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Cover crops for the long haul

Growing cover crops to improve soil quality is a hot topic on the farm-meeting circuit these days. But it's old hat for Ohio farmer Dave Brandt. The conservation-minded farmer from Carroll, Ohio, has been no-tilling for 39 years and incorporating cover crops into crop rotations for 34 years.

“This approach has benefitted our farm by eliminating soil loss, building soil organic matter, improving crop yields, and reducing input costs,” says Brandt. “The impact is amazing.

“Soil erosion is down to less than 100 pounds per acre, organic matter levels have increased from less than 1% to more than 5%, soil compaction is reduced, and we've cut fertilizer and herbicide use by 40%- to 70%, while reducing production cost by as much as $135 per acre,” he says.

Brandt follows a corn/soybean/wheat/cover crop rotation. Cover crops planted into wheat stubble two to three weeks after harvest are terminated either by a winter freeze or a spring herbicide application. Currently, his preferred method is to use his White no-till planter to precision-plant two cover crop species in alternating 15-inch rows.

Peas and radishes

Brandt says, “We've found there's a symbiotic effect between different crops. They just grow better together. Our current focus is on Austrian winter peas and oilseed radishes. A small sugar beet plate meters radish seed in every other planter box, while a soybean plate meters peas in the others. This method minimizes our seed costs while maximizing the benefits the cover crops provide.”

Brandt is experimenting with other legumes to use in his system, but the oilseed radish is a permanent fixture.

“When growing beside legumes, the radishes suck up any residual nitrogen, storing it in the tuber and leaves, and they force the legume to work harder to replace it. We've counted twice as many nodules when peas are grown this way. And the radishes get two to three times larger when they're growing beside peas rather than growing alone,” he says.

The alternating rows of radishes serve several other functions. “They're our form of strip-tillage. The tubers push 1 foot or more into the ground and form a taproot that can go another 30 inches deep. These roots take up nutrients that are deep in the soil. The roots store the nutrients in the tubers or leaves where the nutrients are released into the root zone of our crops when the radish decays.

“We've had tubers analyzed and found they can recycle 250 pounds of nitrogen, 230 pounds of potassium, and 23 pounds of phosphorus per acre, along with sulfur and other nutrients,” says Brandt.

“By corn-planting time, the radish tubers are quickly breaking down, leaving those nutrients behind, along with a channel from the tuber and root for water to infiltrate and crop roots to follow,” he says. “The tubers also push up the soil slightly, so there's a raised bed that's clear of residue. That's because with their low carbon/nitrogen ratio, the radish leaves decay rapidly. Using RTK guidance, we plant corn right on those old radish rows because the soil is warmer (3°F.) and drier.”

Looking for Legumes

Though he's focused on peas, Brandt is experimenting with other legumes to pair with his radishes. In plots last year that received only 50 pounds per acre of applied nitrogen, he produced 229 bushels of corn per acre where Austrian winter peas were used, 235 bushels where sunn hemp was the legume, 219 bushels with crimson clover, and 194 bushels with fava beans.

“We really liked the sunn hemp and will plant more this year,” says Brandt. “It grew 2½ feet tall, and that forced the radishes to grow more to compete for sunlight. Some nodules on the sunn hemp were as large as golf balls. It also has a very long maturity, so it doesn't bloom. And it freezes out early – at 34°F. We don't want our legumes to bloom and make seed, because that transfers nitrogen out of the roots.”

Brandt is confident in the nitrogen contribution his cover crops can make, but he still checks it by using a handheld chlorophyll meter to test leaves during the season. “We know that a reading of 42 on the meter means we're on track for 200-bushel corn. In our plots last year, we had a reading of 57 where sunn hemp had been the legume, 47 following the peas, and 30 behind the fava beans. If we find that levels are low, we sidedress nitrogen on the crop,” he says.

Other benefits

Brandt admits he doesn't understand all the biological benefits that cover cropping provides, but the effects are clear.

“We measure soil bulk density and have found that soil compaction has been reduced by 40%,” he says. “Our soils are now at nearly the same bulk density as nearby forested woodlots that have never been farmed. We soil-test annually, and in addition to the steady climb in soil organic matter, we're seeing a 10% to 20% increase in residual P and K levels, even though our application rates have been cut in half. Our agronomist says that can't happen. But it certainly is happening.

“Besides improving crop nutrients, cover cropping has improved our soil tilth and water infiltration rate, reduced weed-control problems, reduced pest and disease problems like the cyst nematode, and also prevented any soil or nitrogen loss that could impact the environment,” he says.

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