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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
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.