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EFFECT OF FOUR CREEPING BENTGRASS CULTIVARS AND QUANTIFIED
FOOT TRAFFIC ON THE INVASION OF ANNUAL BLUEGRASS INTO A
PUTTING GREEN
By

Aaron D. Hathaway

A THESIS
Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of
MASTER OF SCIENCE
Department of Crop and Soil Sciences

2006

ABSTRACT
EFFECT OF FOUR CREEPTNG BENTGRASS CULTIVARS AND QUANTIFIED
FOOT TRAFFIC ON THE INVASION OF ANNUAL BLUEGRASS INTO A
PUTTING GREEN
By
Aaron D. Hathaway
Research was conducted to determine the relationship between creeping bentgrass
shoot density and the invasion of annual bluegrass (Poa annua L.) and determine the
effect of foot traffic on annual bluegrass invasion. Putting green plots were seeded with
Penncross, Providence, Penn G-2, and Bengal on 30 May, 2003. Annual bluegrass
centers were counted in each plot seven times from 23 September, 2003 to 28 September,
2004. Creeping bentgrass shoot unit area'1 were measured once in October, 2004. An
observational study was conducted to determine the amount of traffic placed on a putting
green and its variability as daily pin placements are moved. Because pins are traditionally
moved daily, any one area on a putting green only receives large amounts of foot traffic
one day out of the week as observed in this study. Foot traffic was applied to the
aforementioned creeping bentgrass plots as if each plot was a 2.6 m2 area of a putting
green and the pin was rotated daily. By 6 July, 2004, the accumulation of foot traffic
significantly increased the invasion of annual bluegrass. The addition of foot traffic did
not significantly affect creeping bentgrass densities. Penncross possessed the lowest
shoot density of the cultivars, although the number of annual bluegrass centers was equal
or more abundant in Providence, Penn G-2, and Bengal than Penncross on every rating

date, except for 7 April, 2004. Creeping bentgrass shoot densities did not affect the rate

of annual bluegrass invasion in this research.

To Jettie and Alenna, for your love and support.

ACKNOWLEDGEMENTS

I extend my deepest gratitude to Ron Calhoun for providing many opportunities for me
and strategically allowing me to learn so many valuable lessons along the way. He taught
me through experience and allowed me to build my own opinions. I thank Dr. Kevin
Frank and Dr. Doug Buhler for advising me, always listening, and always making
themselves available. I thank Dr. Thom Nikolai for providing a unique idea for foot
traffic and helping me incorporate it into my research. I appreciate Dr. Joe Vargas for
prodding me to think beyond the obvious. I am greatful to Mark Collins, Frank
Roggenbuck, and the HTRC crew for their invaluable assistance. I appreciate Chris
Riedinger, Tim VanLoo, and Alec Kowalewski for diluting the monotony of daily foot

traffic.

iv

TABLE OF CONTENTS

Page
List of Tables ....................................................................................... vi
Chapter One: A Putting Green Traffic Methodology for Research Applications
Established by In Situ Modeling... 1
Introduction ................................................................................. 1
Materials and Methods .................................................................... 4
Results and Discussion .................................................................... 6
References .................................................................................. 8
Chapter Two: Effect of Creeping Bentgrass Cultivar and Traffic on Shoot
Density and Annual Bluegrass Invasion .................................................... 10
Introduction ................................................................................. 1 0
Materials and Methods ....................................................................... 20
Traffic .............................................................................. 21
Results and Discussion .................................................................... 26
Annual Bluegrass Invasion ...................................................... 26
Shoot Density ...................................................................... 32
Turfgrass Quality ................................................................. 34
Conclusions .................................................................................. 38
References .................................................................................. 40

LIST OF TABLES

Table Page
1 Count and distribution of footsteps for six pin placements after 78 rounds
of golf on a putting green ............................................................. 7
2 Table adapted from six separate trials reporting creeping bentgrass shoot
densities (shoots dm'z) ................................................................ 14
3 Fertility schedule for a creeping bentgrass putting green ........................ 22

4 Traffic schedule for HTRC creeping bentgrass plots; footsteps estimated

for 200 rounds of golf per day ....................................................... 23
5 Analysis of variance for annual bluegrass center counts in a creeping

bentgrass green ......................................................................... 27
6 Annual bluegrass invasion of a creeping bentgrass putting green as affected

by the main effect of traffic using the line-intersecting grid rating

method .................................................................................. 28

7 Annual bluegrass invasion of a creeping bentgrass putting green as affected

by the main effect of traffic .......................................................... 29
8 Annual bluegrass invasion of a putting green as affected by the main effect
of creeping bentgrass cultivar ....................................................... 30

9 Shoot counts of 3 putting green turf as affected by the main effect of
creeping bentgrass cultivar ........................................................... 33

10 Analysis of variance for turfgrass quality in a creeping bentgrass green. . . 35

11 Quality of a putting green as affected by the main effect of creeping
bentgrass cultivar ...................................................................... 36

12 Quality of a creeping bentgrass putting green as affected by the main effect
of traffic ................................................................................. 37

vi

Chapter 1
A Putting Green Traffic Methodology for Research Applications Established by In
Situ Modeling
INTRODUCTION

Though golf greens are now constructed to alleviate the effects of traffic, there is
no question that increased play continues to affect the health of turfgrass. Any researcher
that presented research regarding putting greens invariably hears the question, “did you
apply traffic?” Unfortunately, often times, the reply is “No” due to the fact that there is
no consensus on the best way to apply simulated traffic to putting green studies.

Over the decades there have been numerous studies that have reported or, at least,
employed many different traffic applications to research putting greens. The sheer
numbers of footsteps a golf green incurs every day has impacted the development of
machines to simulate traffic for researchers in an efficient manner (Canaway, 1990;
Dudeck and Burt, 1975; Kohlmeier and Eggens, 1983; Murphy et al., 2000; Neylan and
Robinson, 1999; Shearman, 1989; Trenholm et al., 2001). There has been a variety of
human foot traffic techniques employed for putting green traffic simulation as many golf
spike studies and energetic researchers have worked to develop new strategies, whether
the traffic is counted in minutes or in traverses (Brahler et al., 2001; Ferguson, 1958;
Ferguson, 1959; Grau and Ferguson, 1948; Hall et al., 2001; Hamilton et al., 1997; Rose-
Fricker et al., 1999). Many researchers, though, have not specified the exact amount of
footsteps, minutes, or traverses applied to their plots, rather reported that they have

trafficked a typical amount (Torello etal., 1997).

General ideas of putting green traffic application and simulation are nmnerous,
however, other ultra-specific observations about putting green traffic are found. A
common referenced article (Gibeault et al., 1983) for traffic application cites the
observations of Charles Cogan, Green Committee chairman at Irvine Coast Country
Club, California who explains:

The average golf shoe has 12 spikes; i.e., 24 spikes per golfer. I have
found golfers take an average of 26 full steps (52 paces) per green.
Therefore, each golfer leaves (26 x 24) 624 spike marks on each green.

On 18 greens, he leaves 11,232 spike marks. If there are 200 rounds of
golf played a day, there are 2,246,400 spike marks left behind. If this goes
on for 30 days, you have 67,392,000 spike marks per month. And now,
you wonder why you can’t sink a putt?

In Putt Like the Pros. Pelz (1989) reports on his observation of a foursome leaving behind

 

more than 500 footsteps on a putting green as they entered, putted, and exited. That is an
average of 125 footsteps per golfer. These observations show that much variation should
be expected when counting footsteps on putting greens—there is no universal number.
An obvious, yet important, observation was made while trafficking putting greens
long ago. Ferguson (1959), reporting on two golf-shoe sole studies, concluded that
“frequent changes of cup locations and tee markers is extremely important.”
Observations like these helped to transform the maintenance and cultural practices on
putting greens. It is now common practice to rotate pin locations on a putting green to

disperse foot traffic.

There is much confusion and discussion about traffic methods and amounts of
traffic adequate for traffic simulation on putting green research plots. The objectives of
this observational study were a) to determine the relationship between putting green
traffic and daily cup rotation on a putting green and b) to explore and present a new

method of putting green traffic simulation.

MATERIALS AND METHODS

An observational trial was conducted on 3 June, 2003 at Forest Akers West Golf
Course on the 13th green at Michigan State University in East Lansing, MI. During a golf
outing, golfer’s footsteps were systematically counted as they walked onto the putting
green, made their putts, and walked off of the green. Golfers were coming through the
course as foursomes.

Six sets of two concentric circles were “etched” into the green, representing six
different pin placements for six different days of the week. The circles were made using
a wire brush measuring 1.3 cm wide, scuffing the turf in such a manner that the golfers
did not easily notice the circles. Each set of circles represented a different pin
placement. The outside circle measured 1.5 m2 while the inside circle measured 1.2 m”.
The sets of circles were placed in six different sectors on the putting green, each sector
representing a different day in the pin rotation.

Footsteps were counted by two observers standing near the green as golfers
entered the green, putted,iand exited the green. Any portion of a shoe entering any part
of the circle was counted as a footstep, and footsteps in the outer and inner circles were
counted separately. The golfers were playing traditional golf, not a scramble or best ball
competition. Over the course of the data collection, 78 individual rounds of golf were
played.

Foot traffic is applied to a green by golfers in relation to a particular pin
placement on a particular day. Pins are generally moved daily, or moved six times per
week, as some golf courses close for one day a week. The majority of the foot traffic

moves daily with the movement of the pin. Thus, the number of footsteps counted in

each set of circles simulated the amount of traffic placed on one specific area on a putting
green over an average week of play. This specific area is assumed to be congruent with
all other equal areas on the putting green and is, therefore, one sample representing the

putting green as a whole.

RESULTS AND DISCUSSION

The trial showed that foot traffic on a putting green is highly variable as the pin
placement is changed. One specific area on a green, assuming pins are moved six days a
week, only receives major amounts of foot traffic on the day that the pin is placed in that
vicinity.

The concentration of foot traffic on a golf putting green is highly variable as
golfers generally enter a green where they park their carts or drop their bags and exit in
the same area as they return to those carts or bags, which directly relates to the location of
the ensuing tee. It would be expected that foot traffic would be most concentrated around
the cup or pin placement that day. Therefore, most putting greens have one area that
generally receives the most entrance and exit traffic, which indicates that not all of the
traffic is necessarily relative to the pin placement, but, certainly, most of the traffic,
according to our observations, is related to the placement of the pin.

It is not a revelation that 70% of the footsteps (Table 1) were placed around the
actual pin placement, but the data does remind us why superintendents rotate the pin
placements daily. This data (Table 1) provide researchers a basis for the amount of
footsteps or traffic to apply to putting green research plots and shows researchers that
simulated putting green traffic should be rotated in the same manner a pin is rotated on a
putting green. Just as traffic has a profound negative effect on the health of turfgrass,
recovery time because of pin rotation has a profoundly positive effect on the health of

turfgrass and should be expressed when applying traffic to putting green research plots.

Table 1. Count and distribution of footsteps for six pin placements after 78 rounds of golf
on a putting green.

 

Distance Number of Footsteps Distribution of F oot-

 

 

Simulated from Pin steps (percentL
Placement ' (in) Inner Circle Outer Circle Both CifCICS

1 l 2 0 0 0

2 14 7 10 5

3 1 8 5 1 0 3

4 1 4 1 3 1 9 8

5 8 22 44 1 4

Pin 106 l 84 70

 

REFERENCES

Brahler, C.J., J. MacGowan, M. Kapper, K. Murphy, M. Pequignot, C. Seidelson, V.
Denlinger, and C. Crites. 2001. A Disengaging Metal Spike and Putting Green
Quality. Golf Course Management 69(11): 54-57.

Canaway, RM. 1990. Report on the Establishment of Golf Greens Using Coronet Turf
as Compared with Other Methods. [Online]. Sports Turf Research Institute.
Bingley, W. Yorkshire.

Dudeck, A.E., and E.O. Burt. 1975. Effects of Simulated Golf Traffic on the
Establishment and Performance of Several Overseeded Turfgrasses. Florida Turf
8(4): 3-5.

Ferguson, M.H. 1958. Effects of Golf-Shoe Soles on Putting Green Turf. USGA J. and
Turf Management 11(6): 25-28.

Ferguson, M.H. 1959. Turf Damage From Foot Traffic. USGA J. and Turf
Management 12(5): 29-32.

Gibeault, V.A., V.B. Younger, and W.H. Bengeyfield. 1983. Golf Shoe Study 11.
USGA Green Section Record 21(5): 1-7.

Grau, F.V., and M.H. Ferguson. 1948. Steel Spikes vs. Lug Soles for Golf Shoes: A
Report on 1948 Trials by USGA Green Section. USGA J. and Turf Management
1(6): 12-15.

Hall, E.J.G., R.J. Gibbs, P.R. Munro, B.K. Hannan, and K.W. McAuliffe. 2001.
Evaluation of Golf Footwear for New Zealand Golf Course Conditions.
International Turfgrass Soc. Research J. 9(2): 875-881.

Hamilton Jr., G.W., J.S. Gregos, D.R. Gean, and A.E. Gover. 1997. Golf Shoe Treads
Affect Putting Green Quality. Golf Course Management 65(4): 53-56.

Kohlmeier, GP, and J .L. Eggens. 1983. The Influence of Wear and Nitrogen on
Creeping Bentgrass Growth. Canadian J. of Plant Sci. 63: 189-193.

Murphy, J ., H. Samaranayake, J. Honig, T.J. Lawson, W. Meyer, and B. Clarke. 2000.
2000 Turfgrass and Environmental Research Summary [USGA] p. 19.

Neylan, J., and M. Robinson. 1999. Green Speed: The effects of Maintenance on the
Speed of Bentgrass (Agrostis sp.) Putting Greens. Australian Turfgrass
Management 1(3): 23-26.

Pelz, D., and N. Mastroni. 1989. “The Battle of the ‘Lumpy Doughnut.”’ p. 24-3 8. In
Putt Like the Pros. Harper Collins Pub., New York, NY.

Rose-Fricker, C., M. Fraser, and R. Vaughan. 1999. New Bentgrass Cultivars and
Alternative Golf Shoes. Golf Course Management 67(5): 67-70.

Shearman, RC. 1989. Turfgrass Culture and Water Conservation. Turfgrass Research
Summary 1989 [Nebraska] p. 33-47.

Torello, W.A., Y. Su, and C. Dixon. 1997. More Options Afoot for Spikeless Courses.
Golf Course Management 65(4): 57-59.

Trenholm, L.E., R.N. Carrow, and RR. Duncan. 2001. Wear Tolerance, Growth, and
Quality of Seashore Paspalum in Response to Nitrogen and Potassium.
HortScience 36(4): 780-783.

Chapter 2

Effect of Creeping Bentgrass Cultivar and Traffic on Shoot Density and Annual
Bluegrass Invasion

INTRODUCTION

Annual bluegrass (Poa annua L.) is ofien a part of putting greens whether it is
welcomed or shunned. Golf course superintendents are forced to deal with color mottling
as annual bluegrass interacts with creeping bentgrass (Agrostis palustris Huds.) and
massive amounts of seedheads in late spring. Annual bluegrass and creeping bentgrass
are turfgrass species that act very differently in putting green settings. When managing
both species, golf course superintendents must also learn to manage different disease
tolerances and nitrogen requirements. Beard (1970) stated that there are two approaches
to the encroachment of annual bluegrass: control by cultural and/or chemical means or
adoption of cultural practices to maintain annual bluegrass.

Preemergence and postemergence annual bluegrass herbicides are constantly
being introduced and tested for use on putting greens. Chemicals have been tested as far
back as the 19305 when lead arsenate emerged as an effective annual bluegrass herbicide
(Sprague eta1., 193 7). Though many herbicides, such as bensulide, paclobutrozol,
flurprimidol, and, recently, bispyribac sodium have proven useful for annual bluegrass
control in creeping bentgrass putting greens, annual bluegrass often returns, making these
herbicides short term control devices even when they work well.

Beard et a1. (1978) stated that annual bluegrass occurrence in turf is due to
reduced competition from the permanent turfgrasses and favorable conditions for annual
bluegrass during at least a portion of the growing season. Beard et a1. (1978) continued,

stating that this reduced competition is usually caused by close mowing, excessive

10

irrigation, poor drainage, compacted soils, intense traffic, improperly timed soil
cultivation and vertical mowing, and/or use of non-adapted species or cultivars. The
aforementioned are often inherent characteristics of putting greens, which, in part,
explains why annual bluegrass is such an accomplished invader of putting greens.

Watschke and Schmidt (1992) stated, “most ofien the turfgrass community is
composed of a poly-stand of species that are competing for light, water, nutrients, carbon
dioxide, oxygen, and space. Seasonal growth patterns, growth habit and rate, and stress
tolerance influence the competitive ability of each species.”

Sprague and Burton (1937) did some of the first work with different strains of
creeping bentgrass and their relative abilities to resist the infestation of annual bluegrass.
Seaside, Virginia, Metropolitan, and Washington creeping bentgrasses were evaluated.
They concluded that the density of the turf was “a controlling factor in determining the
abundance of Poa annua.” A dense stand of turfgrass, whether a golf course green or a
home lawn, is more able to compete with weeds, such as annual bluegrass, for water,
nutrients, and sunlight (Beard, 1973).

The first seeded variety of creeping bentgrass, Seaside, was released in 1923 and
was said to have a medium shoot density (Beard, 1973). Great improvements were made
in terms of adaptation, disease resistance, and shoot density when Penncross 'was released
in 1954 (Beard, 1973; Musser, 1962). Providence followed Penncross and also became a
widely used cultivar because of its improved dollar spot resistance and many other
cultivars followed in time. As putting green heights continued to decrease, the need for

creeping bentgrass varieties able to produce dense stands at low heights increased.

11

The Penn A- and G-series cultivars were developed with much higher shoot
densities and are often advertised, specifically, to resist annual bluegrass invasion. The
Penn A- and G-series are now commonly referred to as high shoot density cultivars
relative to older cultivars or standard cultivars. Vargas and Turgeon (2004) separated
creeping bentgrass cultivars for putting greens into three categories: low-density (600 to
900 shoots dm'z), including Penncross, medium-density (1200 to 1600 shoots dm'z),
including Pennlinks, Providence, Putter, and L-93, and high-density (2200 to 2800 shoots
dm'z), including the Penn A- and G-series creeping bentgrasses. As research moved to
improving shoot densities of new creeping bentgrass cultivars, new studies surfaced
testing these new cultivars and their abilities to form dense putting green surfaces as a
result of different management strategies.

Generally, a turfgrass with a higher tillering capacity has a better competitive
advantage over a pest such as annual bluegrass (Danneberger, 1993). However, this
tillering capacity is not always fully expressed (Danneberger, 1993). Lush (1988)
showed that the tillering capacity of annual bluegrass exceeded that of creeping bentgrass
from the end of autumn to the end of spring, while the tillering capacity of annual
bluegrass was fully expressed. In contrast, creeping bentgrass became the dominant
species in the putting green near the end of spring because its tillering was fully
expressed and dominant relative to annual bluegrass. So, as creeping bentgrass cultivars
are continually bred with larger tillering capacities, these capacities may not be fully
expressed depending on controllable and uncontrollable aspects. Furthermore,

researchers may never develop a creeping bentgrass cultivar with a tillering capacity

12

comparable to that of some greens-type, high tillering annual bluegrasses when they are
fully expressed.

Since 1999, six experiments, reporting actual shoot densities of new and old
creeping bentgrass cultivars, have been published (Beard et al., 2001; Croce et al., 1999;
Guertal, 2004; Jordan et al., 2003; Sifers et al., 2001; Sweeney et al., 2001).

Table 2 shows the shoot density results in shoots drn'2 from these experiments. Although
shoot densities from each experiment were affected by different factors, the large
variability between experiments, locations, and years are indicative of the sensitivity of
creeping bentgrass shoot densities to many different factors. These experiments have set
out to find and measure these sensitivities (Beard et al., 2001; Croce et al., 1999; Guertal,
2004; Jordan et al., 2003; Sifers et al., 2001; Sweeney et al., 2001).

Beard et a]. (2001) compared high shoot density cultivars separately from
standard cultivars as there is definite separation between the two classes. After three
sampling dates (Table 2), Penn G2 averaged 2344 shoots dm'z, Providence averaged 1656
shoots din"2 and Penncross averaged 1369 shoots dm'2 (Beard et al., 2001 ). Sweeney et
al. (2001) also found the Penn A- and G-series cultivars to have greater shoot densities
than the standard cultivars. These six experiments (Beard et al., 2001; Croce et al., 1999;
Guertal, 2004; Jordan et al., 2003; Sifers et al., 2001; Sweeney et al., 2001) repeatedly
ranked Penncross in the least dense category and it was clear that the Penn A- and G-
series creeping bentgrasses consistently produced denser stands of turf than the standard
cultivars in any situation.

Jordan et al. (2003) found that shoot density can be increased by increasing the

time interval between irrigation events. Sifers et a1. (2001) found there was a general

13

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decline for most creeping bentgrass cultivars after a humid-hot stress period, except for
Penncross, Seaside II, and Pennlinks, suggesting better adaptation to summer heat stress
condition. Because these cultivars’ characteristics, such as shoot density, are
differentially affected by so many factors, known and unknown, it is difficult to compare
those cultivars and their characteristics when measuring their relative abilities, such as
competitiveness.

Two of the aforementioned studies included annual bluegrass invasion data along
with shoot density data (Beard et al., 2001; Croce et al., 1999). Beard et al. (2001)
transplanted annual bluegrass plugs into the existing creeping bentgrass cultivars and
measured the creeping bentgrass shoot invasion or the outward annual bluegrass shoot
encroachment. This assessment, although very reliable for vegetative encroachment,
does not necessarily represent a cultivar’s ability to limit annual bluegrass germination or
seedling survival within the creeping bentgrass stand. Beard et al. (2001) found that the
use of high shoot density cultivars does improve a putting green’s ability to withstand
annual bluegrass invasion. More specifically, Beard et al. (2001) found that those
cultivars with densities above 2000 shoots dm'2 exhibited the most competitiveness in the
suppression of annual bluegrass in a putting green. Croce et al. (1999) assessed annual
bluegrass invasion visually and found that those creeping bentgrass cultivars with higher
shoot densities were, generally, less prone to annual bluegrass invasion. The lowest
ranking cultivars, in terms of annual bluegrass invasion, were the oldest cultivars
(National, Emerald, Seaside, Astoria). Like Beard et al. (2001), Croce et al. (1999) found

the Penn A- and G-series cultivars to rank the lowest in annual bluegrass invasion.

15

Turgeon (2002) conducted an experiment comparing ten annual bluegrass
selections. They were plugged into three creeping bentgrass cultivars, Penn A-4,
Penncross, and Pennlinks at fairway and putting green heights. Under the fairway-type
culture, each of the annual bluegrass selections was overgrown by all of the creeping
bentgrass varieties within the first year. At greens height, though, most of the annual
bluegrass selections persisted with the creeping bentgrass varieties varying in competitive
ability. Penn A-4 was most effective in restricting the growth of annual bluegrass.
Turgeon reported, while the annual bluegrass plugs generally increased in size, they
appeared to retreat in the summer months and expand in the winter months.

Murphy et al. (2000), in an experiment comparing fifteen creeping and velvet
bentgrasses, also found that high density cultivars exhibited improved ability to resist
annual bluegrass encroachment as opposed to older cultivars even under a range of traffic
conditions.

Foot traffic on a putting green causes wear on the turfgrass and compaction on the
soil. For recreational turfgrass, it is common that wear and compaction occur at the same
time, but one or the other is normally the predominant stress (Carrow and Wiecko, 1989).
It is intuitive that wear would be the primary stress of traffic on sandy soils and,
conversely, soil compaction would be the main stress on soils high in silt and clay
(Carrow and Wiecko, 1989). Wear is tolerated and resisted on different levels for
different turfgrass species and different cultivars within species. Likewise, different
turfgrass species and cultivars have different tolerances for soil compaction.

Annual bluegrass has a profound ability to persist in compacted soils. Creeping

bentgrass, on the other hand, has a very low compaction tolerance making soil

l6

compaction, caused by daily traffic and mowing, a significant factor in the encroachment
of annual bluegrass into creeping bentgrass putting greens (Beard, 1970). Since golf
course superintendents use sand topdressing, core cultivation, and other methods to
prevent and alleviate compaction, creeping bentgrass is not usually impeded by soil
compaction in putting greens.

Wear injury incurred by turfgrasses from foot traffic is marked by abrasion,
tearing, and stripping of leaf tissue, resulting in chlorophyll degradation and subsequent
reduced photosynthesis (Trenholm et al., 2000). Wear injury can also leave turfgrasses
more susceptible to insect and fungal attacks. Lush (1990) concluded that above-ground
biomass is a more useful indicator of wear tolerance than shoot density. The power or
self-thinning rule states that shoot density increases at the expense of canopy biomass
(Lush, 1990). Sifers et al. (2001), when comparing twelve creeping bentgrass cultivars at
greens height, found that those cultivars with higher or lower shoot densities did not
necessarily have lower or higher shoot/mat/thatch dry weights, respectively.

However, Trenholm et al. (2000) observed increased wear tolerance of seashore
paspalum (Paspalum vaginatum Swartz) cultivars with greater shoot densities, stating
that it could have been due to the greater number of meristematic growth points and,
therefore, inherent growth rate. So, although high shoot density creeping bentgrass
cultivars may have decreased wear tolerance, relative to lower shoot density cultivars,
their ability to recover from wear injury may be greater and may even be a larger asset in
wear tolerance as a whole.

Murphy et al. (2000) included wear and compaction separately when studying the

population dynamics of creeping bentgrass and annual bluegrass in a putting green. In

17

preliminary results, they found that high density turfs, including Penn A-4 and some
velvet bentgrass cultivars, showed good to excellent tolerance to wear and compaction
treatments and showed excellent resistance to annual bluegrass encroachment under
traffic conditions on a sandy loam soil. Murphy et al. (2000) also found that wear was
more detrimental, in terms of population, for some bentgrass cultivars than others. Rose-
F ricker et al. (1999) conducted a study comparing wear tolerances of twelve creeping
bentgrass cultivars in a putting green to foot traffic with alternative golf shoes. They
concluded that metal spikes inflicted the most damage and the denser creeping bentgrass
cultivars, including many of the Penn A- and G-series cultivars, showed less damage
initially when trafficked with the metal spikes. Penncross, though incurring more
damage, had the quickest recovery from browning during the summer test.

Wear from foot traffic affects annual bluegrass and creeping bentgrass in many of
the same ways, but wear also provides opportunity for the annual bluegrass population.
Ball marks and spike marks can reduce creeping bentgrass competition for light by
creating voids and exposing soil. In soils with large annual bluegrass seed-banks, these
voids are often filled by germinating annual bluegrass plants. Those soils with small
annual bluegrass seed-banks may be stocked by seed on soles of shoes or on any machine
that is contaminated. Since annual bluegrass can seed even at a cutting height of 3 mm,
putting green soils are always receiving contributions, either from annual bluegrass plants
or seeds brought in from other areas of a golf course. When voids are formed, the race to
fill that void by annual bluegrass or creeping bentgrass is affected by many different
factors. Once annual bluegrass seed germinates in putting greens, it is well suited to

compete with the surrounding plants because annual bluegrass has been shown to have

18

the highest relative seedling grth rate when compared to 132 other species (Grime and
Hunt, 1975).

The objectives of this research were a) to evaluate the effect of foot traffic on the
shoot densities of four creeping bentgrass cultivars and b) to determine the effects of four
creeping bentgrass cultivars with varying shoot densities maintained with and without

traffic on the invasion of annual bluegrass into a putting green.

MATERIALS AND METHODS

Research was initiated in 2003 at the Michigan State University Hancock
Turfgrass Research Center (HTRC) in East Lansing, MI. The site was maintained for ten
years as an annual bluegrass (Poa annua) fairway ensuring a large soil seed-bank of
annual bluegrass seed. This turf and thatch were stripped with a sod cutter and on 30
May, 2003 an 18.3 x 18.3 m putting green was established in its place. The soil type is
an Aubbeenaubbee-Capac sandy loam.

The study was designed as a two-factor split-plot design with four replications.
The main factor consisted of four creeping bentgrass (Agrostis palustris Huds.) cultivars:
Penncross, Providence, Penn G-2, and Bengal. The second factor consisted of two levels
of traffic: traffic and no traffic.

Each main plot, measuring 3.3 x 1.6 m, of the putting green was seeded at 48.8 kg
pure live creeping bentgrass seed (PLS) ha'lon 30 May, 2003 using a shaker bottle. Each
main plot was then split into two sub-plots measuring 1.6 x 1.6 m, with each subplot
randomly assigned traffic or no traffic. Buffers, 30.5 cm wide, surrounded each main
plot and were planted with Penn G-2 creeping bentgrass. Buffers between each main
plot, 0.3 m wide, and a large buffer around the entire area was seeded with Penn G-2.
Germination blankets (A.M. Leonard, Piqua, OH) were placed over the seeded area and
were removed on 9 June.

Before seeding, a soil analysis revealed that phosphorus and potassium were not
limiting. Starter fertilizer (13N-1 lP-IOK) was applied at a rate of 24 kg N ha’1 on the day
of seeding. During the grow-in period, between 9 June and 23 September, 216 kg N ha‘I

were applied to the turf on nine occasions at 24 kg N ha'1 in evenly spaced increments.

20

Once established, N was sprayed on the putting green in increments of 10 kg N ha’1 for a
total of 90 kg N ha'1 during the growing season. One fertilization at a higher rate, 24 kg
N ha", was made in the spring of 2004 to promote annual bluegrass seedhead production,
so the two species could be more easily distinguished for rating purposes. The fertility
schedule and use of two different sources of nitrogen is outlined in Table 3.

The putting green was mowed five days per week with a Toro Greensmaster 1000
walk-mower (Minneapolis, MN) at a bench height of 3.2 mm (0.125 inches). Clippings
were removed from the green. The putting green was lightly topdressed using a Tom
Quickpass (Minneapolis, MN) with sand at intervals of approximately one week between
9 July and 23 September of 2003 to create a smooth surface so the desired mowing height
could be met without scalping the turf. Sand topdressing was reinitiated in June of 2004,
but was reduced in frequency to twice per month. The green was irrigated as needed to
return 80% of evapotranspiration (ETp).

Traffic

The traffic data collected at Forest Akers Golf Course (Chapter 1) from 78 rounds
of golf were extrapolated to 200 rounds of golf (Table 4) and were applied to 16 square
plots with inner and outer rings whose surface areas were equal to the circles at Forest
Akers Golf Course. The traffic was applied on the putting green at the HTRC as if a pin
were being moved daily. Specific amounts of foot traffic, proportional to the data taken
from the observational study (Chapter 1), were applied to outer and inner square rings
which made up each trafficked plot on the putting green. Traffic was applied by two

people weighing between 77 and 90 kg, each wearing Foot-Joy® DryJoy® golf

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22

Table 4: Traffic schedule for HTRC creeping bentgrass plots; footsteps estimated for 200
rounds of golf per day.

Day Traffic Footsteps

 

 

Executed Pin Placement"r . . Time (seconds)
Inner Circle Outer Circle
Saturday 1 0 o -1
Tuesday 2 13 26 _
Friday 3 13 26 -

Wednesday 4 33 49 _

Monday 5 56 1 1 3 83

Thursday 0 272 472 420

 

‘l' Corresponds to one of six sectors on the putting green in Chapter 1 used to quantify

traffic.
I Footsteps were few enough to count for each plot.

23

shoes equipped with Softspikes® Black Widow® spikes. On Mondays and Thursdays,
the highest traffic days, an interval of time was used to quantify the number of footsteps
applied (Table 4), so traffickers could measure applied traffic using a time limit per plot
instead of counting our actual footsteps. This time limit was obtained by timing three
foot traffic occasions and using the average of the three. On all other days, the footsteps
were actually counted. Traffic began on 24 September 2003, when the turf had
sufficiently grown in, and ended 2 weeks later. In 2004, traffic began on 21 April and
ended in early October.

Plots were evaluated using visual quality ratings, annual bluegrass quantification
by two different methods, and plant counts of each bentgrass cultivar. Visual ratings of
quality were based on a 1-9 scale where 1=dead, 5=acceptable, and 9=excellent. Quality
ratings included turf color, density, uprightness, and uniformity. Four subsamples per
plot were collected in October, 2004 with a soil probe measuring 19 mm in diameter, and
shoot counts were from these subsamples. Shoots were counted by using tweezers to
remove shoots from each sample one by one. Annual bluegrass invasion was measured
on a near-monthly basis by counting the centers of annual bluegrass in each plot. Annual
bluegrass centers are small populations that colonize within the creeping bentgrass turf
over time. These ratings were later supplemented with another method using line-
intersecting grid counts. The grid was constructed to fit the 1.6 x 1.6 m sub-plots and
consisted of 441 intersections, each measuring 76 x 76 mm. Annual bluegrass invasion
was measured by counting the number of grid intersections which touched any part of an
annual bluegrass plant. All annual bluegrass invasion data were collected from each

trafficked plot, the inner and outer rings, as a whole.

24

The experimental design was a split plot randomized block design with four
replications. Creeping bentgrass and traffic rate were treatment factors. Analysis of
variance was used to determine significant effects (P<0.05) and, when significant,
treatment differences were analyzed using the Proc Mixed procedure of SAS (SAS
Institute, 2002). The 23 September, 2003 annual bluegrass invasion rating date was
analyzed as a single factor, creeping bentgrass cultivar, design because traffic had not yet
begun. When appropriate, means were separated using Fischer’s LSD procedure at the

0.05 level of probability.

25

RESULTS AND DISCUSSION
Annual Bluegrass Invasion

The creeping bentgrass cultivars grew for four months before fall foot traffic
began. After four months there was an average of 73 annual bluegrass centers, measuring
approximately 3.3 cm2, per plot. In 2004, annual bluegrass centers, averaged over all
treatments, steadily increased from April to August and made a marked jump from 137 to
349 centers per plot between August and October.

There were only significant differences between traffic treatments on annual
bluegrass invasion on the last three rating dates (Table 5). Analysis of the line-
intersecting grid counts, performed in correspondence with the last three annual bluegrass
center counts, revealed that trafficked plots had the greatest annual bluegrass invasion
(Table 6), which supported the findings on the last three annual bluegrass center counts
(Table 7). Intuitively, as traffic accumulates on a putting green, the health of the
turfgrass decreases making it less able to compete with any weed. Foot traffic increases
the ability of annual bluegrass seed to germinate within a turf stand by creating openings.
There was a definite threshold at which the accmnulated amount of foot traffic became a
significant effect of annual bluegrass invasion into the creeping bentgrass putting green.
Traffic did not become a significant effect of annual bluegrass invasion until 11 weeks of
foot traffic accumulated at 1076 foot steps week'l plot".

Results from annual bluegrass invasion ratings revealed that creeping bentgrass
cultivar had a significant main effect on five of seven rating dates (Table 5). Providence
had the highest relative annual bluegrass invasion on every rating date except for one, 7

April, 2004 (Table 8). Conversely, Penncross and Bengal each had the lowest annual

26

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27

Table 6. Annual bluegrass invasion of a creeping bentgrass putting green as affected by
the main effect of traffic using the line-intersecting grid rating method.

 

 

 

 

 

2004
Traffic Treatment
8 June 10 Aug 28 Sep
——annual bluegrass plantsT
Traffic 76 111 132
No Traffic 42 74 84
LSD (p=0.05) 12 17 41

 

1' Number of annual bluegrass plants found from 441 line-intersections.

28

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bluegrass invasion on every rating date but one, Penncross on 7 April and Bengal on 28
September, 2004. Significantly fewer annual bluegrass centers were counted in Penn G-2
plots than Providence plots on the first rating date in 2003; thereafter, there were no
differences in annual bluegrass invasion ratings between Penn G-2 and Providence (Table
8). Analysis of the line-intersecting grid counts of annual bluegrass, performed in
correspondence with the last three annual bluegrass center counts, revealed no significant
differences between creeping bentgrass cultivars on any of the last three dates (data not
presented).

The putting green was established over an area previously maintained as an
annual bluegrass fairway for many years and, therefore, is certain to have an atypically
large annual bluegrass seed-bank. The resulting weed pressure from the large seed-bank
could have diminished any cultivar main effects observed early in the study and helps to
explain the lack of differences later. If this area was not previously maintained
exclusively for annual bluegrass survival and dominance, the annual bluegrass seed-bank
would have needed time to develop. Initially, annual bluegrass invasion may have been
more subtle and differences among creeping bentgrass cultivars may have been more
apparent and/or prolonged because weed pressure would have been initially very low and
steadily increased as the annual bluegrass seed-bank increased.

There were no interactions between creeping bentgrass cultivars and traffic rates
on any rating date. Although the accumulation of foot traffic did increase the annual
bluegrass invasion averaged over all creeping bentgrass cultivars, this effect was not

enhanced on any one creeping bentgrass cultivar on any rating date.

31

Shoot Density

Creeping bentgrass shoot densities ranged from 977 to 1379 shoots dm'z. The
main effect of traffic on creeping bentgrass shoot density was not significant. The main
effect of creeping bentgrass cultivar on creeping bentgrass shoot density was significant
(Table 9). Bengal and Penn G-2 had the highest shoot densities, while Providence and
Penncross had the lowest shoot densities (Table 9). These shoot density rankings were
consistent with previous research, while actual shoot density numbers were lower than
many researchers have reported (Beard et al., 2001; Croce et al., 1999; Jordan etal.,
2003; Sifers etal., 2001). The shoot densities, though, were very comparable to shoot
densities observed by Sweeney et al. (2001) and much higher than those found by Geurtal
(2004).

It was expected that the creeping bentgrass cultivar with the highest plant density
would have accumulated the least annual bluegrass. However, in this case, Bengal,
which had the highest shoot density in October of 2004 (Table 9), also had the highest
annual bluegrass invasion on 28 September, 2004 (Table 8). Penncross, the oldest of the
four cultivars and notorious for its prostrate growth habit had the lowest plant density in
October of 2004 (Table 9), but was in the least annual bluegrass invasion category with
Penn G—2 on 28 September, 2004 (Table 8).

Beard et al. (2001) found that Penncross and Pennlinks ranked lowest among 13
cultivars in aggressiveness against annual bluegrass invasion, while high-shoot density
creeping bentgrass cultivars discouraged annual bluegrass invasion. Turgeon (2002) also
found that Penn A-4, a high-shoot density creeping bentgrass cultivar, was more

competitive against annual bluegrass than Penncross and Pennlinks.

32

Table 9. Shoot counts of a putting green turf as affected by the main
effect of creeping bentgrass cultivar.

 

 

 

 

Cultivar 2004

October
shoots/dm2

Penncross 977ct
Providence 1 1 19bc
Penn G-2 1316ab

Bengal 1379a

LSD (p=0.05) 235

 

1' Means in a column followed by the same letter are not significantly
different according toFischer’s protected LSD (p=0.05).

33

However, Beard et al. (2001) and Turgeon (2002) were only evaluating creeping
bentgrass competitive ability with the vegetative aspect or lateral grth of annual
bluegrass. They observed the growth of an annual bluegrass plug within a creeping
bentgrass stand, whereas our research evaluated creeping bentgrass competition with
annual bluegrass lateral growth and seed germination.

Although Penn G-2 and Bengal produced denser turf stands than Penncross
(Table 9), the data from this research revealed that Penncross was able to compete with
annual bluegrass as well or better than Penn G-2 and Bengal on every rating date, except
7 April, 2004, which is counterintuitive to the findings of Beard et al. (2001) and Turgeon
(2002)
Turfgrass Quality

There were significant differences in quality among creeping bentgrass cultivars
on each of the four rating dates (Table 10). Penncross had the lowest quality on every
rating date, while Bengal had the highest quality on every rating date. Penn G-2 quality
was only significantly lower than Bengal on 22 April, 2004 (Table 11). Traffic
negatively affected turfgrass quality on the last three rating dates (Table 12). High
density creeping bentgrass cultivars, such as Penn G-2 have been reported to have higher

turfgrass quality than low density cultivars (Croce et al., 1999; Sifers et al., 2001).

34

Table 10. Analysis of variance for turfgrass quality in a creeping bentgrass green.

 

 

2004
Source of Variation df , ,
7 Apr11 22 April 13 May 6 July
Blocks 3
Cultivar 3 * * * *
Traffic 1 NS "‘ * *
Cult*Traffic 3 NS NS NS NS
Error 12

 

* and NS indicate significant and not significant at the a = 0.05 probability level,
respectively.

35

Table 11. Quality of a putting green as affected by the main effect of creeping bentgrass
cultivar.

 

 

 

 

 

 

. 2004

Cultivar , ,

7 Aprll 22 April 13 May 6 July
Quality?
Penncross 4.6 bf 4.6 b 4.9 c 3.9 c
Providence 5.6 a 5.0 b 5.4 bc 4.6 b
Penn G-2 5.6 a 5.0 b 5.9 ab 6.8 a
Bengal 5.9 a 6.1 a 6.5 a 6.8 a
LSD (p=0.05) 0.7 0.5 0.8 0.6

 

'1' Quality: 1=poor, 5=acceptable, and 9=excellent.
it Means in a column followed by the same letter are not significantly different according
to Fischer’s protected LSD (p=0.05).

36

Table 12. Quality of a creeping bentgrass putting green as affected by the main effect of
traffic.

 

 

 

 

 

 

2004
Traffic Treatment
7 April 22 April 13 May 6 July
fiQualityT
Traffic 5.5 4.8 5.1 5.1
No Traffic 5.4 5.6 6.2 5.9
LSD (p=0.05) NS 0.5 0.4 0.4

 

1' Quality: 1=poor, 5=acceptable, and 9=excellent.
NS indicates not significantly different at the p=0.05 probability level.

37

CONCLUSIONS

Competition between turfgrass species can occur in tillers and/or roots
(Danneberger, 1993). Generally, though, the competitive outcome between two turf
species is decided by tillering capacity (Grimes and Hunt, 1975; Lush, 1988). Tillering
capacities of turfs differentially fluctuate between species and cultivars within species
due to temperature optimums for each (Danneberger, 1993). Furthermore, grth limits
imposed by space, nutrients, and energy availability (Danneberger, 1993) differ between
creeping bentgrass cultivars with differing characteristics, such as shoot density, root
biomass, and leaf width. Factors differing among creeping bentgrass cultivars, such as
shoot density and leaf width also affect annual bluegrass seed germination.

Among twelve creeping bentgrass cultivars, Beard and Sifers (1997) reported
Penncross, Penn G-2, and Penn G-6 possessed the highest rooting biomass levels. They
also found that Penncross and Penn G-2 had the best summer-stressed root biomass
levels. Among these twelve cultivars, Beard and Sifers (1997) reported that all cultivars
exhibited a decline in shoot density after the summer heat stress period, except for
Penncross, Pennlinks, and Seaside II.

In this research, Penncross and Penn G-2 had the lowest annual bluegrass
invasion on the last rating date (Table 4), which followed the hottest stretch of summer in
2004, while annual bluegrass centers in Bengal and Providence dramatically increased.
These results support the findings of Beard and Sifers (1997) that Penncross and Penn G-
2 performed well relative to other cultivars through summer-stress periods.

Although parts of this research may parallel other research findings, it is difficult

to be certain of the reasons for these four cultivars fluctuating competitive abilities with

38

annual bluegrass because there are so many possible factors. Penncross competed with
annual bluegrass equally as well as Penn G-2 and Bengal on most rating dates, although it
has a much lower shoot density than both. In this study, shoot density was not the
governing creeping bentgrass cultivar characteristic for annual bluegrass invasion. Many
factors affecting tillering capacity govern a creeping bentgrass’s ability to effectively
compete with annual bluegrass.

The main effect of traffic on creeping bentgrass shoot density was not significant.
Although traffic disfavors the health of any turfgrass, it is also possible that it may do so
without decreasing the turf density, which occurred in this study. However, a trafficked,
and, thus, less healthy turfgrass may not compete with annual bluegrass as well as the
same turf without applied traffic, which occurred in this study, although both may have

the same number of shoots unit area".

39

REFERENCES

Beard, J. B. 1970. An Ecological Study of Annual Bluegrass. USGA Green Sect. Rec.
8:13-18.

Beard, J .B. 1973. Turfgrass: Science and Culture. Englewood Cliffs, N.J.: Prentice Hall,
Inc.

Beard, J.B., P.E. Rieke, A.J. Turgeon, and J .M. Vargas, Jr. 1978. Annual Bluegrass (Poa
annua L.): Description, Adaptation, Culture and Control. Research Report from
Ag. Exp. Station 352: 3-32.

Beard, J .B., P. Croce, M. Mocioni, A. De Luca, and M. Volterrani. 2001. The
Comparative Competitive Ability of Thirteen Agrostis Stolonifera Cultivars to
Poa Annua. International Turfgrass Soc. Research J. 9: 828-831.

Beard, J .B. and SJ. Sifers. 1997. Bentgrasses for Putting Greens: Which “New” Cultivars
Can Tolerate Today’s Mowing Heights? Golf Course Management. 65(5): 54-60.

Carrow, RN. and G. Wiecko. 1989. Soil Compaction and Wear Stresses on Turfgrasses:
Future Research Directions. Proceedings of The 6th International Turfgrass
Research Conf., Tokyo. 31 July-5 August. pp. 37-42.

Croce P., M. Mocioni, J .B. Beard. 1999. Bentgrass (Agrostis spp.) Cultivar
Characterizations for Closely Mowed Putting Greens in a Mediterranean Climate.
Proceedings of the 69th Annual Michigan Turfgrass Conf. 28: 109-114.

Danneberger, T.K. 1993. “Population Dynamics.” In Turfgrass: Ecology and
Management. Clevelend: Franzak & Foster.

Grime, JP. and R. Hunt. 1975. Relative Growth-rate: Its Range and Adaptive
Significance in a Local Flora. J. of Ecology. 63(2): 393-422.

Guertal, EA. 2004. Boron Fertilization of Bentgrass. Crop Sci. 44: 204-208.

Jordan, J .E., R.H. White, D.M. Victor, T.C. Hale, J.C. Thomas, and MC. Engilke. 2003.
Effect of Irrigation Frequency on Turf Quality, Shoot Density, and Root Length
Density of Five Bentgrass Cultivars. Crop Sci. 43: 282-287.

Lush, W.M. 1988. Biology of Poa Annua in a Temperate Zone Golf Putting Green
(Agrostis stolonifera / Poa annua). J. of Applied Ecology. 25(3): 977-988.

Lush, W.M. 1990. Turf Growth and Performance Evaluation Based on Turf Biomass and
Tiller Density. Agron. J. 82: 505-511.

40

Murphy, J .H., H. Samaranayake, J. Honig, T.J. Lawson, W. Meyer, and B. Clarke. 2000.
Cultivar and Traffic Effects on Population Dynamics of Agrostis spp. and Poa
Annua Mixtures. Progress Report to the USGA. pp. 681-696.

Musser HE. 1962. Turf Management (Rev. ed.). New York: McGraw Hill Book Co., Inc.

Rose-Fricker, C., M. Fraser, R. Vaughan. 1999. New Bentgrass Cultivars and Alternative
Golf Shoes: Traffic Leaves Its Mark, But Damage Varies. Golf Course
Management: 67(5): 67-70.

SAS Institute. 2002. SAS Institute, Inc., Cary, NC.

Sifers, S.I., J .B. Beard, and ML. Fraser. 2001. Botanical Comparisons of Twelve
Agrostis Cultivars in a Warm-Humid Climate. International Turfgrass Soc.
Research J. 9: 213-217.

Sprague, N. B. and G. W. Burton. 1937. Annual Blue Grass (Poa annua L.) and its
Requirements for Growth. New Jersey Ag. Exp. Station Bull 630: 1-24.

Sweeney, P., T.K. Danneberger, D. Wang, and M. McBride. 2001. Root Weight,
Nonstructural Carbohydrate Content, and Shoot Density of High-density Creeping
Bentgrass Cultivars. HortSci 36(2): 368-370.

Trenholm, L.E., R.N. Carrow, and RR. Duncan. 2000. Mechanisms of Wear Tolerance
in Seashore Paspalum and Bermudagrass. Crop Sci. 40: 1350-1357.

Turgeon, A.J. 2002. Competition Between A grostis Stolonifera and Poa Annua
Populations in Turfgrass Communities. p. 643-647. In E. Thain (ed.) Science and
Golf IV. London: Routledge.

Vargas, Jr., J .M and A.J. Turgeon. 2004. Poa Annua: Physiology, Culture, and Control of
Annual Bluegrass. Hoboken: John Wiley and Sons, Inc.

Watschke, T. L. and RE. Schmidt. 1992. Ecological Aspects of Turf Communities. p.

129-174. In: D.V. Waddington et al. (eds.) Turfgrass Agron. Monogr. 32 ASA,
CSSA, and SSSA, Madison, WI.

41