Today's corn hybrids leave virtual tree trunks in a combine's wake. Managing stalk residue ranks as one of the chief challenges faced by continuous-corn producers.
The amount of crop residue left behind after corn harvest is roughly equal to the weight of grain harvested from the field, according to agronomists at Purdue University. For example, a 180-bu./acre corn crop leaves behind approximately 10,000 lbs. of crop residue/acre(on a 15% moisture basis).
Residue management begins at harvest. Using a shredding head with knife rolls or making sure that the back-end spinner is well maintained and working properly can assure the residue is spread as evenly as possible, says Dick Wolkowski, University of Wisconsin-Madison Extension soil scientist. Aim to spread the residue over at least 80% of the combine pass.
Moving residue away from the row area with residue-clearing coulters is important to help the soil warm up faster next spring. This will also reduce hair-pinning problems in the planter slot and help close the furrow properly. Don't think you have to bury the residue. It's extremely beneficial for curbing water and wind erosion.
Poor or uneven residue distribution and excessive wheel traffic impact the physical and chemical properties of the soil and can lead to poor stand establishment, especially in continuous corn, according to Tony Vyn, Purdue University Extension agronomist. “Uneven plant growth within the rows, as well as row-to-row, is one of the most critical factors that causes yield drag in continuous corn,” he says.
Because decomposing corn residue can tie up nitrogen (N), he recommends applying at least 30-40 lbs. N close to young corn plants to increase nutrient availability.
If no-tilling, planting new corn rows about 7 in. away from the old corn rows can help, as well as using tined row cleaners to free the row areas from excessive residue buildup.
Managing residue in continuous corn is something that Bernie Kleiber and his wife Nancy have perfected over seven years. Kleiber ridge-tills 425 acres of continuous corn in southwestern Jefferson County, WI. He uses a Buffalo planter and Buffalo 6400 high-clearance cultivator (both 12-rows) equipped with 18-in. cutting coulters, Texas sweeps and slightly taller ridge wings.
With continuous corn, Kleiber likes to broadcast a burndown with a 28% N carrier (15 gal./acre) before planting at seed populations of 34,000/acre on 30-in. rows.
Depending on soil tests, he also applies a 18-46-0 dry starter fertilizer at 160 lbs./acre. “I think an early application boost of nitrogen is important with continuous corn,” he says. “I apply potash separately about every two or three years.”
In early June, when the corn is about 4-6 in. high, Kleiber uses the Buffalo cultivator and also side-dresses with 28% N at 30 gal./acre. The second cultivation is done when the corn is about knee high.
“During the first cultivation, I like to undercut the residue in the valleys at depths of three to four inches, which reduces plugging and helps mix it with the soil without much risk of clipping the roots,” he says. “Getting through the trash the first time is more critical.”
The second cultivation is much shallower at 1 in., further mixing the residue and clearing out the valleys. It also helps reform the ridges and takes care of any weed escapes.
“The ridges keep the old residue away from the new crop,” says Kleiber. During harvest, Nancy follows behind the combine with a six-row John Deere stalk chopper, making sure the residue spreads out evenly in the valleys.
Five years of continuous corn have taught Bob Miller and his son Luke a few things about residue management. They have 3,300 acres of continuous corn in Dodge, Waukesha and Jefferson Counties, WI.
“We want the residue to decompose as quickly as possible so that it dries out well in the spring and doesn't cause skips during planting,” Bob says.
The Millers plant with an 18-row (on 20-in. centers) Rawson Zone Till Cart planter with John Deere units.
They plant at 35,500-36,000 seeds/acre, and apply 5 gal./acre of 10-34-0 directly on the seedbed. Applications of 32% N at 35 gal./acre and 15 gal./acre of 6-21-5-5 (sulfur) are also done during planting time. A 0-0-60 is applied at 200 lbs./acre every other year.
In fall, Luke says they use a Calmer corn head on a Case IH combine to slit the stalks and to help promote microbial breakdown.
As a trial in fall 2006, the Millers applied 28% N at 10 gal./acre to speed further decomposition. “It's just a trial,” says Bob. “We may find that we're better off to incorporate more of the stalk residue into the soil and then apply nitrogen with the corn planter in spring.”
For fall tillage and seedbed preparation, the Millers use Great Plains' Turbo-Till, which covers a 30-ft. width, and the deep tillage Verti-Till with a working width of 17.5 ft.
Pulled behind a Case IH STX 430 Quadtrac, the Verti-Till is typically used in the fall, deep tilling at a depth of 12-14 in. and at ground speeds of about 5.5 mph. “It takes a lot of power,” says Bob, “and that's one of its drawbacks.”
The Turbo-Till, which is normally used in spring, runs at depths of 2-3 in., requires less power and operates at 8-9 mph groundspeeds.
“Both units work well together in developing nice seedbeds,” says Luke. “The Turbo-Till reduces the stalk size down to 6-7 in. or less, and fluffs up the residue on the soil surface. As a result, the planter row managers do a better job. We're seeing more even seed emergence.”
In the future, the Millers may consider replacing the Verti-Till with an Aerway unit to get away from deeper tillage but yet still mix the soil and surface residue. “In our area, deep tillage tends to pull up too many rocks,” says Bob.