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NAME: Jodi DeJong-Hughes
POSITION: Regional Extension Educator, University of Minnesota
LOCATION: Marshall, Minn. (works with Minnesota, South Dakota and North Dakota farmers and landowners)
YEARS IN PROFESSION: 11
EXPERTISE: Soil fertility and quality, and compaction management
We've learned a lot about strip-tillage in the western Corn Belt and Great Plains, and the more we learn, the better it looks. While significant growth in strip-tilled acres is relatively new in Minnesota and the eastern Dakotas, this “middle ground” that combines the benefits of no-till and chisel plow systems is paying big benefits to farmers who make the change.
Many of the advantages of strip-tilling are captured by growers moving away from chisel plowing into a conservation-tillage system. Yet, some growers who have struggled making no-till work find strip-till is a better alternative than going back to moving substantial amounts of soil through conventional tillage.
On-farm experiences, plus university and industry trial results, point to numerous advantages of using strip-till on soils that are often very cool and wet in the spring, such as our glacial, heavy clays. These include:
- Seedbed soil dries out, warms up faster.
- Water infiltration improves.
- Soil sediment and phosphorus runoff losses slow or stop.
- Tile ditches stay clean.
- Saved residue boosts organic matter levels.
- Soil structure improves.
- Yields equal or beat other tillage systems.
- Fuel and fertilizer costs drop.
- Strip-till qualifies for Environmental Quality Incentive Program (EQIP) payments and carbon credits.
So, with all of these positives, why aren’t more growers strip-tilling? Well, all new farming methods have a learning curve, and there is still much concern about changing from conventional-tillage systems that have been successfully used for generations.
Also, strip-tilling means added up-front equipment costs or custom operator charges. And like any other production method, strip-till is simply not right for every corn and soybean grower, regardless of its potential. Nevertheless, we’re seeing relatively fast-growing awareness and interest.
The 2007 Northern Strip-Till Expo, which I helped organize last August on a local farm, drew more than 450 people to see a dozen manufacturers demonstrate strip-till equipment side by side. We also fill the bleachers at area strip-till workshops held during the winter.
In my presentation to growers, I call strip-till, “Tillage for Today and Tomorrow.” It seems to be an appropriate title. With its many benefits, strip-tilling boosts potential for growing a good crop this year, while steady improvements in soil quality assure more productive fields down the line.
Some farmers tend to confuse strip-till with zone-till. The big difference is that zone-tillage typically uses a straight shank to cut through the soil to a depth of about 20 inches, which is much deeper than done by strip-till machines. Strip-till machines are usually adjusted to cut a slot 7 to 9 inches deep, using a number of different shank designs.
At last count, manufacturers were selling about 20 strip-till brands, ranging from $15,000 to $120,000, depending on the attachments and whether you buy an air cart for fertilizer application. Many farmers are able to match a strip-till rig to their existing 30-inch planting and harvest equipment for $25,000 to $60,000.
Even with the significant cost, I encourage growers to buy the best strip-till equipment they can afford. Newer designs do a better job and require less energy. Strip-tilling with newer rigs takes between 12 and 17 horsepower (hp) per shank, so most operators should be able to handle a 16-row, 30-inch machine with existing tractors. In contrast, a zone-tillage rig, with shanks penetrating 20 inches, demand a range of 30 to 50 hp per shank.
Most of my strip-till work is with 30-inch-row corn and soybeans. I work closely with Dr. Laura Overstreet, soil scientist at North Dakota State University, who has been studying strip-till in narrower rows.
We have used both shank and coulter strip-till rigs with equal success in on-farm field comparisons and at our strip-till events. The most common designs — the shank machines — have coulters that cut residue; residue managers (also called trashwhippers) that push the residue to the side; shovel shanks that penetrate and lift the soil; and closing discs that create a berm.
Moving an adequate amount of residue off the strip in the fall is rule No. 1. In fine-textured soils, we recommend clearing the berm to less than 10% residue for faster soil warm-up in the spring.
In the spring, corn is planted directly into the cleared strip. We know that air warms up 10,000 times faster than water, so if you have light, fluffy soil in the strip, it follows that the seedbed is going to reach optimum temperatures for quicker germination.
Coulter systems are less aggressive than shank machines in that they don’t lift the soil. With these rigs, residue managers move the trash off the row while offset deep-till coulters mix soil and air to form a berm.
Both systems can apply phosphorus, potassium and nitrogen in a band. Most strip-tillers now dribble or inject nitrogen at planting or sidedressing time. Broadcasting urea forms of nitrogen is not recommended on heavy residue. Starter fertilizer, incidentally, is advised for strip-tilling. We estimate that in our heavy clays, we get a positive response from starter three out of four years.
Because strip-tilling leaves more than 30% residue after planting, it meets federal standards for conservation tillage, thus qualifying for EQIP and carbon credits. In our on-farm studies, surface residue in strip-till was often 50% or higher.
We believe fall strip-till is least risky for the 80% of our growers who farm heavier soils. Fall strip-till gives the soil a chance to start warming up even before field conditions allow spring work. Also, berms built in the fall usually mellow out by planting time. Optional rolling baskets that smooth out soil clods on top of the berm are beneficial when strip-tilling in the spring just prior to planting.
Building the Berm
My first advice to new strip-tillers: be sure your equipment dealer or manufacturer has an experienced customer-service person to help you adjust the strip-till machine for your fields. The goal is to build a clean berm that is high enough in the fall — usually 3 to 5 inches — so that it is at least 1 inch high at planting. If the tilled area is level or if there is a trough in the spring, the berm was not high enough for rapid soil drying.
Adjusting the strip-till machine is also required when moving between corn and soybeans to accommodate different stubble heights.
Staying on the Berm
Be sure to match the width of the strip-till bar with that of the planter to ensure row alignment. Staying on the berm is a valid concern because if you go off, you’re suddenly planting into a no-till environment. In tests, we found soil temperatures were usually 5 to 8 degrees cooler under the residue left between the berms.
While assisted steering is not a requirement, it makes aligning the planter on the strips much easier. In square fields, it’s not as big an issue. But some of our growers have found that automated steering is nearly a must on hilly or irregularly shaped fields.
Continuous corn strip-tillers can hit a snag planting into the past year’s corn root balls. Some growers offset the strip 4 inches from last year’s row, while others build the berm in the middle of the old 30-inch row. Manufacturers are responding with optional attachments that remove root balls from the planting row and push them onto the untilled area where the balls deteriorate during the growing season.
I advise growers who don’t have GPS to rotate between row areas each year — even in corn following soybeans — simply because it makes their job easier.
A 180-bushel corn crop produces about 10,000 pounds of residue per acre. That number understandably concerns growers, who have been working that heavy load beneath the soil with chisel plows and field cultivators. On the other hand, aggressive tillage leaves the soil surface unprotected.
To learn more about residue management and other aspects of strip-tilling for our area, we worked with 10 cooperating producers in a 2-year, on-farm comparison of four tillage systems where corn followed soybeans.
Table 1 (on Page 8) shows the average percent surface-residue cover for four systems. While no-till maintained the most cover, strip-till kept 45% residue cover in 2004 and 49% in 2005.
On average, chisel plowing left less than 30% residue after planting, while one-pass just met the requirements in 2004 but slipped below in 2005. We concluded the differences were the result of past tillage, row spacing and the yields of previous soybean crops.
The important message from these comparisons: strip-tilling, when managed properly, will consistently leave enough residue to qualify as conservation tillage. More important, it adds up to improved soil quality over time.
Does strip-tilling cost you yield? Our on-farm comparisons say no. While chisel-plow-plus outyielded no-till by 9 bushels per acre in the colder 2004 season, strip-till held its own with only a 2-bushel difference (Table 2). In the warmer 2005 season, all four systems basically yielded the same.
Another interesting University of Minnesota study comparing tillage systems reported no significant yield difference between moldboard plowing and strip-till, but average surface residue in the strip-till field was 49% vs. only 10%.
Earlier research by Monsanto in 2000-02 supports this data. In those trials, average yields from strip-till vs. conventional-tilled fields differed by only 1 bushel per acre.
The key message: we don’t sell strip-tillage because of yield, but these comparisons show you can most likely expect no significant yield drag when switching to strip-till. And in theory, at least, strip-till should outyield conventional fields 5 years from now because you’ll be farming better soil.
(A copy of a University of Minnesota bulletin detailing the most recent on-farm tillage system comparisons is available at www.extension.umn.edu.)
What About Cost?
Based on farm machinery costs estimated by University of Minnesota ag economists, charges for a 12-row, strip-till rig are nearly $9.50 per acre less than chisel-plow-plus cultivation and only about $1 more than a one-pass spring field cultivation.
You can also save nearly $10 per acre by eliminating stalk chopping, a common field operation with conventional-tillage systems. We encourage strip-tillers to leave upright stalks for improved water infiltration, better air movement and faster drying.
Banding fertilizer while strip-tilling drops cost by one-third. Banding phosphorus and potassium, compared to broadcast applications, saves $14.25 per acre — just about equal to the cost of the strip-till machinery charge!
Another bottom line bump comes in the hard-to-determine value we might put on long-term soil improvement, erosion control, fewer drainage ditch clean-outs and so on.
In addition to matching the strip-till unit to the planter, it will pay to consider other machinery compatibilities. Always keep tractor tires in line with the strip-tiller tires. I observed one farmer, for example, who was running with staggered wheels so that the tractor tire was running over and smashing down the berm, pretty much defeating the whole concept of strip-till.
Also, be aware of potential problems if you try to strip-till with a 12-row unit in a field that has been harvested with an 8-row combine. We advise growers in this situation to keep the combine tires off the row when harvesting. By doing that and leaving the stalks upright, they shouldn’t have any trouble.
The Value of Carbon
Farmers like the idea of selling carbon credits. However, they often don’t understand the effects tillage has on losing carbon into the air as carbon dioxide (CO2 ) gas vs. keeping it in the soil as the building component of organic matter, thus making them eligible to get into the carbon market.
In a 2005 corn-on-corn study, University of Minnesota researchers measured pounds of CO2 lost per acre through fall moldboard plowing, disc ripping and strip-till the first day after tilling. In 24 hours, the plowed plot lost 579 pounds of CO2, compared to only 108 pounds for strip-till (only 18% lost vs. plowing). Disc ripping came in about halfway with a 271-pound CO2 loss.
Tillage depth also makes a difference. An Agricultural Research Service (ARS) study revealed that plots plowed 11 inches deep lost over 1,600 pounds of CO2 in 24 hours, while an area plowed to a depth of 4 inches lost only 419 pounds per acre. Still, the no-till plot only lost 87 pounds CO2 per acre.
Another ARS study at Morris, Minn., shows a dramatic difference in longer-term carbon loss. After 19 days, the amount of CO2 escaping from moldboard plowing was five times more than from a no-till field.
The key message: when you shift to strip-till or no-till, you create a soil environment for carbon to be converted by soil microbes into organic matter rather than being lost into the air. The accumulative effects of this process are far-reaching.
Study the Soil
It’s been rewarding during my 11 years in Extension to see farmers more interested in learning about soil and how it works. I’ve enjoyed teaching an intensive one-day “Soils 101” course that provides a basic understanding of soil science. We limit class size to 15 producers, and charge $60 for lunch and materials. We’ve filled up every time.
As farmers learn more about pH, cation exchange capacity, soil microbes, nutrient movement and compaction, they gain a better perspective on how managing their soil can be a direct link to erosion control, reduced tillage, lower fertilizer costs and consistent yields.