FPTT Innovator Award / G. Clarke Topp / Eastern Cereal and Oilseed Research Center / Agriculture and Agri-Food Canada

FPTT Innovator Award

Agriculture and Agri-Food Canada

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In recognition of outstanding technical innovation and scientific achievement on the application of
Time Domain Reflectometry which has revolutionized the measurement of soil water content and resulted in world-wide adoption as a standard measurement technique

G. Clarke Topp
Eastern Cereal and Oilseed Research Centre

In the early days, before the impact of his work had been fully realized, Dr. Clarke Topp was known to show up at a conference with a bucket of soil and, as one admirer described it, "the zeal of a preacher who'd just found the best religion on earth." In a scientific way, he had. Like many great innovators, Dr. Topp recognized a good idea and, like others before him, had the insight and creativity to adapt that idea to what he knew best. In this case, the expertise of the Agriculture and Agri-Food Canada research scientist resided in soil. Since 1975, despite the initial skepticism of many of his peers, Dr. Topp has relentlessly promoted and pursued his inspiration: the application of electromagnetic techniques to the measurement of soil moisture. Today, his groundbreaking work in the methodology and technology that forms the basis of gauging soil water content has almost single-handedly revolutionized fields such as soil physics, environmental science and water management.

Dr. Topp's research and continuing legacy revolves around Time Domain Reflectometry (TDR), originally developed by the telecommunications industry to determine breaks, shorts and the presence of water in buried coaxial cable. With TDR, for example, a break is located by applying a fast rise electrical pulse at the free end of the cable and then measuring the time it takes for a signal to travel to and reflect back from the point of disruption. Using his considerable expertise in electromagnetic field propagation, Dr. Topp altered the technique by applying the electrical pulse to probes inserted into the earth. Analysing the reflected signal, he was able to calculate the amount of moisture in a range of soils, since the speed of the pulse depends on dielectric properties of the soil, which in turn are highly correlated with moisture. Dr. Topp's formula known around the world as the "Topp equation" or "Topp curve" is now a standard calibration curve used to convert TDR measurements to soil water content.

His discovery has opened the door to a new set of instruments, a new way of thinking and a new industry. Introduced to the soil science and agricultural community in the early 1980s, TDR was soon used to measure not only water content of soil, grains and food oils but also soil solutes and the movement of chemical contaminants through soil and into groundwater. A proponent of sustainable agricultural practices, Dr. Topp has conducted on-site training in developing countries such as Pakistan, India and Brazil to demonstrate how TDR can be used to measure water for irrigation and salt accumulation in dryland farming. Among his recent inventions, Dr. Topp developed a portable soil cone penetrometer, patented in the U.S. in 1995 and in Canada in 1996, that provides a measure of soil strength or compaction.

Several companies worldwide that have developed TDR instruments, including firms in Germany and the United States, have yet to scratch the surface of its potential. "Dr. Topp's work will also bring social benefits and enhanced quality of life to those regions where water is in desperately short supply," says Gail Gabel, president of Environmental Sensors Inc., a British Columbia firm that manufactures and exports TDR instruments to 38 countries. "The fact is that Clarke Topp's research will be far-reaching for generations to come."

Sponsored by:
The Impact Group

From left to right: Ron Freedman, The Impact Group (sponsor); Jacques Lyrette, Technology and Industry Support, NRC; G. Clarke Topp, Eastern Cereal and Oilseed Research Centre, AAFC; and Jeffery Crelinsten, The Impact Group (sponsor)