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Thick residue has always been a thorn in the side of farmers who grow corn-on-corn.
That was particularly true in states like Illinois in 2010. Although many corn yields suffered, corn-on-corn particularly took a hit. One likely reason was above-normal 2009 surface residue had a toxic impact on 2010 corn.
“If I can handle the residue, I can grow continuous corn,” says John Obery, a Metamora, Illinois, farmer. “I want to reverse the toxic effect of old roots and stalks.”
Obery thinks he's found a way to do it with a twist on strip-till. Last fall following harvest, he used a modified Great Plains Turbo-Till unit and/or a modified Blu-Jet SubTiller II tillage tool. These tools slice and dice the residue and leave a planting strip for spring.
He's equipped both units with homemade hillers. “They raise a mound of dirt so it dries out and warms up in the spring,” Obery says. “I also get mixing of residue in the top few inches of the soil.”
The system doesn't meet the definition of strip-till for the National Corn Growers Association (NCGA) yield contest. No more than one third of the row width can be disturbed, according to NCGA. In Obery's system, the entire field is lightly tilled.
Still, it works. “I can handle lots of residue,” says Obery.
The strips he makes in the fall enable plants to push through and grow in mellow, dry, and warm soils.
The tillage combination used hinges on soil compaction levels. On compacted soils and on end rows, Obery first makes a fall pass with the Turbo-Till followed by the SubTiller II. The Turbo-Till sizes the residue and lightly tills the soil surface. The SubTiller II's shanks run at 12 to 14 inches deep to remove compaction.
On less compacted fields, Obery makes two passes with the Turbo-Till. Two gangs of blades spaced 10 inches apart act to move soil every 5 inches at a 6-inch depth.
To boost consistent penetration, he added 4,800 pounds of weight on top of the Turbo-Till. This creates more consistent depth and ensures the Turbo-Till stays in the soil rather than jumping out.
The homemade hillers on the back of both units bring a bit of ridge-till to Obery's system. The system isn't technically ridge-till, since ridges are built in fall rather than summer. Still, they enable early planting to occur next spring.
“What I like about my ridges is they don't melt down and become hard to see in the spring,” he says. “If I get heavy rain in the late winter and early spring, I can get erosion from conventional strips. I don't have that with my hillers. The ridges are big enough where they shed water and not invert.”
His hillers differ from others on the market due to location of the pinch point. It is at the top of the disc hillers on the rear of the tillage tools, rather than the bottom.
Having the pinch point on top of the hillers rather than the bottom allows soil and residue to freely flow through. “It lets gravity work with me instead of against me,” he says.
Twin Rows And Tramlines
Complementing this tillage strategy are twin rows. Obery plants 12 twin rows 8 inches apart on 30-inch centers. Also in the same planter path are four single rows with two 38-inch row centers.
The reason for the split is that Obery incorporates tramlines based on 120-inch centers into the system.
“I do everything in increments of 40 feet,” says Obery. “Sidedressing is set up for 40 feet, my sprayer is on 120-foot centers, I dribble N on with 120 feet, and I plant with 40-foot planters.
Obery notes that some research has shown little advantage for narrow rows compared to 30-inch rows. However, he thinks that's due to pinched roots that result from field operations too close to narrow rows.
“That's why I have tramlines,” he says. “I'm concentrating my wheel compaction with controlled traffic so I limit pinched roots. I use tramlines to spray herbicides, to sidedress and dribble on nitrogen (N), and to make late-season fungicide applications.”
It also limits compacted areas in the rest of the field.
“Before I added tramlines and had 30-inch rows, I could see pale green corn growing near wheel tracks,” says Obery.
Obery also straddles and plants in between the old twin rows on a test basis. He notes the twin rows give plants more space. “The diameter of the twin-row corn is girthier, and plants seem to be able to grow faster,” he says.
Split Fertility Strategy
Obery uses multiple applications to spoon-feed fertilizer to corn. In late winter or early spring, he surface-broadcasts around 125 pounds per acre of N in the form of ammonium sulfate. Before planting, he uses a Great Plains Nutri-Pro fertilizer bar. to apply about 25 more pounds per acre of N in the form of 32% N, along with micronutrients.
After planting, he starts dribbling or sidedressing a mix of 32% N and ammonium sulfate from emergence to the V10 stage (five weeks after emergence).
“I vary the rate according to how much N I applied previously and how much rain I received,” says Obery.
If needed, he adds late-season N. “We have already dribbled it on prior to VT (tassel) with good success, he says. “In 2009, aerial photos showed huge color differences when I dribbled 40 pounds per acre of N on at this time.”
At harvest, Obery figures this application boosted yields 16 to 18 bushels per acre. Still, success hinges on weather. “If I don't get more rain, it's not going to help,” he says.
All this is no substitute for good weather. Obery's yields were spotty in 2010.
“My corn went in the ground in the best shape ever, but soon afterward, it started raining,” Obery recalls. “The corn was under a lot of water. It was waterlogged and couldn't take up the proper nutrition.”
Still, the corn seemingly persevered. “By the second week of July, ear and kernel counts looked like I had the potential to grow 275-bushel-per-acre corn,” he says. “In 10 days time, that had shrunk by 70 bushels. Some of the corn was 13 feet tall. But with no rain in July and extreme heat, the corn yield just kept shrinking.
“There were fields with yields of 140 to 150 bushels an acre and 200-bushel yields 10 miles away,” he says. “An inch or two of late-summer rain made a big difference.”
Still, Obery says the system bodes well for the future.“I don't have erosion the way I did in the 1970s and 1980s, when I rotated corn with soybeans,” he says.
The extra residue also helps build organic matter, Obery says. Organic matter helps crops withstand dry conditions, protect against erosion, and ensures excellent soil structure.
“I had some fields in the early 1970s register 1.8% to 2.2% organic matter levels,” says Obery. “Now, recent tests show 4% to 6% and above levels.”