Giant radishes invade county farm bringing peace and possibly improved yields

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Catherine W. Idzerda
Sunday, October 27, 2013

JANESVILLE—For most of us, the radish is an uncomplicated vegetable.

It's pink or red, mildly to moderately spicy and makes for a lovely floral garnish in a salad bar.

For the last five years, researchers at the Rock County farm have been studying a different kind of radish, one you won't find at a salad bar any time soon. These are cover-crop radishes, giant versions of their grocery-store cousins.

These radishes range from 10- to 18-inches long and from 2- to 4-inches around.

“This is one of the newest developments in cover crops,” said Jim Stute, UW Extension crops and soils agents. “These are giant, and they are beautiful.”

For farmers, cover crops can help reduce the cost of inputs such as fertilizer and fuel.

For the rest of us, cover crops are a way to keep agricultural chemicals out of lakes, streams and rivers—and the groundwater.

Water quality is especially important for the tourism industry in Rock and Walworth counties.


 “The definition of a cover crop is any crop grown when another crop is usually not present to protect and improve the soil,” Stute said. “They are typically not intended for harvest.”

Traditional cover crops include winter rye, which is planted after corn silage is taken off; red clover, planted after wheat; and oats, planted after canning crops are harvested.

Bare soil is not a natural condition, Stute explained.

Soil is an aggregate of a number of different particles, including sand, silt, clay and such organic material as decaying plant matter.

When rain hits unprotected soil, the particles come apart, and the most valuable part of the soil, the silt, is washed away.

“Cover crops intercept the energy of rain so soil particles don't get detached as runoff,” Stute said. “Cover crops cut wind erosion, too.”

Farm runoff can raise phosphate levels in the watershed.

Giant radishes provide the needed protection, and they have the additional advantage of providing “bio tillage.”

Frost kills the plants in the fall. Over the winter, the radishes break down, leaving holes in the ground.

The holes aerate and loosen the soil, improving its overall health. In the spring, corn can be planted without tilling the soil.

Testing claims

Cover crops are marketed just like anything else for sale: glossy brochures, up-tempo Internet sites and ads in farming publications.

 “These radishes are becoming wildly popular with farmers,” Stute said. “They go by such snappy proprietary names as “PileDriver” and “GroundHog.”

But the input costs—seed, fertilizer, fuel—are significantly higher for radishes than they are for other cover crops, Stute said.

It costs between $30 to $40 an acre to plant a cover crop such as red clover; cover crop radishes average between $60 and $70 an acre.

Theoretically, those extra costs should be absorbed by increased crop yields the next year, due to soil improvement.

Stute is co-adviser to the project with Matt Ruark, a soil scientist at UW-Madison. Graduate student Megan Chawner is the primary researcher.

The trio is considering all of the marketing claims made by the seed industry: How much fertilizer does a crop need? Which seed variety works best? Are the “bio tillage” benefits worth the extra cost? What's the impact on the corn crop the next year? Do the radishes have the expected effect on the soil pest population?

The trials started two years ago at sites in Rock, Sheboygan and Washington counties. Trials are expected to continue in an effort to average out such seasonal variables as weather conditions.

“In our first year, the drought really wiped out all the treatment effects,” Stute said.

Just a few days ago, researchers harvested the second season's corn harvest, and the yield information has not been calculated yet.

Why make the effort?

“Our research is driven by the questions that farmers have,” Stute said. “The information we use in our education programs is the true yield.”

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