How effective are tillage radishes in rejuvenating poor soil and pastures?
Staff at Clearwater County have been experimenting with tillage radishes to see if their theoretical benefits hold up in the real world. The fast-growing brassica can be used in forages as a cover crop and as feed for cattle; its long taproot can open and loosen soil where machinery can’t reach; and it can also suppress fall weeds.
“The big root goes down into the soil profile and pulls up nutrients from below, farther down than your regular crops can pull nutrients from,” Annie Bertagnolli, administrative assistant with Clearwater County Agricultural Services, said during a recent agriculture tour. “These nutrients are stored in the root over winter and in the winter, when it rots, the tillage radish releases all those nutrients, making them available to the next crop.”
Its root, which can grow up to 14 inches in length, resembles a daikon radish. It grows through compacted soil and hardpan, and when the roots rots, they leave thumb-sized holes in the ground, which allow for air and water infiltration.
And that’s just what it did in a trial last year.
“It all worked beautifully,” said Bertagnolli. “The nitrogen in the soil went from 10 (pounds per acre) to 75. It worked really well. We know we can grow them in Clearwater County and it’s a success.”
This year, county researchers tried to grow tillage radish on several pastures. Radish seed, along with grass seed, was drilled directly into the pastures at three sites.
At the first site, dandelion, plantain and white clover had completely taken over the pasture, which was divided into five plots. Radishes were seeded at a quarter-inch deep, but that turned out to be too shallow.
“We should have gone a lot deeper in a drought year,” said Bertagnolli. “The plants should be bigger than they are and there are very few that established.”
With seeding around July 24, getting seed-to-soil contact was also an issue but planting the fast-growing plants earlier wasn’t an option.
“If you plant them too early and they start to bulb, then you’re not going to get your big roots. And it’s the roots that we are aiming for,” she said.
One plot was seeded without fertilizer; a second with fertilizer; and a third with fertilizer and grass seed.
“Most of the species you see in this pasture, the dandelion, plantain and alfalfa, have sucked most of the moisture out of the soil already,” she said.
A fourth plot was doused with Roundup before seeding, and the radishes came up best there, because they had no competition. The fifth plot was conventionally tilled, with plowing, disking and harrowing before seeding.
“We got a few showers on the first week they were seeded,” said Bertagnolli. “Some of them didn’t germinate, but quite a few did. When we walked through them, we had hope. But then we had a week of 32 C to 35 C heat. A radish at the cotyledon stage cannot take those conditions, and they turned yellow.”
Her group has been in touch with American researchers who have had success by turning cattle into a pasture for two to three days right after seeding. The hoof action punches the seed into the ground, allowing for better seed-to-soil contact and germination.
“Next year, I think we’re going to try that. We’re learning as we go,” said Bertagnolli.
Tillage radish is an excellent feed source as the plant’s stems and leaves have about 27 per cent protein.
“It’s almost too rich and you should probably put it with a ryegrass or something to mix it up a bit,” she said.
The tillage radishes were also seeded at Marty Winchell’s place. Before seeding on Aug. 2 the area was grazed heavily by sheep and cattle and also benefited from the soil disturbance caused by a hailstorm two days later. They didn’t emerge until after the 35 C weather and seemed to flourish in the fresh manure left on the fields.
“When I look at how this would fit into my own operation, I’m excited about it from a grazing standpoint,” said Winchell, agricultural program supervisor with Clearwater County. “When you look at what Annie got in the cultivated area, with the huge amount of top growth and the 24 per cent protein, if you can graze that at the end of the season and get your animals on a high-protein diet in the field, I think they’ll finish off quite nicely.”