How do you count cranberries? One zap at a time.
Ben Tilberg figured there had to be a better way to count cranberries.
It's Tilberg's job to estimate yields on cranberry beds in Wisconsin, the nation's top cranberry producer. That entails picking every ruby red berry in square-foot research plots and counting them.
With annual harvests of more than 5 million barrels — each barrel is 100 pounds of fruit — Wisconsin grows more than half of all commercial cranberries on the planet.
That's a lot of cranberries.
"It's very labor-intensive. We bring them back to the lab to count them and weigh them," said Tilberg, a Babcock-based scientist for Ocean Spray Cranberries. "I said this is crazy;there has to be a way technology can help us."
It turns out there is a better technology and it's very similar to weather radar.
Cranberries are filled with water and the surrounding vines are not. Just as the strength of the reflected signal in weather radar indicates how much water is contained in clouds, the same technology can be used to detect the number of cranberries in a field.
While researching online,Tilberg learned scientists were using microwaves and satellites to peer through dense rain forests. He wondered whether engineers at the University of Wisconsin-Madison could come up with something for cranberry fields, and he contacted Susan Hagness and John Booske, UW electrical and computer engineering professors.
"It's kind of like — 'OK, we have this giant bush and there's something hidden inside. How do we look inside without tearing branches off?' " said Tilberg.
Hagness has a background in microwave sensing, though in medical uses, not agriculture. So this was a first for her.
"The common theme here is that we are sensing water content," said Hagness, who has worked on using microwave technology to detect breast cancer. "The reason why this technology shows so much promise in the cranberry industry is because cranberries have so much more water content than the surrounding foliage."
Hagness, Booske and graduate student Alex Haufler conducted feasibility studies in the lab and developed a small, box-shaped device that's suspended over cranberry beds to transmit a microwave signal that measures the number of berries.
The prototype was used with good results last fall on cranberry beds in Necedah and Junction City. Now Haufler is working on streamlining the algorithms used to convert microwave signals into cranberry measurements.
The team is devising a next-generation device that will be attached to a boom to be tested during the next growing season.
"It's definitely a novel application of the technology," said Haufler, who is working on his PhD in electrical engineering. "The way we're using it others have used it in monitoring cement curing and other material property measurements. Cranberries is definitely a new application."
Booske noted that folks in agriculture typically don't have exposure to electromagnetic fields, while scientists don't necessarily have expertise in farming. So for Tilberg to find the UW scientists online and think of the possibility of radar technology applying to the cranberry industry is an unusual confluence.
"It's just one of those random human-to-human connections you celebrate when they happen," said Booske.
"It's a work in progress. We've got a basic concept that on the first trial yielded promising results. Now that we have so much more insight, we'll go out for another trial run."
Using a device to measure yields throughout much of Wisconsin's 21,000 acres of cranberries will help farmers better understand their land, determining whether one area is producing more fruit than other areas and why, said Tilberg.
While corn growers have used precision farming for several years and know to a relative degree of certainty how many bushels will grow in a specific spot, estimating yields in cranberry bogs continues to be relatively archaic.
Tilberg and the UW team are hoping the cranberry-counting device will ultimately make cranberry growers smarter about their fields.
"Yields are impacted by different environmental situations and by some of the cultural practices cranberry growers use. If we can accurately estimate yield, we can change some of our practices," said Tilberg.