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Soil Physics and How Water Moves in Soil

On June 11, 2015, Dr. Walter Hale Gardner died at age 98.  Who was Dr. Gardner?  If you ever used one of those devices to measure soil moisture content, then you’ve indirectly met Dr. Gardner.  He was a Professor of Soil Physics at Washington State University (Pullman, WA).  He co-authored a textbook on soil physics, which is defined as the study of soil physical properties and processes, and deals with the dynamics of physical soil components and their phases as solid, liquids, and gases.  He had many scientific accomplishments in the field of soil science, but he may by best known for his time-lapse movie.

Figue 1

Dr. Gardner showing movement of water through soil.

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For the first time, this 1959 movie showed water flow through soils of different textures, water flow through layered soil profiles, the effects of soil management techniques on water movement into and through the soil, and more.  For a long time, this movie was shown in college soil science classes as a 16 mm reel-to-reel film.

There is an updated version, but Gardner’s movie is still considered the classic.  Dr. Gardner also was among the first to use the attenuation of neutron beams to measure soil moisture.

Updated Version

That pioneering research made it possible for the eventual production and sale of devices such as the FieldScout TDR 300 Soil Moisture Meter (Spectrum Technologies), the Pogo (Stevens Water Monitoring Systems), and others.  Who are the next generation of soil physicists to continue Dr. Gardner’s research of water movement in soil and root/water interactions?  Dr. Tammo Steenhuis (Cornell University), Dr. Stefan Doerr (Swansea Unviersity), and my ‘Italian cousin’ Dr. Andrea Carminati (University of Göttingen) are leading the way.  So how does water move through the soil?  It is both a simple and very complex process, involving soil physical, chemical, and biological properties.

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