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

Soil behavior can be considered from different levels of perception: by the user, by experts and by specialists. The most comprehensive and effective characterization of soil behavior is likely obtained when these three levels are considered together as is illustrated in six case studies. Soil behavior is determined by interacting physical, chemical and biological processes of natural and man-induced origin. Three procedures for characterizing soil behavior are discussed: (1) monitoring of soil processes in situ; (2) monitoring the effects of soil processes as expressed on the soil surface, and (3) prediction of soil behavior for actual and potential environmental conditions by process oriented simulation modelling. A case is made to combine real-time monitoring and simulation modelling for predictions of soil behavior over periods for which extended weather forecasts are available. Heterogeneous field conditions require application of special techniques that account for soil horizons and patterns of heterogenity to be characterized with morphological techniques. Electronic techniques allow widespread generation of continuous monitoring data crucial for calibration and validation of process-oriented simulation models, and for updating expert knowledge. Modem remote sensing techniques, using satellites, airplanes and handheld equipment, allow detailed characterization of conditions at the soil surface or of the crop cover, reflecting soil conditions within the rootzone. A research approach is advocated, based on a critical problem-analysis and on quantitative ground-truth data. Some problems can be solved by expert knowledge, whereas others require additional measurements or simulations.