Practical ways of assessing structural damage and how to remove it - - PDF document

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Practical ways of assessing structural damage and how to remove it - - PDF document

May 18, 2023 93 likes •444 views

David White - practical ways of assessing structural demage and how to remove it Practical ways of assessing structural damage and how to remove it David R White Senior Lecturer - Harper Adams University Options for compaction reduction

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David White - practical ways of assessing structural demage and how to remove it

www.soilandwater.org.uk

David R White

Senior Lecturer - Harper Adams University

Practical ways of assessing structural damage and how to remove it

After: Tullberg et al. 2003

Reduced pressure/axle weight and central tyre inflation pressure control systems Options for compaction reduction

Controlled traffic

Source: CTF Europe

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David White - practical ways of assessing structural demage and how to remove it

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Outline Traction Tillage Planting a crop this year Concluding remarks

Wheels

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David White - practical ways of assessing structural demage and how to remove it

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Tracks Our ancestors knew something - keep off the soil.

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David White - practical ways of assessing structural demage and how to remove it

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Traction

  • Thrust is a force which arises from the

interaction between a track or wheel and the soil.

Drawbar Pull Thrust Rolling Resistance

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David White - practical ways of assessing structural demage and how to remove it

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The bigger the drawbar pull, the bigger the wheel/ track thrust needed.

Thrust depends on:

  • The weight on the wheel or track
  • Soil cohesion
  • Soil friction
  • Tyre track contact area
  • Slip
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David White - practical ways of assessing structural demage and how to remove it

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M ost agricultural soils in the UK have both cohesion and soil/soil friction and, therefore, benefits can be gained in traction terms from increasing both weight and contact area

Ways of increasing tyre contact area

  • Tracks
  • Dual tyres
  • Wide tyres
  • Large diameter tyres
  • Extra axle
  • Lower tyre pressure
  • Radial tyres
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David White - practical ways of assessing structural demage and how to remove it

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Ballast

  • Wheel weights
  • Front end weights
  • Partly fill tyres with water
  • Dynamic weight transfer – attach the

implement to the tractor as per the instruction manual.

Note

  • Y
  • u can over ballast tractors.
  • Aim for correct wheel slip i.e. between 8 and

15 %.

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David White - practical ways of assessing structural demage and how to remove it

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Drawbar Power = Pull X Speed

Conclusion

  • Slow and high drawbar force (very wide

implement) requires large wheel thrusts.

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David White - practical ways of assessing structural demage and how to remove it

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Heavy loads

M aximum gross weight of vehicles:

10 20 30 40 50 60 D r i l l s S p r a y e r S p r e a d e r T r a c t

  • r

C

  • m

b i n e T r a i l e r T a n k e r T r u c k B e e t H a r v e s t e r Gross weight (tonne)

After: Erickson et al 1974 Updated by Godwin 2007

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David White - practical ways of assessing structural demage and how to remove it

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M aximum tyre inflation pressure

  • f vehicles:

1 2 3 4 5 6 7 8 Drills Sprayer Spreader Tractor Combine Trailer Tanker Truck Beet Harvester Inflation pressure (bar)

After: Erickson et al 1974 Updated by Godwin 2007

Tyre load and inflation pressure

W

Pi

A

Pc Pcs

Pc= Pi+Pcs

Pi – inflation pressure Pcs – tyre carcass stiffness

Pc= W / A

Pc – contact pressure W – tyre load A – tyre contact area

  • Large contact area
  • Low load
  • Low tyre stiffness
  • Low contact pressure
  • Uniform contact pressure
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David White - practical ways of assessing structural demage and how to remove it

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Compaction issues

25 tonnes 20 + tonnes 7 bar 2 bar (1 bar better)

Conclusion Do not allow vehicles with high inflation pressure tyres in the field

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David White - practical ways of assessing structural demage and how to remove it

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Deeper compaction

650mm

Conclusion

Compaction at this depth is difficult to remove, avoid putting it there in the first place.

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David White - practical ways of assessing structural demage and how to remove it

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Compaction of soil by repetitive loads

First pass causes the most compaction. Controlled wheeling is better than random wheeling.

Conclusion

  • The first pass of a wheel, or track, does the

most damage. Further passes only add a bit more compaction.

  • M ake as few passes over the field as possible.
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David White - practical ways of assessing structural demage and how to remove it

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Contact pressure below tyres

  • Large contact area
  • Low load
  • Low contact pressure
  • Uniform contact pressure

(Sohne, 1958) (Sohne, 1958) IP = 12psi, loads: 660, 1100, 1650, 2200 lbs

Conclusion

  • Reduce tyre pressures to lowest

recommended by manufacture for given load.

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David White - practical ways of assessing structural demage and how to remove it

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Normal stress under a track & tyre

After: Reaves and Cooper 1960

Tillage

  • If a tillage operation is not going to be of

benefit do not do it.

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David White - practical ways of assessing structural demage and how to remove it

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Aims Of Tillage

  • Prepare a suitable growing medium for a

crop (Germination, emergence, action of herbicides)

  • Bury/ incorporate surface residues/ fym
  • Remove local or general soil compaction

problems (promote drainage).

  • Provide adequate soil strength to support

surface traffic.

After: Godwin, 1974

Tine geometry and soil disturbance

2 key factors: 1.Rake angle 2.Depth/ width ratio

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David White - practical ways of assessing structural demage and how to remove it

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Soil failure patterns

Depth/width = < 0.5 > 1 to < 6 >6

Effect of rake angle on soil forces

  • 1

1 2 3 4 5 22.5 45 67.5 90 113 RAKE ANGLE (degrees) FORCE (kN)

HORIZONTAL VERTICAL

UPWARD DOWNWARD

After: Godwin 1974

Rake angle Direction of travel Soil surface Implement face

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David White - practical ways of assessing structural demage and how to remove it

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Conclusion

  • Backward inclined tines need more force to

pull them than forward inclined tines at the same depth (therefore, more wheel thrust, more ballast).

  • Consider lifting out backward inclined tines
  • n drills, tillage trains, etc. under adverse

soil conditions Effect of depth of tine on soil forces

1 2 3 4 5 6 7 8 9 50 100 150 200 DEPTH (mm) FORCE (kN) HORIZONTAL VERTICAL

After: Godwin 1974

Rule of thumb: double depth, quadruple draft

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David White - practical ways of assessing structural demage and how to remove it

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Effect of depth of work on disc forces

Spherical disc in a sandy loam soil at a sweep angle of 25o

0.2 0.4 0.6 0.8 1 1.2 50 100

Force, kN Depth, mm

From: Godwin et al,1987

Horizontal Vertical

Conclusion

  • Doubling the working depth, approximately

quadruples the drawbar force.

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David White - practical ways of assessing structural demage and how to remove it

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A wheel is a backward inclined tine

motion

Conclusion

  • Wheels cause compaction.
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David White - practical ways of assessing structural demage and how to remove it

www.soilandwater.org.uk Selection of implement rake angle for tillage operations

Low Vertical High

Direction of travel

Operation: Loosening Sorting Compacting Cutting Disintegrating Disintegrating Inverting Rearranging Smoothing Consolidating e.g.: Chisel tines Harrows - drag Rollers Plough shares - power Scrubber boards Bulldozer blades Pneumatic tyres Soil surface

After: Spoor, 1968

Critical depth

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David White - practical ways of assessing structural demage and how to remove it

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As a general rule of thumb, critical depth occurs at approximately six times the individual loosening tine’s width for friable soils; for example, a tine foot that is 8 cm in width, will have a critical depth of around 48 cm. For plastic soils this can almost come to the soil surface. (Godwin, 1975)

Conclusion

  • Check what the implement is actually doing.
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David White - practical ways of assessing structural demage and how to remove it

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Worn components

Conclusion

  • Using worn components is false economy.
  • They will produce a poor job and possibly

need a higher drawbar pull.

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David White - practical ways of assessing structural demage and how to remove it

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Subsoiling

After: Spoor and Godwin, 1978

Plain tine Wide point, high lift wing Narrow point, low lift wing

Effects of winged tines Shear planes

After: Spoor and Godwin, 1978

Horizontal cracks

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David White - practical ways of assessing structural demage and how to remove it

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Total soil disturbance Tip Wing

After: Spoor and Godwin, 1978

Effect of wings

Draught 20.43 kN 26.58 kN Disturbed area 0.098 m2 0.184 m2 Specific resistance 208 kN/ m 2 144 kN/ m2

After: Spoor and Godwin, 1978

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David White - practical ways of assessing structural demage and how to remove it

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Leading shallow tines

After: Spoor & Godwin, 1978

Soil disturbance

After: Spoor & Godwin 1978

Plus shallow leading tines Wings only Draught Force (tonnes) Area of disturbance (m2) Specific resistance (tonnes/m2)

2.39 0.24 9.6 2.35 0.42 5.4

Similar: Almost double: 45% reduction

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David White - practical ways of assessing structural demage and how to remove it

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Effects of tine spacing Spacing Too close Optimum Too wide

After: Godwin, Spoor and Soomro, 1984

M ultiple tine spacing

  • Simple tines = 1.5 x depth of work
  • Winged tines = 2.0 x depth of work
  • Winged tines + = 2. 5 x depth of work (of shallow

leading tines deeper tine)

After: Spoor & Godwin, 1978

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David White - practical ways of assessing structural demage and how to remove it

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Note

  • If you subsoil plastic soil you will simply

make “square moles” i.e. waste of time

M oisture profiles after 7 days of drying

Undisturbed soil Fine tilth Coarse tilth

After: Spoor and Godwin, 1984 M oisture content, % by weight Depth, mm

Dry Friable/ M oist Plastic

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David White - practical ways of assessing structural demage and how to remove it

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Conclusion

Avoid bringing up wet soil e.g. deep tillage

no discs, tines @ 150mm, plus wings, no packer. discs @ 60mm, tines @ 100mm, plus wings, hard packer. discs @ 60mm, tines @ 150m, no wings, no packer. discs @ 60mm, tines @ 100mm, plus wings, no packer.

Implement adjustment –

clod size distribution and residue levels

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David White - practical ways of assessing structural demage and how to remove it

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Conclusion

M ake sure no component is “getting a free ride”

M achinery manufactures recommendations General working recommendations :-

  • 1. M ake as few passes over the field as possible.

(although a field that has been laid wet over winter may benefit from a once over with a tined cultivator to get some air in)

  • 2. Work headlands last (or not at all)

(Vaderstad 2012)

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David White - practical ways of assessing structural demage and how to remove it

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M achinery manufactures recommendations

M achine set up :-

  • 1. Read instruction books carefully (none of us ever look at them!)
  • 2. Get the basics right
  • 3. Pay attention to detail
  • 4. Inflate tyre pressures as recommended
  • 5. Soil engaging parts should be replaced or in good condition

...scalloped discs work and drive better if they are not worn down

  • 6. Set wheel scrapers as recommended
  • 7. Set front tools (on cultivator drills) to minimum depth (or out
  • f work) to minimise draft requirement
  • 8. Don't fill seed hopper completely to minimise overall weight

(Vaderstad 2012)

Agronomy views

  • Do not be in too much of a hurry – resist the

temptation to fill up the drill.

  • Do not force seed into poor soil conditions – it might

lead to a costly re-drill.

  • Allow green material to remain there as long as
  • possible. Consider killing with glyphosate as late as

possible

  • Dig a hole with a spade to check cultivation work for

smearing

(Blake et al 2012)

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David White - practical ways of assessing structural demage and how to remove it

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Spring 2013 strategies

  • Cultivate to minimum depth
  • Lightest tractor
  • Lowest tyre pressure or tracks
  • Consider reducing machine width
  • Broadcast and harrow
  • Leave it in a cover crop

(Blake et al)

Overall

conclusions/ recommendations

  • We do not have a “ magic solution”
  • Assess your own fields
  • M onitor what your machinery is doing to the soil
  • Read instruction manuals
  • It will take time to repair your soils
  • Speak to your agronomist
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David White - practical ways of assessing structural demage and how to remove it

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Any questions?

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