pr ocedures for characterizing soil behavior are discussed: (1) monitorin g of soil processes in situ; (2) monitoring the effects of soil proces ses as expressed on the soil surface, and (3) prediction of soil behav ior for actual and potential environmental conditions by process orien ted simulation modelling. A case is made to combine real-time monitori ng and simulation modelling for predictions of soil behavior over peri ods for which extended weather forecasts are available. Heterogeneous field conditions require application of special techniques that accoun t for soil horizons and patterns of heterogenity to be characterized w ith morphological techniques. Electronic techniques allow widespread g eneration of continuous monitoring data crucial for calibration and va lidation of process-oriented simulation models, and for updating exper t knowledge. Modem remote sensing techniques, using satellites, airpla nes and handheld equipment, allow detailed characterization of conditi ons at the soil surface or of the crop cover, reflecting soil conditio ns within the rootzone. A research approach is advocated, based on a c ritical problem-analysis and on quantitative ground-truth data. Some p roblems can be solved by expert knowledge, whereas others require addi tional measurements or simulations.