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Upper Midwest Tillage Guide - Part 2: Tillage implements, purpose and ideal use

Upper Midwest Tillage Guide
Tillage Implements, Purpose, Ideal Use
Jodi DeJong-Hughes (University of Minnesota) and Aaron Daigh (North Dakota State University)
Tilling the soil has been a practice used for centuries to produc e crops.
Tillage is dened as the mechanical manipulation of the soil with
the purpose of managing crop residue, incorporating amendments,
preparing a seedbed, controlling weeds, and removing surface
compaction and rutting.
Since the mid-nineteenth century, most farmers used the moldboard
plow as their primary tool. This implement over-turned the soil and
buried the previous crop’s residue, leaving only fragments covering
less than 15 percent of the soil surface. In the last 50 years, farmers
across the country began to use less aggressive primary tillage tools
such as the chisel plow. This tool allowed farmers to conduct tillage
more efciently, at a lower cost, and had the benet of reducing soil
erosion due to wind and water.
Today, numerous additional tillage implements are available on the
market that increase tillage efciency and reduce soil disturbance
and erosion even more. These new implements have options of
countless congurations of shanks, coulters, disks and harrows with
adjustable depths and pitches. Modern implements allow farmers to
control the aggressiveness of their primary tillage and to manage the
amount of residue left on the soil surface.
This chapter describes some of the more popular implements,
common tillage depths, number of passes needed to prepare a
seedbed, and expectations of crop residue coverage during the
spring months when the soil is most vulnerable to erosion. Included
are emerging technological advances, environmental factors, and
methods to successfully leave more residue.
Moldboard plow
Photo credit - Jodi DeJong-Hughes
Deep tillage (>10 inches)
Moldboard plow: Moldboard plowing inverts the soil to a depth of 8-12
inches, which is measured to the moldboard share’s bottom edge.
Typically, moldboard plowing is conducted in the fall, requiring farmers
to make one or two secondary tillage passes with a eld cultivator
or tandem disk before planting to smooth the soil and pulverize any
remaining large soil clods.
Moldboard plowing is the most aggressive tillage practice available
and leaves less than 15 percent percent of the soil surface protected
with crop residue during the months after planting. Because it is the
most aggressive tillage option, it also has the highest potential for
soil erosion by wind and water and has high fuel, time, and labor cost
Photo credit - Jodi DeJong-Hughes
Moldboard plow in the eld
Upper Midwest Tillage Guide
Disk ripper: Unlike the moldboard plow, a disk ripper does not
completely invert the soil. Instead, it tills the soils to a depth of 12-
16 inches with a series of shallow disks, shallow leading shanks
(optional), and then deeper, larger shanks. Some models have
broad or winged points on the shanks that increase the amount of
soil disturbance. Disk ripping often leaves 35-45 percent of the soil
surface covered by crop residue, even though it tills deeper than a
moldboard plow.
After disk ripping in the fall, one or two secondary tillage passes with
a eld cultivator or a tandem disk are needed in the spring before
planting. Since more crop residue is left on the soil surface, the
potential for erosion is less than the moldboard plow. However, disk
ripping has high fuel, time, and labor cost requirements due to the
deep depth of tillage.
Disk ripper
Photo credit - Jodi DeJong-Hughes
Disk ripper in the eld
Photo credit - Jodi DeJong-Hughes
Deep Zone till (in-line subsoiler, ripper, paraplow): In-line subsoiling,
ripping, or paraplowing are more generally referred to as deep zone
tillage. These “in-line” implements create evenly spaced rows (30-inch
spacing) of deep slots to a depth of 15-20 inches using a narrow subsoil
shank. Shanks may be completely straight or have a bent leg (paraplow).
Deep zone tillage is done in the fall and the crop is then planted directly
over the tilled rows.
These implements fracture and break up deep compaction zones and
incorporate little crop residues. Therefore, crop residue coverage at the
soil surface is left nearly intact. Farmers should only consider zone tillage
if deep soil compaction is known to exist. If the subsoil is not compacted,
then farmers will not see yield benets from subsoiling. These implements
also have a high horsepower requirement of 30-50 hp per shank.
In-line ripper close up
Photo credit - Jodi DeJong-Hughes
Medium depth tillage (5-10 inches)
Ridge Till implements build 6- to 8-inch high ridges on
30-inch centers leaving chopped crop residues left on the soil surface
between ridges. Ridges are typically built in the fall and then the
tops removed for seeds to be placed in during spring planting. The
ridges provide a dry and warm seedbed at planting. Tillage is then
limited to that performed by the planter and one to two in-season row
cultivations for controlling weeds and rebuilding ridges. The height
of rebuilt ridges within the season should be controlled to not bury
the lower pods if elds are planted to soybeans. After planting, crop
residues can cover up to 40 to 50 percent of the soil surface. This
percentage will decrease after the rst cultivation pass, which should
be done before the crop canopies.
Ridge till
Photo credit - Brad Carlson, UMN Extension
Chisel plow tills the soil to a depth of 6-8 inches using rows of
staggered shanks that can be congured in several different
designs. The choice of chisel plow point (shovels, straight points,
or sweeps) will vary the level of soil disturbance and affects the
amount of crop residues remaining on the soil surface. Preceding
the shanks are a gang of straight coulters or disks that size the
residue to reduce plugging. Chisel plowing is typically conducted
in the fall and is followed by secondary tillage with a eld cultivator
or tandem disk in the spring before planting. The secondary tillage
pass in the spring further lowers the residue coverage. It is ideal
to leave more than 30 percent residue coverage after planting
to reduce erosion. Therefore, fall chisel plowing should leave
40-45 percent residue on the surface after the chisel pass.
Farmers have the choice of numerous designs and adjustments to
the shanks, shovels, and sweeps to effect the amount of residue
incorporation. For example, a chisel plow equipped with 2-inch
straight shovels will leave 11 percent more residue than a 3-inch
twisted shovel (Hanna et al, ISU).
Fall chisel plowing that results in 30 percent crop residue cover after
planting can reduce the gross amount of soil erosion by 50 to 65
percent as compared to moldboard plowing that leaves less than 15
percent residue. Additionally, chisel plowing in the fall has a medium
fuel, time and labor cost requirement.
Chisel plow in the eld
Photo credit - Jodi DeJong-Hughes
Strip till
Photo credit - Jodi DeJong-Hughes
Strip till in the eld
Photo credit - Jodi DeJong-Hughes
Chisel plow shank
Photo credit - Jodi DeJong-Hughes
Strip till combines the benets of chisel plowing and no-till
simultaneously in row crop elds. The setup of strip-till implements
can vary but most have the following tools set in a series: a at or
wavy residue-cutting coulter, followed by adjustable row cleaners, a
primary mole knife (or coulters) for tilling the strip, two disc blades
to gather and berm soil into the tilled strip, and then rotary packing
wheels or conditioning baskets to rm the tilled strip of soil. This
prepares narrow 7- to 10-inch wide bands of soil for planting, while
leaving the soil and residue between the plant rows untouched as in
Fertilizer is often placed 5-8 inches deep in the soil immediately
behind the primary shank (or coulter) during tillage. This combines
the best of both tillage worlds. Strip till has a warmer, drier seedbed
compared to no-till that makes it possible to match the early planting
dates and high yields of conventional tillage, while its higher residue
cover provides the erosion control and improved water inltration that
no-till offers.
The spacing of tilled strips corresponds to planter row widths of the
next crop so that seeds are planted directly into the tilled strips. As
a result, strip till is well suited for controlled trafc management.
Most strip-till equipment manufacturers in the northern Great Plains
produce strip till implements with 30-inch, 22-inch, or 20-inch row
spacing. Strip tilling is normally done in the fall, but it also can be done
in the spring before planting. The cost per acre is similar to chisel plow,
however, chisel plow systems need an extra pass for broadcasting
fertilizer and an additional tillage pass for fertilizer incorporation and
seedbed preparation.
Upper Midwest Tillage Guide
Disk loosens and lifts the soil to a typical depth of 5-8 inches with
rows or gangs of concave disks set at an angle. If the gangs are
arranged with two sections adjoined on one side, it is called an offset
disc harrow. If the gangs are arranged with four sections in an X or
a diamond shape, it is called a tandem disc harrow. Disks are an
aggressive tillage option that incorporates a large amount of residue,
eliminates soil clumps and clods, and loosens the depth of tilled soil.
Shallow tillage (1-4 inches)
Vertical till cuts or sizes crop residue and lightly tills the top 1-4 inches
of soil. For the purpose of this publication, vertical till is any tillage
operation that does not cause a horizontal shearing or a smearing
plane in the soil prole. This eliminates any use of shanks, points,
and disks. Most vertical-till equipment consists of vertical coulters
set between 0-degree and 10-degree angles. Vertical till typically
maintains a crop residue cover of at least 50 percent of the soil
surface. However, a potential downside to vertical till may occur if
crop residues are sized too small and become easily blown or
washed away reducing soil coverage. Vertical till is not recommended
for incorporating nitrogen fertilizers since much of the nitrogen may
be left on the soil surface and is susceptible to volatilization loss.
Vertical till
Photo credit - Jodi DeJong-Hughes
Disk in the eld
Photo credit - Brad Carlson, UMN Extension
Field cultivator is a common secondary tillage practice done once in
the spring before planting to pulverize smaller soil clods remaining
after primary tillage and incorporate broadcasted fertilizers. Field
cultivators are also used as a less aggressive primary tillage practice
that is used in soybean stubble prior to planting corn. It leaves
soybean crop residues covering 20-30 percent of the soil surface and
tends to be a good option for medium textured, well-drained soils.
Field cultivation in the spring has a much lower fuel, time and labor
cost requirement than deep and medium depth tillage systems.
Vertical till in the eld
Photo credit - Jodi DeJong-Hughes Field cultivator
Photo credit - Great Plains -
Field cultivator in the eld
Photo credit -ower Soybeans growing in no-till corn residue
Photo credit - Jodi DeJong-Hughes
Tandem disk is similar to the disk but is less aggressive and therefore
provides a shallower tillage option for the top 2 to 4 inches of the soil.
Tandem disking is a common secondary tillage practice used in the
spring to prepare a smooth seedbed and incorporate broadcasted
fertilizers. However, if used as a primary tillage tool, the tandem disk
can have the same potential downside as vertical till as crop residue
becomes prone to blowing or washing away.
Tandem disk
Photo credit -
No-till is the complete absence of any primary or secondary tillage
practices with the goal of leaving the soil undisturbed as much as
possible during the entire year. Most no-till planters have residue
managers, nger coulters and double disk openers that move some
residue from the row and improve seed to soil contact. Similarly, grain
drills have a wavy coulter ahead of the seed tube to provide optimal
seed placement. This is the only soil disturbance in no-tilled elds.
The high amount of crop residues remaining on the soil surface helps
maintain or increase soil organic matter, improve moisture retention
and decrease soil erosion.
No-till requires special fertilizer application techniques for corn,
complete chemical weed control, and specially equipped planters.
Due to the potential slower soil warm-up in the spring, no-till typically
has been successful in regions with lower precipitation or well-drained
coarse or medium-textured soils.
Cost and soil structure impact of tillage
Below is a chart that categorizes tillage implements based on their
relative cost per acre to operate and the potential to have negative soil
effects. These numbers are based on an estimate created from the
Soil Tillage Intensity Rating (STIR) values of the tillage practice and
the Iowa State University Custom Rate Survey.
Negative soil effects of tillage include soil crusting, soil erosion, losing
soil organic matter, and poor soil structure. Lower numbers from the
chart indicate that tillage systems such as no-till, strip till, and vertical
Have less potential for soil loss by erosion
Will maintain soil aggregation
Can maintain or build organic matter
Are less expensive to operate
Tandem disk in the eld
Photo credit -
Upper Midwest Tillage Guide
Aggressive systems such as moldboard or chisel plowing and deep
ripping have a much higher potential for destroying soil structure,
creating individual soil particles that are prone to wind and water
erosion, and cost the most in fuel and wear and tear on machinery.
Note there is a variety of tillage implements that cover the spectrum
of cost and soil impacts.
Relative comparison of common tillage practices with respect to cost
($) and soil impact (E).
1 2 3 4 5 6 7 8 9 10
Moldboard Plow $ E
Disk-rip E $
Zone Till $ E
Chisel Plow $ E
Strip Till E $
Ridge Till E $
Disk-harrow $ E
Vertical Till $ E
Field Cultivation $ E
Tandem Disk $ E
No-till E $
From lowest (1) to highest (10) soil impact due to depth and aggressiveness of tillage pass.
E = structural impact on the soil due to depth and aggressiveness of tillage pass.
$ = the associated cost of the tillage equipment.
Sources: USADA-NRCS STIR equation, 2016 ISU Custom Rate Survey
Field activities performed under wet conditions often cause surface
compaction. Primary tillage alleviates the problem, provided elds
are not re-compacted. However, tillage is not the only way to correct
surface compaction. Biological “tillage” from rotating forage crops or
planting cover crops can also help. Perennial crops such as alfalfa, or
cover crops such as annual rye or “tillage radish,” may help break up
compacted layers. Additionally, in Minnesota many soils have a high
content of expanding smectite clay minerals and experience annual
wetting and drying cycles. These properties shrink and swell the soil,
creating deep cracks that can repair compaction damage naturally.
Earthworms are another form of bio-tillage. They create large pores,
which increase water inltration and root growth. Their castings
improve microbial growth, nutrient availability and soil structure.
Earthworms are quite active and feed by bringing organic debris
(residue) from the surface down into their burrows. In a well-populated
Minnesota soil, earthworms can recycle 8,000 pounds of soil per acre
per year. Full-width systems, such as moldboard and chisel plowing
disrupt earthworm channels resulting in reduced numbers in tilled
elds compared to no-till or similar low-disturbance systems.
Cover crop roots growing through a dense soil in North Dakota
Photo credit - Jodi DeJong-Hughes
Earthworm burrows in the soil
Photo credit - Jodi DeJong-Hughes
New technology
Tillage equipment manufacturers have recently been developing
new technological advances for tillage implements. Companies
are investing in research and the development of variable-depth
or variable-intensity tillage implements that can be controlled by
wireless touchscreen devices or integrated with emerging soil sensor
technologies and decision-support tools for a fully automated tillage
management system.
Gates Manufacturing, a North Dakota based company, has patented
technology to se nse or “read” the crop residu e levels and automatically
adjust the vertical-till gangs to be more or less aggressive based
on the sensed reading. Other features include using preset gang
adjustments for different elds with differing residue levels and soil
Salford, an Ontario based company, has recently introduced a
variable-depth tillage implement that combines a chisel plow and a
wavy coulter vertical till. A farmer can engage both the chisel plow
and vertical till for high crop residue conditions or for clayey soils and
then automatically raise up the chisel plow for use of only the vertical
till coulters when on slopes, sandier soils or low residue areas.
Gates Manufacturing On-the-Go adjustable gang angles
Photo credit - Gates Mfg
Salford variable depth tillage with chisel plow and vertical tillage units
Photo credit - Salford Group Inc.
Each tillage implement will disturb the soil differently based on
the depth of tillage, size and set-up of shanks, coulters, disks and
harrows, speed of operation, the number of passes, and whether the
implement turns the soil over or slices through the soil.
A Soil Tillage Intensity Rating (or STIR value) of 10 or less is required
to qualify for Natural Resources Conservation Service (NRCS) no-till
incentive programs. The STIR value is calculated using the RUSLE2
computer model that predicts long-term average annual erosion by
water. This model is based on crop management decisions applied in
a eld. The NRCS assigns a numerical value to each tillage operation.
STIR values range from 0 to 200, with lower scores indicating less
soil disturbance. Based on the STIR values, most strip till systems
can be used to qualify for the NRCS conservation management/no-
till incentive programs.
USDA-NRCS STIR values for common tillage operations.
Operation STIR
No tillage 0
Double-disk opener planter 2.4
Strip till – coulter, 5” depth, 8” berm 7.7
Strip till – shank, 7” depth, 10” berm 15
Tandem disk, light nishing 19
Vertical till 20
Field cultivator, 6 to 12 inch sweeps 23
Tandem disk 32-39
Ripper 33
Chisel, twisted shovel or sweeps 42-49
Moldboard plow 55-65
Soil structure is formed by the aggregation of individual soil particles
(clay, silt, sand, pieces of organic matter) into structural units or peds. Soil
aggregation is the movement and then sticking of soil particles together.
Microscopic bacteria and fungi in the soil, as well as plant roots, play a
vital role for soil particles to stick and stay together as peds. Their sticky
exudates and hyphae physically hold the soil together, helping soil
structure to form and persist over time. The more diverse and abundant
the microbial population, the faster soil aggregation can build. Between
aggregates, many large pore spaces allow roots to penetrate the soil
easier, and air and water to pass readily through. Additional benets of
improved soil structure are:
Reduced bulk density
Increased aggregate stability
Resistance to soil compaction
Enhanced soil fertility
Improved water inltration and drainage
Enhanced retention of plant available water
Less soil erosion
Enhanced biological activity
Protection of soil organic matter
All these benets are based on building and preserving soil structure.
Tillage breaks apart soil aggregates, damaging the existing soil structure,
and adds oxygen to the s oil that facilitates the breakdown of or ganic matter
by microbes. Over time, tillage reduces soil biological life. The deeper and
more aggressive the tillage, the weaker the soil structure. This leads to
more ne aggregates and individual soil particles, which can clog pores
Upper Midwest Tillage Guide
Compacted layer created by annual tillage
Photo credit - Jodi DeJong-Hughes
A poorly aggregated and compacted soil
Photo credit - Jodi DeJong-Hughes
A well aggregated soil
Photo credit - Jodi DeJong-Hughes
Windblown soil that has moved from a low residue eld to the adjoining ditch
Photo credit - Jodi DeJong-Hughes
and crust the soil surface, slowing water inltration and increasing runoff.
Smaller soil particles are also highly susceptible to being swept away by
wind and water. Valuable topsoil moves into the ditch, or the neighbor’s
eld, or the next state, and is lost forever.
The loss of topsoil severely diminishes a eld’s productivity. The soil that
is moving downslope or off the eld is the eld’s most productive soil.
It contains carbon, nitrogen, phosphorus, sulfur, and other nutrients, is
lower in salts, and has a more favorable pH than the soil remaining after
erosion occurs.
Additionally, as the soil loses structure, it becomes denser and more
susceptible to compaction because of the loss of larger pore spaces.
Compaction inhibits root growth and decreases water-holding capacity.
Repeated tillage operations at the same depth may cause serious
compacted layers, or tillage pans, just below the depth of tillage. Higher
horsepower equipment is needed to get through compacted soil, which
results in more wear-and-tear on equipment. Reducing tillage helps
preserve the soil’s natural structure, making the soil more resistant to
erosion and the negative effects of heavy eld equipment.
There is not one tillage management system that will work for every
eld. Factors such as soil moisture and physical characteristics, slope,
and crop rotation play a vital role when deciding which implement is
best for each eld.
Soil Texture: In the Midwest, sandy and loamy sand soils warm up
faster and have good internal drainage. However, they have lower
organic matter content and do not have soil structure. It is not possible
to create soil structure on sands and loamy sand soils, but the addition
of organic materials can improve water holding capacity and internal
drainage. Reducing tillage or using no tillage on these coarse soils
protects soil productivity and cuts yield risk.
Clay and clay loam soils in the upper Midwest are rich in organic matter,
which gives them their characteristic dark brown or black color, and if
managed properly, develop well-dened structure. These ne-textured
soils have poor internal drainage, drying more slowly than sands. In
addition, light-colored residue reects the sun’s heat, impeding spring
warm-up. With high levels of residue, these poorly drained soils may
remain cool and wet long into the spring months, resulting in delayed
planting. That is why, traditionally, more tillage is performed on clayey
soils. However, improving soil structure will boost internal drainage,
speeding up spring warming and drying. Furthermore, systems such
as strip till and no-till do not destroy the continuity of large pores and
Soil structure difference with a loamy sand (above) and a clay loam soil (below)
Photo credit - Jodi DeJong-Hughes
therefore increase inltration and aeration. Subsurface drainage (tile
drains) also improve soils with poor internal drainage, making it more
feasible to reduce tillage.
Wet Soil Conditions: This is probably the most important factor
to evaluate. If the soil is too wet for proper soil fracturing in the fall,
tillage may be creating more damage to the soil than benets from the
residue incorporation. If the soil is dry near the surface but wet below,
shallow up the shanks or disks so that they do not smear the wet layer
of soil. A smeared soil will need an additional, deeper pass or two in
the spring to break up the dense layer.
For example, if a chisel plow is used in a wet soil to a depth of 8”, using
a 3” spring eld cultivation will not alleviate the smeared soil layers
created by the chisel plow. This situation might need an in-line ripper
set at a 9-10” depth to eliminate the smeared layers created by the
chisel operation during wet conditions.
Field cultivating at 3-inch depth in a wet soil restricted the corn roots from growing much deeper
Photo credit - Jodi DeJong-Hughes
Moderate Soil Moisture Conditions: If the soil has moderate moisture
in the fall (moisture levels below eld capacity), a chisel plow or a disk
ripper will incorporate some residue and break through compaction
and cloddy soils. However, note that disks are extremely destructive
to soil structure, creating a ne, pulverized soil that can easily blow
or wash away. Disks can also create a plow layer. For example, if
you look where a roadbed is being built, you will usually see a disk
sitting along with the other construction equipment. These implements
are extremely effective at creating a dense soil. Also, recall that soil
with poor structure can compact more easily. Use the disk sparingly.
Conversely, equipment with points and shanks lifts and separates the
soil more along its natural fracture lines and is less destructive than a
Upper Midwest Tillage Guide
Dry Soil Conditions: If the soil is exceptionally dry in the fall, do not use
deep tillage equipment. A chisel plow set at an 8” depth will heave-up
large clods of soil. Experience has shown that the deeper the tillage
in these extremely dry soils, the larger the clods lifted to the surface.
In 2011, basketball-sized and larger clods were seen across western
Minnesota due to tillage during extremely dry soil conditions. Two to
three tillage passes were needed in the spring to create an acceptable
Cloddy soil due to deep tillage in a dry soil
Photo credit - Jodi DeJong-Hughes
Natural alleviation of soil compaction is possible in soils that shrink
and swell (crack in dry conditions) during dry conditions. Consider this
a form of free, deep tillage. Since dry soils are naturally ”tilling” deep
into the soil, farmers can focus on creating a good seedbed in the top
3 inches with shallow tillage. In dry conditions, reduced-tillage systems
preserve moisture in the seedbed, enhancing uniform germination
and plant establishment.
Cracks in the soil created by dry soil conditions are breaking up compacted areas in the soil
Photo credit - Jodi DeJong-Hughes
Soil Compaction: In the Midwest, research results evaluating the
effects of subsoiling have shown few positive yield responses. When
yield benets do occur, they are variable and relatively small.
Accurately predicting the effects of subsoiling on crop yields is
very difcult, due to differences in soil texture, the level of subsoil
compaction, the soil water content, subsequent trafc, and differences
in the crop grown and in tillage methods.
In a University of Minnesota study near Waseca, MN, a eld was
uniformly compacted with a grain cart weighing 20 tons an axle. The
eld was subsoiled to a depth of 16 inches to break up the compacted
soil. Subsoiling failed to increase yields on the 20 ton per axle
treatments for either corn or soybeans and decreased corn yield 11 bu/
ac in one of the two years. Similarly, a two-year study near Elrosa, MN,
found that corn and the following soybean yields were not affected by
subsoiling down to 20-inch depth.
A eld subsoiled in a wet soil to a depth of 20 inches near Elrosa, Minnesota
Photo credit - Jodi DeJong-Hughes
To increase the probability of obtaining benecial effects from
subsoiling, the following steps should be considered:
Determine that a compaction problem actually exists. Dig
some plants to examine rooting. Are visual crop symptoms
consistent with past wheel trafc? Is there standing water
after a rain that also shows a pattern consistent with wheel
traf c?
Determine the depth of the compacted layer.
Set the tillage implement 1-2 inches deeper than the
compacted zone depth. Make sure the soil is dry and
fractures to the depth of the shank when subsoiling.
Leave some areas of the eld not subsoiled for yield and
visual comparison.
Avoid re-compacting loosened soil by avoiding future
operations on wet soils and using the controlled trafc
Slope: Sloping elds are prone to water erosion. Erosion potential
depends on the length and steepness of slope and the soil texture.
Highly erodible land (HEL) may require large reductions in tillage
intensity to limit erosion and maintain soil productivity. Flat elds have
less erosion potential, but sediment loss can be a problem on these
elds during intense rain or wind events. Reduced tillage leaves more
residue on the soil surface. This residue protects the soil from raindrop
impact and slows the downhill movement of soil and water. In addition,
standing residue will slow the wind’s erosive speed and wick rainfall
into the soil faster than bare soil.
Eroded hilltops near Fergus Falls, Minnesota
Photo credit - Jodi DeJong-Hughes
If elds have more than a 3 percent slope, minimize the depth and
intensity of the tillage pass. The steeper the slope and the more
aggressive the tillage, the more mid-slope buffers and planting on the
contour are needed and have a return on investment. A handful of
creative farmers will not till the tops and sides of slopes in the elds
leaving the residue to protect the vulnerable soil.
Crop Rotation and Residue Levels: Crops differ in their adaptability to
respond to soil temperature and moisture. Corn, a determinant crop,
is sensitive to moisture and temperature. High levels of crop residues
can cause uneven emergence and may decrease corn yields. On the
other hand, soybean and wheat have greater ability to thrive in a large
range of crop residue levels.
The amount of residue in a eld before tillage depends on the previous
crop and yield. Corn, for example, generates much more biomass
than edible beans, soybeans, potatoes, or sugarbeets. Therefore, it is
easier to maintain higher residue levels following corn using a variety
of tillage systems. Residue durability also differs by crop. While corn
residue breaks down slowly, soybean residue is fragile and easily
destroyed by tillage, so maintaining adequate residue cover following
soybeans is more difcult. Consider the entire crop rotation when
evaluating residue cover and tillage systems. In general, a corn-
soybean rotation offers more tillage exibility than continuous corn.
While not a tillage issue, it is very important to spread residue over the
width of the combine to prevent strips of higher residue levels directly
behind the combine. This area of high residue can create uneven
residue incorporation during tillage and uneven seed placement
during planting. Chopping heads and chaff spreaders can help spread
stalks and chaff evenly across the eld.
Many different tillage choices are available. If you have a 2 or
3-year crop rotation (corn-soybeans, corn-soybeans-wheat), a less
aggressive tillage pass can be very effective at managing the crop
residues. However, there are fewer choices available to handle the
high residue levels of three or more years of continuous corn. Each
implement has benets and challenges.
Residue cover directly after harvesting corn (top) and soybeans (bottom)
Photo credit - USDA-NRCS
Upper Midwest Tillage Guide
Managed properly, the benecial aspects of maintaining high levels of
crop residue with reduced-tillage systems outweigh the few negative
aspects. Look at your specic situation (soil texture, crop rotation,
slope, and soil moisture) to decide what is right for you. In the end,
reducing your tillage is key to the long-term productivity of your soil.
When possible wait until spring to till, especially on elds
with soybean residue. Where fall tillage is conducted use
systems that are done on the contour and leave 40-50%
Reduce the number of tillage passes
Set chisels and disks to a shallower depth
Use straight points or sweeps on chisel plows instead of
twisted points
Plant a cover crop, especially after low residue or early
season crops
Spread residue evenly with the combine
Minimize tillage operations up and down slopes
Avoid working the soil when it is wet Spreading out the chaff evenly behind a combine
Photo credit - Jodi DeJong-Hughes
Upper Midwest Tillage Guide is a collaboration between the
University of Minnesota and North Dakota State University
Peer review by Richard Wolkowski, Extension Soil Scientist,
Emeritus, University of Wisconsin - Madison
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