Farm Progress

Keith Hartmann built a machine that interseeds cover crops into corn while sidedressing fertilizer.

Paula Mohr, Editor, The Farmer

November 3, 2016

5 Min Read

After having success with his three-row interseeder prototype in 2015, Keith Hartmann decided to build a bigger machine — and to add nitrogen sidedressing at the same time.

The Gibbon farmer was encouraged by the success he had when working last year with his prototype that simply interseeded into V6 corn.


Sow cover crops while sidedressing N

WILLING TO EXPERIMENT: Keith Hartmann is experimenting with interseeding cover crops while sidedressing corn. He also raises Berkshire hogs on pasture, marketing them at 300 to 325 pounds.

“My goal was to reduce tillage and hold nutrients in the soil,” he says. “Those cover-crop roots do what tillage does. I saw no difference in yield [in fields seeded and nonseeded with cover crops] in 2015. After harvest, the cover crops lived until November. It took a 20-degree [F] temperature to kill the crop.”

He conducted soil nitrate tests, and the cover crops held the N, too.

“The cover crop absorbed 20 pounds of nitrogen,” he adds. “It went there instead of leaching out into the soil.”

Sow cover crops while sidedressing N

HIS OWN INVENTION: Hartmann combined a fertilizer applicator, air seeding, fresheners and firming wheels so he could interseed cover crops and sidedress N in one pass.

Hartmann also tested herbicide residuals on his farm and on a few other farmers’ fields last year to see if the cover crops could withstand all of their herbicide practices. Herbicides were applied, and three days later, he seeded cover crops. The chemicals did not harm the cover crop at all.

“After seeing the results I had in 2015, I wanted to build a 12-row, 30-inch interseeder. And since I was applying sidedress N, too, I wanted to do it all at once,” Hartmann says. So, he started looking into components needed. As he pieced one together on paper, the unit ended up costing around $60,000.

That’s when he started exploring options to secure grants to help build the machine. He learned about two different grants available through the Minnesota Department of Agriculture — a three-year Sustainable Ag Development grant and a Nutrient Management Initiative grant. The Minnesota Corn Growers Association also had its new Innovation Grant available, which is renewable annually. And there were the traditional NRCS Environmental Quality Incentives Program funds available, too. He applied for all four grants and received enough funding to proceed. Both the MDA sustainable ag and MCGA grants require Hartmann to host a field day to show what he did and learned.

Sow cover crops while sidedressing N

THE SEQUENCE: This photo shows how the fertilizing and seeding process flows.

“My focus on the interseeding is to get cover crops established,” Hartmann reiterates. “In our northern climate, there are not enough heat units to get the crop going in the fall. That’s the reason why I’m focusing on interseeding early in the growing season and making this investment.”

Hartmann farms 320 acres, raising corn and soybeans for market, and field peas and barley for his small organic farrow-to-finish pastured hog operation. He and his wife, Shelby, bought their farm in 2013 from a retiring farmer. Soils on the farm are predominately clay loams.

The components

The unit Hartmann built for the 2016 growing season uses a Great Plains NutriPro 4000 fertilizer applicator with a sidedress bar for liquid nitrogen. He mounted a bar on the applicator for the Yetter strip fresheners, which follow behind the fertilizer coulters. A Gandy Orbit air seeder drops seed in the row, which gets rolled by firming wheels.

Sow cover crops while sidedressing N

BROTHER'S HELP: Hartmann’s brother, Philip, designed the brackets holding the firming wheels on the strip freshener.

On his three-row prototype, Hartmann used old lawn-mower wheels. On his new equipment, he went with larger wheels and had his brother, Philip, who is a machinist and welder, design the firming-wheel bracket that bolts onto the strip freshener.

On June 21, Hartmann seeded125 acres at 10 pounds of seed mix per acre while sidedressing 85 pounds of 28% N. He had applied 75 pounds N at preplant. He planted three replicated strips 30 feet wide by 700 feet long. The cover-crop mix consisted of annual ryegrass, radish, turnip, rapeseed and crimson clover. The cover crops emerged in three days and averaged 28 plants per square foot.

He again conducted stalk N tests and found the corn was at optimal N.

“That was a positive sign for me, given all of the rain and that we applied the average amount of N,” he says. Again this growing season, the cover crops did not compromise corn yield.

“This was probably the best year for interseeding,” he adds. “The cover-crop growth was really lush, and we still had optimal N.”

Sow cover crops while sidedressing N

LUSH GROWTH: Cover crops grew well last year and again this year in between rows of corn.

After the corn came off his fields this fall, Hartmann left the stalks to overwinter, and he will rotate to soybeans in the spring. He no-tilled soybeans into strip trials where rye grass survived in last year’s interseeding, and then terminated the rye grass. He saw no difference in yield in the tilled vs. the no-tilled beans planted into the cover crop.

Whether or not he will interseed cover crops into soybeans remains to be seen. It’s challenging with herbicide selection, and timing is crucial, he says. Some farmers rely on aerial seeding, having it done when leaves drop in the beginning of September.

“If I interseed soybeans, I’d like to do it before [soybean] canopy,” he says, “and possibly plant a clover or maybe annual ryegrass.”


About the Author(s)

Paula Mohr

Editor, The Farmer

Mohr is former editor of The Farmer.

Subscribe to receive top agriculture news
Be informed daily with these free e-newsletters

You May Also Like