Sorter Uses Electromagnetism To Cull Best Seeds For Planting

March 12, 1999

GAINESVILLE — The news is usually about drought or pests, but vegetable farmers lose millions each year to an invisible but expensive source: bad seeds.

As the spring planting season gets under way, a University of Florida agricultural engineering researcher has created a prototype of a machine that uses electromagnetism to help solve this problem. Irek Debicki’s prototype separates poor seeds from good ones based on their internal composition, an advance he says may save farmers millions of dollars by improving conventional machines that determine seed quality based on color, size or weight.

“My method looks into whether any changes have taken place within the seed itself,” said Debicki, a doctoral student in agricultural and biological engineering.

Depending on plant type and soil quality, today’s vegetable farmers may lose 5 to 15 percent of healthy plants to bad seeds, said L.N. Shaw, a UF professor of agricultural and biological engineering. These losses can occur in the greenhouse, where many vegetables are grown before transplanting, or at first planting in the field. As a result, workers have to sort through plant trays to find viable plants, and farmers may not wind up with enough quality transplants.

For field-germinated plants, farmers may have to overcompensate by planting too many seeds. That, in turn, can increase labor costs as workers are required to thin excess plants, Shaw said.

“It’s a significant cost issue, but it’s hard to quantify how much, because it varies by time of year,” Shaw said. “In very hot seasons in Florida, some growers only get half their greenhouse trays filled, because of heat and other factors.”

Failed seeds also can affect the quality and marketability of nearby plants, Debicki said. Lettuce and other salad greens, for example, lose their familiar bunched-up form if not grown directly beside other greens.

Debicki’s prototype sorts seeds using an unlikely but successful method: subjecting them to an electromagnetic field generated by two large copper coils.

Poor seeds have deteriorating cell membranes, Debicki said. When soaked in deionized water, they absorb more moisture than seeds with intact membranes; poor seeds conduct electricity better than good seeds.

To take advantage of this property, Debicki’s prototype subjects the seeds to an electromagnetic force generated in a channel between the two coils. The force pushes high- and low-conducting seeds in opposite directions, sorting good seeds and bad ones, Debicki said.

Tests of the prototype using soaked okra seeds had promising results. The prototype upgraded the quality of 100-seed seed lots from 80 percent good seeds to 93 percent good seeds, Debicki said. He determined the machine’s success rate by drying all the seeds, then propagating them in controlled identical conditions.

If the results were applied on a national scale, the machine could save U.S. farmers $45 million lost to poor seeds annually, Debicki said. Shaw said it also would dovetail with another technology under development at the UF agricultural and biological engineering department: a mechanical transplanter. The transplanter is much simpler to design if every plant in each tray is alive, he said.

Shaw said he and Debicki are exploring the idea of patenting the prototype. It currently only sorts about one seed each second, a speed that would have to be increased considerably before the design could be marketed, Debicki said.

“That would be the next step: to automate it to a point where we could run 10 seeds per second, which is a feasible rate for industry,” Debicki said.