Released June 25, 2008

TWIN FALLS, Idaho —- To help Idaho potato growers meet the market demand for organic spuds, two University of Idaho agricultural scientists are evaluating seven varieties of potatoes under organic production methods in a one-acre field at Kimberly.

“There’s a lot of interest and a lot of curiosity by growers,” said Nora Olsen, University of Idaho Extension potato specialist. “A lot of people are wondering, ‘OK, if I were to jump into this, how would it work?”

Olsen and Extension soil specialist Amber Moore are digging up answers in order to make science-based information available to Idaho producers. This year, they planted two varieties of processing potatoes—Alturas and the late blight-resistant Defender—alongside four fresh-market potatoes—Yukon Gold, Dark Red Norland, Norkotah and Norkotah-8—and Idaho’s mainstay Russet Burbank.

They will monitor the potatoes closely for pest problems and treat damaging levels of Colorado potato beetles with the organically approved pesticide Spinosad. Before planting, they fertilized some of their experimental plots with dairy manure and others with dairy compost and will add fish emulsion—and possibly humic acid—during the growing season.

“Two of the biggest challenges that organic farmers face are controlling weed pressure and effectively managing plant nutrients,” Moore said.

The scientists expect to cultivate at least four times for weeds, including one early-season pass that proved necessary for volunteer alfalfa. The field—undergoing transition to full organic status—had been in alfalfa the past two years.

“It’s a new challenge for us and we’re learning,” said Olsen of the Idaho Potato Commission-supported project. “There are a lot of potatoes grown in this area and consequently there will be plenty of potato pests. We could have all of the same problems that neighboring conventional growers do, and we’ll need to deal with those problems in a modified way.”

Olsen and Moore say that making sure their potatoes get the nitrogen they need during the vine-ripening and tuber-bulking stages could be the biggest challenge the scientists face. Conventional growers typically apply pre-determined levels of nitrogen fertilizer at planting, then follow up with precisely measured supplementary applications through their sprinkler systems during the growing season. But much of the nitrogen in manure and compost must be converted by soil microbes into a form plants can use—a slower and less predictable process.

Moore will take numerous samples of soils and plant tissue this summer to determine when nitrogen is becoming available to the plants and whether it’s available at sufficient rates. She and Olsen will also compare the potato varieties to see which perform best under organic production methods: some may produce larger canopies and shade weeds more effectively, while others stand up better to insects or diseases, tolerate more competition from weeds or use fertilizers more efficiently.

They will also track costs, yields and crop quality and compare their crops with conventionally grown potatoes to help Idaho’s increasingly interested growers assess the pros and cons of organic production.

According to Margaret Misner, organic program manager for the Idaho State Department of Agriculture, Idaho growers are producing 1,176 acres of organic potatoes in 2008, compared with 495 acres in 2007 and 157 acres in 2006.

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http://news.ag.uidaho.edu:591/News/FMPro?-db=AgNews&-lay=generic&-format=story.htm&NewStoryID=980&-find

Contacts: Nora Olsen, (208) 736-3621, norao@uidaho.edu

Amber Moore, (208) 736-3629, amberm@uidaho.edu

Marlene Fritz, (208) 364-6165, mfritz@uidaho.edu.