Open Journal of Soil Science, 2013, 3, 225-234
http://dx.doi.org/10.4236/ojss.2013.35027 Published Online September 2013 (http://www.scirp.org/journal/ojss)
225
Comparison of Methods to Remediate Compacted Soils for
Infiltration and Vegetative Establishment
Matthew A. Haynes, Richard A. McLaughlin, Joshua L. Heitman
Department of Soil Science, North Carolina State University, Raleigh, US.
Received June 14th, 2013; revised July 14th, 2013; accepted July 21st, 2013
Copyright © 2013 Matthew A. Haynes et al. This is an open access article distributed under the Creative Commons Attribution Li-
cense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
ABSTRACT
The process of constructing roads and buildings usually involves the removal of topsoil and grading of the subsoil fol-
lowed by a variety of activities using heavy equipment. This presents multiple challenges in attempts to establish vege-
tation on these areas: low nutrient soils with little organic matter, high bulk densities, and low infiltration rates. The
goals of this preliminary study were to quantify the impacts of soil compaction remediation methods on infiltration,
runoff water quality, and vegetation establishment. The objectives were to measure: 1) steady state infiltration rate (IR);
2) quantity and quality of storm water runoff; and 3) ground cover, biomass production, and rooting depth of vegetation
during early establishment. We evaluated four treatments: a compacted soil (C), a compacted soil with core aeration (A),
a compacted soil with deep (20 - 30 cm) tillage (DT), and a compacted soil with deep tillage and incorporated compost
(CT). Sites 1 and 2 received C, A and DT treatments and Site 3 received only DT and CT treatments. At Site 1, runoff
from natural rainfall events was collected in plastic tubs at the bottom of each 2 × 1 m plot, and samples were measured
for volume and sediment. Infiltration rates were determined using a Cornell Sprinkle Infiltrometer at all three sites. At
Site 1, the A treatment had a higher erosion rate during two of four rain events and higher runoff volume during three of
four rain events, when compared to C and DT. However, the aerator was only able to penetrate 1 - 2 cm due to the com-
pacted soil. Average event runoff ranged from 0 to 22% (0 - 9.3 mm), 10 to 60% (1.9 - 26.2 mm), and 0 to 3.5% (0 - 1.1
mm) of the total rainfall for C, A, and DT, respectively. There was no difference between C and A for vegetative bio-
mass and IR, but both biomass and IR were greater in the DT plots. Treatment DT had an average IR of 15 cm·hr−1,
compared to 0.16 and 0.21 cm·hr−1 for C and A, respectively. Roots were much more abundant at the 20 - 50 cm depths
with DT. At Site 2, there were no significant differences in IR, with many values too low to be measured with the infil-
trometer. Vegetative cover also did not differ between the three treatments due to poor (16% - 22% cover) grass estab-
lishment. Infiltration rates at Site 3 were measured immediately after tillage and were 10× those at Site 2, measured 2
months after tillage, but DT and CT values were not different. The results suggest that deep tillage prior to seeding
could maximize long-term vegetation growth and provide areas of high infiltration to minimize post-construction
stormwater discharges, as long as vigorous vegetation can be established quickly.
Keywords: Compaction; Infiltration; Tillage; Root Growth; Construction Sites
1. Introduction
Soil compaction increases storm water runoff, which
carries sediment and other harmful pollutants into water
bodies. Soil on construction sites may be compacted for
structural strength or inadvertently compacted by heavy
machinery [1]. Such compaction can also result in a de-
crease in vegetative stand [2] and can inhibit root growth,
reduce nutrient uptake, and increase plant disease [3].
Heavy axle loads found on construction equipment,
such as backhoes, dump trucks, and pickup trucks, can
increase bulk density substantially [1]. In sandy soils in
Florida (USA), Gregory et al. found bulk density was
consistently higher inside construction areas compared to
outside areas, which led to root limiting densities aver-
aging 1.94 Mg·m−3, with the untrafficked controls aver-
aging 1.74 Mg·m−3 [1]. Land grading activities on clay
soils of Denmark have been demonstrated to compact
soil to 1.8 - 2.0 Mg·m−3 [4].
Infiltration rates are significantly reduced by compac-
tion due to the destruction of soil structure, resulting in
increased surface runoff. In the Florida study, infiltration
rates were decreased 70% - 99% under even the lowest

Comparison of Methods to Remediate Compacted Soils for Infiltration and Vegetative Establishment 226
of different compaction treatments simulating wheel traf-
fic [1]. Construction activity in Alabama (USA) reduced
mean infiltration rates in sandy soils from 381 mm·h−1 to
46 mm·hr−1 and in clayey soils from 168 to 1.0 mm·h−1
[5]. Fullen reported infiltration rates in tractor tire ruts
were 0.13 mm·h−1 compared to 343 mm·h−1 in adjacent
pastures, resulting in ponding and higher runoff rates
containing sediment concentrations of 4000 - 6000
mg· L −1 [6].
Deep tillage is a common management practice used
in agronomic settings to improve infiltration, aeration,
and rooting depth [7]. Traffic pans, dense layers formed
in the subsoil where equipment frequently passes, can be
broken up by deep tillage to allow roots to penetrate
deeper for water and nutrients. Varsa et al. found that
35% of corn roots were below 60 cm in deep (90 cm)
tilled plots compared to only 5% in reduced and no-till
treatments in silt loam soil [8]. Grain yield was always
highest in the deepest tillage treatment up to four years
afterward. In a wheat-soybean double-crop system, Bus-
scher et al. also found yield for both crops was in-
creased significantly under deep tilled treatments on a
loamy sand with a compacted plow layer [9].
In established residential lawns, Legg et al. found
some evidence that infiltration can improve somewhat
over many decades, but in the first several years new
lawns had relatively high runoff rates [10]. Core aeration
is used in turf management as a way to improve aeration
and infiltration without full tillage. Hollow tine aeration
involves pulling a core out of the soil while solid tines
penetrate the soil to create a void; the former may be
more effective in promoting infiltration in turf [11]. Core
aeration followed by sand topdressing increased infiltra-
tion rates up to 211% in golf course settings, with pene-
tration of the thatch layer being one explanation [12,13].
Aeration treatment of compacted loamy sand bentgrass
green was found to increase total porosity when using
hollow and solid tine aeration, but no improvement in
hydraulic conductivity or root growth was found [14]. In
contrast, other studies demonstrated adverse effects of
core aeration. Bulk density was found to increase as the
number of annual aerifications increased and total sus-
pended solid concentrations in runoff were up to 30%
higher on aerated sites due to surface disturbance [15].
Higher P concentrations following aeration were also
found in runoff due to rainfall impact and more sediment
being transported by stormwater runoff [16]. Aeration by
cutting slits in the soil is another approach, but Shah et al.
did not find any reduction in runoff nor improvement in
forage production [17].
The purpose of this study was to determine the effec-
tiveness of two approaches, deep tillage and core aeration,
for remediating compacted soils typical on construction
sites. Objectives were to determine if hollow tine aera-
tion and deep tillage were methods that could be used to
1) alleviate soil compaction, 2) improve and maintain
infiltration rates, 3) improve grass establishment, and 4)
decrease stormwater runoff and erosion. This was a pre-
liminary, short-term study to investigate the concepts and
potential for this approach to improve infiltration and
grass growth in compacted soils.
2. Materials and Methods
2.1. Site Description
The study was conducted at the North Carolina State
University Lake Wheeler Field Laboratory in Raleigh,
N.C. The climate is humid sub-tropical with evenly dis-
tributed precipitation throughout the year. Site 1 was
located at the top of a fill slope made up of excess sub-
soil materials from nearby construction sites. The site
was selected because it had regular vehicular traffic, ex-
pected to result in compaction. The area has a relatively
uniform 3% slope (Table 1). Site 2 was approximately 6
m from an excavation and approximately 100 m uphill
from Site 1. It consisted of fill material from the excava-
tion. Site 3 was located directly adjacent to Site 2 and
exhibited similar characteristics. The area for all three
sites is mapped as a Cecil sandy loam (fine, kaolinitic,
thermic Typic Kanhapludult) derived from residuum of
felsic bedrock [18]. Only Sites 2 and 3 had subsoil mate-
rial from the experimental site, but the fill material at Site
1 was similar in appearance. All three sites were chosen
due to the presence of subsoil material at the surface
similar to construction sites. There was vegetation pre-
sent at each of the three sites before the study was con-
ducted, dominated by a mixture of Bermuda grass
(Cynodon dactylon) and large crabgrass (Digitaria san-
guinalis), with several other weeds.
2.2. Plot Setup
Preliminary bulk density samples were taken at locations
around each site in order to determine the most uniform
and compacted areas for plot establishment. Once the
area was chosen, the plots were further compacted using
a pickup truck with a gross weight of 3084 kg and a
wheel pressure estimated at 1689 kPa. Flags were placed
Table 1. General summary of site characteristics.
Site 1 Site 2 Site 3
Planting DateApril 27, 2009October 22, 2009 January 26, 2009
Slope 3% 0.5% 0.5%
Treatments1C, A, and DTC, A, and DT CT and DT
Soil Texture2CL, SCL, SLCL, SCL, C C
1Compacted (C), core aerated (A), deep tillage (DT), deep tillage with com-
post amendment (CT); 2According to USDA categories clay loam (CL),
sandy clay loam (SCL), sandy loam (SL), and clay (C).

Comparison of Methods to Remediate Compacted Soils for Infiltration and Vegetative Establishment 227
20.3 cm apart, which was approximately the tire width of
the pickup, and the truck was driven back and forth, re-
peatedly, until the entire area of each plot had at least 10
passes. Remaining vegetation that was not killed during
the compaction treatment was killed using a glyphosate
herbicide application in order to have an unvegetated soil
surface similar to a construction site. Just prior to plot
installation, the dead vegetation was removed by running
a string trimmer back and forth across the surface of soil.
For Site 1, once the area was selected based on the
bulk density sampling, individual plots were flagged 2 m
in length parallel to the slope and 1 m wide. Fifteen ad-
jacent plots were installed with 0.15 m buffers to allow
for access without impacting the plots (Figure 1). The 15
plots were divided into 5 blocks of 3 plots and the treat-
ments were assigned randomly within each block. To
isolate each plot from outside runoff, plastic garden edg-
ing (10 cm high) was installed on all sides by driving the
siding 3 - 5 cm into the soil. At the lower border, a gap
was left into which a 10 cm pipe was installed. Gaps be-
tween the pipe and the edging, as well as between edging
pieces, were filled using expandable foam (Great Stuff,
DOW Chemical Company, Wilmington, IL, USA). Run-
off produced by rain events exited the plot through the
pipe and into a 68 L plastic tub in an excavated ditch
downhill from the plots. Assuming 100% runoff, the tub
size allowed the capture of all runoff from a 0.5-year,
24-hour storm in Raleigh N.C., which is 36.6 mm
(NOAA Atlas 14). A sheet of plastic was draped over the
pipe and the tub to exclude precipitation. Water which
accumulated in the ditch from adjacent areas was re-
moved using a sump pump with a float switch. Site 2 was
established to replicate the treatments at Site 1 on a fairly
uniform area of fill from an adjacent excavation, but only
to collect infiltration and vegetation establishment data.
The plots were smaller at 0.6 × 1.2 m and were not bor-
dered with plastic barriers since runoff was not being
collected. Poor grass stands at Site 2 after several months
led to the establishment of Site 3 on an adjacent area to
evaluate only the DT treatment with and without com-
post. Again, the grass stand was very sparse due to the
weather, so only the initial infiltration data are included
to compare to the adjacent Site 2 data.
2.3. Plot Setup
Three treatments were included: deep tillage (DT), core
aeration (A), and a control (C), which received no treat-
ment. There were 5 replications for each of the three
treatments. Each plot was wetted with a hose for 1 min
and allowed to dry 1 min prior to DT or A. This proce-
dure was repeated twice in order to moisten the surface
soil, which was very dry and difficult for the tiller and
aerator to penetrate.
The DT treatment was performed using a rear-tine
Figure 1. Site 1 immediately after installation. Plastic sheet-
ing over runoff containers kept out rain.
tiller (Troy-Bilt, Cleveland, OH, USA) to till the soil to a
25 - 30 cm depth. Due to the heavy compaction at Site 1,
a backhoe was used to loosen the soil initially in order to
allow the tiller to penetrate. The tiller was run across the
plots in two directions until the desired depth was
achieved. The A plots were plugged using a walk-behind
hollow tine aerator (Ryan, Johnson Creek, WI, USA).
Each of the A plots received ten passes until the plots
were thoroughly treated. We observed very shallow pene-
tration due to the compaction. The plugs were left in
place with no further treatment. The C plots received no
treatments after compaction, but were watered in the
same manner to insure that all plots were installed under
similar moisture conditions.
At site 3 two treatments were included: DT and deep
tillage with a compost amendment (CT). There were 3
replications of each treatment randomly assigned to plots.
Tillage was to approximately 25 cm depth using the same
equipment as the previous sites. As for Site 2, no back-
hoe was used to break up the soil on this site because the
soil moisture condition allowed the surface to be broken
up using only the tiller. The compost was a mushroom
blend (Old Castle Lawn & Garden Inc, Atlanta, GA),
applied at a recommended 0.02 m3 1000 m−2 [19] and
tilled in to the full depth of 25 cm.
Each plot received the fertilizer, lime, and seed mixes
recommended by the North Carolina Department of
Transportation for their construction sites [20]. Fertilizer
(10-20-20) was applied at a rate of 560 kg·ha−1 and pul-
verized dolomitic limestone at a rate of 3364 kg·ha−1.
Fertilizer and lime were both applied after the DT and A
treatments. They were raked into the DT plots on Sites 1
and 2 but were surface applied to the C and A plots to
avoid disturbance. The fertilizer and lime were tilled in at
Site 3. A grass seed mix of tall fescue, centipede, and
Bermuda grass (hulled) was applied at 56, 11, and 28
kg·ha−1, respectively, for Site 1 on April 27, 2009. Sites 2

Comparison of Methods to Remediate Compacted Soils for Infiltration and Vegetative Establishment 228
and 3 had the same grass seed mix except that the Ber-
muda grass was added at 39 kg·ha−1 due to colder plant-
ing dates. Site 2 was planted on October 22, 2009 and
Site 3 on January 26, 2010. All seed was applied directly
after fertilizer and lime application. Once seeded, straw
was applied at 3.7 Mg·ha−1 and fastened down with jute
netting to avoid seed loss due to raindrop impact as well
as to keep the straw in place. After all inputs were added,
each plot was wetted for 45 sec using a garden hose to
insure that each treatment had similar moisture condi-
tions at the beginning of the experiment.
2.4. Data Collection and Analysis
Bulk density was measured using an AMS 6.4 cm di-
ameter soil core sampler (American Falls, ID, USA).
Samples were taken from the top 2.5 - 12.5 cm of the
profile with the top 2.5 cm being discarded. As men-
tioned above, initial samples were taken in order to iden-
tify an area for all sites. Samples were then taken within
each plot immediately before each treatment application.
Subsequent bulk density samples were taken again at 7,
11, and 3 weeks after treatment for Sites 1, 2, and 3, re-
spectively. A single core was taken from each plot and
dried at 103˚C - 105˚C for bulk density determination.
Particle size analysis was also performed on each bulk
density sample using the hydrometer method [21].
After each of the first four rain events at Site 1,
polyacrylamide (PAM; 2 - 3 mg·L−1) was mixed to the
water in each tub in order to settle the suspended
sediment. Depending on the size of the sample, this was
done either in the lab or in the field. The supernatant was
decanted from the container and the volume was
measured. The sediment remaining was oven dried at
103˚C - 105˚C for 24 h and weighed. Some samples did
not fully settle after flocculation, and these were sub-
sampled and analyzed for total suspended solids (TSS)
by filtration [22]. The TSS values were converted to
sediment loss and added to the amount of sediment
settled using PAM to determine the total sediment loss
from each plot.
Total stormwater runoff was determined by collecting
and measuring all runoff in the tubs after each storm
event. Rainfall amounts were obtained from the NC
Climate Office for the Lake Wheeler Road Field
Laboratory weather station (http://www.nc-climate.ncsu.
edu/cronos/search.php), located approximately 1.6 km
from the plots.
Steady state infiltration rates (IR) were determined
using both a Cornell Sprinkle Infiltrometer (Cornell
University, Ithaca, NY) and an overhead sprinkler to
simulate rainfall at Site 1 [23]. Only the infiltrometer was
used to determine IR at Sites 2 and 3. The infiltrometer
was used 11 weeks, 7 weeks, and 1 day after planting at
Sites 1, 2, and 3, respectively. The infiltrometer was
calibrated to provide a 250 - 300 mm·h−1 rainfall (9.8 -
11.8 in h−1) [24]. The infiltrometer was allowed to run at
a constant rainfall rate until the runoff rate reached
steady state. The IR was calculated as the difference be-
tween the rainfall rate and the runoff rate at steady state.
At Site 1, 10 weeks after plot establishment, rainfall
was simulated by suspending a single Fulljet 1/2HH-
SS50WSQ nozzle 3 m above two adjacent plots simulta-
neously, and spraying at a pressure of 42 kPa to provide
approximately 100 mm·h−1 rainfall [25]. At the start of
each simulation, the actual rainfall rate was determined
by placing five 300 cm3 containers, evenly spaced within
each plot, and collecting irrigation for 5 minutes. The
amount of water in each container was then measured
and averaged to determine the rainfall rate. The simulator
was run for at least 45 min or until steady state runoff
was achieved. Runoff was collected from the PVC pipes
for 20 sec every 3 min and the volume measured in a
graduated cylinder. The IR was determined as the dif-
ference between the rainfall rate and the runoff rate at
steady state.
Above ground biomass (Site 1 only) and cover sam-
ples were collected 6 weeks (Site 1) and 4 months (Site 2)
after planting. The difference was due to the rapid
growth in the April-May period at Site 1 and slow
growth in the November-February period at Site 2.
Above ground biomass was measured by randomly se-
lecting three 20 × 20 cm squares in a grid placed in each
plot and removing all vegetation in each of the squares
using scissors. The vegetation from each square was
combined, oven dried at 103˚C - 105˚C for 24 h, and
weighed. At the same time that biomass samples were
taken, visual estimations of percent ground cover were
made independently by four people to determine the
above ground vegetative coverage of each plot. The es-
timates from each person were averaged for each plot.
For measuring root density and depth (Site 1 only), a
modified profile wall method was used [26]. Sixteen
months after plot establishment, pits were dug in each
plot down to a depth of approximately 1 m using a
backhoe. A pressure washer was used to wash the face of
the pit to remove loose soil and expose the roots. A 50 ×
50 cm grid, which consisted of 100 5 × 5 cm squares,
was placed level with the soil surface and fastened to the
profile wall using sod staples at the top of the grid. The
number of roots in each of the 50 squares was counted
and averaged at each 5 cm depth increment. The results
were categorized using a rating system with four levels
based on approximate root density (Table 2). The rating
system was chosen due to the fibrous rooting system of
the vegetation planted; this method allowed more con-
sistency than individual root counts. SAS Software was
used to perform all statistical analyses (SAS version 9.1,
SAS Institute, Cary, NC). Analysis of Variance (ANO-

Comparison of Methods to Remediate Compacted Soils for Infiltration and Vegetative Establishment 229
Table 2. Root density rating system for modified profile
wall method of analyzing roots.
Number of roots per grid square Rating
0 0
1 - 10 1
11 - 30 2
31+ 3
VA) was performed on all data to analyze main effects
and Tukey’s Least Significant Difference (LSD) was
used to separate treatments. Error rates were controlled at
α = 0.05.
3. Results
3.1. Bulk Density
At Site 1, the depths of 5 plugs in each plot were meas-
ured and averaged only 1.5 - 2 cm, matching our obser-
vation of poor penetration. This is important to note in
considering our results. Furthermore, it suggests that
much heavier equipment may be necessary to attempt
core aeration on highly compacted soils. The average
bulk density in the compacted area was 1.6 g·cm−3 and
there were no significant differences in bulk density
among plots (Table 3; p = 0.48). The bulk density taken
at 7 weeks after treatment was unchanged in the C and A
plots but was significantly reduced in the DT treatment.
At Site 2, bulk densities were similar to Site 1 and there
were no differences in bulk densities prior to treatment.
After 11 weeks, the DT plots had a significantly lower
average bulk density, with the averages decreasing from
1.6 to 1.4 g·cm−3 (p = 0.001), just as at Site 1. The C and
A treatments showed no differences in bulk density from
their pre-treatment values. The average pre-treatment
bulk densities of Site 3 were similar for the CT plots and
the DT plots. Five weeks after tillage, the bulk densities
of both treatments were lower than their pretreatment
values, but these differences were not statistically sig-
nificant due to variability. The CT plots were also not
significantly different from the DT plots after five weeks,
indicating that the compost did not affect bulk density
more than tillage alone. The decreased bulk densities of
the DT plots in all three sites are consistent with other
studies comparing different levels of tillage, with con-
ventional or deep tillage resulting in the lowest values
[27,28].
3.2. Infiltration
At Site 1, the overhead sprinkler method produced simi-
lar rates of simulated rainfall in each treatment with no
significant differences (p = 0.69). In these tests, the av-
erage IR for the C and A treatments were similar and
significantly lower that of the DT treatment (Table 4).
Table 3. Average pre- and post-treatment bulk density at
each site. Means of pre- and post-treatment measurements
at each site followed by the same letter are not significantly
different (p = 0.05).
Bulk Density (g·cm−3)
Site 1 Site 2 Site 3
Treatment Pre Post Pre Post Pre Post
Control 1.6a 1.6a 1.6a 1.6a na na
Aerated 1.6a 1.6a 1.7a 1.7a na na
Tilled 1.6a1.4b 1.6a 1.4b 1.6a 1.3a
Compost + Tilled na na na na 1.5a1.3a
Table 4. Infiltration rates (IR) measured using two simula-
tion methods at Site 1. Means followed by the same letter
within a column are not significantly different (p = 0.05).
Overhead sprinkler Infiltrometer
TreatmentRainfall RateIR Rainfall Rate IR
(cm·h−1)
Control9.75a 2.70a 24.0a 0.16a
Aerated10.62a 2.22a 23.0a 0.21a
Tilled 10.57a 5.67b 28.2a 14.8b
The DT IR was very similar to highest rates found else-
where on home lawns for 65 - 70 year old lawns under
simulated rainfall and double-ring infiltrometer tests [10,
29]. The infiltrometer method produced rainfall rates
more than 2X that of the sprinkler, which may have in-
fluenced differences among treatments. Similar to the
sprinkler method, there were no differences in IR be-
tween the C and A plots, averaging 0.16 and 0.21 cm·hr−1,
respectively. Infiltration was nearly two orders of mag-
nitude higher in the DT plots (14.4 cm·hr−1; p = 0.002).
The average IR for the infiltrometer was much lower
for C and A treatments and higher for the DT treatment
compared to the overhead sprinkler method (Table 4).
Raindrop impact is more intense under the overhead
sprinkler method, where the simulated rainfall is falling
from 3 m, compared to the infiltrometer method, with
only a 5 cm drop. The higher impact can dislodge soil
particles and cause them to re-deposit to form surface
crusts, and the looser DT soil would have been more
susceptible. These surface seals can substantially lower
IR because of their low hydraulic conductivities [30-32].
Also, the overhead sprinkler testing was conducted six
weeks after planting and the infiltrometer testing two
weeks later, so vegetative cover may have slightly im-
proved. This does not, however, explain the lower values
observed for the C and A treatments when comparing
infiltrometer measurements to the values obtained with
the overhead sprinkler. In general, because of differences
in the two methods, comparison between them should
probably be limited. Instead, each should be viewed

Comparison of Methods to Remediate Compacted Soils for Infiltration and Vegetative Establishment 230
separately as a comparison between treatments, both in-
dicating similar trends. For the four natural events, with
much lower peak intensities of 3.6 - 29 mm·h−1, the infil-
tration rate as a fraction of input was as high as 98% for
the DT compared to 68% and 84% for the A and C
treatments, respectively.
Overall, the DT treatment resulted in the lowest bulk
densities and the highest IR using both infiltration meth-
ods. The A treatment did not result in any measureable
change in bulk density or IR relative to the control. For
this particular site, soils with bulk densities above ap-
proximately 1.4 g·cm−3 had greatly reduced IR using the
infiltrometer method (Figure 2). Texture varied substan-
tially from the first to the last plot, ranging from clay
loam to sandy loam, but there were no correlations be-
tween any of the measured variables and sand or clay
content (data not shown).
At Site 2, IR was measured by infiltrometer approxi-
mately seven weeks after plot establishment as we waited
for the vegetation to become established during a cold,
wet period. There were no significant differences in IR
for any of the treatments at this site (p = 0.56, Table 5).
Infiltration was too low to be read by the infiltrometer on
10 of the 15 plots. Compared to Site 1, IR was lower for
the C and A treatments and much lower (25X) for the DT
treatment. Within the site, the maximum observed IR in
the DT plots was more than 3X the C and A plots, but the
variability was too great to detect any significant differ-
ence in the means, probably due to the very low infiltra-
tion rates. The lower IR at Site 2 relative to Site 1 may
have been the result of poor vegetative establishment and
poor root growth (see below), which might have allowed
the soil to settle more than at Site 1. The sparse vegeta-
tion also left the soil more exposed than at Site 1, making
it more susceptible to raindrop impact and surface crust-
ing. Site 2 received precipitation 6 out of 10 days after
treatment, with the largest being a 12.7 mm storm with a
peak intensity of 5 mm·h−1, on the 10th day. The site had
very little slope for erosion to occur, but these rain events
could have caused impermeable surface layers that may
Figure 2. Re lationship betw een infiltration and bulk density
at Site 1.
have inhibited germination and root penetration. Site 2
IR measurements were taken seven weeks (early De-
cember) after installation to allow the vegetation to be-
come established, but unusually cold temperatures during
the period prevented significant plant growth. During this
period, there were a total of 23 storms with 210 mm of
precipitation, and with the plots essentially bare consid-
erable raindrop impact and crusting could have occurred.
Texture ranged from clay loam to clay across the plots at
Site 2. As expected, there were no significant relation-
ships between IR and either bulk density or clay content
due to the majority of the plots having no measureable
infiltration.
Site 3 was installed adjacent to Site 2, primarily to de-
termine the IR immediately after tillage instead of wait-
ing for vegetation to become established, but also to in-
vestigate the effect of compost addition on initial IR.
There were no differences in IR detected between DT
and CT (p = 0.52, Table 5). The numerical increase in IR
with compost could be attributed to higher surface
roughness generated by the incorporation of compost,
which delays runoff [33]. The irrigation rate on Site 3
was adjusted to more than 2X that used at Site 2, due to
the longer time it was taking for runoff to occur since IRs
were substantially higher. The main difference between
the two sites was that IR measurement was right after
tillage on Site 3, while measurements on Site 2 were
taken seven weeks after treatment to allow vegetation
establishment. Presumably Site 2 had similar, high infil-
tration rates right after tillage but it was greatly reduced
in just seven weeks of frequent rainfall and little vegeta-
tive growth. Heavy and intense rainfall immediately after
establishment of Site 2 may have led to surface sealing
and crusting as well.
3.3. Vegetative Establishment
The vegetative cover of the C, A, and DT treatments
were 65, 62, and 85%, respectively, after six weeks of
growth at Site 1 (Figure 3, Table 6). There were no sig-
Table 5. Infiltration rates (IR) measured by the Cornell
Sprinkle Infiltrometer method at Sites 2 and 3. Means fol-
lowed by the same letter within a column and site are not
significantly different (p = 0.05)
Site 2 Site 3
Treatment Rainfall Rate IR Rainfall RateIR
(cm·h−1)
Control 28.3a 0.10b na na
Aerated 23.9a 0.18b na na
Tilled 21.9a 0.60b 57.5a 6.4b
Compost + Tilledna na 58.5b 10.1b

Comparison of Methods to Remediate Compacted Soils for Infiltration and Vegetative Establishment 231
nificant differences (p = 0.06), although DT was much
higher numerically than the other treatments. A similar
trend was found for biomass, but in this case the differ-
ences were significant. Both cover estimates and above
ground biomass were also correlated with bulk density at
Site 1 (data not shown). Balbuena et al. also found sig-
nificant (58%) reduction in grass production when bulk
density was increased after 10 passes with a tractor [2].
Cover was the only vegetative measurement taken on
Site 2. More than three months after establishment, there
were no differences in cover estimates between the
treatments; the mean value across treatments was much
lower than at Site 1 (Table 6). This is likely due to the
time of year (November - February) and surface crusting
at Site 2. There was no correlation between vegetative
cover and clay content for either site (data not shown),
suggesting that texture was not the driving variable con-
trolling vegetative growth.
Even with limitations observed at Site 2, our data sug-
gest that IR and vegetative establishment are improved
with the higher porosity and lower bulk density achieved
through deep tillage. Environmental conditions were
better for grass establishment when we installed Site 1
due to warm weather and relatively gentle rains, which
may have been at least partly responsible for maintaining
the reduced bulk density and higher IR, compared to Site
2.
There were no differences in rooting density among
Figure 3. Example of vegetation growth in compacted (left)
and deep-tilled (right) plots at Site 1.
Table 6. Vegetation establishment at Sites 1 and 2. Numbers
followed by the same letter within a column are not signifi-
cantly different (p = 0.05).
Site 1 Site 2
Treatment Cover (%) Biomass (kg·ha−1) Cover (%)
Control 65a 32.1a 22a
Aerated 62a 31.3a 16a
Tillage 85a 88.7b 23a
the three treatments for the upper 15 cm of the soil pro-
file on Site 1 (Table 7). The rooting systems of the C and
A treatments were very dense and had numerous short
roots; whereas, the DT treatments had longer roots that
extended deeper through the profile. Below 15 cm, the
DT plots had higher average root densities than the C and
A, and this persisted down to the 50 cm depth. Aeration
did not improve root densities at depth, which is not sur-
prising since the penetration was <2 cm. Tillage tools,
including chisel, moldboard, and paraplow systems, all
have been demonstrated to reduce soil bulk density and
penetration resistance to the depth of tillage when com-
pared to a no-till system [34].
3.4. Stormwater Runoff
The total amount of precipitation for storm 1, seven days
after plot establishment, was 19.6 mm with a peak inten-
sity of 3.6 mm·h−1 (Figure 4). The average runoff depths
of the C, A, and DT plots were 1.0, 1.9, and 0.6 mm,
respectively. This indicates that on average, more than
90% of precipitation infiltrated on all three treatments.
There were no significant differences in the amount of
runoff for any of the treatments. The second storm oc-
curred 13 days after the first storm and was much more
intense, with a total precipitation of 43.7 mm and a peak
intensity of 29 mm·h−1. The average amounts of runoff
were 7.5, 26.2, and 0 mm, which equates to 17.2, 60.5,
and 0% of the total rainfall for the C, A, and DT plots,
respectively. The A treatment produced significantly
more runoff than the C and DT treatments (p = < 0.0001),
suggesting that the treatment may have actually com-
pacted the soils further. There were no differences be-
tween the C and DT treatments. The total precipitation
for storm 3, occurring 12 days after the second storm,
was 11.68 mm with a peak intensity of 11.2 mm·h−1. The
Table 7. Root density ratings for each treatment at Site 1.
Numbers followed by different letters within each depth
level are significantly different (p < 0.05).
Average Rating
Depth (cm)Control Aerated Tilled P-value
5 3.0a 3.0a 2.8a 0.41
10 2.6a 2.8a 2.8a 0.75
15 2.1a 2.1a 2.6a 0.16
20 1.4a 1.3a 2.6b 0.0002
25 0.9a 0.7a 2.4b <0.0001
30 0.4a 0.4a 1.7b 0.001
35 0.4a 0.4a 1.1b 0.008
40 0.2a 0.3a 0.7b 0.02
45 0.2a 0.3a 0.7b 0.02
50 0.2a 0.2a 0.6b 0.02

Comparison of Methods to Remediate Compacted Soils for Infiltration and Vegetative Establishment 232
Figure 4. Runoff from Site 1 plots during the first four rain
events after establishment.
average runoff depths for the C, A, and DT plots were
2.5, 2.1, and 0.2 mm, respectively. As for Storm 1, the
runoff rates were very low due to the low intensity (3.6
mm·h−1 peak) and, on average, approximately 80% of the
total precipitation on all treatments infiltrated. There
were no significant differences between treatments for
this storm event. Storm 4 occurred seven days after
Storm 3, with a total of 33.3 mm of precipitation and a
peak intensity of 13.5 mm·h−1. The average runoff depths
for the C, A, and DT treatments were 7.8, 6.0, and 1.1
mm, which equate to 23.7, 18.3, and 3.5% of the total
rainfall, respectively, but the differences were not sig-
nificant.
For the four natural rainfall events monitored in the 39
days after plot establishment, the A treatment produced
the highest total runoff in 2 of 4 storm events when
compared to the DT treatments. The total runoff for all
four storms was significantly greater in the A treatment
compared to DT. Even though bulk density was un-
changed in the A treatment there could have been some
further compaction at the surface caused by the aerator,
which increased stormwater runoff volumes. There were
no differences in runoff for any storm event between the
C and DT plots due to variability, although the DT plots
were numerically lower for every storm. Runoff volume
in the C and A treatments was the greatest when the peak
intensity was the highest (storm 2) and lowest for low
peak intensity rainfalls (storm 1). The DT treatment pro-
duced the lowest amounts of runoff and peak intensity
did not appear to have any effect on runoff responses in
these four storms.
Compared to the C and DT plots, sediment losses were
significantly greater for the aerated plots during the in-
tense second storm event (Figure 5). The total sediment
loss from the A treatment was 5-10X that of the others,
due to the combination of high runoff rates with the
slightly loosened soil from the hollow tines. In our tests
on highly compacted soils, the aeration treatment ap-
peared to have no beneficial effects and it increased soil
Figure 5. Sediment loss from Site 1 plots during the first
four rain events after establishment.
losses compared to no treatment of the compacted soil.
However, the aeration equipment we used could only
penetrate the compacted soil 1 - 2 cm and we did not
attempt to remove or break up the cores as is commonly
practiced on grassed areas, so our results may not be
representative.
4. Conclusion
Soil compaction clearly has negative impacts on storm-
water runoff, infiltration, and vegetative establishment.
This study suggests that the combination of tillage and
rapid vegetation establishment can greatly reduce runoff
from treated areas. However, the importance of vigorous
vegetation appears to be critical to the success of deep
tillage over time, as demonstrated by the failure of our
second site in maintaining high IR due to very poor grass
growth during a cold, wet period in the winter. The grass
established under more ideal conditions responded to
deep tillage with significantly more roots below 15 cm,
suggesting this as an important factor in maintaining in-
filtration rates. While we only measured the effects dur-
ing the first growing season, the relatively high infiltra-
tion rate of almost 15 cm·h−1 shows promise in reducing
post-construction stormwater runoff from vegetated ar-
eas.
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