Going Deep:

Aerification of

Compacted Athletic

Fields Beth Guertal

Auburn University, AL

Athletic Field Traffic – Wear and Tear on Turfgrass

Worn turf – Soil compaction

Soil Compaction – where people go

Arrrrg.

Terms for Physical Soil Properties

• Porosity

• Bulk density

• Hydraulic conductivity

• Infiltration

• Water holding capacity

Porosity

• The holes in the soil that are filled with

air or water.

• Pore space is typically around 50% of

the total soil volume.

• We separate pores into two size

classes: macropores and micropores.

Macropores & Micropores – Pore Size Distribution

• Macropores – aid in water drainage,

greater in sandy and well-aggregrated

soils.

• Micropores – water holding capacity,

capillary mvt of water, greater in fine-

textured soils.

• Would like about half micro- and half

macropores in our distribution of pore

sizes.

Mass of soil divided by the volume that soil

occupies

Bulk Density

Bulk density =

Weight of the

oven dry soil

Volume of soil

Bulk density increases with compaction, traffic, clay content.

1.4

1.5

1.6

1.7

1.8

0 10 20 30 40

bu

lk d

en

sit

y (

g c

m-3

)

Relative Level of Traffic

Bulk Density as Affected by Traffic

Jun-97

Jun-00

Hydraulic Conductivity

• Quantity of water that flows through a

column of saturated soil

Infiltration

• Rate at which water enters a soil

time

Infiltra

tion

rate

So, what do we want aerification to do?

• Lessen soil compaction.

• Improve aeration and

drainage.

• Provide a hole to

accommodate topdressing or

amendment.

• Help turf heal and recover.

• Eliminate layered soils.

Questions We Want to Answer about

Aerification of Turfgrass

• How many times a year should we aerify?

• What tines work best?

• Does topdressing help?

• What about soil moisture content?

• Does adding different amendments help?

How Do We Get Answers to Those Questions?

• In-use hybrid bermudagrass

athletic fields (sometimes).

• Put out replicated treatments over

multiple years.

• Collect quantitative data.

• Don’t irritate the football coaches.

Quantitative Data Collection

• Soil resistance as measured by a

penetrometer

• Soil hardness (impact resistance) – Clegg

hammer

• Bulk density

• Porosity

• Infiltration rates

• Saturated hydraulic conductivity

Saturated Hydraulic Conductivity

Constant Head method (Klute and Dirksen,1986)

TGRU 2000

# Aerifications Ksat, in hr-1

4 18 a

1 11 b

Bulk Density as a Function of Treatments Soil bulk density (g cm-3) as affected by aerification treatments,

TGRU

Aerifications bulk density

4 1.66 b

2 1.74 a

1 1.74 a

Clegg Impact Soil Tester

• Measures the hardness of the surface via a weight dropped

from an 18 inch height

• Provides a measure of surface hardness

• Units are Gmax with typical values from 30 to 120. (Tiled

concrete floor: 1280, tiled floor covered with carpet pad: 260)

Rimik CP-20 Cone Penetrometer

• Most accurate of the field hand-held penetrometers

• Provides a measure of resistance over depth

• Takes a while to learn to use well – not as easy as it

looks

y = 0.13x + 1.52 R2 = 0.17

1

1.5

2

2.5

3

3.5

4

4.5

5

1 1.5 2 2.5 3 3.5 4 4.5 5

Rimik soil penetrometer (MPa)

Lang s

oil

penetr

om

ete

r (M

Pa)

83

83.5

84

84.5

85

85.5

86

86.5

0.5 1 1.5 2

Nm

lbs N 1,000 ft-2 month

Torque reading of established Tifway bermudagrass as

affected by N rate, June 2003

Other Quantitative Data

• Clipping Yield

• Root length and mass

• Shoot density

• Measures of slip

• Wear recovery

Aerification frequency?

• Two locations: AU Band field and Auburn

Turf Unit (TGRU)

• ‘Tifway’ hybrid bermudagrass

• RCB with 4 replications

• Deep-tine aerification applied at 1, 2 or 4

times a year (Jan, Apr, July, Oct)

beginning in October 1998

• With and without sand topdressing

Cone resistance as affected by aerification

frequency, AU Band Field; 1st year

Nov 98 July 99 Aug 99

Treatments: = 4 x year = 2 x year = 1 x year

Cone resistance as affected by aerification

frequency, AU Band Field; 2nd year

Nov 99 July 00 Aug 00

Treatments: = 4 x year = 2 x year = 1 x year

Clegg hammer values as affected by aerification

frequency and topdressing, TGRU 1999 - 2000

Date 12/17/00 2/7/00 7/29/00 8/30/00

No. Aerifications

4 102 a (Oct 99) 71 b (Jan 00) 70 b (July 00) 73 a 2 104 a (July 99) 80 a (July 99) 79 a (July 00) 72 a 1 102 a (July 99) 80 a (July 99) 82 a (July 00) 75 a

Topdress

Y 103 a 76 a 80 a 72 a

N 102 a 77 a 79 a 75 a

Conclusions

• Soil resistance unaffected in top inch.

• Effects of aerification typically lasted

~ 1 month.

• Aerification effect was shortened if

traffic was extreme.

• Topdressing never affected soil

resistance or bulk density.

Conclusions - continued

• Treatments had no significant effect

on root mass or thatch

• Aerification treatments increased

hydraulic conductivity significantly for

TGRU in 2000 and 2001

What Tine is Most Effective?

• Two locations: AU Football practice field

and Auburn Turf Unit (TGRU)

• ‘Tifway’ hybrid bermudagrass

• Aerification applied 4 times per year

(May, June, July and August)

• All plots topdressed with sand after

aerification

• Compaction at the Practice Field natural,

roller applied at TGRU

Treatments

• Six treatments: 1) standard depth (4 in.) hollow or

2) solid tine, 3) deep depth (8 in.) hollow or 4)

solid tine, and 5) pull behind aerifier. 6) A non-

aerified control was also included.

• These treatments were arranged in a randomized

block design of 4 (AU Field) or 5 (TGRU)

replications.

• AU Field – 2001 and 2002

• TGRU – 2002 and 2004

• Treatments reapplied in same areas in each year.

Standard tines Deep depth tines

Aerification units and tines

10 cm long, 1.9 cm diam., hollow or solid 20 cm long, 2.2 cm diam., hollow or solid

Pull Behind Aerifier

9 cm long, 1.3 cm diam., hollow

Research Methods - Data

• Soil penetrometer to 24 cm

• 1 and 4 wk after May, June, July trt

• for 6 wks after Aug trt

• Root Mass 2x/year

• Clegg impact readings 2x/month

• 1 and 4 wk after May, June, July trt

• for 6 wks after Aug trt

• Shoot count 2x/year

Week after the August, 2001 aerification

Trt 1

17 Aug

2

24 Aug

3

31 Aug

4

7 Sept

5

14 Sept

6

21 Sept

Clegg reading (gmax)

SRH 44 d 50 c 49 b 41 b 39 b 39 c

SRS 48 bc 57 b 54 ab 47 a 43 ab 42 c

GA60H 46 cd 59 ab 54 ab 46 a 41 ab 42 c

GA60S 53 a 63 a 63 a 51 a 44 a 50 a

Pull Behind 51 ab 60 ab 61 a 47 a 42 ab 44 bc

No

aerification

53 a 61 ab 61 a 51 a 45 a 46 ab

Soil hardness as measured via Clegg

hammer, 2001, AU Practice Field

Soil

Resistance

Over

Depth.

1 wk after

June, 2001

treatments.

AU

Practice

Field

0

15

30

45

60

75

90

105

120

135

150

165

180

195

210

225

240

0 1000 2000 3000 4000 5000 6000

depth

(m

m)

soil resistance (kPa)

SRH

SRS

GA60H

GA60S

Pull behind

0

15

30

45

60

75

90

105

120

135

150

165

180

195

210

225

240

0 500 1000 1500 2000 2500 3000

depth

(m

m)

soil resistance (kPa)

Pull behind

No aerification

Soil

Resistance

Over Depth.

1 wk after

Aug, 2004

treatments.

TGRU

0

15

30

45

60

75

90

105

120

135

150

165

180

195

210

225

240

0 1000 2000 3000 4000 5000 6000

depth

(m

m)

soil resistance (kPa)

SRH No aerification

Soil

Resistance

Over Depth

1 wk after

Aug, 2001

treatments.

AU Practice

Field

X

X

X

X

X

X

XY

XY

XY

XY

X

X

X

X

X

0

15

30

45

60

75

90

105

120

135

150

165

180

195

210

225

240

0 1000 2000 3000 4000 5000 6000

depth

(m

m)

Soil resistance (kPa)

SRH No Aerification

Soil

Resistance

Over Depth.

4 wk after

Aug, 2001

treatments.

AU Practice

Field

X

X

X

X

X

XY

XY

XY

X

X

0

15

30

45

60

75

90

105

120

135

150

165

180

195

210

225

240

0 1000 2000 3000 4000

depth

(m

m)

soil resistance (kPa)

GA60H No Aerification

Soil

Resistance

Over Depth.

1 wk after

Aug, 2002

treatments.

TGRU

XY

XY

XY

X

0

15

30

45

60

75

90

105

120

135

150

165

180

195

210

225

240

0 1000 2000 3000 4000 5000 6000

depth

(m

m)

soil resistance (kPa)

GA60S No aerification

Soil

Resistance

Over

Depth.

6 wk after

Aug, 2002

treatments.

AU

Practice

Field

X

XY

XY

XY

X

X

0

15

30

45

60

75

90

105

120

135

150

165

180

195

210

225

240

0 500 1000 1500 2000 2500 3000

depth

(m

m)

soil resistance (kPa)

GA60S No aerification

Soil

Resistance

Over Depth.

6 wk after

Aug, 2004

treatments

TGRU

X

X

X

X

X

Root Weight and Shoot Density

September 7, 2001

AU Practice Field

Dry weight of

roots

Shoot density

Trt g core-1 number core-1

SRH 3.9 a 101.1 c

SRS 4.4 a 120.7 a

GA60H 5.3 a 105.7 bc

GA60S 6.0 a 99.8 c

Pull Behind 4.8 a 115.3 a

No Aerification 1.6 b 105.9 bc

Conclusions

• Use of deep depth tines (SRH or SRS) often

significantly reduced soil resistance beyond that

measured in other aerification treatments and the non-

aerified control.

• This reduction in soil resistance occurred throughout

much of the 12 inch sampling depth.

• Use of hollow tines (regardless of depth) often produced

a softer turf surface.

• Continued use of the GA60S treatment often produced a

aerification pan at the bottom of the stroke of the tine.

Conclusions

• The pull behind treatment rarely affected soil

softness or resistance beyond that measured

in the non-aerified control.

• Root and shoot density was affected by

aerification treatment, but differences were

not consistent and differed from year-to-year

and location-to-location.

Does Adding Different Amendments Help?

• Many inorganic amendments have appeared in the

turf market in last decade.

• Most of the published research has centered on at-

construction inclusion of the products.

• Far less work on ‘drill and fill’ remediation with the

products.

• None of the work has been done on in-use golf

course putting greens.

Treatments: __________________________________________

Amendment Percentage (by vol)

Sand 100

Profile (illite) 50

Profile 25

Clinolite (zeolite) 50

Clinolite 25

Axis (diatomaceous earth) 50

Axis 25

None 0

__________________________________________

4 replications of each treatment in a RCB design.

• Installed each June

in 2004, 2005 and

2006 in 5 x 10 foot

plots.

• Saugahactee CC,

Auburn, AL.

• Tifdwarf hybrid

bermudagrass

• P. rye overseeding

each Fall.

Mehlich Extractable soil P, K, Ca and Mg, and soil pH – 10 mo. after 3rd

incorporation (April, 2007)

Trt P K Ca Mg pH

---------------------------------- lb/A ------------------------------

Sand 70 a 50 c 602 ab 68 a 6.0 a

Profile (50) 77 a 70 bc 623 ab 77 a 5.9 a

Profile (25) 70 a 60 bc 613 ab 71 a 6.0 a

Clinolite (50) 76 a 100 a 774 a 77 a 6.1 a

Clinolite (25) 80 a 118 a 628 ab 76 a 6.1 a

Axis (50) 74 a 56 c 545 b 63 a 5.8 a

Axis (25) 77 a 62 bc 593 ab 68 a 5.9 a

Nothing 79 a 70 bc 714 ab 81 a 6.0 a

Mehlich Soil-Test Extraction – Results after Year 3

Trt in/hr

Sand 3.0 a

Profile (50) 2.4 a

Profile (25) 2.8 a

Clinolite (50) 2.2 a

Clinolite (25) 3.4 a

Axis (50) 3.4 a

Axis (25) 2.2 a

Nothing 3.4 a

Double-ring infiltration measurements, in the field.

August 30th, 2005. (Two mo. after 2nd application)

Trt Sept 04 Nov 05 Mar 05

inches/hour

Sand 16 a 18 ab 10 ab

Profile (50) 13 a 14 ab 11 ab

Profile (25) 11 a 11 b 7 ab

Clinolite (50) 12 a 23 ab 12 ab

Clinolite (25) 14 a 12 b 14 a

Axis (50) 14 a 24 a 13 ab

Axis (25) 10 a 15 ab 6 b

Nothing 11 a 14 ab 8 ab

Laboratory hydraulic saturated conductivity measurements

The Sum Up

• In heavy traffic more aerification is better.

• Core aerification did not consistently improve

rooting, shoot density or thatch reduction.

• Topdressing did not affect soil compaction or

surface softness.

• Core aerification does help decrease soil

compaction, and (in some cases) soften the turf

surface.

• Hollow cores better than solid.

• Deeper better if compaction is the real problem.

• Effects seems to last 4-6 weeks.