Dealing with Poor Soil Structure and Soil Compaction - Dr. Sjoerd Duiker, Extension Agronomist, Penn State University, from the 2020 Conservation Tillage and Technology Conference, held March 3-4, 2020, Ada, OH, USA.

1. Sjoerd W. Duiker, PhD, CCA
DEALING WITH POOR SOIL STRUCTURE
AND SOIL COMPACTION

2. Causes of Soil Compaction
• Tillage compaction
– Moldboard
– Reduced tillage tools
• Compaction by heavy
equipment traffic
– Surface > 35 psi
– Subsoil >10 ton/axle
• Animal trampling

3. Tillage Compaction
Most
Less
Least

4. Tillage compaction on dairy farms in
southeast Pennsylvania using chisel plow
Source: Penn State Study

5. Compaction by Heavy Farm Equipment

6. Soil Compaction by Animals
Source: Soil Types and Structures Module, DEPI Victoria

7. Workability
&
trafficability

Germination
and root
growth 
Pests and
diseases 
Runoff 
Nutrient and
water uptake

Effects of
Compaction

8. Compaction Effects on
Emergence
Young seedlings will
have trouble emerging
Increased likelihood of
seedling disease and
pest attacks

9. Compaction Restricts Root Growth

10. Compaction Restricts Nutrient
Uptake
• P and K –
relatively
immobile
nutrients in the
soil
• Restricted root
system limits
uptake

11. Compaction Restricts Nutrient
Uptake and Increases Losses
Increased nitrogen losses
due to denitrification,
ammonia volatilization,
reduced infiltration
N-rate (lbs / A)
0 50 100 150
Drymatteryield(tons/A)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
1.30
1.55
bulk density (g / cm3)
Twice N-rate needed to get same yield in compacted soil!

12. Compaction Limits Plant Growth
• Due to restricted
emergence and root
growth
Compacted with 30-ton truck w. road tires
in spring (10 ton axle load), chisel plowed
Compacted Control
Note drought-stressed
corn

13. Compaction Increases Runoff
• Due to decreased
macroporosity and
soil structure
destruction

14. Understand causes of surface vs subsoil compaction

15. Understand how continuous no-till impacts
soil resilience to compaction
Long-
Term
No-Till
2 yrs old
No-Till
1 yr old
No-Till
Strip-Till

16. % water
Bulk
density
(g/cm3)
1.65
1.40 No-Till – high OM
Conventional Till – low OM
Top 5 cm, proctor, Thomas et al., 1996
Continuous No-Till Increases
Soil Resistance to Compaction

17. Soil Structure – ‘Ped’ scale
The arrangement of sand, silt, and clay particles to form larger
aggregates or peds.
• Macropores (large pores) between
aggregates are filled with air in a
moist soil (>0.003 in)
• Mesopores (intermediate pores) are
filled with water in a moist soil and
with air in a dry soil (0.001 – 0.003
in).
• Micropores (very small pores)
between particles that make up soil
aggregates are filled with water in
all but the driest soil (<0.001 in).1/10 inch

18. Undesirable Desirable
Depth(“)
0
2
4
6
8
10
12
14
16
18
20
22
24
Plow pan,
Massive,
platy
structure
Crust - platy
Pulverized
soil
aggregates
Crop
Residue
High OM,
crumb
Platy
structure
(not desired)
Bio pores
Firm, blocky
Aggregates
Middens
Soil Structure – Profile Scale

19. Organic matter decreases bulk density
Hudson, B.D. 1994. Soil organic matter and available water capacity. J. Soil& Water Cons 49:189-194.
SOM
(wt %)
Bulk
Density
(g cm-3)
0 1.56
1 1.50
2 1.44
3 1.38
4 1.32
5 1.26
Texture = silt loam

20. 0
5
10
15
20
25
30
35
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Trafficabledays(#/month)
Well-structured pasture without
plow-pan
Arable land with plowpan
Continuous No-Till Decreases the
Risks of Soil Compaction
Long-term undisturbed soil with active root system has good trafficability

21. Yield decrease due to Compaction
in continuous no-till
27%
14%
10%
Wet summersDry summer
Compaction every spring
when soil was wet with 30 T
manure truck, road tires.
Several passes to cover
every square inch of field

22. Compaction Study in No-Till
Benefit of flotation tires

24. 600 Bu. 20 tons/axle
Covering the plot twice
The benefits of subsoiling tend to
be less on continuous no-till –
lessons from NW Ohio

25. Corn-soybean rotation w/o cover crop. Ohio State Study on Hoytville silty clay loam, tile drained. Study was started
in 1987 – chisel plowing until 2002, then converted to no-till. Compaction (2 times repeated, every inch) was done
with 600 bu graincart. Subsoiling done annually with low-disturbance subsoiler after compaction treatment.
Compaction Compaction Compaction

26. 1.35
1.4
1.45
1.5
1.55
1.6
1.65
w/o Rye with Rye
Early
Late
a a a
b
0-4” depth
Rye effect on bulk density (g/cm3)
in following corn crop in July
Early = early killed cover crop
Late = late killed cover crop
With Rye w/o Rye
Both samples under manure spreader tracks on dairy farm operation
Make Soil Resist Compaction Better with Cover Crops

27. Alfalfa roots – taproots penetrate subsoil
Annual Ryegrass established in
standing corn with interseeder
Make Soil Resist Compaction Better with Cover Crops
and Perennial Deep-Rooted Crops in Rotation

28. Canola roots
penetrate plow pan
in winter when soil
is soft
Soybean roots
follow root
channels created by
canola
Williams and Weil, 2004
Repair Compaction with Cover Crops

29. Alleviate Compaction using Living
Root System 24/7/365
16” deep after 40 days
Courtesy Randall Reeder, OSU
‘Zone-till’ using cover crop
mixtures – radish and legume

30. Cover crop roots to alleviate compaction
1st
year
2nd
year
High Compaction Medium Compaction No Compaction
Tap-rooted species seem to be more effective to alleviate
compaction
• less friction with soil
* Less ‘buckling’
Chen, G., and R.R. Weil. 2010. Penetration of cover crop roots through compacted soil. Plant Soil 331:31-43.

31. Alleviate Compaction by Stimulating
Biological Activity
Worm holes covered with
organic matter
Feed the soil and it will feed you!

32. Nightcrawler burrow
Fresh Cast
Removed midden

33. Conclusions
• Soil Structure critical for
healthy soil
• Soil compaction avoidance is
key – respect soil moisture,
reduce axle load and contact
pressure
• Soil compaction – work with
nature to increase SOM
content, improve soil structure
and stimulate biological
activity, through no-till,
permanent living root system,
deep-rooted crops
• Soil compaction – use tillage
only as a help to let nature

34. Additional Resources
Penn State Fact sheets :
• Avoiding Soil Compaction
• Effects of Soil Compaction
• Diagnosing Soil Compaction using a Penetrometer
• Quick & Easy Worksheet for Assessing Traffic-Induced Soil Compaction Risk
• And more …….