Farmers Use Radishes to Enrich Soil

Jan 19, 2013

Many of farmer Jim Kelly’s fields in Murray are bright green with winter wheat even after several frosts. But tromp around some of his other crop fields and you’ll find the withering leaves of radishes. And he’s just going to keep letting them rot.

"These things are in the process of dying. See, some of them already have," he said.

Kelly’s crop usually consists of tobacco, wheat, soybeans, corn and hay. But this year he’s adding radishes to his rotation in his soybean fields as a cover crop. The pale yellow vegetable looks a lot like a carrot and digs down breaking up the soil. Kelly won’t harvest the radishes. They grow until the first hard freeze then begin to die.

Kelly digs up one of the six inch radishes and snaps it in half to reveal a frosty, frozen middle that will eventually thaw, decay and provide nutrition for his fields.

Western Illinois University professor Joel Gruver has been researching radishes since the summer of 2007. He says farmers like Kelly can get additional benefits from radishes that other cover crops like cereal rye and clover don’t provide. They grow very quickly in the fall. They’re excellent at scavenging nitrogen and other nutrients. And they are excellent at outcompeting weeds.

"But what is probably most valuable about them is that radishes grow this deep taproot that’s an excellent channel for the following crop’s roots to follow and radishes die out in the winter time," Gruver said. "So you have very little residue to manage in the spring."

Using radishes as a cover crop is a relatively new method. In his research Gruver has worked with the farmer who first started using tillage radishes, which differ from the conventional red, round radish. The cover crop radish even smells differently than you’d expect. It’s more like a potato and less like the spicy scent you’d expect from the horseradish tasting vegetable. Gruver says since using the tillage radish is a fairly new method, farmers are experimenting with them for all kinds of crops including peanuts.

This is Kelly’s first time using radishes as a cover crop – he usually plants winter wheat in his fields. Cover crops like radishes help build up the soil with the residue they leave behind and they prevent soil erosion, which Kelly says is of upmost importance in farming because he says all farmers aren’t corn, soybean or wheat farmers. They are actually all soil farmers since that is what all products in agriculture rely on to grow.

This soil in Calloway County is real tight structured, got a clay base in it. It has a tendency to compact and not let the nutrients down. So we’re looking for something that will eliminate that and that’s what this does.

The winter freezes will kill off the plants. That way farmers don’t have to use herbicide to kill them come spring. However, the decaying radishes do temporarily leave behind a foul smell. If you drive by Kelly’s fields after a warm spell you might get an unpleasant whiff of what smells like rotten eggs or a natural gas leak. Gruver says some people have even reported a gas leak to authorities when the smell was really just rotting radishes.

"You know, it’s a volatile compound that contains reduced sulfur, but our noses for some reason are very sensitive to those types of compounds," he said. "We can smell parts per billion."

While cover crop radishes seem to have few disadvantages other than the smell, not all farmers rave about their success. Bill Gentry planted cover crop radishes a year ago on his 3,200 acre Henderson County farm.

Gentry hoped the radishes would help with soil compaction and leave behind some organic matter that would enrich the soil and improve his corn crop. But the drought this summer made it impossible to tell if the radishes improved the quality or quantity of his corn. 

"We did not see a lot of change in terms of compaction and then in terms or any organic matter or increase in yield, it simply wasn’t going to happen in a drought," Gentry said.

The biggest obstacle Gentry faced with the radishes was timing. They thrive best when planted in mid-August. But Gentry’s corn isn’t harvested until mid-September or October, which is too late to plant the radishes. He says for his farm using radishes as a cover crop was a one time occurrence.

Kelly’s timing though works out much better than Gentry’s because he’s using them in rotation with soybeans instead of corn. Although the cover crop radishes are fairly expensive at about 35 dollars per acre, Kelly says he expects to recoup that money long term because of the decrease in fertilizer he has to use. Contrary to what some think about chemicals used in farming, Kelly says farmers want to use the least amount possible because of the high cost of fertilizer.

"In spite of what some people in the big cities think about farmers, we’re not out to just put something out and let our dirt wash away from us or put stuff on there that’s not justified because we have to pay for those things and we make our living from the soil," he said.

Ultimately, Kelly just wants to grow food to support his family, and he thinks planting radishes in the fall and letting them rot until spring is a good way to do that. As long as he has his hands in the dirt and is nourishing plants, he’s a happy man.

"I can’t tell you about the emotional high of getting out here and working the dirt and getting a good seed bed and putting a little tiny seed in there and seeing what it produces," Kelly said.

He’s willing to deal with the occasional foul smelling field to build up his soil and can’t wait to see how the tiny radish seeds flourish and eventually strengthen the ground that sustains his family.