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Corn+Soybean Digest

DEEP Tillage Crushes Hardpan

Give Wendell Friesen a bent-shank paraplow and a big enough tractor to pull it, and he'll most likely produce corn and soybeans that out-yield the county average. Take that plow away from him and he'll quit farming.

Friesen has managed a couple of farms in south central Kansas the past decade. He's worked with owner Bill Keller the past five years in Greensburg. And there's not a harvested acre on those farms that hasn't seen a 16-18" deep tillage at least once every two or three years.

“Hardpan is not a word we use on this farm because there is no such thing on this farm,” says Friesen. Using a 23'-wide, eight-leg Paratill built by Bigham Brothers in Lubbock, TX, Keller and Friesen produce corn, beans, wheat and most recently cotton, on some 4,500 acres. Row crops are grown in 30" spacing. Beans are double-cropped behind wheat. The pivot irrigated yields top 190 bu for corn and 55 bu for beans. His dryland cotton yielded an amazing 1¼ bales in the crop's first year in 2001.

Friesen gives his deep tillage program much of the credit for the solid yields. “It's important that we maintain a good soil texture that allows for good root production,” says Friesen, who farms in a silt loam soil.

“We do that with the paraplow, pulled behind a John Deere 9100 tractor at 5½ mph. The plow pulls easier than a conventional ripper plow and does not disturb the topsoil.”

The paraplow is highlighted by a bent leg design. The 36" leg is bent at a 45° angle ⅔ of the way down. Its 12-18" working depth enables Friesen to lift the soil. This loosening provides for better water infiltration and absorption, encourages root development and allows for deeper fertilizer placement.

“We average up to 5% more yields than we would with a conventional ripper plow,” says Friesen. “We don't have to fight any clods. And, we can accomplish the paraplowing for about $1.50/acre in out-of-pocket expense for fuel and new ripper points.”

Randall Reeder, Ohio State University extension agricultural engineer, says typical soils across much of the eastern Corn Belt can benefit from similar tillage practices.

“Deep tillage, especially on silty loam, helps break up the hardpan and improves water infiltration and drainage,” he says. “Hoytville soil in northwest Ohio seems to compact naturally. We know that soil benefits from deep loosening, even if you don't drive big machinery over it.”

He adds that subsoiler plows, like the paratill or a traditional V-ripper, are good where wind and water erosion are critical factors and there's a need to leave residue on the surface.

Normie Buehring, Mississippi State University agricultural engineer, agrees.

“I prefer deep tillage systems which maximize or leave most of the crop residue on the soil surface,” says Buehring. “The crop residue reduces the energy of the raindrop (or irrigation water) and therefore reduces soil erosion. In other words, instead of raindrops hitting bare soil, they hit residue first that dissipates raindrop energy and reduces soil erosion.”

He says that paraplowed bottomland clay soil produced a 15% higher yield for both corn and soybeans compared to no-till and 8% more than ridge-till.

However, not all soils respond to the deep tillage. Buehring says, “On blackbelt prairie clay soil, paraplowing shows no advantage over a fall chisel-harrow system.”

Friesen says deep tilling every two or three years will normally help him maintain the proper soil condition needed for best crop performance. “I wouldn't farm without the paratill,” he says. “It provides too many benefits that encourage good crop production.”

It Pays To Go Easy On The Ground

Whatever tillage system best fits your operation, consider the benefits of a controlled traffic program.

“The ideal situation is to subsoil, if necessary, then immediately adopt a controlled traffic program,” says Randall Reeder, Ohio State University extension agricultural engineer. “Try to hold the amount of ground being driven on to 20-30%, with the rest never touched by tires or tracks.

“Our research has shown that controlled traffic helps maintain soil structure improvements. Soil physical properties showed continuing benefits two years after tillage in areas not trafficked. However, in tire tracks, two passes of a tractor recompacted the soil to a condition as bad or worse than before subsoiling.”

Natural Tolerance Or Resistance?

The widespread use of Roundup Ready crops has the entire industry on point for weeds that have developed resistance to glyphosate products. Waterhemp is one of the weedy menaces on that list.

Rather than a developed resistance, however, it appears that waterhemp may have a natural tolerance to glyphosate, according to Bob Hartzler, Iowa State University weed scientist.

“Iowa, Missouri and Illinois are all looking at problem populations of waterhemp that aren't controlled consistently with glyphosate,” he says. “But, it often has appeared the first time a farmer plants a glyphosate-tolerant crop. That indicates the weed has an inherent tolerance rather than one developed through selection from repeated exposure to the herbicide.

“We tested 30 populations of waterhemp and could find no correlation to glyphosate tolerance and years of herbicide usage,” he says.

Hartzler notes that most farmers are using higher rates of glyphosate than when Roundup Ready crops were first introduced. “It takes more now to get the same job done,” he says. “We're not sure what has driven this increase. It could either be an increased level of tolerance within a particular weed species, or simply due to increased densities of weeds with a natural tolerance to glyposate.”

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