Managing Soil Compaction in Agricultural Fields

RESEARCH

Managing Soil Compaction in

Agricultural Fields

Randy L. RaperOklahoma Agricultural Experiment

StationOklahoma State University

RESEARCH

Advice to Manage Soil Compaction

• Only traffic when soil moisture is low!• Adopt conservation agricultural system including cover

crops!• Use controlled traffic systems!• Use smallest vehicle possible for job!• Minimize inflation pressure in radial tires!• Reduce contact pressure by using duals or tracks!

• If necessary to remove effect of traffic, use in-row or bentleg subsoilers that minimally disturb soil surface and only till slightly below depth of compaction!

RESEARCH

What is soil compaction?

Quite simply, it is a reduction in pore space.Quite simply, it is a reduction in pore space.

RESEARCH

Why is Soil Compaction Important?

• Reduced Crop Yields– Reduced root growth– Decreased infiltration– Increased erosion

RESEARCH

Causes of soil compaction

• Vehicle Traffic

RESEARCH

Vehicle Traffic

0

10000

20000

30000

40000

50000

60000

Weight, lbs.

1948 2000

RESEARCH

Vehicle Traffic

RESEARCH

New Equipment: 80,000#!

RESEARCH

Sample Pressures Exerted on the Soil

5 – 23 psi

30 psi

56 psi

RESEARCH

Cone Resistance (MPa)Cone Resistance (MPa)00 22 33 44 5511

00

5050

1010

2020

3030

4040

Depth (cm

)Depth (cm

)

Not grazedNot grazed

GrazedGrazed

Short-term Grazing

RESEARCH

Causes of soil compaction

• Vehicle Traffic• Natural Soil

Reconsolidation

RESEARCH

Causes of soil compaction

• Vehicle Traffic• Natural Soil

Reconsolidation– Well-graded soils

more susceptible to compaction than poorly- graded soils

0

20

40

60

80

100

0.0010.110

Particle Diameter, mm

Percent Finer

Poorly-Graded

Well-Graded

RESEARCH

Measurement of soil compaction

• Bulk Density– Time consuming

– Difficult to compare across soil types

RESEARCH

Measurement of soil compaction

• Bulk Density• Soil Cone Penetrometer

– Standardized unit• ASAE Standard S313• ASAE Engineering Practice EP542

– Quickly obtain information

– Researchers have related results to crop response

• 300 psi (2 MPa) restricts root growth

Cone Resistance (MPa)Cone Resistance (MPa)00 22 33 44 5511

00

5050

1010

2020

3030

4040

Depth (cm

)Depth (cm

)

Not grazedNot grazed

GrazedGrazed

RESEARCH

Handheld Penetrometer

RESEARCH

Recording Penetrometer

RESEARCH

Multiple-probe PenetrometerPositions of Penetrometer

Measurements

RESEARCH

Commercial Tractor-Mounted

Penetrometer

RESEARCH

Advice to Manage Soil Compaction

• Only traffic when soil moisture is low!• Adopt conservation agricultural system including cover

crops!• Use controlled traffic systems!• Use smallest vehicle possible for job!• Minimize inflation pressure in radial tires!• Reduce contact pressure by using duals or tracks!

• If necessary to remove effect of traffic, use in-row or bentleg subsoilers that minimally disturb soil surface and only till slightly below depth of compaction!

RESEARCH

Preventing it

• Avoid Weak Soil– Moisture Content

Effect

Liquidity index

-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6P

re-c

ompr

essi

on s

tres

s, k

Pa

1

10

100

1000

RESEARCH

Advice to Manage Soil Compaction

• Only traffic when soil moisture is low!• Adopt conservation agricultural system including cover

crops!• Use controlled traffic systems!• Use smallest vehicle possible for job!• Minimize inflation pressure in radial tires!• Reduce contact pressure by using duals or tracks!

• If necessary to remove effect of traffic, use in-row or bentleg subsoilers that minimally disturb soil surface and only till slightly below depth of compaction!

RESEARCH

Conservation Agricultural System

• Reduced Vehicle Traffic– Conventional Tillage System

• 80% of field may be trafficked from numerous field operations

• 1st pass is responsible for 80% of compaction

– Conservation Agricultural System• Greater soil strength in row middles• Plant into old rows – controlled traffic• Reduced number of field trips - reduced compaction

over entire field

RESEARCH

2020 1010 00 1010 2020

44

88

1212

1616

2020

2424

Distance from Row (in)Distance from Row (in)

Dep

th (

in)

Dep

th (

in) 1515

2020

20202020

2525

2020

Cover CropCover CropCover Crop15%1515%%

20%2020%%

25%2525%%

15%1515%%

20%2020%%

25%2525%%

0-6”00--66””

6-12”66--1212””

2020 1010 00 1010 2020

44

88

1212

1616

2020

2424

Distance from Row (in)Distance from Row (in)

Dep

th (

in)

Dep

th (

in) 1515

1515

15151515

20202020

Cover CropCover CropCover Crop15%1515%%

20%2020%%

25%2525%%

15%1515%%

20%2020%%

25%2525%%

0-6”00--66””

6-12”66--1212””

No-Till

RESEARCH

Yield Improvements with Cover Crops

b

b

a

a

0

1000

2000

3000

4000

5000

2003 2004 2005 2006Year

Yie

ld (

kg/h

a)

No Cover Cover

ns

ns

RESEARCH

Advice to Manage Soil Compaction

• Only traffic when soil moisture is low!• Adopt conservation agricultural system including cover

crops!• Use controlled traffic systems!• Use smallest vehicle possible for job!• Minimize inflation pressure in radial tires!• Reduce contact pressure by using duals or tracks!

• If necessary to remove effect of traffic, use in-row or bentleg subsoilers that minimally disturb soil surface and only till slightly below depth of compaction!

RESEARCH

Controlled Traffic

• Wide-span vehicles

RESEARCH

Controlled Traffic

• Wide-span vehicles• Wide-span tractors

RESEARCH

Controlled Traffic

• Wide-span vehicles

• Wide-span tractors

• Automatic-steered tractors

RESEARCH

Uncontrolled Traffic!

RESEARCH

Controlled Traffic Using Autosteer

RESEARCH

9”

}}

2”

Yield Reductions from Uncontrolled

Traffic

• 16% reduction from misalignment of row and strip-tilled zone by 2”.

• 29% reduction from misalignment of row and strip-tilled zone by 9”.

RESEARCH

Advice to Manage Soil Compaction

• Only traffic when soil moisture is low!• Adopt conservation agricultural system including cover

crops!• Use controlled traffic systems!• Use smallest vehicle possible for job!• Minimize inflation pressure in radial tires!• Reduce contact pressure by using duals or tracks!

• If necessary to remove effect of traffic, use in-row or bentleg subsoilers that minimally disturb soil surface and only till slightly below depth of compaction!

RESEARCH

Preventing Soil Compaction

Research Summary

• Assuming moist, arable soil:– 4.4 tons/axle compacts to

12 in.– 6.6 tons/axle compacts to

15.8 in.– 11 tons/axle compacts to

19.7 in.– 16.5 tons/axle compacts to

23.6 in. and deeper• Common to see

persistence of subsoil compaction 6-7 years later.

Hakaansson, and Reeder, 1994

RESEARCH

Approximate Axle LoadsEquipmentEquipment Axle LoadAxle Load

(ton/axle)(ton/axle)

100 hp 2100 hp 2--wheel drive tractorwheel drive tractor 44

200 hp 2200 hp 2--wheel drive tractorwheel drive tractor 88

320 hp 4320 hp 4--wheel drive tractorwheel drive tractor 99

66--row combine (empty)row combine (empty) 1111

1212--row combine (full)row combine (full) 2626

Single axle 27 ydSingle axle 27 yd33 grain cart (full)grain cart (full) 2222

Double dualDouble dual--axle 50 ydaxle 50 yd33 manure tanker manure tanker (full)(full)

35 (rear)35 (rear)

13 (front)13 (front)

RESEARCH

Advice to Manage Soil Compaction

• Only traffic when soil moisture is low!• Adopt conservation agricultural system including cover

crops!• Use controlled traffic systems!• Use smallest vehicle possible for job!• Minimize inflation pressure in radial tires!• Reduce contact pressure by using duals or tracks!

• If necessary to remove effect of traffic, use in-row or bentleg subsoilers that minimally disturb soil surface and only till slightly below depth of compaction!

RESEARCH

Radial Tires

6 psi18 psi

RESEARCH

Stresses (kPa) on Lug at 6 tons/axle

AXLE

FRONT

REARInflation Pressure = 41 kPa Inflation Pressure = 124 kPa

6 psi 18 psi

RESEARCH

Tractive Performance Data

RESEARCH

Goodyear Farm, Specialty, and Terra Tire Goodyear Farm, Specialty, and Terra Tire HandbookHandbook

RESEARCH

Advice to Manage Soil Compaction

• Only traffic when soil moisture is low!• Adopt conservation agricultural system including cover

crops!• Use controlled traffic systems!• Use smallest vehicle possible for job!• Minimize inflation pressure in radial tires!• Reduce contact pressure by using duals or tracks!

• If necessary to remove effect of traffic, use in-row or bentleg subsoilers that minimally disturb soil surface and only till slightly below depth of compaction!

RESEARCH

Benefits of Duals

SingleDuals

Taylor et al., 1975

RESEARCH

Ground Pressure under a Loaded Rubber Belt

Tractor

200

0

Rear Roller

Front Roller

12614 lbs.

Turner et al., 1997.

RESEARCH

Ground Pressure under a Loaded MFWD

Tractor

200

0

Rear TireFront Tire

12656 lbs.

Turner et al., 1997.

RESEARCH

Effects of Duals and Tracks on Soil

Density

1.3

1.35

1.4

1.45

1.5

1.55

1.6

1.65

'10-20 '20-30 '30-40 '40-50

Depth, cm

Dry

Den

sity

, gm

/cc

D-overC65C75D-correctUntraffic

Abu-Hamdeh et al., 1995

RESEARCH

Width of Footprint

Dual Tires Track

RESEARCH

Advice to Manage Soil Compaction

• Only traffic when soil moisture is low!• Adopt conservation agricultural system including cover

crops!• Use controlled traffic systems!• Use smallest vehicle possible for job!• Minimize inflation pressure in radial tires!• Reduce contact pressure by using duals or tracks!

• If necessary to remove effect of traffic, use in-row or bentleg subsoilers that minimally disturb soil surface and only till slightly below depth of compaction!

RESEARCH

Moldboard Plowing

RESEARCH

Strip Till, In-Row Subsoil,

Non-inversion Subsoil

RESEARCH

Straight Shanks

RESEARCH

Bentleg Shanks

RESEARCH

Residue Cover After In-Row Subsoiling

0

20

40

60

80

100

8 12 16

Tillage Depth (in)

Percent Residue Rem

aining (%)

KMC

Paratill

Terramax

RESEARCH

Tillage Effect on Seed Cotton Yield

Tennessee Valley Soil in Northern AL

RESEARCH

Subsoiling Forces

0

1

2

3

4

5

6

9 12 15

Tillage Depth (in)

Draft Force (kN

)

RESEARCH

Completely Subsoiled 5 Years Previous

RESEARCH

Advice To Manage Soil Compaction:

• Only traffic when soil moisture is low!• Adopt conservation agricultural system including cover

crops!• Use controlled traffic systems!• Use smallest vehicle possible for job!• Minimize inflation pressure in radial tires!• Reduce contact pressure by using duals or tracks!

• If necessary to remove effect of traffic, use in-row or bentleg subsoilers that minimally disturb soil surface and only till slightly below depth of compaction!

RESEARCH

Any Questions?

• Randy L. Raper– randy.raper@okstate.edu

– (405) 744-9607