Soil Compaction Tracks vs. Tires

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Soil CompactionTracks vs. Tires

• Jodi DeJong-Hughes
• U of M Extension Service

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Soil Compaction

• Soil compaction occurs when soil particles are
  pressed together, reducing pore space between
  them.

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Soil Compaction
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Soil Compaction - Myths?

• Minnesota soils have high freeze/thaw potential
  which will break up compaction
• - Only in top 4
• Deep tillage fixes compaction
• - No research data to support long-term fix
• Compaction results in a similar yield loss each
  year.
• - Yield response, due to compaction, interacts
  with weather

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Soil Compaction Over Time1870 Wadsworth Wagon
Trail

• 50 reduction in air and water permeability
• 10 increase in bulk density
• Evidence of erosion

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Visual Symptoms

• Dark soil streaks
• Ponded water
• surface runoff
• erosion on sloping land
• Different power requirements within field

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Symptoms in Wet Years

• Decreased Pore Space

• Excess soil moisture
• Denitrification
• Increase nutrient deficiencies (N and K)
• Increase disease potential
• Reduced yields

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Symptoms in Dry Years

• Decreased Pore Space

• Decreased root growth
• Small, stunted plants
• Early plant water stress
• Reduced yields

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Compaction vs. Yield
Yield
Compaction
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Types of Compaction
Remember PSI surface compaction Axle Load
depth of compaction
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Soil Compaction - Causes

• Heavy field equipment
• Working soil too wet

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Axle Load

• As the load increases,
• compaction increases in
• Depth
• Width
• Degree

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• Equipment Axle Load
• (Tons)
• Slurry tanker, 4,200 gallons 10 - 12
• Slurry tanker, 7,200 gallons 17 - 18
• 6-row combine, empty 8
• JD 9610 w/o head, empty 12
• JD 9610 w/head, full 23
• Beet cart, full 24
• Grain cart, 1,200 bu, 1 axle 35 - 40
• Common limit on public 8 - 10
• hard-surface roads

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• Equipment PTO HP Axle Load (lbs)
• 45 Rear, 55 Front
• 4WD 325 20,500 25,000
• 200 12,600 15,400
• 60 Rear, 40 Front
• MFWD 200 16,800 11,200
• 150 13,000 8,400
• 70 Rear, 30 Front
• 2WD 200 19,600 8,400
• 150 14,700 6,300

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Ultimate Manure Spreader
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Research Locations
Ward Voorhees, USDA/ARS, Morris, MN
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Relative Corn Yield Waseca, MN
Ward Voorhees, USDA/ARS, Morris, MN
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Relative Corn Yield Waseca, MN
6 yield decrease
dry
wet
wet
Ward Voorhees, USDA/ARS, Morris, MN
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Corn Yields From Waseca Study

• 1st Year
• Non-compacted 170 bu/a
• 10 T/axle 155 bu/a
• 20 T/axle 125 bu/a
• 6 Yield Decrease over 12 years
• Non-compacted 170 bu/a
• 20 T/axle 160 bu/a
• (12 years 120 bu/a)

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Soil Compaction- Control

• Lighten the load
• Working at proper moisture range
• Singles vs. duals/tracks

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Soil Moisture

• Water acts as a lubricant, allowing pressure to
  move soil particles together.
• Greatest soil compaction occurs at soil moistures
  near field capacity (22 water content).
• Water filled pore space cannot be compacted.

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Soil Moisture

• Tilling and planting in a
• saturated soil will result in
• rutting
• clods
• poor chemical incorporation
• other undesirable side effects

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Soil Moisture
hard dry soil
moist soil
wet soil

• (Tire size 11 x 28, load 1,650 lbs.,
  pressure 12 psi)
• As the soil moisture is increased, the depth of
  compaction increases.

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Different Tracks
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Tractor Weight Track Print
PSI (lbs.) (inches)

• Quad Track 52,100 30 x 71 6.1
• JD 8400T 28,000 16 x 105 8.3
• 28,000 30 x 105 5.7
• JD 9000T 40,000 30 x 111 6.0
• 40,000 36 x 111 5.0
• Challenger 65 41,000 25 x 107 7.7
• Challenger 75 41,000 30 x 107 6.4
• Challenger 85 41,000 35 x 107 5.5
• STX 375 45,000 Duals 7 8
• 46,000 Triples 7 8.5
• JD 8870 37,300 Singles 10
• 38,300 Duals 6 - 10

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Axle Number for Tracks

• Industry claims that these are 6 and 5 axle
  systems.
• One could argue that they should be considered as
  one axle!
• In reality, they act similar to 2 axles.

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Tractor with Single Rear Tires
4
6
8
12
Tires inflated to 26 front and 24 rear psi
Kinney et al., 1992
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Tractor with Dual Rear Tires
Tires inflated to 19 psi
4
6
4
8
6
8
12
12
Front Wheel and Inside Rear Dual
Outside Rear Dual
Kinney et al., 1992
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Tractor with Tracks
22 wide x 7 long, steel tracks
4
8
12
Kinney et al., 1992
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Tracks vs. Duals
4
6
4
8
8
12
12
17,600 pounds, 4.8 psi
17,600 pounds, 21 psi
Kinney et al., 1992
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Reducing Surface Compaction

• Duals/tracks vs. singles
• Radial vs. bias tires
• Decrease tire pressure
• Larger diameter or wider tires
• Remove ballast when not needed

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Summary

• Control wheel traffic
• Limit grain truck traffic within field,
  especially in wet falls
• Empty combine as often as possible
• Crop rotation (fibrous and tap roots)
• Build soil organic matter levels

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Questions?