Conversations from the Hall of Fame

Stuart O. Nelson, agricultural engineer, interviewed 2002

(Time: ~7:04 minutes)

I was born on a farm in Stanton County, Nebraska. That's northeast Nebraska. Father and mother were hard working Nebraska farmers. We lived about nine miles from the small town. My mother started taking us for piano lessons, Don and myself. I guess I was ten years old and I remember a lot of times when she would plow the mud for those nine miles, well I guess for about four miles to a paved road to get into town for our music lessons. 

Why Science?

Our parents were very interested in education. My dad had gone to the school of agriculture which was a winter time course for farm boys back in those days. They trusted my brother and I, who we were about 12, 10 and 12,  9 and 12 something like that and we wired all the barns and the other buildings on the farm. So that was an early interest in electrical things. I stayed in agricultural engineering which I had started before going into the service. 

I was assigned to the flag ship of a destroyer division 12. Radio transmitters, the radar equipment, the sonar equipment, the movie projects whatever was electronic on the ship. I decided that there should be a lot of places in agriculture where electronics would be helpful.

Gist of the Research

When you use high frequency dielectric heating or microwave heating, the rate of heating of the material depends on its electrical properties which we call dielectric properties. 

The first data on dielectric properties of grain and the technique that I used for measuring it
reliably was published in 1953 so I've been working fifty years on dielectric properties. I have taken measurements on fruits and vegetables, various kinds of grains and oil seed crops. 

Back in those days there weren't any computer programs for doing the statistics when I took the courses it was the mechanical calculators that you learned to run.

I checked with three of the laboratories where this type of work was being done and none of them had a computer program to work with the loss in materials like we were taking measurements on grain and insects and so LaVerne Stetson, Carl Schlaphoff, who was the applied math major, and I worked for a couple of years putting together a very versatile and general computer program for these types of measurements and then we furnished those to various laboratories. I think about forty different laboratories around the world who are interested in the program.

Spinoffs

Because I had developed these systems to cover wide ranges of frequency there were other agencies that became interested. An inquiry from people with the Bureau of Mines who were interested in using microwave heating for factionating rocks. To break them apart so that they can get the minerals out, extract the minerals and this got me into working with various dielectric mixture equations and I found some that work very well for that purpose and that was, that was interesting work.
Influences

Other than my parents. Professor T. T. Smith taught the basic electricity and magnetism courses and made one suggestion that I have always thought was good. He says, "Always question your measurements and you'll do good work."

Harry Borthwick was one fellow that I, was one of the early members of the ARS Hall of Fame, that I visited with and I remember something Harry told me to. I was looking for some seed physiologist or somebody to examine the seeds to tell us what we were really doing to these seeds because we were making them grow, rendering them permeable and Harry says, "Well why don't you do it yourself." 
Well I have done all a lot of things myself through the years sometimes that's the best way you learn in doing those things. 

Improving Seed Germination

The work we did on seeds to improve germination was using dielectric heating. With alfalfa and some of the other small seeded legumes, like red clover and ladino clover, we got consistent improvement whenever the seed lots had a high hard seed percentage, those are hard seeds or those that are impermeable to water and water is one of the requirements for germination and we were all able to improve the germination of alfalfa seed when it had a high hard seed content.  

Potential Uses

I still hope that this might someday be useful because it is a technique that does not damage the seed as the scarification, the mechanical scarification, can damage the seed and it can't be held over until the following year because the germination quality deteriorates. A high frequency or a microwave dielectric heating treatment will render those seeds permeable and therefore they will grow. 

Future of the Work

I have no plans to retire because I'm still enjoying the work as long as my health is good and as long as the agency is interested in my continuing. We, I have had a lot of help from visiting scientists and junior engineers as I've mentioned. In the past ten or fifteen years we've concentrated on microwave measurements for moisture sensing to improve the reliability of sensing moisture in grain and particularly for online moving grain. 

Words of Wisdom

Find some interesting work. Work that you like to do, where you can ask questions and design experiments or do whatever work you need to do to answer those questions.