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TURFGRASS RE-ESTABLISHEMENT TECHNIQUES
FOLLOWING WINTERKILL

presented by
ERICA NICOLE BOGLE

has been accepted towards fulfillment
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Master of degree in Crop and Soil Sciences
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I 5/08 K‘IProj/AcoSPresIClRC/DateDue.indd

RIB-ESTABLISHMENT TECHNIQUES FOLLOWING WINTERKILL

By

Erica Nicole Bogle

A THESIS
Submitted to
Michigan State University
In partial fulfillment of the requirements
For the degree of
MASTER OF SCIENCE

Crop and Soil Sciences

2009

ABSTRACT
TURF GRASS RE-ESTABLISHMENT FOLLOWING WINTERKILL
By
Erica Nicole Bogle
Research was conducted to determine the effects of fertilizer application
timing, use of clear plastic cover, and cultivar selection in the re-establishment of a
creeping bentgrass (Agrostis palustris) and Poa annua green following simulated
winterkill. The study was completed over the 2006 through 2008 growing seasons.
Winterkill conditions were simulated using glyphosate herbicide in March and April
for all years. Before reseeding, the damaged area was prepared using a Job Saver®
attachment on a greens aerifier. The area was seeded with three cultivars of
creeping bentgrass, Alpha, Penn A-4, and Providence. Poa annua florets were
collected from a nearby green containing Poa annua for use in establishing Poa
annua plots. Upon emergence, a clear 4 Mil plastic cover was used when night
temperatures were below 10°C. Fertilizer treatments were also initiated upon
emergence, granular fertilizer was applied at 0.15 g N m'z, every three weeks, and
liquid fertilizer applied weekly at 0.05 g N m°2. Treatments were applied from May
to August for 2006-07 and through July for 2008. Re-establishment of the plots was
assessed using visual estimates and digital image analysis using Sigma ScanTM
software. Temperature measurements were taken at soil surface level for the
duration of the 2007 and 2008 studies. There were no significant differences among
the re-establishment rates of the creeping bentgrass cultivars, however there were
significant differences among the creeping bentgrass cultivars and annual bluegrass
for all three years and both locations. There were significant differences found
between the fertilizer treatments for all three years and both locations. There were

significant differences between cover treatments for only the 2008 year.

To Andrew, without your support this never would have been completed.

iii

ACKNOWLEDGEMENTS

I would like to thank Dr. Kevin Frank for giving me this opportunity, and for all
his guidance throughout the process. Also to Jeff Bryan for all his help with the
physical research and showing me the ropes at the Hancock Turfgrass Research
Center. I appreciate all the advice and experience from everyone in the
Turfgrass department at Michigan State University, it has been an honor to have

been a member in the department.

iv

TABLE OF CONTENTS

LIST OF TABLES ...........................................................................
INTRODUCTION ............................................................................
LITERATURE REVIEW ...................................................................
MATERIALS AND METHODS ...........................................................
RESULTS AND DISCUSSION ............................................................
Fertilizer Timing ..............................................................

Plastic Cover ..................................................................
CONCLUSIONS ...............................................................................
APPENDICES ..............................................................................

REFERENCES ...............................................................................

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LIST OF TABLES

Table 1: Analysis of variance of percent turfgrass cover during re—
establishment of a creeping bentgrass putting green following simulated
Winterkill in 2006 at HTRC, East Lansing, MI ......................................

Table 2: Analysis of variance of digital image analysis of percent turfgrass
cover for re-establishing a creeping bentgrass putting green after simulated
Winterkill in 2006, at HTRC, East Lansing, MI .....................................

Table 3: Analysis of variance of percent turfgrass cover during re-
establishment of a creeping bentgrass putting green following simulated
Winterkill in 2007 at HTRC, East Lansing, MI ......................................

Table 4: Analysis of variance of digital image analysis of percent turfgrass
cover for re-establishing a creeping bentgrass putting green after simulated
Winterkill in 2007, at HTRC, East Lansing, MI .....................................

Table 5: Analysis of variance of percent turfgrass cover during re-
establishment of a Poa annua putting green following simulated Winterkill in
2007 at HTRC, East Lansing, MI ......................................................

Table 6: Analysis of variance of digital image analysis of percent turfgrass
cover for re-establishing a Poa annua putting green after simulated Winterkill
in 2007, at HTRC, East Lansing, MI ..................................................

Table 7: Analysis of variance of percent turfgrass cover during re-
establishment of a creeping bentgrass putting green following simulated
Winterkill in 2008 at HTRC, East Lansing, MI ......................................

Table 8: Analysis of variance of digital image analysis of percent turfgrass
cover for re-establishing a creeping bentgrass putting green afier simulated
Winterkill in 2008, at HTRC, East Lansing, MI .....................................

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18

19

20

21

22

23

24

Table 9: Analysis of variance of percent turfgrass cover during re-
establishment of a Poa annua putting green following simulated Winterkill in
2008 at HTRC, East Lansing, MI ......................................................

Table 10: Analysis of variance of digital image analysis of percent turfgrass
cover for re-establishing a Poa annua putting green after simulated Winterkill
in 2008, at HTRC, East Lansing, MI ..................................................

Table 11: Effect of cultivar/species on percent turfgrass cover during re-
establishment of a creeping bentgrass putting green following simulated
Winterkill in 2006, at HTRC, East Lansing, MI .....................................

Table 12: Digital image analysis of effects of cultivar/species on percent
turfgrass cover during re-establishment of a creeping bentgrass putting green
following simulated Winterkill in 2006, at HTRC, East Lansing, MI ............

Table 13: Effects of cultivar/species on percent turfgrass cover during re-
establishment of a creeping bentgrass putting green following simulated
Winterkill in 2007, HTRC, East Lansing, MI ........................................

Table 14: Digital image analysis of effects of cultivar/species during re-
establishment of a creeping bentgrass putting green following simulated
vvinterkill in 2007, at HTRC, East Lansing, MI .....................................

Table 15: Effects of cultivar/species on percent turfgrass cover during re-
establishment of a creeping bentgrass putting green following simulated
Winterkill in 2008 at HTRC, East Lansing, MI ......................................

Table 16: Digital image analysis of effects of cultivar/species on percent
turfgrass cover during re-establishment of a creeping bentgrass putting green
following simulated Winterkill in 2008, HTRC, East Lansing, MI ...............

vii

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26

27

28

29

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32

Table 17 : Effects of cultivar/species on percent turfgrass cover during re-
establishment of a Poa annua putting green following simulated Winterkill in
2007, HTRC, East Lansing, MI ........................................................

Table 18: Digital image analysis of effects of cultivar/species on percent
turfgrass cover during re-establishment of a Poa annua putting green
following simulated Winterkill in 2007, HTRC, East Lansing, MI ...............

Table 19: Effects of cultivar/species on percent turfgrass cover during re-
establishment of a Poa annua putting green following simulated Winterkill in
2008, HTRC, East Lansing, MI ........................................................

Table 20: Digital image analysis of effects of cultivar/species on percent
turfgrass cover during re-establishment of a Poa annua putting green
following simulated Winterkill in 2008, HTRC, East Lansing, MI ...............

Table 21 : Effect of fertilizer timing on percent turfgrass cover during re-
establishment of a creeping bentgrass putting green following simulated
Winterkill in 2006, at HTRC, East Lansing, MI .....................................

Table 22 : Digital image analysis of effects of fertilizer timing on percent
turfgrass cover during re-establishment of a creeping bentgrass putting green
following simulated Winterkill in 2006, at HTRC, East Lansing, MI ............

Table 23: Effects of fertilizer rate on percent turfgrass cover during re-
establishment of a Creeping Bentgrass putting green following simulated
Winterkill in 2007, HTRC, East Lansing, MI ........................................

Table 24: Digital image analysis of effect of fertilization rate on percent
turfgrass cover during re-establishment of a creeping bentgrass putting green
following simulated Winterkill in 2007, HTRC, East Lansing, MI ...............

viii

33

34

35

36

39

40

41

42

Table 25: Effect of cover treatment on percent turfgrass cover during re-
establishment of a creeping bentgrass putting green following simulated
Winterkill in 2008, HTRC, East Lansing, MI ........................................

Table 26: Digital image analysis of effects of fertilization rate on percent
turfgrass cover during re-establishment of a creeping bentgrass putting green
following simulated Winterkill in 2008, HTRC, East Lansing, MI ...............

Table 27: Digital image analysis of effects of fertilization rate on percent
turfgrass cover during re-establishment of a Poa annua putting green
following simulated Winterkill in 2008, HTRC, East Lansing, MI ...............

Table 28: Effects of cover treatment on percent turfgrass cover during re-
establishment of a Poa annua putting green following simulated Winterkill in
2008, HTRC, East Lansing, MI ........................................................

Table 29: Average air temperatures for April 25-May 30 for 2006 - 2008 at
HTRC, East Lansing, MI ...............................................................

Table 30: Days until turfgrass cover of turfgrass cultivar/species on a
Creeping bentgrass putting green 2006 ..............................................................

Table 31: Days until Percent Turfgrass Cover with fertilizer timing factor on

a Creeping bentgrass putting green 2006

Table 32: Days until Percent Turfgrass Cover of turfgrass cultivar/ species

on a Creeping bentgrass putting green 2007...........

Table 33. Days until turfgrass cover of turfgrass cultivar/ species on a Poa
annua putting green 2007..

Table 34: Days until turfgrass cover with fertilizer timing factor on a
Creeping bentgrass putting green 2007 .................................................

ix

48

44

45

49

50

52

53

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Table 35: Days until turfgrass cover with fertilizer timing factor on a Poa
annua putting green 2007 ...............................................................

Table 36: Days until turfgrass cover of turfgrass cultivar/ species on a
Creeping bentgrass putting green 2008 .................................................

Table 37: Days turfgrass cover of turfgrass cultivar/ species on a Poa annua
putting green 2008 ...........................................................................

Table 38: Days until turfgrass cover with fertilizer timing factor on a
Creeping bentgrass putting green 2008 .................................................

Table 39: Days until turfgrass cover with fertilizer timing factor on a Poa
annua putting green 2008 ...............................................................

Table 40: Days until turfgrass cover with cover treatment factor on a
Creeping bentgrass putting green 2008

Table 41: Days until turfgrass cover with cover treatment factor on a Poa
annua putting green 2008 ...............................................................

Table 42: Degree Day accumulation beginning March 1 ..........................

Table 43: Treatment factors for re-establishment of creeping bentgrass
putting greens following simulated Winterkill at HTRC in 2006- 2008 ..........

54

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55

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56

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10

INTRODUCTION

Winterkill is a non-specific term used to represent any injury to turf incurred over
winter. The loss of turf on golf courses is a common problem that occurs every winter
especially in the northern United States. Many environmental factors such as temperature
fluctuation, ice or snow cover, and wind can cause Winterkill (Beard, 1969). Cultural
factors such as fall hardening off technique, the practice of reducing fertilization and
irrigation to promote turfgrass winter survival (Christians, 2007), preventive fungicide
applications (Vargas, 2007), drainage installation, use of protective covers (Lettner,
1988), and snow or ice removal also influence the occurrence of Winterkill (Beard, 1969;
Snow, 1979). Scattered-to-widespread turf loss can occur in areas prone to winterkill.
Different types of Winterkill have been identified such as desiccation (Kaufmann, I973),
crown hydration (Roberts, 1995), ice and snow suffocation (Tompkins, 2004), and low
temperature fungi (Vargas, 2005) and can occur simultaneously. Regardless of type of
winter injury, there remains the task of re-establishing the lost turf. Re-establishment
must be done as soon as possible to ensure a quality playing surface that will be
consistent throughout the season. The need to begin the re-establishrnent process as soon
as the injury is assessed in late winter can be problematic because the ideal environmental
conditions for re-establishment are rarely present when injury is first observed (White,
2004). Because injury can be sporadic and varying in degree of severity within an area,
the amount and location of damage often determines the choice of re-establishment

methods.

Sodding is one possible solution to repair a damaged area in a creeping bentgrass
green. However, the cost of bentgrass sod can vary from $4.50 to $10 per m2 (MSGA,
2007), and the disruption of the playing surface can cause sod to not be the most suitable
option. To be effective, replacement sod must have the same soil profile as the damaged
area. In Michigan, special measures must be taken to locate appropriate sod. Commercial
sod is mainly grown on native silt and clay soil, while golf course greens are typically
sand based. Differences in soil particle size distribution can restrict water infiltration
within the soil profile restricting root growth from expanding past the sod layer. The
resulting restricted root layer can cause reduced nutrient permeation in the soil, and sod
death (Nelson, 2008). The easiest way to ensure sod with the same or similar soil profile
is for courses to maintain a nursery green. For courses lacking a nursery green, matched
sod can prove difficult to find, and management may need to order specially grown or
washed sod (Nelson, 2008). Even if sodding is successful, because it requires removal of
the entire damaged area, the playing surface will be disrupted after installation for 3 to 6
weeks (MSGA, 2007).

Another option for re-establishing a putting green is to seed into the existing stand.
Seeding is often a more economical option averaging $35 per kg of seed, which can be
applied throughout the season. Seeding also allows for minimally invasive re-
establishment in sporadically injured areas. The 8 to 10 weeks needed to achieve a fully
established stand of turf, even in ideal environmental conditions, is a disadvantage in the
use of seeding for re-establishment (Beard, 1973; Murphy et al., 2005). Due to the lack
of ideal environmental conditions in early spring, a greater emphasis must be placed on

effective cultural practices. Proper fertilizer type and timing (Nus, 1989), and the use of

clear plastic covers (Hall et al., 1979; Schmidt et al., 1989), have been found to improve
establishment of new turf and aid in spring green up. However, their effect on re-
establishing turf from Winterkill is not known.

Objectives of this study were to evaluate the effects of fertilizer application timing,
use of clear plastic cover, and species and cultivar on re-establishment of creeping

bentgrass and Poa annua putting greens following simulated winterkill.

LITERATURE REVIEW

Winterkill, the general loss of turf over winter (Beard, 1969) is common
throughout the northern United States. Although it is used as a generic term, there are
specific types of Winterkill, such as direct low temperature kill, winter desiccation, and
snow mold injury (Kaufmann, 1973). All can occur throughout the winter and can occur
simultaneously. Most causes are independent of snow or ice cover and all thrive on
winter conditions. Each type of Winterkill is recognized by a specific mode of action. The
most widespread cause of Winterkill is winter desiccation (Beard, 1969). Winter
desiccation occurs mainly on exposed or elevated areas, during winters with little to no
snowfall, and affects turf at many heights of cut. Desiccation occurs when loss of water
in the leaf tissue is greater than the water uptake from the soil, dehydrating the plant
throughout the winter. Ways to reduce this type of Winterkill are to use protective covers
water through the winter, or topdress the areas prone to damage (Beard, 1969; Kaufmann,

1973).

More common in low areas of greens or areas with poor drainage is the type of
direct low temperature kill known as crown hydration (Kaufmann, 1973; Roberts, 1995).
Crown hydration is initiated when turfgrass is re-hydrated, then the temperature drops,
and the intracellular water, residing within the plant, freezes. Resulting in collapsing
plant tissues and destroying plant integrity, which causes plant death. Crown hydration
injury is most common in the late winter to early spring when temperatures fluctuate.

Certain turf species are more prone to crown hydration with Poa annua being more

susceptible than creeping bentgrass (Roberts, 1995). Crown hydration injury may be
potentially avoided by increasing cold hardiness, the ability of the plant to withstand low
temperatures, with certain cultural practices. Proper drainage to prevent standing water,
avoidance of excessive late fall irrigation, avoidance of excess nitrogen application in late
fall, and avoidance of close mowing going into winter can all help in crown hydration

prevention (Beard, 1969, 1973; Kaufmann, 1973).

Low temperature kill caused by prolonged ice or snow cover can also occur. The
lack of oxygen causes anaerobic conditions under the ice cover, which leads to plant
suffocation, or direct kill by the accumulation of toxic gasses under the ice cover
(Tompkins et al., 2004). The cause of turf death is rarely actual suffocation, but rather
damage done as the ice was forming, extracellular ice formation, or crown hydration
injury as the ice melts (Beard, I969; Tompkins et al., 2004). Extracellular ice formation
is an equilibrium freezing process that redistributes water vapor from within the cell to
the extracellular regions, causing frost desiccation to the protoplasm of the cells.
Suffocation of bentgrass greens has been observed to occur only when the duration of ice
cover is longer than 60 consecutive days (Tompkins et al., 2004). Creeping bentgrass has
been observed to survive 150 d of ice cover, however Poa annua can suffer damage in as
little as 45 d of ice cover. Breaking and removing ice cover before it can melt or
preventing the formation of ice with covers and drainage are ways of preventing ice

damage (Beard, 1969; Kaufmann, 1973).

Another cause of Winterkill is the cool weather fungal diseases, most commonly
grey, T yphula spp., and pink snow mold, Microdochium nivale, which can occur with or

without snow cover. Cool weather fungal diseases are the only type of Winterkill where

there is a potential for prevention. Preventative fimgicide treatments in the late fall and
occasionally throughout the winter season can prevent a snow mold problem. However,
history of snow mold disease and proper fungicide timing and management is essential to

eliminate this as a factor of Winterkill (Vargas, 2005).

Except for the snow mold diseases, there is no set kill pattern for Winterkill, it
may be sporadic or widespread and can vary in degree within the affected area. Its effects
can easily be seen beginning in early spring. Immediate kill of the entire turfgrass plant
will leave the plant completely dead by the time of spring thaw. When low temperature
kill of the crown has occurred the leaf tissue can remain alive. Once growth and
transpiration are stimulated from warmer temperatures, and there is no living root
structure to replace water lost, the turf will die (Beard, 1969). When Winterkill of an area
is suspected, a sample of the turf may be taken indoors to stimulate growth and observe if

damage has occurred.

The most difficult factors in the repair of winterkilled areas are the unpredictable
environmental conditions and the increasing demand for course play. For many '
occurrences of Winterkill, and especially areas with 30% or more of dead turf, the area
must be re-established in order to repair the damage done (Snow, 1979). Due to the low
temperatures and high potential for rain and snow at the time of year that Winterkill is
observed, cultural factors can be helpful in speeding up the re-establishment process. In
order to establish or re-establish an area there are two primary methods to use, seeding or
sodding. The size of the area, level of damage, expectation of golfers, and budget of the
course are factors in choosing which method to use (White, 2004). Both of these methods

are available for nearly all cultivars of creeping bentgrass. Winterkill itself may not be

viewed as detrimental to the course depending upon which areas are affected. Due to its
natural vulnerability to the winter elements, Poa annua has a higher likelihood than
creeping bentgrass of being damaged or killed over a winter season. For superintendents
looking to eradicate Poa annua from their course, Winterkill of Poa annua may be a
blessing to be capitalized upon to re-establish a desired bentgrass cultivar (Stier, 2005).
Alternatively, courses with extensive Poa annua are susceptible to higher levels of
Winterkill and can potentially be left with limited recovery options, as Poa annua seed or
sod is available only if the course maintains its own nursery green. Large areas of
creeping bentgrass suffering from complete kill may be resodded to re-establish the
playing surface, while smaller areas, or areas with sporadic or uneven damage are usually
re-established via seeding (Snow, 1979). Seeding is an economical option for re-
establishment as courses often keep seed in stock for various necessary repairs. Sod needs
to be compatible with the current soil profile of the course in order to ensure continuity.
This usually requires a course to maintain a nursery green or to buy washed sod.
Although a seemingly quick and easy repair to damaged areas, sodding requires the
removal of the entire damaged area and disrupts the playing surface until fully
established which can be up to three weeks (MSGA, 2008; Nelson, 2008). Seeding takes
a longer timeframe when trying to re-establish a completely dead area, especially if that
area is large. If seeding can occur with optimal growing conditions there can be
emergence from seed in as little as six days, but will not be able to sustain play and
completely fill an area for another six weeks, as most bentgrasses take 65 days to become

physiologically mature (Beard, 1973). However, the time needed to grow seed may be

justified by its lower cost and the flexibility of not requiring removal of the existing dead

turf.

Fertilizer timing has been shown to have an effect on the speed of establishing
seed. The amount of nitrogen applied can have varied effects on how the turf will grow.
This leads to the majority of fertility programs to be based on levels of nitrogen
(Christians, 2007). Lighter more frequent applications of nitrogen have been shown to
benefit new turf growth, while heavier applications timed further apart have been shown
to aid in the establishment of rooting systems (Christians, 1985; Nus et al., 1989). Both
types of growth are necessary for re-establishment and can also encourage surrounding
live turf to continue to thrive and potentially encroach and fill the dead area. During the
establishment period of turf a higher level of nitrogen is used to encourage quick seedling
growth. Additional fertilizations at 3 to 4 week intervals can help achieve a rapid
formation of quality turf (Beard, 1973). The amount of fertilizer needed within a given
timeframe depends upon the type of turf grown and its given life stage. Choosing which
timing program to follow can depend upon labor available as well as product price and

can vary throughout the season.

Most Winterkill repair is started as soon as the damage is observed. This is usually
when temperatures are less than desirable for bentgrass germination, as the optimal air
temperature for creeping bentgrass germination is 15-30 °C, with the soil temperature of
15-25 °C (Toole etal., 1977). In order to ensure the highest rate of germination the
canopy and soil temperature may be elevated (Eggens, 1982). This can be done with

underground heating systems, found mainly in sports fields, or the use of cover systems.

Use of cover systems has been shown to raise canopy and soil temperatures aiding in

seed establishment (Lettner, 1988; Schmidt et al., 1989).

Soil temperature under a cover system can be increased from 1 to 10 °C. Making
germination in late winter and early spring possible. Many types of cover systems are
available and different types of materials are used. Some of the more common cover
systems are: geotextile fabrics, spun-bonded polyester, and polyolefin plastic (Lettner,
1988). Plastic is also an economical option as it is widely available and easy to tailor to
specific needs as plastic sheets can be made to cover an entire green. Proven to help in
the prevention of low temperature kill and desiccation, the use of covers may also prove

to aid in the re-establishment process once damage has occurred (Lettner, 198 8).

MATERIALS AND METHODS

Research was conducted over three spring seasons, in April of 2006 and again,
with slight modifications, in April of 2007 and 2008. The research was conducted at the
Hancock Turfgrass Research Center (HTRC) located at Michigan State University in East
Lansing, Michigan.

In 2006 the area of the simulated winterkill experiment was 149 m2, divided into
three blocks; each with 16 individual treatment plots measuring 2.2 m2 (Table 43). There
were a total of two areas in both 2007 and 2008 years, the original creeping bentgrass
(Agrostis palustris) green from 2006 and a primarily Poa annua green. The particle size
distribution of the creeping bentgrass green was 90 g kg”1 sand, 8 g kg'1 silt, and 2 g kg"
clay. The Poa annua green was 74 g kg'1 sand, 24 g kg'1 silt, and 2 g kg'1 clay.

Table 43: Treatment factors for re-
establishment of creeping bentgrass
putting greens following simulated
winterkill at HTRC in 2006 - 2008.
Species - Cultivar

A. palustris - Penn A-4

A. palustris - Alpha‘

A. palustris - Providence

Poa annua

Fertilizer - rate Mm'f)‘ - timing
46-0-0 - 0.05 - every 7 days
19-25-5 - 0.15 - every 21 days
Cover treatment — 4 Mil plastic

When night temps. < 10°C
No cover

:t 2007 and 2008 study only;
:I: 0.15 g N m2 , total applied monthly per
plot.

 

 

 

 

 

 

 

10

In order to simulate winterkill, an area of pre-existing creeping bentgrass was
treated with non—selective herbicide (glyphosate), in a 5% a.i. solution, and applied with a
backpack sprayer at 207 kPa. Herbicide for the spring 2006 study was applied on 28
March 2006, and 10 April 2006. For the spring 2007 study, the applications were made
in October 2006, 25 March 2007, and 8 April 2007. The applications for the 2008 study
were made on 17 and 24 of April 2008.

The winterkill area was prepared for seeding using the Job SaverTM attachment on
a Jacobsen GA30 greens aerifier to create indentations for the seed to settle. The Job
SaverTM attachment alters the performance of a standard aerifier, it does not damage the
tissues of the turf plant, nor does it slice or dig into the soil surface. It creates small
indentations on the soil surface similar to dimples on a golf ball; also the Job SaverTM
does not remove the existing turf.

The creeping bentgrass cultivars used in 2006 were Penn A-4 and Providence,
with the addition of Alpha in 2007, and were seeded at a rate of 10 g m'z. The Poa annua
was established by collecting florets from a nearby Poa annua putting green, and then
spreading the florets evenly over the desired plots. The Poa annua florets were collected
by mowing a neighboring Poa annua green at a height of 12 mm, when it was seeding,
on 17 April 2006 and 2007, and on 28 April 2008.

The florets were then transferred to plastic bags. Sub-samples for each Poa
annua treatment were weighed, and number of florets in 1 g of each sample was counted.
In the 2006 study there was an estimated over 100 florets in 10 g of clippings, and in
spring 2007 and 2008 there was an estimated 2,500 florets in 10 g of clippings applied

per Poa annua plot.

11

The bentgrass cultivars were seeded by hand on 21 April, 2006 and 2007, and on
2 May 2008, the Poa annua florets were seeded by hand on May 4, 2006 and 2007, and
on May 9 2008, and raked to ensure even distribution over each plot. Immediately
following seeding, a topdressing of clean sand was applied at 562 g m'z, and starter
fertilizer (19N-25P-5K) was applied at 5 g N m'2 per plot.

Once emergence was observed on 19 May 2006, 10 May 2007, and 14 May 2008,
a 4 Mil thick transparent plastic sheet was placed over plots receiving the cover treatment.
Watch Dog® temperature data loggers were placed on the soil surface from seeding for
the duration of the cover treatment. This treatment was applied whenever the night
temperatures were expected to fall below 10 °C. The covers were applied in the late
evening, with 2 h of sunlight remaining, using plastic tarp tacks. The covers were
removed by early morning before the morning irrigation cycle.

Fertilization programs were also initiated upon emergence. Plots received
fertilization every 7 or 21 days. For the weekly, every 7days, application, urea (46N-0P-
0K) was applied at 0.05 g N m'z, dissolved in water and sprayed using a C02 backpack
sprayer at 207 kPa. For the every 21 days application, which will be referred to as every
3 wk application, a granular starter fertilizer with 4.4% methylene urea as the nitrogen
source (19N-25P-5K) was applied at 0.15 g N/ m'z, manually by hand shaker. Plots were
irrigated immediately following the fertilizer applications. Both applications were
continued for 11 wk in all years. The Poa annua green was fiilly established at the first
week of July for the 2007 and 2008 years and applications on that area were halted at that

time.

12

Irrigation was applied multiple times daily from 21 April to 30 April in 2006 and
2007, and from 2 May to 14 May in 2008, then every other day for the remainder of the
study in all years. Irrigation amounts varied to return 75% of potential evapotranspiration
(PET) everyday. PET was estimated with the modified Penman method calculated by the
on—site Michigan Agricultural Weather Network weather station. Two weeks after
seedlings had emerged, plots were mowed every other day for the entire study at a height
of 12 mm.

Data were collected weekly starting 7 d after the first cover and fertilizer
treatment applications from 25 May through 10 August in 2006, from 25 May through 8
August in 2007, and from 22 May through 9 July 2008. Cover was assessed using two
methods, visual estimate of percent cover (1%= poor, 60%= acceptable, 90% = excellent)
(NTEP, 2007), and digital image analysis ratings of percent cover (1% = poor/no cover,
60% = acceptable cover, 100% = fully established) (Karcher, 2005; Patton et al., 2005).
Digital images of each respective plot were taken on each rating date using a Cannon E05
Rebel XL camera with an E05 18-35 mm lens. Settings on the camera guarantee the
same frame size and pixel count were used for each image. Variability was further
reduced in the images by encasing the camera inside a box and providing a consistent
light source and ensuring the pictures were taken at the same height. The box was
created specifically for the purpose of digital image analysis. Sigma Scan® software
program (Systat Software Inc.) using the turf macro developed by Dr. Doug Karcher
(2005), analyzed these images by pixel for the amount of green pixels in each individual

image, which translated into the percent of turfgrass cover in the image.

13

The experimental design was a randomized complete block with three-factor
factorial treatment design. The three factors were turfgrass cultivar or species,
fertilization timing, and cover treatment. Treatment differences were analyzed using Proc
Mixed statistical analysis (SAS Institute Inc., 2007). Means were separated using Fisher’s

Protected LSD.

14

RESULTS AND DISSCUSSION

The data were analyzed by combining all years and both the creeping bentgrass
and P00 annua green, into one data set and then run through the SAS program as a three
factor factorial design. This resulted in significant year and significant location effects.
Because year and location were significant factors, the data were then separated into each
respective year and each respective location and mean separation was performed, when

appropriate.

Cultivar

The main effect of bentgrass cultivar or species, Poa annua, was significantly
different for all three years, using both methods of percent cover analysis on both a
creeping bentgrass and Poa annua green locations (Tables 1-10). The creeping bentgrass
cultivars had higher percent cover than Poa annua for every week in all three years with
both methods of percent cover analysis on the creeping bentgrass green (Tables 11-20).
There were also significant differences among creeping bentgrass cultivars within the

2006 and 2007 years.

For percent turfgrass cover, there was a significant difference among the creeping
bentgrass cultivars on wks 5, 7, and 8 in 2006 (Table 11). Providence had higher percent
cover, at 62%, than Penn A-4 with 58% on wk 5, and Penn A-4 had higher percent cover
than Providence on wks 7 and 8. Significant difference among creeping bentgrass
cultivars was found in 2006 using digital image analysis of percent turfgrass cover with
Penn A-4 having higher percent cover than Providence in wks 7 and 10 (Table 12). This

correlates with the visual ratings taken on wk 7.

15

In 2007, significant difference in percent turfgrass cover was found among
cultivars on wks 2 and 4, with Penn A-4 and Providence having higher percent cover than
Alpha. On wk 5, Providence with 71% and Alpha with 70% was significantly different
for percent cover than A-4 with 66% (Table 13). Using digital image analysis there were
significant differences among the creeping bentgrass cultivars on wks 2, 5, 8, 9, 10 with
Alpha and Providence having higher percent cover than Penn A-4 in 2007 (Table 14).
There were no significant differences among cultivars using both methods of percent

cover analysis in 2008 (Tables 15 & 16).

In 2007, a separate Poa annua green location was also established. This green
was chosen based on the hypothesis that the Poa annua seed already in the soil seedbank
might aid in re-establishing the Poa annua plots as well as decrease the time needed until
complete cover is achieved for the entire green. The main effect of bentgrass cultivar or
species, Poa annua, was significantly different for both years with the cultivars of
creeping bentgrass achieving higher percent cover than the Poa annua for every week
with both methods of percent cover analysis (Tables 7-10). There were also significant

differences among creeping bentgrass cultivars within each year.

There were significant differences among the creeping bentgrass cultivars for
percent cover at wk 4 of 2007. Penn A-4 and Providence had 78% cover, Alpha had 74%
cover (Table 17). There were significant differences among creeping bentgrass cultivars
for digital image analysis, Penn A-4 with 86% cover, and Providence with 81% cover,

and Alpha had 79% cover at wk 1 of 2007 (Table 18).

16

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32

Table 17: Effects of cultivar/species on percent turfgrass cover during re-
establishment of a Poa annua putting green following simulated winterkill in
2007, HTRC, East Lansing, MI.

 

 

 

Cultivar/species wk 1 wk 2 wk 4
Alpha 78 a‘ 80 a 74 b
Penn A-4 80 a 80 a 78 a
Providence 79 a 80 a 78 a
Poa annua 65 b 73 b 69 c
LSD (p=0.05) 3 2 3

 

1 Lower case letters within the same column represent significant differences
at the 0.05 probability level.

NS, Not significant at the 0.05 probability level

33

Table 18: Digital image analysis of effects of cultivar/species on percent turfgrass
cover during re-establishment of a Poa annua putting green following simulated
winterkill in 2007, HTRC, East Lansing, MI.

 

 

 

Cultivar/species wk 1
Alpha 79 b‘
Penn A-4 86 3
Providence 81 a
Poa annua 57 c
LSD (p=0.05) 7

 

’ Lower case letters within the same column represent significant differences at the
0.05 probability level.

NS, Not significant at the 0.05 probability level

34

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36

There were no significant differences among creeping bentgrass cultivars for
percent cover in 2008 (Table 19). There were significant differences among turfgrass
cultivars for digital image analysis. Alpha and Penn A-4 had higher percent cover than

Providence in wks l, 2, and 6 of 2008 (Table 20).

All plots on the Poa annua green reached full establishment (85% cover or
greater) five weeks before the creeping bentgrass green in 2007 and three weeks before
the creeping bentgrass green in 2008. Despite having an existing Poa annua seedbank,

the Poa annua plots had significantly lower percent coverage throughout the study.
Fertilizer timing

There was a significant fertilizer program effect for all years and locations, using
both methods of cover analysis (Tables 1-4 and 8). For each date when there was a
significant difference, the 0.15 g N m'2 applied every three weeks had higher levels of

turfgrass cover than the 0.05 g N m'2 treatment applied weekly.

There were significant differences between fertilizer programs for percent cover
for wks 5-10 in 2006. The every three week fertilizer treatment had an average of 14%
higher turfgrass cover than the weekly fertilizer treatment for 2006 (Table 21). In 2006
there were significant differences between fertilizer programs for wks 7 and 8 using
digital image analysis (Table 22). In 2007 there were significant differences between

fertilizer programs for percent cover for wks 4 and 5 (Table 23). Using digital image

37

analysis there were significant differences on wks 2, 4, 5, and 8-10 (Table 24).

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39

Table 23: Effects of fertilizer rate on percent turfgrass cover during re.
establishment of a Creeping Bentgrass putting green following simulated
winterkill in 2007, HTRC, East Lansing, MI.

 

 

 

Fertilizer Rate gN/m7 wk 4 wk 5
0.05 48 b' 62 b
0.15 59 a 66 a

LSD (p=0.05) 4 2

 

' Lower case letters within the same column represent significant differences
at the 0.05 probability level.
NS, Not significant at the 0.05 probability level

40

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41

In 2008, the every three week program had over 10% higher turfgrass cover than the

weekly fertilizer program on wks 4-6 (Table 26), using digital image analysis.

The fertilizer used in the weekly application was urea (46N-OP-OK) dissolved in
water and applied with a pressurized backpack sprayer. This application method results in
the product being applied foliarly, with a quick release nitrogen source. The granular
fertilizer had 40% of its nitrogen, methelene urea, as slow release, providing continual
nutrient release. The every three week application was a complete fertilizer with a 19N-
25P-5K analysis. This inclusion of high levels of phosphorus may explain why the every
three-week application resulted in significantly higher percent turfgrass cover.
Phosphorus is known to be beneficial in the development of new turf growth and cell
development (Christians, 2007), allowing for quicker establishment and higher percent

turfgrass cover.

There were no significant differences between fertilizer programs using either
method of percent cover analysis on the Poa annua green in 2007 (Tables 5 & 6). There
were no significant differences between fertilizer programs for percent cover in 2008
(Table 9). Significant differences were found between fertilizer programs on the Poa
annua green using digital image analysis in the 2008 year (Table 10). There were
significant differences found on wks 1, 2, and 6 of 2008 (Table 27). In each of the
significant dates the 0.15 g N m'2 applied every three week resulted in an average of 10%

higher turfgrass cover than the 0.05 g N rn'2 every week rate.

42

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44

Plastic cover

There were no significant cover treatment effects in 2006 and 2007 using either
turfgrass cover or digital image analysis for either location. There was also no significant

cover treatment effect using digital image analysis in 2008 (Tables 1-8, & 10).

However, there were significant cover treatment effects in 2008, for percent cover
(Tables 4, 9, 25, & 28). The plots receiving the 4 Mil plastic cover at night when temps
were below 10 °C had significantly higher percent cover than those that did not receive
the cover for wks 2-6 at both locations (Tables 25 & 28). The lack of significance found
by digital image analysis in 2008 may be accounted for by the limitations of the computer
software. The digital image program reads each photo as a two dimensional image, the
human eye can account for more plant tissue growing vertically than the software,

potentially affecting ratings.

Using a local weather station in the Michigan Automated Weather Network,
located at the Hancock Turfgrass Research Center, the average nighttime air temperature
was recorded for 2006-2008 (Table 29). The temperature readings from the WatchDog®
temperature data loggers on the covered and uncovered plots were checked for
significance within each day, week, and month of the duration of the cover treatment for
2007-2008. Temperature data loggers were not used in 2006. The average temperatures

for the covered and uncovered plots were not significantly different fi'om each other for

45

either the 2007 or 2008 years for both the creeping bentgrass and the Poa annua greens.

46

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47

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48

The average air temperatures for 2006-2008 were also similar (Table 29). This
lack of significance in plot temperatures and similar air temperatures may explain the
lack of significance in cover treatments for 2006 -2008 in both the visual and digital
image analysis respectively (Tables 1-8, & 10). Eggens (1982) found that if soil and
canopy temperature can be elevated into the optimum growth range then establishment
may be accelerated. The optimum canopy temperature range of 15 °C to 30 °C (Toole et

al., 1977) was not met with our cover treatment.

Table 29: Average air temperatures for April 25-May 30 for 2006 - 2008 at
HTRC, East Lansing, MI.

 

 

Year 2006 2007 2008
Minimum 7* 8 5
Maximum 20 21 19
Average 13 15 12

 

T Temperatures are °C

49

CONCLUSIONS

In this research on the re-establishment of creeping bentgrass following
simulated winterkill, the use of creeping bentgrass cultivars Alpha, Penn A-4, and
Providence resulted in quicker and higher percent coverage of turf than by
attempting to establish Poa annua. The creeping bentgrass plots achieved 85% or
higher turfgrass cover on an average of 35 days, where Poa annua plots did not
achieve 85% or higher turfgrass cover on a creeping bentgrass green. There were
few significant differences among the bentgrass cultivars, and this can be explained
by the lack of ideal growing conditions at the time of establishment (Danneberger,
1993). The amount of Poa annua that did establish is estimated to originate from
the seedbank. The importance of the P00 annua seedbank is illustrated by the data
from the P00 annua green in 2007-2008, where establishment of the Pan annua
plots averaged 90% cover by the end of the study, and the P00 annua plots on the
creeping bentgrass green only reached an average of 70% cover by the end of the

study.

The fertilizer program using the complete (19N-25P-5K) fertilizer resulted in
the highest percent of turf cover on the dates when significant. Although nitrogen is
essential and highly influential in plant growth (Christians, 2007), the every three-
week program included other important nutrients, phosphorus and potassium, in a
formulation to be used specifically for turfgrass establishment. Both programs

applied the same amount of nitrogen in the same timeframe. The inclusion of

50

phosphorus in the monthly program may explain the significant differences

between the two fertilizer programs during this re-establishment period.

The cover treatment was ineffective for all three years. The plastic used was
impermeable and may have potentially hindered seedling growth by limiting plant
respiration (Schmidt et al., 1989). In order for a cover treatment to be effective in
increasing plant growth it must provide an optimum temperature for plant
development (Eggens, 1982). This cover treatment did not raise the canopy
temperature high enough to promote turfgrass growth. There was no significant
difference in temperature between covered and uncovered plots for 2007-2008.
Although temperature data loggers were not used in 2006, when daily air
temperatures were compared with the air temperatures of 2007-2008 they were
very similar, potentially accounting for the lack of significance in cover treatment in

2006.

Winterkill is an elusive problem due to its myriad of causes. There are many
factors that come into play for its prevention, cause, and recovery. The most
significant factor in winterkill recovery in this study was the use of a creeping
bentgrass cultivar versus trying to establish with Poa annua seedheads. Even a
predominantly Poa annua green was able to re-establish creeping bentgrass
successfully. A complete fertilizer containing nitrogen, phosphorus, and potassium,
applied once every 21 days, also aided in increasing percent turfgrass cover during

re-establishment in this study.

51

APPENDIX

52

Table 30: Days until turfgrass cover of turfgrass cultivar/ species on a
Creeping bentgrass puttinggreen 2006.

 

 

 

Tuigrass cover

 

Cultivar! Species 60% 90%
Penn A-4 30* 60
Providence 30 60

P03 annua 60 NA*

 

T Units are in days
1’ NA, not achieved in this study

Table 31: Days until Percent Turfgrass Cover with fertilizer timing factor
on a Creepigg bentgrass putting_green 2006.

 

Turfgrass cover

 

 

Fertilizer Timing 60% 90%
Every 7 days 56* 77
Every 21 days 49 77

 

T Units are in days

Table 32: Days until Percent Turfgrass Cover of turfgrass cultivar/
species on a Creeping bentgrasgputtigq green 2007.

 

Turfgrass cover

 

 

Cultivar! Species 60% 90%
Alpha 21* 70
Penn A-4 14 70
Providence 14 70
Poa annua 42 NAT

 

T Units are in days
1 NA, not achieved in this study

53

Table 33: Days until turfgrass cover of turfgrass cultivar/ species on a
Poa annua puttinggreen 2007.

 

Turffiass cover

 

 

Cultivar! Species 60% 90%
Alpha 14’F 28
Penn A4 14 28
Providence 14 28
Poa annua 28 35

 

T Units are in days

Table 34: Days until turfgrass cover with fertilizer timing factor on a
Creepingbentgrass putting green 2007.

 

 

Turfgass cover

 

 

Fertilizer TiminL 60% 90%
Every 7 days 35* 63
Every 21 days 28 56

 

T Units are in days

Table 35: Days until turfgrass cover with fertilizer timing factor on a Poa
annua puttinggreen 2007.

 

 

Tufigrass cover

 

 

Fertilizer Timing 60% 90%
Every 7 days 56¥ 70
Every 21 dafi 35 56

 

T Units are in days

54

Table 36: Days until turfgrass cover of turfgrass cultivar/ species on a
Creeping bentgrass putting green 2008.

 

Turfgrass cover

 

 

Cultivar! Species 60% 90%
Alpha 42* 63
Penn A-4 42 63
Providence 42 63
Poa annua 70 NA’r
T Units are in days

 

1' NA, not achieved in this study

Table 37: Days turfgrass cover of turfgrass cultivar/ species on a Poa
annlgputting green 2008.

 

Turfgrass cover

 

 

Cultivar! Species 60% 90%
Alpha 28T 56
Penn A4 28 56
Providence 28 56
Poa annua 70 NAT
T Units are in days

 

1‘ NA, not achieved in this study

Table 38: Days until turfgrass cover with fertilizer timing factor on a
Creeping bentgrassputtinggreen 2008.

 

 

 

 

Turfgrass cover
Fertilizer Timing 60% 90%
Every 7 days 35* 63
Every 21 days 28 56
T Units are in days

 

55

Table 39: Days until turfgrass cover with fertilizer timing factor on a Poa
annua puttinggreen 2008.

 

 

Turfggass cover

 

 

Fertilizer TiminL 60% 90%
Every 7 days 28F 70
Every 21 days 28 70

 

T Units are in days

Table 40: Days until turfgrass cover with cover treatment factor on a
Creeping beggrass gutting green 2008.

 

 

Turfgrass cover

 

 

Cover Treatment 60% 90%
None 56* > 70
4 mil plastic 49 70

 

T Units are in days

Table 41: Days until turfgrass cover with cover treatment factor on a Poa
annua puttimeen 2008.

 

 

Turfgrass cover

 

 

Cover Treatment 60% 90%
None 42‘ ‘ 7O
4 mil plastic 35 70

 

T Units are in days
1' N/A, not achieved in this study

56

 

«68 Sam. admm v.89 33 we: a

 

o—

o

2 .. 2 as 598983....an

 

88

88 88 .8>

 

 

.siaaasmégagaasaosassfia

57

 

Table 43: Treatment factors for re-
establishment of creeping bentgrass
putting greens following simulated
winterkill at HTRC in 2006 - 2008.

 

Species - Cultivar

 

A. palustris — Penn A—4
A. palustn's — Alpha‘
A. palustn's - Providence

Poa annua

 

Fertilizer - rate (9 N m'2)* - timing

 

46-0-0 - 0.05 - every 7 days
19-25-5 - 0.15 - every 21 days

 

Cover treatment - 4 Mil plastic

 

When night temps. < 10°C

No cover

 

:l: 2007 and 2008 study only;

1 0.15 g N m2 , total applied monthly per
plot.

58

REFERENCES

59

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62

   

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