FARGO, N.D. – If tile drainage and deep rippers are too rich for the budget, maybe a good crop of radishes can solve hardpan and salinity problems.
Gerald Bosse says it works for him on his farm in southeastern North Dakota.
A decade of too much rain on the Bosse farm has created expanding alkaline spots where once there was productive farmland.
Some farmers on the northern Great Plains have successfully installed tile drainage to remove excess water and flush away salts trapped above the hardpan layer. It works, but tile drainage is expensive.
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Deep tillage is another solution. It works for a while and is cheaper than tiles, but hardpan eventually returns.
Enter radishes.
Bosse said the radish variety he plants on his alkali spots has a taproot that bores down 120 centimetres. Hardpan is usually found at about 60 cm.
Roots of nearly all field crops typically turn and run horizontally when they hit hardpan, but not radishes. The aggressive roots bore through the solid soil layer, opening cracks that allow excess water and salts to leech into the soil below.
“It’s a tough taproot. When we dig a soil profile, we can see that it goes straight down four feet (120 cm). No turning to follow the hardpan layer,” Bosse said.
“It busts right through. Nobody really knows why or how, but it happens. Once the hardpan is fractured, the excess water and salts leech away. It all happens quickly.
“Plant radishes this summer and the alkali spot is ready for a regular crop next spring.”
He first tried radishes on a wildlife feed plot, along with turnips and rapeseed.
The experience taught him that he could plant the radishes anytime from mid-July to late August.
“The taproots went deep like sunflowers. You don’t need to fertilize them. And you can put the cattle out to graze them in the fall.
“They like the tops. But the main thing was the way radishes got rid of so much excess moisture in the wet spots. It only takes one radish crop. When spring comes, the radishes have decomposed and the ground is in good condition to grow a real crop.”
Bosse said he plants radishes only where salinity has taken over.
The increase in salinity means he now plants 300 to 400 acres a year to radishes.
He said these tillage radishes are not to be confused with the little red vegetable grown in gardens. They have been bred to do exactly what their name suggests – tillage.
The Conservation Cropping System Project (CCSP) has been working with producers in southeastern North Dakota who want to try alternatives such as radishes.
Kelly Cooper, manager of the project’s research farm, cautions
producers when buying radish seed.
“There’s a lot of radish seed on the market lately that isn’t really
the tillage variety,” he said.
“The problem is that we can’t tell visually. We have to grow it out
to see if it’s a tillage variety. Even then, we can’t be sure if it will
form a good deep taproot or simply set seed. We’ve bought seed from
reputable seed dealers and it turned out to be garden radishes. Nobody’s
trying to trick anybody. They can’t tell the difference either.”
Cooper said variety verification needs to be addressed if tillage
radishes are to become a significant tool for farmers.
He said seeding rates can range from three to eight pounds per acre,
and seed usually costs $10 to $15 per acre. The crop responds well to
nitrogen but is often seeded with no fertilizer.
Tillage radishes are ravenous consumers of nitrogen and bring it up
from deep in the earth where it had been trapped below the hardpan.
When the radish plant dies in the fall, this nitrogen is deposited
near the surface.
Researchers have begun studying the plant’s nitrogen contribution in
northern climates.
At a CCSP field day this summer, Cooper dug a 120 cm deep trench to
show how far the roots go. The radishes had been planted July 15, 2009,
and the field day was held July 15, 2010.
“The radishes died off last fall, but we can still see the distinct
root going to the bottom of the trench,” Cooper said.
It means the plants were still providing a channel for excess water a
year after they were seeded.
“Radishes have a high nitrogen to carbon ratio, so they’re relatively
low in organic matter,” Cooper said.
“They decompose quickly and leave a lot of nitrogen behind.”
He said the research farm is studying what he calls biological strip
tillage.
Researchers use a wide row spacing format to plant a strip of
radishes on wheat stubble. They use a high seeding rate, along with
phosphorus, potassium and nitrogen fertilizer.
They plant a row of peas between each radish row to provide
additional nitrogen for the subsequent crop.
Tillage radishes not only bust through hardpan but also leave a
mellow surface the following spring.
Cooper said he expects the research farm will be able to plant corn
directly into this seedbed without first using strip tillage equipment.
For more information, visit www.tillageradish.com
or phone Cooper at 701-724-6226 extension 3, or Bosse at 701-724-3921.
