Using Century Old Research to Teach Fundamental Soil Science Concepts Today.

Great advances in our understanding of soil processes have been made in the past century.  What is now considered common, fundamental knowledge was once, however, cutting edge research reported in the literature of the day. It is this same fundamental knowledge that we strive to instill in students in introductory soil science classes and laboratories. Putting this knowledge into the context of the historical literature can be beneficial in understanding the development of both the discipline of soil science in particular and the scientific method in general. Examples were drawn from the literature to illustrate both physical and chemical processes that students typically find challenging. The angle of repose of soil material can be used to illustrate the effects of pore water pressure on the mechanical strength of soil through capillary action. Recreating Webster’s (1919) experiments and analysis neatly demonstrates the relationship between water content and the angle of repose attained in a sandy material. A natural extension of this work is to use materials of different grain (and pore) size distributions. Similarly, osmosis tends to be a difficult process for students to understand as it appears to be the opposite of the dilution process they would expect. Internet searches on osmosis bring up scores of biological examples of cell walls acting as semi-permeable membranes but these are not intuitively transferable to the same process in soil. The experiments of Lynde (1912) and Lynde and Bates (1912) concisely demonstrate how water flows through soil in response to a solution concentration gradient. These experiments are also intuitively expandable to include variable conditions in both soil type and solution concentrations. These examples provide not only experimental demonstrations of particular soil processes but also facilitate the expansion and evolution of ideas through the scientific method.