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Susan Winsor
December 1, 2010
4 Min Read
Your soil is a factory fueled by residue. A no-till system uses residue to your advantage, says Paul Jasa, Extension engineer, University of Nebraska-Lincoln and a 29-year continuous no-till veteran.
“Once you get the no-till biological system going, it digests crop residue and feeds your crop,” he says.
Important mechanisms in a no-till system are the nearly invisible mycorrhiza fungi, bacteria and all the other soil biological life surrounding plant roots that help convert residue into nutrients.
Jasa’s no-till rainfed corn in eastern Nebraska typically yields over 200 bu. That’s because he systematizes his no-till, where each seed has a uniform amount of residue, nutrients and moisture.
“Uniformity and a systems approach are your friends,” he says. “Growers don’t think enough about a consistent environment for each seed.
“Once your soil structure is built, rainfall and snow melt soak in, compared to the way they pond or run off on a tilled field,” he says.
Think of residue as the insulation your plants need to reduce evaporation. Jasa recommends at least 80% residue cover on the soil surface and urges you to look at your corn plant for clues on how uniform your system is:
Compare the uniformity of stalk internode distances and stalk diameters.
Your corn ears shouldn’t fill completely to the tip; that’s an indication you’ve left resources in the field.
Optimize a no-till system
Here is the best way to optimize a no-till system, Jasa says:
Uniform planting depth is key. While some producers like a 1- to 1.5-in. planting depth, I like 2.5 to 3 in. for a better root system. The chart shows a 9-bu. yield bump from those extra 2 in. planting depth. “We’ve experimented with several planting depths in corn and beans; I see no reason to go deeper than 3 in., for corn,” he says.
“Each seed should grow in the same amount of residue,” Jasa says. “Many producers hate residue, thinking it’s a non-starter on cold and wet soils. Keep the residue on the surface; cooler, wetter soil is your best friend in the heat of July and August.”
Use an early preplant herbicide to stay ahead of weeds and reduce competition for nutrients and light.
The first step in your no-till system begins at harvest, when you set things up right for planting, Jasa says.
Harvest so that it distributes residue for planting. With platform heads, harvest on the downwind side of field for best residue distribution. A chaff spreader is a must with a platform head.
If your corn head is doing its job right, the combine doesn’t have to spread much residue. “When people have trouble with their planter, I ask what kind of combine head they use,” Jasa says.
“I like the way tapered snapping rolls or knife-to-knife snapping rolls process the residue, sending very little residue through the combine,” Jasa says.
You want uniform soil temperatures and moisture, and you don’t want a residue windrow after harvest. Your goal is uniform emergence –much more important than uniform spacing.
“I like taller corn stalks to trap residue; I don’t recommend chopping your stalks,” Jasa says.
Let your planter handle the residue. Use disk openers to cut the residue when placing seeds and nutrients. “We plant our corn-on-corn next to last year’s row rather than in the wheel tracks,” he says.
When you plant, make sure you have enough down pressure on the row units. The big central seed hoppers on today’s planters don’t have their weight uniformly distributed along the entire toolbar; you may have to add weight at the ends of the planter bars. generally lack enough down pressure; you may have to add weight at the ends of the planter bars.
Properly close the seed V. In hard soils this may require extra closing force, but cast-iron angle-closing wheels may be too aggressive in wet soils. I like to see the planter tail-down, not nose-down, for best seed V closing. Spiked or fingered closing wheels may be needed to crumble the soil around the seed for better closing and to reduce the chances of the seed V opening back up.
The nutrient engines of your soil
Mycorrhizae are the almost-invisible fungi living in plant roots that increase plants’ ability to absorb soil nutrient minerals, including phosphorus, zinc and micronutrients. Along with bacteria, they recycle crop residue into nutrients, says Jill Clapperton, rhizosphere ecologist and agronomic consultant, Florence, MT.
An increase of 1% in soil organic matter (from crop residue or other sources) can increase its water-holding capacity by up to 16,000 gal./acre-foot, says Francis Yeatman, agricultural advisor, Integrations Farming Systems, Soil and Crop Nutrition,South Africa and Appropriate Technology Transfer for Rural Areas (ATTRA). “Soils with adequate organic matter (3-6%) will have better structure and therefore water- and nutrient-holding capacity. Organic matter is a storehouse for plant nutrients and a very high capacity for holding cations as well as soil moisture. Because of its active holding sites it is also an important factor for determining herbicide selection and adjusting application rates.”
What is your corn residue worth?
Paul Jasa, University of Nebraska-Lincoln Extension engineer, calculates that 1 ton of corn residue is worth $100, or about $250/acre.
That includes $26/ton in nutrient value (N, P, K). Add to that the value of retained soil moisture (3 in. extra), representing roughly $30/acre in irrigation value and 30 bu. lost yield (10-bu./acre-in. of moisture x 3 in.).
“So, for me, residue’s value is $100/ton, or $250/acre (@2.5 tons residue/acre) in nutrients and moisture retention,” Jasa says.
December 2010
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