Kerry and Angela Knuth, Mead, Neb., began strip-tilling corn in the spring of 2005 and only recently switched to fall strip-till. The Knuths, who farm about 35 miles west of Omaha, grow corn and soybeans in about a 50-50 rotation on 2,000 acres, both dryland and irrigated.

In 2010, the Knuths started working with Kevin Kimberley, owner of Kimberley Ag Consulting in Maxwell, Iowa. With Kimberley’s advice, Kerry put together a strip-till rig that winter.

In the fall of 2010, the Knuths strip-tilled about 25% of their corn acres to see how it would work. And starting last year, the Knuths strip-till all their corn acres in the fall.

By strip-tilling in the fall, they can start planting corn sooner in the spring.

“After we strip-tilled in fall 2011, the soil conditions were ideal this spring,” Kerry Knuth says. “During the winter, the soil in the berms settled.”

Knuth said it was clear this spring that the fall strip-tilled soil was better to plant into than spring strip-tilled in previous years.

“With the fall strip-till, the soil warmed up quickly this spring and I was able to just go out and plant corn,” he says. “The advantage of strip-tilling in the fall is that after we finish planting corn, we can begin planting soybeans earlier than we had with spring strip-till. And planting soybeans earlier can produce higher yields than if you’re delayed.”

DEEP ROOTS. Mead, Neb., strip-tiller Kerry Knuth says that roots of the corn he dug around June 13 were about as deep — 30 inches — as the vegetative growth above ground. (Photo courtesy Kimberley Ag Consulting)

Switching from spring strip-till to the fall also allowed Knuth to make a change in tractors.

“With spring strip-till, I needed two large 4-wheel-drive tractors, but now I’m downsizing from a Deere 9630 with 525 horsepower to one Deere 9510R, which has 510 horsepower.”

Knuth uses Deere’s RTK system, which has 1-inch accuracy.

“We started using RTK about 5 years ago and we also use Deere’s iGuide, which is passive implement guidance,” he says. “We were a beta tester for the iGuide system on our strip-till rig and our planter. Implement guidance makes a big difference if you want to hit that strip, especially on contours.

“Before we started using iGuide, we could be off easily 15 inches from the strip when we planted corn.”

More Corn, More Profit

Strip-tilling also enables the Knuths to grow more corn on his farm.

Kerry recalls asking Kimberley in the fall of 2010 if his farm could handle strip-tilling continuous corn. Kimberley agreed it was possible, if Kerry could get the strips clean in the fall so they’re ready to plant to corn into in the spring.

In fall 2010, Knuth strip-tilled 150 acres of corn-on-corn. This year, he doubled that to 300 acres.

There are two ways of looking at the pros and cons of growing corn-on-corn, Knuth says. Yields can be less than growing corn after soybeans, but corn-on-corn acres can produce more corn in total, he says. And higher corn prices today means more gross revenue.

“In 2011, our corn-on-corn yields were 6% less than corn after soybeans,” Knuth says. “But the price last fall for corn was good, and with continuous corn I pre-sold more corn at a better price.”

The Knuths irrigate all of their continuous corn, and he points out that growing continuous corn allows him to fully use their center pivots.

“When we grow soybeans on a field with a center pivot, the pivot is idle until August,” he says. “But continuous corn lets us put the pivot to use throughout the growing season.

“Last year, we put in a corner system so that pivot can water 94% of the field. You don’t have as much dryland corn in the field. Without the corn system, the pivot only waters 73% of the field.”

One of the differences between strip-tilling in the spring and in the fall is that Knuth uses a wider Waco moleknife and a 20-inch Great Plains Turbo Till coulter in the fall. Knuth and Kimberley cut the Waco moleknife down so it is ¾ of an inch wide.
Using a narrower moleknife eliminates air pockets and blowouts, Kimberley says.

Custom Application

While the Knuths switched to fall strip-till, they aren’t banding fertilizer as they strip-till. They have a custom applicator using variable-rate technology to broadcast dry fertilizer and, when needed, lime. This is done in separate passes.

“We think it’s so important to get strip-tilling done in the fall that this fall, we may hire someone to run the combine so we’re ready to strip-till ASAP,” Knuth says.
From the time the Knuths finish harvesting fields to when they strip-till, there’s about a 2-week interval.

First, Angela Knuth takes soil tests, usually the day after the combine gets out of a field. It takes about 3 days to get results back from a lab in Omaha. Then the Knuths have a custom applicator VR a flat rate of micronutrients and phosphate. And if needed, a custom applicator variable-rate applies lime in another pass.

It may take a week for the custom applicators to spread dry fertilizer and lime.

“It’s about 2 weeks from the time we get the soybeans off before we can get going on strip-tilling,” Knuth says. “But it doesn’t take long to strip-till, if that’s all you have to do and you don’t apply fertilizer. With dry fertilizer, we would have to stop about every 30 or 40 acres to refill a dry fertilizer cart.”

MORE CORN. Strip-tilling has allowed Kerry Knuth to grow more irrigated, continuous corn on his farm in eastern Nebraska. (Photo courtesy Kimberley Ag Consulting)

Before the Knuths plant corn in the spring, they include 85 pounds of 32 percent liquid nitrogen when they spray herbicide, Knuth says. Then they sidedress 200 pounds of AMS — 44 pounds of nitrogen — per acre.

For irrigated corn, Knuth takes tissue tests. Depending on the results, he applies 30-50 pounds of nitrogen per acre through the center pivot. About 55% of Knuth’s corn is irrigated; 45% is dryland.

Lessons Learned

Working with Kimberley, Knuth has learned the advantages of strip-tilling in the fall instead of the spring. He strip-tills about 10 inches deep in the fall, with a knife-and-coulter system on the Blu-Jet strip-till rig.

“First, there’s a row cleaner, then it’s followed by a coulter that runs up to 10 inches deep, almost as deep as the knife,” Knuth says. “And then the knife behind the coulter runs 10 inches deep. Most of our compaction is in the top 7 inches to 8 inches. If we have deeper compaction, we will run an inline ripper through those areas.”

After Knuth asked Kimberley if he should deep rip all of their fields, they dug holes with a backhoe to locate compaction.

“It was very interesting digging the holes,” Knuth says. “We found a lot of our compaction was about 7-8 inches down.”

Kimberley says that hardpan was farther down, about 10-12 inches, where water sits in lower spots in fields after big rains.

“But for 98% of the fields, the compaction 7-8 inches deep,” Kimberley says. “That’s why we run the knives on the Blu-Jet 10 inches deep to break up compaction, but also so the soil can absorb moisture and have the corn roots go deep.

Better Roots

Knuth likes what he’s seeing from strip-tilling during the past 3 years. The corn roots are growing better.

“We dug roots when Kevin was here in mid-June,” Knuth says. “We had corn plants that were 30 inches tall and with roots that were 30 inches long. And we saw that the corn roots grow down at a 45-degree angle. Where they hit hard areas outside the strip, the roots would kind of bend and then grow through that hard soil.”

But strip-till does even more than till the area where seeds will be planted. When it rains, water runs off the soil between rows and down into the strips, Kimberley explained to Knuth. And the consultant demonstrated this by pouring a gallon of water on the surface between the strips.

“The water ran both ways, into the strip,” Knuth says. “Once it hit the strips, it soaked into the bottom, 10 inches down. What would happen if we had no-tilled? Where would that water go? It would run off and go down into the creek.”