Mid-Columbia growers add hot mustard to fields

By Drew Foster, Herald staff writer

Chinese hot mustard, like horseradish and habanero, is best consumed in small portions.

That's part of the thinking behind efforts by many Mid-Columbia farmers, particularly potato growers, to raise fields of mustard around this time of year. The mustard is grown from August to late fall -- it can reach 5 to 7 feet tall before it's chopped and tilled.

The chopped and buried mustard plants release chemicals that kill root-knot, root-lesion and stubby-root nematodes -- all enemies of Mid-Columbia potatoes.

"The chemicals in the mustard plant are the same chemicals as the mustard seed," said Andy McGuire, agriculture systems educator for the Washington State University Extension Office in Ephrata.

Mustard seed, when cracked and ground, is used to make the hot mustard offered at many Chinese restaurants. "You know that feeling you get when you eat hot mustard? ... It's the same reaction in the soil," he said.

In a sense, the pesky nematodes are bathed in the sinus-searing condiment.

"It gets into the water they're living in and kills them," McGuire said.

Using mustard as a so-called green manure crop in the Mid-Columbia dates back more than a decade. Besides killing nematodes, chopped and tilled mustard also fights soil-born fungal pathogens such as verticillium wilt.

"There are a lot of benefits to the green manure that have been known for a long time," McGuire said.

Green manure such as mustard also can increase water filtration in the soil and reduce wind erosion, which are the reasons farmer Dale Gies began experimenting with mustard as a green manure cover crop about 15 years ago. He soon found mustard also killed nematodes and fungal pathogens.

"This one really fit the bill," he said.

Use of mustard as a green manure in the Mid-Columbia had humble beginnings.

"When it started out, you know, we were the only ones. Then some neighbors wanted to try it," Gies said.

Now about 24,000 acres of green manure mustard is grown in the area. Gies' company, High Performance Seeds, sells mustard seed to 25 countries around the globe.

Rick Boydston, a weed scientist with the U.S. Department of Agriculture's Agricultural Research Service in Prosser, has worked with mustard as a pest and weed controller for more than a decade.

While tilled mustard kills nematodes and fungal pathogens, Boydston said the growing plant suppresses weed growth as well. Tilled mustard, acting as a biofumigant, also has the potential to inhibit weed germination.

However, he said, "If it's suppressing weeds, it can suppress your crop."

Boydston said the key to reducing weed germination but not affecting the potato crop is timing it so the chemicals released by the mustard diminish by the time potato planting begins in the spring. The large size of the potato tubers also helps protect them from the mustard chemicals, he said.

Professor Ekaterini Riga, a nematologist with WSU in Prosser, has done limited work involving use of mustard in vineyards.

Several years ago, she tested the soil in a Yakima Valley vineyard and found high levels of dagger nematodes, which hinder grape production. In cooperation with the vineyard owner, Riga planted mustard where grapes were to be planted in the coming years.

Mustard crops were grown, chopped and tilled two years in a row. Grapes have been grown in the area for about a year. Riga said dagger nematode populations were reduced by the mustard but re-established in about two years.

"It is my understanding they are now seeing some damage," Riga said.

Now that vines are planted, Riga said growing and tilling mustard, or using a mustard seed meal, isn't practical because it could damage the vines' roots. She has other ideas to incorporate mustard into the soil, but isn't ready to apply them. She's also unsure if she'll be able to continue working with the vineyard.

"I have a very hard time finding funding for this kind of work," she said.

Gies said many growers face hurdles -- often financial -- in planting mustard, but he expects the practice to grow. He said green manure improves soil content and describes use of other chemicals and fumigants as "chemotherapy."

"This improves soil, fumigants don't," he said.

Large fields of mustard can still be seen growing across Benton and Franklin counties. Many of the fields now blanketed in yellow and green would otherwise be barren dirt if the farmers weren't growing mustard, Gies said.

-- Drew Foster: 585-7207; dfoster@tricityherald.com

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Sunday, Nov. 08, 2009

Mid-Columbia growers add hot mustard to fields

By Drew Foster, Herald staff writer