December 28, 2011
Emerson Nafziger remembers pulling a three-bottom moldboard plow years ago. “When it takes that long to till each acre, it really is tillage,” says the University of Illinois Extension crop-production specialist.
Since that time, he’s advised countless growers to till the least amount possible for their particular situation. He hopes “we can get to responsible tillage” if complete no-till isn’t practical on your farm. This is especially true in northern climates, where growers battle cooler temperatures and emergence issues, he says.
Conventional tillage is not essential for high corn yields, says Tony Vyn, Purdue agronomist. He’s researched no-till corn for 33 years.“Your tillage system has less consequence for high yields than hybrid selection, optimum plant density and fertility levels.”
Vyn’s research finds “it’s entirely possible to yield above 250 bu. in continuous no-till. No-till corn yields after soybeans are rarely lower than those after conventional tillage.
“Tillage has generally only been beneficial for continuous corn; the yield advantage with the fall chisel-plow system vs. no-till over the last 10 years has varied from as little as 4 bu./acre (mean)
between 2008 and 2011, to as much as 24 bu./acre (mean) between 2002 and 2007.”
Continuous-corn yields during that 10-year period averaged 192 bu./acre while corn after soybeans averaged 208 bu./acre, his research shows. Final plant populations with no-till in those years averaged just 400 fewer plants/acre than chisel plowing, and so plant-stand differences could not account for yield differences, he says.
The optimum amount of tillage “depends on where you are and what your soils are,” Illinois’ Nafziger says.
How do you determine that optimal tillage degree for your operation? “It’s not on a spreadsheet somewhere,” Nafziger says. “Concentrate on what you’re making happen in the soil. Your soil is a complete system. We know that it needs to be anchored in place, and that we need to leave residue on sloping ground.
Tillage has three purposes, experts say:
To warm up the soil
To dry the soil for earlier planting
To make a better rooting and seed-placement zone
Or, as Jodi DeJong-Hughes says, “to undo the compaction from the previous tillage.” She is a University of Minnesota regional Extension educator.
“Tillage begets more tillage,” she says. “It breaks aggregates apart and fluffs the soil up with air so growers think they are reducing compaction. While they are breaking up compacted soil, they are also breaking up soil structure. Structure is their No. 1 defense against compaction. When you destroy the structure and fluff the soil up with air, air cannot hold up the weight of equipment or even other soil particles. Eventually, it’ll fall in on itself and more tillage will be needed to loosen-up the soil.”
Using no-till saves $25-30/acre in corn, and $18-20/acre for soybeans in input cost of production compared to conventional tillage, according to Iowa State University (ISU) research by Mahdi Al-Kaisi, Extension soil management specialist. “These savings result from reducing field-operation passes from eight passes in conventional tillage per growing season to five per year with no-till in corn prodution.”
University of Minnesota-Morris research spanning four years pegs strip-till savings at $32/year over moldboard and deep ripping, says DeJong-Hughes. The strip-till trials found an average of 12-bu. yield difference between strip-till and full-width tillage.
“Strip-till truly is the system of choice for continuous corn,” says Purdue’s Vyn. “Even in continuous corn when no-till yields are somewhat lower, strip-till usually yields equal to chisel plowing while providing superior erosion protection.”
In eastern Nebraska, Extension Engineer Paul Jasa, University of Nebraska-Lincoln, a systematic approach to continuous no-till over 30 years typically has corn yields over 200 bu/acre. He emphasizes that each plant needs a uniform amount of light, nutrients and moisture.
Jasa, Vyn, DeJong-Hughes, Nafziger and Al-Kaisi offer the following tips to reduce tillage and improve profitability:
*Aim for uniform emergence and seedling growth early in the season, Vyn says. “No-till yield hits in continuous corn result from uneven plant emergence, not from lower soil-temperatures, although no-till corn does grow more slowly in the beginning. If no-till plants were just shorter but as uniform in height, yields would match those with conventional tillage.”
*“Uniform planting depth and a systems approach are your friends,” Jasa says. “Growers don’t think enough about a consistent environment for each seed.”
Jasa likes 2.5-3 in. for corn for a better root system. “Planting a little deeper buffers and evens out the soil moisture and temperature, resulting in a more uniform emergence,” he says.
“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.
Jasa recommends at least 80% residue cover on the soil surface and urges you to compare the uniformity of stalk-internode distances and stalk diameters to determine how uniform your system is.
*Accommodate your soil type: “Poorly drained soils show a yield drag with no-till,” Al-Kaisi says. Generally, his long-term ISU tillage studies show some yield advantage to no-till, but they are very site-specific.
"No-till usually has a yield advantage on well drained or sandy soils in the western Corn Belt where moisture conservation is needed," says Nebraska’s Jasa.
*Rotation. A corn-soybean rotation opens up some tillage options over continuous corn. “Even a corn-corn-soybean rotation works with strip-till if you pay attention to the details,” DeJong-Hughes says. “For example, be sure to use starter and micronutrients as determined by soil-test results.”
Continuous corn typically requires full-width tillage in her western Minnesota region unless you bale your residue, she says.
“In the North, continuous no-till corn is not considered by many to be viable,” Nafziger says. “In the central Corn Belt, we’ve often been able to produce good yields with no-till, but there are still times when tillage pays. I consider no-till a success if it doesn’t reduce yields. We tend to see increased yields with no-till in dry years where you benefit from moisture conservation.”
Every year is a dry year in Nebraska, Jasa says, and that explains no-till’s success there. Still he sees benefits to rotation, “which lessens the need for tillage to overcome the problems with mono-crop continuous corn.”
*Consider ridge planting, Jasa says. “Nebraska research proved many years ago that the ridge-plant system is one of the best for continuous-corn yields. The ridge provides a warmer seedbed without the costs and problems of strip-till. No-tilling on top of the ridges works quite well, and cultivation to rebuild the ridges doesn't have to be done every year, only as needed to maintain ridge height,” Jasa says.
*Strip-tillers need to stay in the center of the strip-till berm to capture higher spring soil temperatures and banded nutrients, says DeJong-Hughes. “This generally requires sub-inch guidance accuracy,” she adds.
“The first month after planting, soil temperatures are critical, say Al-Kaisi and DeJong-Hughes. Mineralization, which converts nitrogen to a plant-available form, can be very slow in cooler soils.
*Starter is very important, especially for strip-till and continuous corn, DeJong-Hughes says.
*Make sure your equipmenteffectively clears residue from the berm. “This requires more preparation and stopping periodically to check on things,” DeJong-Hughes says.
*Know your soil’s pH, texture and nutrient data. In western Minnesota where DeJong-Hughes farms, the calcium in high-pH soils ties up broadcast P, making banding more effective.
*Drainage. “Consider tiling, or not cropping low-lying areas,” she says.
“Tilling wet soils compacts soils as deep as 18-20 in.,” Nafziger says. “Typically fall is the only time of year dry enough to do a good job of deep tillage (more than 8 in. deep) to improve root conditions.”
*Don't focus on making the spring planting conditions warmer and drier, but focus on making the summer growing conditions cooler and wetter,” Nebraska’s Jasa advises. “Cool, wet spring soils may slow growth some early in the season, but it's your best friend in the heat of June, July and August.”
Al-Kaisi says he noticed a lot of recreational tillage this fall, due more to warm weather than to any agronomic need. “You can accomplish the same results with strip-till (8 in. wide and 3-4 in. deep) as you can with a chisel plow, so anything more than that is not very justifiable.”
*Don’t put all your eggs in one tillage basket,” DeJong-Hughes says. “I’d like to see producers base their tillage on a field-by-field approach and look at rotation, slope, soil texture, drainage capacity of their soil and seasonal effects. In our studies we found a tillage pan after four years of moldboard plowing in continuous corn. That’s when you bring back the soybeans and reduce the tillage.”
Looking to the future of tillage, Vyn predicts continued growth of no-till, with “the expansion of rotational no-still, which includes strip-till as well as shallow vertical-till systems.
“Strip-till needs a successful spring option if fall weather prevents strip-tilling after harvest,” Vyn says.
*Manage residue.“ISU data shows that residue cleaners on the planter remove residue and warm up the top 2 in. of soil just as well as a chisel plow,” Al-Kaisi says.
“A grower asked me recently about the benefits of buying a deep ripper,” Al-Kaisi says. “I asked him what his site’s yield potential was and what problems he was trying to overcome. He was more influenced by his neighbor using a deep ripper than by any scientific evidence of benefits to his operation. I suggested that he experiment with one on eight or 12 rows before investing $60,000-80,000 on a new toolbar.”
*Hybrid selection: With the emphasis on hybrids with good emergence and tolerance to stress, it’s easier to find hybrids today that work well under different types of tillage, Nafziger says.
“Companies may rate hybrid suitability to, say, no-till, but often that’s based on things like good leaf-disease ratings (to counter more diseases when there’s residue – especially corn residue – on the surface) and for good emergence vigor than it is on lots of testing under different tillage systems,” Nafziger says.
“Thirty years ago, I thought we'd move to no-till corn after soybeans because bean stubble has mellow conditions,” Nafziger says. “But we haven't, and I think it’s because farming operations are much larger and the planting window is so narrow. Growers want to complete an entire field at once, with the least amount of risk to the crop if weather deteriorates.
“Tilling ahead of the planter reduces the risk of having lower stands in parts of fields, especially with today’s equipment speeds.”
Nafziger notes that tillage implements’ aggressive names reflect the attitude that soil is something to dominate (instead of to harmonize with).
Because that thinking has evolved into working with the soils, he jokes: “Maybe with today’s virtual technology, there could be a virtual-tillage for growers to ‘get their fill of till’ without actually going to the field to burn fuel and turn soil.”
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