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ABSTRACT

FACTORS INFLUENCING COMPETITION OF
ANNUAL BLUEGRASS (POA ANNUA L.)
WITHIN ESTABLISHED TURFCRASS COMMUNITIES
AND SEEDLING STANDS

 

By
James E. Bogart
Phenological observations and controlled climate growth

chamber studies were used to investigate the growth responses

of annual bluegrass (Poa annua L.), Merion Kentucky bluegrass

 

(Poa pratensis L.), and Penncross creeping bentgrass (Agrostis

 

palustris Huds.). Measurements of root and shoot dry weights

 

were made at each of seven constant temperature treatments.
Annual bluegrass seedhead production and seed germination were
also observed.

The phenological observations, when combined with the
temperature findings, indicate that Penncross creeping bent-
grass and Merion Kentucky bluegrass began spring growth prior
to annual bluegrass. Penncross creeping bentgrass and Merion
Kentucky bluegrass initiated new shoot growth between 50° and
55°F, while established plants of annual bluegrass did not
initiate new Spring growth until the soil temperature exceeded

55°F.

Penncross creeping bentgrass produced maximum root dry
weight at 60°F while Merion Kentucky bluegrass and annual
bluegrass produced maximum root dry weights at 70°F. Annual
bluegrass root growth was significantly higher than Merion
Kentucky bluegrass and Penncross creeping bentgrass at temper-
atures from 50° to 80°F. All three species produced maximum
shoot dry weights at 60°F. Penncross creeping bentgrass was
adapted to a wider range of temperatures having produced
superior root and shoot dry weights at the extreme tempera-
tures of #00 and 90°F.

Maturity of the three species was attained quicker at
80°F. The root systems of all three species had begun to
turn brown at 80°F. Annual bluegrass plants at 80°F produced
seedheads during the first 15 days of the constant temperature
treatment. However, seedheads at 60°, 70°, and 90°F were not
produced until after day 15.

Annual bluegrass seed germination did not differ signifi-
cantly at constant temperatures from 40° to 70°F. Hewever,
very substantial decreases were observed at 800 and 90°F.

A second phase of the investigation involved a study of
the competitive ability of annual bluegrass as influenced by
cutting height. Annual bluegrass plants were grown in estab-
lished Merion Kentucky bluegrass sod and in monostands.
Measurements were made of shoot dry weight, root organic
matter, tiller number, and shoot density of the annual
bluegrass.

Cutting height treatments significantly influenced the

shoot dry weight, tiller number, and shoot density. The 1.0
inch cutting height ranked highest in shoot dry weight and
tiller number production. It was concluded that the optimum
cutting height for annual bluegrass is 1.0 inch.

The final competitive factor investigated was root
growth and deveIOpment. Annual bluegrass, Penncross creeping
bentgrass, and Nerion Kentucky bluegrass were compared using
special root observation boxes with slanting glass faces.
Root growth and deve10pment was observed over 15-day and 50-
day periods where one set of plants remained uncut while the
other set was clipped three times weekly at 1.0 inch.

The rooting depth among the three species was non-
significant at the end of both growing periods. Root
organic matter produced during the 30-day period was also
non-significant among Species. However, visual observations
during the initial 10 day period indicated that annual blue-
grass root growth was more rapid. The root organic matter
production after 15 days supported this observation. Cutting
the plants at 1.0 inch reduced the rooting depth of all three
species. Penncross creeping bentgrass was the most severely
reduced. These findings showed that annual bluegrass is not
shallow rooted as is commonly believed. Furthermore, the
initial superiority in rooting capability of annual bluegrass
could play an important role in its competition within a

turfgrass community.

FACTORS INFLUENCING COMPETITION OF ANNUAL BLUEGRASS
(POA ANNUA L.) WITHIN ESTABLISHED
TURFGRASS COMMUNITIES AND SEEDLING STANDS

BY

{\

James E? BOgart

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
1972

6‘ ACKNOWLEDGMENTS

The author would like to express his sincere apprecia-
tion to the following persons without whose help and guidance
this study would not have been possible:

The United States Golf Association Greens Section through
whose grant this investigation was partially supported.

My loving wife JOan who aided in the preparation of this
manuscript and without whose inspiration and encouragement
this investigation may have never been completed.

Dr. W. F. Meggitt and J. M. vargas Jr. for their assist-
ance and suggestions as members of the author's guidance
committee.

Dr. P. E. Rieke for his constructive criticism during
the preparation of this manuscript and for serving on the
guidance committee.

And finally, Dr. J. B. Beard; major professor, teacher,
and above all friend; whose inSpiration and guidance, through-
out the course of study and this investigation, were greatly
appreciated.

TABLE OF CONTENTS

IN‘mODUCTIONOOOOOOOOOOOO00....00......00.0.000000000000000001

1.1mm REVIE1JOO00......OOOOOOOOOOOOOOOOOCOOOO000.......03
General macription.OI.OOOOOOOOOOOOOO0.00.00.00.00...0.3

RootinSOOOOOOO0....O0.0...00......OOOOOOOIOOOOOOOOOOOOO

Seed Germination and Dissemination.....................9
ECOtype variability. . O C C C O C O O C O O C O C O O O C O C . C C O C O . O O O O O O 12
Adaptation. 0.. O O O C C C O O O C . O O . C C C O C C O O . O C C O C O O O O O O O O O O O O .14
Temperature-Growth Relationships......................l6
cutting might. C O O O O O C . C C C O O . C O C O . O . O C O C O C C C O O C C O C O O C .20
Fertility Response 0 O O C O . O C O C C O C O C C O O O O O C C O O C O O C O C C O O O .21

MAMMIB Am mmomOOOOOOOOOOOOOOOOO0000.00.00.000000000025
TEMPERATURE-GROW}! REIATIONSI-HPSOOOOOOOOOOOOOOO00.000.000.025
Phen01081cal ObservatIODSOOOOOOOOOOOO0.0.0.0000...0.0025
Controlled Climate Growth Chamber Studies.............30
NITROGEN FERTILITY AND CUTTING HEIGHT STUDIES..............34
Matm 80d merimentOOOOOOOOOOOOOOOOOO0.000.000.0000031"
Annual Bluegrass Menostand Experiment.................36
ROOT GROW AND DMI—DPMNT STIIDIESOOOOOOOOOOOOOOO0.0.0.0003?
RESULTS Am DISCUSSION.OOOOOOOOOOOOOOOOOO00.00000000000000041
WWW-GROW REMTIONSI-HPSOOOO0.00.0.000000000000000041
PhenOIOgical ObservationSOOIOOOO00.000000000000000000041
Controlled Climate Growth Chamber Studies.............43
CUTTING HEIGHT AND NITROGEN FERTILITY STUDIES..............52
Mature 30d mwrmntc.0000..0000.00.00.0000.000.000.052
Annual Bluegrass Monostand............................55
ROOT GROW Am DmmPMNTOOOOOOOOO0.000.000.000000000000056
CONcmSIONSOOOOOOOOOOOOOOO.00.000...00.00.000.000...00.0.0062
BIBlImRAPI'IYOOOOOOOOOO0000.00.00.00.000.00.000...000000000064

APPENDIXOOOOOOOO0.0......O...O...O0.00...0.0.00.0000000000067

TABLE 1.

TABLE 2.

TABLE 3.

TABLE 4.

TABLE 5.

TABLE 6.

TABLE,7.

TABLE 8.

TABLE 9.

LIST OF TABLES

Approximate root depths of cool and warm
season turfgrasses................................7

Clipping yields of two turfgrass species
to six constant temperature treatments...........50

Annual bluegrass seed germination as
influenced by six temperature treatments.........52

The influence of five cutting heights on the

shoot dry weights of individual annual blue-

grass plants grown in a mature Merion Kentucky
blmgass SOdOO0.000000000000000000000000.0.0.0005}

The influence of five cutting heights on the
tillering of individual annual bluegrass

plants grown in a mature Merion Kentucky

bl‘legrass SOdOOOOOOOOOOOOOOIOIOOOOOOOOIOOOOOO000.54

The influence of five cutting heights on
the shoot density of annual bluegrass
plants grown in a nomostand......................55

The rooting depths of three turfgrass
Species grown under two cutting treatments
for 30 days after transplanting..................57

The rooting depths of three turfgrass
species grown under two cutting heights
for 15 days after transplanting..................59

The root organic matter produced by three

turfgrass species when grown under two

cutting treatments for 15 days after trans-
planting.OOOOOOOOOOOOOOO0.00000000000000000000.0060

Figure 1.

Figure 2.

Figure 3.

Figure 4.

Figure 5.

LIST OF FIGURES

Individual plants growing in sand cultures
that were used in controlled Climate growth
ChWber StudyOOOOOOOOOOO0.00.000.00.00000000000032

Root observation box with slanting glass
face used for observation of root growth
and develomntooOOOOOOOOOOOOO0.0.0.00.0...00.0.38

Shoot growth responses of three turfgrass
species to seven constant temperature
tmamntSOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO0.0000u6

Root growth responses of three turfgrass
species to seven constant temperature
treatmnts...‘OOOOOOOOOOOOOOOO0.00.00.000.00..0048

Rooting of three turfgrass species 15 days
af‘ter transplantingooOOOOOOOIOOOOOOOOOOOOOOO000.61

INTRODUCTION

Annual bluegrass (Poa annua L.) is considered by many as

 

one of the most common turfgrass pests. Originally native to
Europe, annual bluegrass is now distributed throughout the
United States as well as in varied parts of the world. The
species grows under a wide range of cultural, soil, and
climatic conditions. Annual bluegrass has been found growing
from seashore to mountain regions. It grows under both low
and high fertility levels as well as a wide range of cutting
heights. Annual bluegrass is comparatively well adapted to
compacted soil conditions.

Several problems cause annual bluegrass to be classified
as a turfgrass pest. The most objectionable of these charac-
teristics is the lack of tolerance to environmental stresses.
Annual bluegrass is susceptible to high and low temperature
injury. Furthermore, the plant lacks hardiness to drought
stress. The second major problem is its prolific seedhead
production. An individual annual bluegrass plant can produce
hundreds of seeds over a growing season. The ability of the
plant to produce abundant seeds occurs even at close cutting
heights. A new problem with annual bluegrass is being recog-
nized in this modern era of atmospheric pollutants. It is
highly susceptible to smog damage.

Much has been said and written over the years concerning
the annual bluegrass problem in intensively cultured turfs.
Most research projects conducted with annual bluegrass have
dealt with methods of chemical control. Many herbicides have
been evaluated in an attempt to produce an effective control
program. The results have been erratic. variability within
the annual bluegrass Species may be one of the reasons for the
erratic control. Because of this, many professional turf
managers have abandoned chemical control programs and have
chosen to "live" with annual bluegrass. Some have been quite
successful in this endeavor, while others have failed due to
a lack of knowledge concerning the cultural requirements of
annual bluegrass.

The objectives of this investigation were to define some
of the cultural and environmental conditions which influence
annual bluegrass infestations. Temperature response, cutting
height, fertility level, and root development rate were
studied to determine their effects on the competitiveness
and survival of annual bluegrass. These effects were studied
within both seedling and established turfgrass communities.
The annual bluegrass reSponses were compared with Merion

Kentucky bluegrass (Poa pratensis L.) and Penncross creeping

 

bentgrass (Agrostis palustris Huds.) throughout the investi-

 

gation.

LITERATURE REVIEW

General Description

 

Annual bluegrass (Poa annua L.) is a diminutive, low

 

growing plant. Although generally considered a bunch-type
grass some strains are creepers (7). Annual bluegrass
possesses a light green to greenish-yellow color (7, 22).
Sprague and Burton (34) reported that annual bluegrass
remained vivid green as autumn approached. Tutin (37)

reported that annual bluegrass was a cross between Poa infirma

 

H.B.K., an annual plant, and £22 supina Schrad. a perennial
plant. The chromosome number of annual bluegrass is 2n=28
(27). The Species possesses two large chromosomes and one
small chromosome. In addition, Koshy (27) reported that
annual bluegrass had three groups of chromosomes containing
2, 4, and 5 chromosomes respectively. Juhren, et. al., (24)
observed that annual bluegrass reached the 2-leaf stage of
develOpment one week after emergence. Some plants were
observed by Arber (2) to have replaced their leaf traces with
branch traces. She also observed a strong tendency of the
inflorescences to remain leafless.

Annual bluegrass is reported to be among the first turf-
grasses to resume growth in the spring (25, 34). In addition,
Kerr (26) felt that the rapid shoot growth of annual bluegrass

3

contributed to its highly competitive nature. The growth
rate was observed to become more rapid when the seedling
plant had developed to the third leaf stage (24). Although
most abundant in spring, annual bluegrass plants began to
disappear in midsummer (34). Monteith (31) also reported the
disappearance of annual bluegrass in May. The lack of toler-
ance to heat and drought stresses may have accounted for
these observations. Sprague and Burton (34) concluded that
midsummer conditions in open areas were unfavorable for the
growth of annual bluegrass. They found that the most favor-
able conditions occurred after mid-August. Sprague and Burton
(34) further believed that annual bluegrass began its growth
in the late summer/early fall period. They reported that
annual bluegrass would continue to grow in the fall as long
as the soil remained unfrozen.

Younger (39) explained the growth pattern of annual blue-
grass by reporting that high soil moisture levels were common
to annual bluegrass survival. Sprague and Evaul (35) also
showed that annual bluegrass was more tolerant of excess
moisture. They found that maximum growth was achieved when
the soil moisture level was 50-60% of the soil water holding
capacity. It was also reported that annual bluegrass was
eliminated at low moisture levels (39). This would explain
the disappearance of annual bluegrass during midsummer drought
periods. Excessive wear during the midsummer period was
another factor contributing to the disappearance of annual

bluegrass (26).

The leaf structure of annual bluegrass is similar to the
other bluegrasses. Annual bluegrass possesses the boat-shaped
leaf tip which is characteristic of all bluegrasses. Brobrov
(11) observed the ligule of annual bluegrass to be larger than
the ligule of Kentucky bluegrass (Egaflpratensis L.) and similar

 

to the ligule of rough bluegrass (Poa trivialis L.). Brobrov

 

(11) described the leaf as being strap-shaped and parallel
veined with a prominent mid-rib. The leaf also possesses
pairs of bulliform cells flanking the mid-rib (2, ll). Arber
(2) reported a simple leaf epidermis consisting of smooth-
walled cells. Brobrov (11) reported that the epidermal cells
were rectangular shaped. The cuticle layer covering the epi-
dermis was found to be thinner on the upper leaf surface than
the lower (11). Brobrov (11) observed that the upper and
lower leaf surfaces were not parallel. She also observed
stomata to be more abundant on the upper surface.
Rooting

Annual bluegrass is commonly referred to as a shallow-
rooted Species although the limited research work suggests
otherwise. This widely accepted concept has resulted from
casual observations of annual bluegrass in the field. However,
in the field annual bluegrass is frequently found under con-
ditions which are not conductive to optimum growth of the
plant. These conditions include soil compaction and close
mowing. under close clipping, root growth is decreased in
most Species (l, 10). Kerr (26) listed the problems associated

with annual bluegrass and blamed the lack of tolerance to heat

stress on the plants' high transpiration rate combined with a
shallow root system. Renney (32) reported that annual blue-
grass will root almost entirely in the mat layer. Gibeault
(l7) referred to the shallow root system of annual bluegrass
as being associated with frequent irrigation under putting
green conditions. Normal root depths for the turfgrasses were
listed by Gibeault (17) (Table 1). Based on this table, annual
bluegrass was reputed to produce a root system 1.0 - 4.0
inches in depth. This was considerably less than the rooting
depths listed for creeping bentgrass and Kentucky bluegrass.
Although the concensus holds that annual bluegrass is
shallow rooted; limited research suggests that the Opposite is
true. The earliest of these studies was conducted by Sprague
and Burton (34) in New Jersey. It was concluded that under
identical soil and cultural conditions annual bluegrass de-
velOped a similar root system to Kentucky bluegrass and
colonial bentgrass. Sprague and Burton (34) also concluded
that annual bluegrass produced a far denser root system in
well aerated soils than in compacted soils. Beard (7) com-

pared the rooting of annual bluegrass to that of Poa pratensis.

 

'He also referred to the shallow rooted nature of annual blue-
grass under compacted conditions (8).

A more detailed study of root growth under compacted
conditions was conducted in Rhode Island by Wilkinson and
Duff (38). Annual bluegrass, Kentucky bluegrass, and Penn-
cross creeping bentgrass were compared at three soil bulk

densities. Root weight measurements of each species were

 

 

 

 

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8

made after eight and twelve weeks. There was no significant
difference in the total root weight of the species at bulk
densities of 1.25 and 1.4. Hewever, at a bulk density of 1.1
Kentucky bluegrass produced less roots after eight weeks. The
root weights decreased with depth in all cases but increased
with bulk density. Similar findings were reported by Sprague
and Burton (34) who listed the percentages of root weights
found in the upper 3 inches under compacted conditions. Ken-
tucky bluegrass possessed 92% of its roots in the upper 3
inches. By comparison colonial bentgrass possessed 88% and
annual bluegrass 86.8% in the upper 3 inches (34). Based on
their results, Wilkinson and Duff (38) conclude that (1) a
bulk density 1.4 was not high enough to limit root growth, and
(2) the root growth of annual bluegrass is equal to that of

Poa pratensis and Agrostis palustris.

 

 

The effects of nutritional levels on root growth of annual
bluegrass were reported by Juska and Hanson (25). They observed
the effects of various combinations of N, P, and K at each of
two levels. These combinations were applied to two soil types
at each of two pH levels. Root weights of annual bluegrass
were not increased materially with any of the fertilizer treat-
ments used. With certain fertilizer treatments, a significant
decline in rooting was observed on the loamy sand soil but not
on the silt loam. The same treatments produced increases in
shoot growth of annual bluegrass. werking with the loamy sand
soil, Juska and Hanson found that a pH of 6.5 increased root

weights Significantly compared to a pH of 4.5.

9

Beard and Daniel (10) investigated the root growth and
development of creeping bentgrass. Bentgrass root production
was observed at temperatures from 60°F to 90°F. The growth
rates at 60°F, 70°F, and 80°F were similar but a significant
reduction was observed at 90°F. However, total root produc-
tion decreased sharply as the temperature was increased. The
initial growth rate was rapid at each temperature with the
peak rate occurring between days 8 and 10 following trans-
planting of the bentgrass plugs. Daily clipping of the plugs
produced a further reduction in root growth.

Due to the Similarity in root development between annual
bluegrass and other turfgrass Species, it is possible that
rooting is more important in the competiveness of annual blue-
grass than was previously thought.

Seed Germination and Dissemination

 

Seedhead production has long been recognized as one of
the major problems associated with annual bluegrass under
turfgrass conditions. Seedhead formation occurs throughout
the growing season but is most intense in late spring (7).
During the growing season annual bluegrass seedheads are
extensive and unsightly in highly maintained turfgrass areas.
Annual bluegrass has the ability to produce seedheads at very
close cutting heights (32). Beard (8) noted the ability of
annual bluegrass to flower even at a 0.25 inch height of cut.
Renney (32) found that a single annual bluegrass plant pro-
duced 360 seeds in a growing season. This observation was

made in British Columbia during a four month period from May

10

through August. Based on this observation, Renney (32) esti-
mated that the surface layer of soil might contain 30,000,000
annual bluegrass seeds per acre. Although seedhead production
was most prolific during the growing season; Arber (2) observed
that annual bluegrass also flowered in the winter in England.
Cockerham and Whitworth (13) observed flowering in February

in New Mexico. Furthermore, they collected viable seed in
mid-March. Annual bluegrass is often referred to as a winter
annual in the warm humid climatic regions.

Seeds of annual bluegrass can be disseminated by wind,
water, animals, and man. In addition, turfgrass mowing equip-
ment would have to be considered a prime mode of tranSportation
for the seeds. Pollination of annual bluegrass is also aided
by these means. Lynch (30) first observed that annual blue-
grass was not a self-fertilizer. Koshy (28) discussed the
cross-pollination of annual bluegrass and also stated that
viable seed had been obtained 24-48 hours following pollina-
tion. Pollination was observed to take place during the
early morning hours (30). Juhren, et. al., (24) found that

Poa annua plants reached the flowering stage in 5-7 weeks.

 

Based on the findings of Gibeault (16) these plants would be
classified as annual types. His investigation showed that
plants of the annual subspecies (var. annua) flowered in 50
days compared to an 81 day period for the perennial subSpecies
(var. reptans).

Several investigations dealing with seed germination of

annual bluegrass have been reported. One of the most detailed

11

studies was conducted by Engel (14) who observed the effects
of four temperature regimes on seed germination of annual
bluegrass and colonial bentgrass (Agrostis tenuis). Three
regimes were observed with and without light. The 86°F
regime was observed under dark conditions only. The annual
bluegrass seed produced higher germination rates throughout
the study when it received eight hours of light per day.
Hovin (21) and Renney (32) both reported that annual bluegrass
seed germination was favored by light. Juhren, et. al., (24)
stated that the optimum conditions for germination consisted
of a 16 hour photoperiod with a maximum of 5000 ft. cdle.
When Engel (14) compared colonial bentgrass (Agrostis tenuis
Sibth.) germination with that of annual bluegrass, he showed
bentgrass germination rates to be higher under both light and
dark conditions. Engel also showed that germination of both
species was reduced at 86°F with annual bluegrass being more
severely reduced. Germination during the first two weeks was
higher at 66°F than with a 59°-86°F regime (14). This agreed
with Cockerham and Whitworth (13) who concluded that 60°F was
the best temperature for annual bluegrass seed germination.
However, alternate low (50°F) and high (70°F) temperatures
have been shown to promote germination of unripe seeds (21).
The time necessary for germination became longer as tempera-
tures were lowered. It was observed that germination took 18-
22 days under cold (17°C day 11°C night) conditions compared
to seven days under Optimal conditions (23°C day 17°C night)
(24). Jackson (22) reported germination in six days.

12

Seed germination is also affected by varability within
the annual bluegrass species. Hovin (21) observed that seed
of perennial types germinated immediately following harvest.
Koshy (28) made a similar finding when he observed seed germi-
nation occurring within panicles which had been removed from
the parent plant. He reported 14% germination by the fourth
day. A more recent investigation supported these earlier
observations pertaining to perennial type annual bluegrass
plants (16). Gibeault (16) also showed that seed of the
annual subspecies possessed a post-harvest dormancy. This
explained the statement by Cockerham and Whitworth (13) that
freshly harvested seed would not germinate. The annual sub-
species is better able to perpetuate itself through post-
harvest dormancy by avoiding the heat and drought stresses of
midsummer. Due to post-harvest dormancy of the annual sub-
Species, Beard (7) concluded that germination is most active
during the moist cool period of late summer.

Ecotype variability

 

It has been observed that variations exist within the
annual bluegrass species. Arber (2) noted that annual blue-
grass had no fixed periodicity. She further observed that
annual bluegrass could produce several generations in a single
year or could become perennial in nature. Arber (2) also
found that some annual bluegrass plants possessed stolonS which
produced flowering shoots. Perenniality in annual bluegrass
was later suggested by Sprague and Burton (34). They felt

that annual bluegrass would survive up to two years under

l3

favorable conditions. Annual bluegrass also has the ability
to form new shoots from its upper nodes (21). Based on the
above observations, Beard (7) concluded that although annual
bluegrass is generally considered a bunch-type grass there
are strains which exist in turfs as creepers.

The first detailed research concerning the variability
within the annual bluegrass species was conducted by Gibeault
(16). He characterized both annual and perennial subspecies
of annual bluegrass. Lower leaf, node, secondary tiller, and
adventitious root numbers were associated with the annual sub-
Species. Gibeault's investigation showed that annual plants
were more erect growing than the perennial plants. The annual
types predominated in non-irrigated areas such as golf course
roughs. Golf greens and other areas which receive moderate or
intensive supplemental irrigation were ideal locations for
development of the perennial subspecies. This is substantiated
by the observations of Adams (1) who found that the annual
bluegrass strains which persist in intensely maintained English
Sports turfs were prostrate and stoloniferous. The perennial
plants were more prostrate in growth habit. Gibeault (16)
found that the perennial subspecies possessed either stolons
or rhizomes that were capable of producing tillers and roots
at their nodes. Further differences between tre two subspecies
involved seedhead production. Although the annual subspecies
produced seed earlier than the perennial subspecies; the seed
exhibited a post-harvest dormancy period. Gibeault's (16)

study dealt with the two extremes. Between these extremes

14

were ecotypes which possessed all possible combinations of
genetic characteristics.

variability within the annual bluegrass Species probably
contributes to the results in chemical control programs.
Turgeon (36) found this to be the case when working with
endothall in Michigan. He reported that the perennial types
severely limited the chemical's effectiveness. Based on this
finding Turgeon concluded that the effectiveness of chemical
control programs depends to a great extent on the nature of
the annual pOpulation. Control programs will be less effec-
tive where a high degree of variability exists in the annual
b luegrass stand .

Adaptation

 

Annual bluegrass grows under a wide range of climatic,
soil, and cultural conditions. Although annual bluegrass was
originally a native of EurOpe, it is now distributed through-
out the world (6). It is not only observed throughout the
world, but is considered a major turfgrass pest in most areas
(1, 29, 33). Arber (2) reported annual bluegrass plants
growing 12,000 feet above sea level in the Himalaya mountains.
Annual bluegrass was observed growing equally well along the
seashore of England. Adams (1) reported that annual bluegrass
invaded greens where non-adapted Species were washed with sea
water. This suggested a possible tolerance to salt. Hewever,
Beard (8) reported a poor tolerance to high soil salinity.

Moist, fine-textured, fertile soils are particularly
favorable for annual bluegrass growth (7, 34). Beard (7)

15

also indicated that a slightly acid soil (pH 5.5-6.5) was
preferred. Juska and Hanson (25) observed a four-fold in-
crease in the seedhead production of annual bluegrass when
grown at a pH of 6.5 on a loamy sand. They also reported a
doubling of shoot growth at pH 6.5. Annual bluegrass was
capable of growing at low fertility levels but rSSponded to
fertilization (26).

Annual bluegrass was also stimulated by irrigation (7).
However, it would not withstand waterlogged conditions (8).
Work was conducted in New Jersey concerning the effect of
moisture levels on annual bluegrass growth. Sprague and
Evaul (35) found that maximum growth of annual bluegrass
occurred when the soil was kept at 50-60% of the water holding
capacity. The growth of annual bluegrass was considerably
reduced above and below this range. It was concluded from
these findings that annual bluegrass was more tolerant of
excess moisture and compacted soils than the more desirable
Species. Furthermore, annual bluegrass is well adapted to
moist shaded conditions.

Sensitivity to smog damage is a growing problem on annual
bluegrass plants in southern California. Brobrov (11) de-
scribed smog damage as a transverse tan band near or above the
mid-blade of mature leaves. She also reported the appearance
of the band within several hours following exposure to the
atmospheric pollutants. Juhren, et. al., (24) found that
damage was greater to plants grown in an eight hour photoperiod
than at Sixteen hours. They also showed that plant sensitivity

16

was affected by environmental conditions but was not correlated
with plant size or growth rate. Plants grown in hot conditions
did not become sensitive until flowering (24). However, Bro-
brov (11) reported a correlation between sensitivity and the
degree of stomatal Opening. She also reported that damage
commonly occurred to cells just reaching maturity with cells
bordering the substomatal chamber being first damaged. It was
shown that senescent and very young leaves were usually not
sensitive to smog damage.
Temperature-Growth Relationships

Beard (5) listed several factors that influence the air

 

and soil temperatures surrounding a turfgrass plant. These
factors include: (a) latitude, (b) altitude, (c) tOpography,
(d) season of the year, and (e) time of day. Hawes (19) dis-
cussed the relationships between soil and air temperatures.

He reported that the soil temperature at a 1.0 inch depth
would not quite reach the maximum reported air temperature.

It was shown that the greatest variation in temperature was at
a height of 1.0 inch above the soil surface (3). Carroll (12)
reported the upper layer of a bare soil as generally being
warmer than the air temperature in the summer. Furthermore,

he observed that large fluctuations occurred in the upper
layers. Beard (3) reported that temperature fluctuations with-
in the upper 2.0 inches of soil were practically the same as
the air temperature at a 1.0 inch height. The soil temperature
remained 5°-10°F warmer during the nocturnal low temperature

period (19). Beard (5, 6) defined optimum as that temperature

17

at which the activity of a particular plant process occurred
at its highest rate. The optimum temperature for root growth
was shown to be more important for overall plant growth than
the shoot Optimum (6). Plant growth declines and eventually
ceases as the temperatures are increased or decreased from the
Optimum.

Hawes (19) reported an Optimum soil temperature for annual
bluegrass of 55°-65°F. This was 10°F less than the Optimum
soil temperature of Penncross bentgrass. Harrison (18) showed
that the roots and rhizomes of Kentucky bluegrass weighed more
at 60°F than at 80°F or 100°F. In addition, he reported that
the grass was denser but shorter at 60°F. Beard (5) further
defined the optimum temperatures of annual bluegrass as 60°-
70°F for shoot growth and 55°-65°F for root growth. JUhren
et. al., (24) reported annual bluegrass Shoot growth to be
most rapid under warm conditions (78°F day 68°F night) and
moderately warm conditions (78°F day 63°F night). They re-
ported that plants grown under cool (68°F day 58°F night) con-
ditions had broad leaves and long internodes on the stems of
lateral shoots. The Opposite was true of plants grown in hot
(86°F day 76°F night) conditions. Hawes (19) compared annual
bluegrass and Penncross creeping bentgrass growth over a range
of temperatures from 45°-95°F. The annual bluegrass produced
more shoot and root growth at 75°F and 65°F. Beard (3) re-
ported higher numbers of bentgrass roots at 60°F although the
growth rate did not vary appreciably at 60°, 70°, or 80°F.
Annual bluegrass plants did not mature as rapidly at 45°F and

18

55°F (19). However, annual bluegrass plants growing at 45°F
produced two to three times as much shoot and root growth as
did Penncross. The annual bluegrass root systems were very
long and extensive at 45°, 55°, and 65°F (19). Hawes Showed
that plants grown at 85° and 95°F matured quickly and died.
Annual bluegrass plants grown at a 0.25 inch cutting height
reSponded to temperature treatments similarly to the unclipped
plants (19).

Lack of tolerance to temperature stresses is a major
problem associated with annual bluegrass. The disappearance
of annual bluegrass in midsummer is a direct result of high
temperature and drought stresses. High temperature stress
involves either indirect or direct injury. Indirect high
temperature stress occurs when plant growth is slowly reduced
and eventually ceases. The first effect of indirect high
temperature injury is a browning and dieback of the root system.
Direct high temperature kill involves denaturation of the pro-
teins. It was reported that annual bluegrass could be killed
at temperatures as low as lO4°F (15). Fischer (15) also showed
that the killing temperature was a function of the exposure
time. Kentucky bluegrass produced very little growth at 100°F
(18). The shoot growth of Kentucky bluegrass decreased consid-
erably at high temperatures. Cockerham and Whitworth (13)
reported injurious effects to annual bluegrass at temperatures
of 80°-90°F for 18 hours per day. By comparison, Carroll (12)
reported that Kentucky bluegrass and bentgrass species were
better able to withstand high air temperatures than annual

l9

bluegrass. Beard (7) also reported annual bluegrass to be in-
ferior to bentgrass and Kentucky bluegrass in heat hardiness.
The upper temperature at which germination failed was 94°-
lOl°F. Engel (14) reported that continuous 86°F temperatures
reduced colonial bentgrass (Agrostis tenuis Sibth.) germina-

 

tion 5l% while annual bluegrass seed germination was even
more severely reduced.

Direct low temperature kill involves mechanical disrup-
tion of the protOplasm by ice crystals (9). The actual killing
temperature depends on the hydration level of the plant tissue.
Carroll (12) stated that the extent of plant injury due to
cold stress depends upon the type of plant and the nature of
its periodicity. He further stated that Kentucky bluegrass
was more low temperature hardy than annual bluegrass. Beard
(4) investigated low temperature effects on several turfgrass
species including annual bluegrass, Merion Kentucky bluegrass,
and Penncross creeping bentgrass. His investigations showed
that bentgrasses exhibited greater low temperature hardiness
than any other turfgrass. Penncross was found to be seriously
injured at soil temperatures below -5°F (4). By comparison
Merion and annual bluegrass exhibited extensive low tempera-
ture kill below 0° and 5°F reSpectively. The low temperature
kill of each Species increased as the soil temperature was
decreased (16). Kill of annual bluegrass increased at a
greater rate than either Penncross or Merion. Beard (6) also
observed turfgrass injury resulting from ice coverage for an

extended period of time. He found that annual bluegrass could

20

be injured in 60-70 days. However, bentgrass was not affected
for as long as 120 days under an ice cover. These findings
indicate that annual bluegrass is inferior to bentgrass and
Kentucky bluegrass in low temperature hardiness as well as
heat hardiness.

Cutting Height

 

The reported effects of cutting height on annual blue-
grass have been based on general observations. Although
several authors (1, 23, 26, 39) have discussed the prominance
of annual bluegrass at short (less than 0.5 inch) heights of
out, no actual data has been published concerning the optimum
cutting height. Youngner (39) reported a significantly higher
number of annual bluegrass plants at the 0.5 inch cutting
height compared to 0.75 inch. This was with annual bluegrass
grown in a bermudagrass stand. Therefore, the significant
increase of annual bluegrass may have been due to a reduction
in the competitiveness of bermudagrass at the shorter cutting
height.

Several general observations concerning cutting height
effects were discussed by Adams (1). Root depth decreases as
the cutting height is lowered to between 1.0-1.5 inches.

Beard and Daniel (10) showed a similar reduction in root growth
of bentgrass cut daily at 0.25 inch. Adams (1) also stated
that the effect on rooting was further influenced by the soil
type. The plant also became more susceptible to wear damage
due to the reduction in root depth. Incremental decreases in

the height of out below 1.0 inch affected the plant in three

21

ways (1). The first of these is reduced rooting depth.
Secondly, tiller production is decreased with decreased
cutting height. This agreed with Harrison's (18) observation
that shorter cutting heights produced less new shoot growth.
The third effect of a decreased cutting height was described
by Adams as a decrease in the fertilizer requirement of the
plant. This appears to be a direct result of decreased tiller
production and rooting. Bentgrass and Kentucky bluegrass
species are similar in their responses to a decrease in the
cutting height.

Fertility Response

 

Annual bluegrass tolerates both low and high fertility
levels (26). Juska and Hanson (25) concluded from their inves-
tigation that annual bluegrass would grow reasonably well on
relatively infertile soils. HOwever, Beard (7) indicated that
a higher intensity of culture was more favorable to annual
bluegrass develOpment. He suggested a nitrogen requirement of
0.2-1.0 # N/1000 sq. ft. per month. This was comparable to
the common bluegrass Species. In addition, it has been shown
that complete fertilizers produced the most abundant growth of
annual bluegrass (25, 35). Adams (1) observed that repeated
nitrogen applications favor annual bluegrass.

Several individuals have studied the effects of individual
nutrients on the growth and develOpment of annual bluegrass.
Juska and Hanson (25) made a detailed investigation of clipping
yields, root weights, and crown weights as affected by the
individual elements. They found significant reSponses for all

22

of the comparisons used in the study. Furthermore, they re-
ported significant interactions from N/P and N/K on clipping
yields; N/K on crown weights; and N/P on root weights. Sprague
and Evaul (35) noted that urea stimulated annual bluegrass.
However, Sprague and Burton (34) reported fewer seedheads
where only nitrogen was applied. The use of nitrogen alone
would also affect the root development of annual bluegrass.
Adams (1) felt that nitrogen was the nutrient that most fre-
quently affects root develOpment on British Sport turfs.

Harrison (18) observed the effects of fertilization on
Kentucky bluegrass. He found that considerably more shoot
growth was produced under continuous nitrogen applications.
However, the same plants exhibited death to rhizomes and roots
from the high fertilization rate. Harrison also showed that
heavy fertilization restricted the plant's ability to replace
the dying roots and rhizomes. Plants receiving a nutrient
solution without nitrogen produced the Opposite reSponse.
These plants produced many new rhizomes during the winter months
(November-February). Harrison (18) showed that the shoots of
the minus-N plants grew very little during the winter period
of short days. The plant roots were growing deeper and were
more extensive during this period. However, nitrogen became
a limiting factor as the days began to lengthen and the plants
were at a standstill. In addition, low nitrogen levels de-
crease the recovery rate of the turf (l).

The effects of nitrogen fertilization on clipping yields
were also investigated by Harrison (18). Clipping yields were

23

greater for the first three weeks after a nitrogen application.
However, the minus-N plants produced a greater yield at the
fourth week. Nitrogen treatments also produced color changes
at different temperatures. Harrison (18) stated that plants
receiving nitrogen turned dark green at 60°F and 80°F but
turned yellow at 100°F. Carroll's (12) results also Showed
that Kentucky bluegrass and annual bluegrass suffered greater
high temperature injury when receiving high amounts of nitrogen.
Color changes were not observed in the plants which did not
receive nitrogen.

The soil reaction (pH) has also been shown to influence
annual bluegrass growth and develOpment. Annual bluegrass
prefers a mildly acid soil (34). Juska and Hanson (25) showed
that the soil reaction had a marked effect on annual bluegrass
yields when grown on a loamy sand soil. They reported a two-
fold increase in Shoot growth at pH 6.5 compared to pH of 4.5.
Sprague and Evaul (35) reported that the best growth of annual
bluegrass occurred at pH 6.1, although good growth was observed
at pH 4.2 and pH 5.0. Juska and Hanson (25) reported signifi-
cant increases in shoot growth at both pH 6.5 and pH 4.5 when
additional nitrogen was applied. They also reported a signifi-
cant increase at pH 4.5 resulting from the addition of phos-
phorus. This reflected the effect of phosphorus becoming
limiting in the soil under acidic conditions. It was concluded
from this investigation (25) that annual bluegrass could grow
better at low pH levels in silt loam soils than Kentucky blue-

grass. Because of its preference for slightly acidic conditions,

24

annual bluegrass was least able to encroach on turf treated
with lime and an abundance of nitrogen (34). Sprague and

Burton (34) also showed that the use of acid forming fertil-
izers was not enough to introduce annual bluegrass infesta-

tions.

MATERIALS AND METHODS

The investigation involved four components of competition
within a turfgrass community: (1) temperature-growth relation-
ships; (2) cutting height; (3) nitrogen fertility level; and
(4) root growth and develOpment. Field observations and con-
trolled climate growth chamber studies were used in the first
phase of this investigation. Cutting height and nitrogen
fertility requirements of annual bluegrass were examined under
conditions of annual bluegrass encroachment into a Merion
Kentucky bluegrass sod. In addition, Optimum cutting height
determinations were made for an annual bluegrass monostand.
The rooting studies involved the use of specially constructed
boxes for observing root elongation.

Annual bluegrass was compared with Merion Kentucky blue-
grass and Penncross creeping bentgrass throughout this inves-
tigation. These three species are commonly used for lawn and

recreational turfs in Michigan.

TEMPERATURE-GROWTH RELATIONSHIPS

Phenological Observations

 

1971 ObservationS: Five locations in the East Lansing,

 

Michigan area were selected for phenological observations of

annual bluegrass. The sites chosen represented varying soil

25

26

and cultural conditions under which annual bluegrass occurred.

The descriptions of the locations were as follows:.

1)

2)

Creeping Bentgrass Green: A portion of a bentgrass
green at the Michigan State University turfgrass
research plots was observed to contain about 25%
annual bluegrass. An individual annual bluegrass
plant growing in bare soil near the edge of the
green was chosen for observation. The green is on

a level well drained site. It was built on a loamy
sand soil with a pH of 7.5. The cultural conditions
at this location included: (a) mowing at 0.25 inch
six times per week with clippings removed; (b) a
nitrogen fertility level of five pounds per 1000 sq.
ft. per year; (c) control of pests as necessary but
no cultivation or dethatching; and (d) irrigation as
needed to prevent wilt.

Kentucky Bluegrass Turf: An annual bluegrass plant
growing in a dense Kentucky bluegrass turf at the
Michigan State university turfgrass research plots
was chosen as the second observation site. The
conditions found here were comparable to a home lawn
receiving minimal traffic. This was an unshaded,
sandy loam site of pH 7.2. The site was level but
well drained. Cultural conditions included: (a)
mowing at 1.2 inches twice weekly with clippings
returned; (b) a nitrogen fertility level of four
pounds per 1000 sq. ft. per year applied in two

3)

4)

27

applications; and (c) irrigation as needed to pre-
vent wilt.

Putting Green Apron: The third observation site was
located at lake '0 The Hills Golf Club, a par-3 golf
course near East Lansing. The annual bluegrass under
observation was growing in the apron of a bentgrass
green. The green was established on a loamy sand
soil. The pH was 6.7. Since the apron leped from
the putting surface, drainage was excellent. The
site was unshaded. The cultural conditions included:
(a) mowing at 1.0 inch twice per week with clippings
returned; (b) a nitrogen fertility level of six
pounds per 1000 sq. ft. per year; (c) pest control
as necessary; and (d) irrigation 3-4 times weekly

to replace moisture lost through evapotranspiration.
In addition, daily syringing was practiced in the
early morning for dew removal.

Golf The: The Forest Akers Golf Course at Michigan
State university was chosen as an observation site
due to the predominance (90-95%) of annual bluegrass
on the tee of a par-3 hole. The tee was an unshaded,
sandy loam Site that received intensive traffic and
divots from iron play. The site was well drained
with a pH of 7.2. The cultural practices for the
tee included: (a) mowing three times weekly at 0.75
inch with clippings returned; (b) nitrogen fertili-
zation at a rate of four pounds per 1000 sq. ft. per

28

year; and (c) irrigation 3-4 times weekly. This
site best fit the description of locations where
Gibeault (l6) usually found perennial type annual
bluegrass plants.

5) Sports Turf: The final site chosen for observing

annual bluegrass growth and development was Landon
Field on the Michigan State university campus.

Landon Field is used for intramural athletics during
the Spring and summer, and for marching band prac-
tice in the fall. Annual bluegrass was widespread

at this site due to the compacted nature of the clay
loam soil. It was expected that annual bluegrass
plants found here would be of the annual type based
on Gibeault's (l6) characteristic locations. The
Site was fairly well drained and level. The cul-
tural intensity of this site represented the lowest
level of the five. The cultural practices utilized
included: (a) mowing every 10-14 days at a height

of 2.0 inches with clippings returned; (b) fertili-
zation twice per year to apply two pounds of nitrogen
per 1000 sq. ft. per year; and (0) very little supple-
mental irrigation.

Soil temperatures and shoot length measurements were made
at the five locations at intervals throughout the 1971 growing
season. These observations were initiated in mid-April and
continued until the first frost. Soil temperature readings
were at a 1.0 inch depth using a weston Model 4200 thermometer.

29

The soil temperatures were taken near mid-day at the time of
each observation. The soil temperatures recorded were the
mean of three readings per site. The thermometer was shaded
from direct radiation to minimize the effect of direct solar
radiation. Early observations showed that the soil tempera-
ture reading stabilized between 4 and 5 minutes after being
inserted into the soil. Therefore, the readings were made five
minutes after inserting the thermometer into the soil.

Measurements of shoot length were made at each observation
interval. These data were used to determine when growth of the
annual bluegrass plant began in the Spring and to follow the
growth pattern throughout the growing season.

In addition to shoot length and soil temperature measure-
ments observations were made of the weather conditions, plant
color and vigor, and seedhead production.

1972 Observations: Further phenological observations were

 

conducted during the early Spring of 1972. The observations
were expanded to include Kentucky bluegrass and creeping bent-
grass in addition to annual bluegrass. All three Species were
observed in the Michigan State University Horticultural Gardens.
This area is a level, well-drained Site. Notations were made
of shoot growth initiation and green-up in relation to the
soil temperature.

Soil temperature measurements were made using a method
similar to the one previously described for the 1971 observa-
tions. The temperature readings were again made at a 1.0

inch soil depth. The measurements were made four times weekly

30

in the early afternoon. Only one reading was made per indi-
vidual site. Two sites were measured for each species; one
to observe spring green-up and the other for observing shoot
growth initiation.

Locations were chosen where each species was predominant.
An area six inches square was used to observe the initiation
of new shoot growth. The area was defoliated by removing all
old leaves and stem material. One square was defoliated for
each of the three Species.

Areas adjacent to the defoliated squares were chosen to
observe spring green-up. The conditions of these areas re-
mained unchanged. The plants contained plant parts which had
died during the winter. Furthermore, the area was not clipped
as in the defoliated areas. This area was observed to determine
plant green-up as a reSponse to soil temperature.

Controlled Climate Growth Chamber Studies

The root and shoot growth of annual bluegrass, Merion

Kentucky bluegrass, and Penncross creeping bentgrass was
measured at 10°F intervals over a range of 40°-110°F using
controlled climate growth chambers. A twelve hour photOperiod
with a light intensity of 2000 foot candles was used through-
out the study.
Study I: The turfgrasses used in this investigation were
watered daily to prevent wilt and received a complete Hoagland's
(20) nutrient solution three times weekly.

The three Species were grown in individual sand cultures

to facilitate measurement of root and shoot growth. The sand

31

cultures consisted of 180 ml (6 oz.) styrofoam cups placed
inside 300 ml (10 oz.) translucent cups (Figure l). The
tOps of the two cups were flush and had an inside diameter
of 2.5 inches. Holes were placed in the bottoms of the styro-
foam cups to allow drainage of water and the nutrient solution
into the larger cup. By placing a hole midway up the side of
the translucent cup, a well is provided for maintaining the
moisture level in the sand cultures. The sand used was #*7
washed quartz.

The plants used in this and other eXperiments were germin-
ated in 20 x 14 x 3 inch deep greenhouse flats containing a
loamy sand soil of pH 6.9. A preliminary study was conducted
to determine differences in the seed germination rates of the
three species using the same seed source throughout. It was
found that Merion Kentucky bluegrass germinated in eight days;
annual bluegrass in five days; and Penncross creeping bent-
grass in four days under greenhouse conditions. The conditions
included daily irrigation; a twelve hour photoperiod of sun-
light and flourescent lighting; and soil temperatures in the
700 to 75°F range. Seedlings germinated in this manner were
transplanted into the sand cultures at the 3-leaf stage of
development. Following transplanting into the sand cultures,
the plants were grown for one week before placing in the growth
chamber.

The turfgrasses were grown at each of the eight constant
temperatures for 30 days. This observation period was preceded
by a two week stabilization period, during which the plants

32

Figure 1. Individual plants growing in sand cultures that
were used in controlled climate growth chamber

study. Left to right: Annual bluegrass, Merion
bluegrass, and Penncross creeping bentgrass.

 

33

were allowed to adapt to the conditions within the controlled
climate growth chambers. Growth response measurements were
made on days 0, l5, and 30 of the experiment. Four replica-
tions of each species were measured on each of these days.
The entire study was arranged in a completely randomized de-
Sign.

The plants were washed gently to remove the sand immedi-
ately after being removed from the controlled climate growth
chambers. The shoots and roots were separated from each plant
and dried at 212°F for 48 hours. Measurements were then made
of the root and Shoot dry weights. Analyses of variance were
conducted to compare root and shoot growth of each species.
An analysis was made at each temperature. Temperature-growth
response curves were made from the results of this investiga-
tion. Observations were also made of the seedhead production
of the annual bluegrass plants.

Study II: The shoot growth rate was also measured through

 

clipping yields. Plugs, 4,25 inches in diameter, of Merion
Kentucky bluegrass and annual bluegrass were grown at each of
the eight constant temperatures. They were arranged in a
randomized block design with three replications of each species.
The turfs were irrigated daily and received a complete Hoag-
1and's (20) nutrient solution three times weekly. Clippings
were collected on days 5, 10, 15, 20, 25, and 30 at each con-
stant temperature level from 40° to 110°F. A uniform cutting
height of 0.75 inch was accomplished by use of a cardboard
collar. The turf plug was placed inside the collar and all

34

plant material above the collar was clipped. The clippings
were dried at 212°F for 48 hours and weighed. The turf plugs
were allowed to stabilize in the controlled climate growth
chambers for two weeks prior to the initial clipping yield
measurements. At day 0 the plugs were clipped to the 0.75
inch cutting height.

Study III: Plastic trays, 7.5 inches square by 2.0 inches

 

deep, were used to investigate the seed germination response
of annual bluegrass at the eight constant temperature levels.
Each tray was filled with loamy sand soil of pH 6.9. Annual
bluegrass was replicated three times in trays arranged in a
randomized block design. One hundred seeds were planted per
tray at a depth of 0.25 inch. A cheesecloth was placed over
the seeds as a moisture barrier. The trays were placed in
the previously described controlled cltmate growth chambers
on day 0, with germination counts made on day 30. The trays
received an application of water daily with the HOagland's
(20) complete nutrient solution applied weekly.

NITROGEN FERTILITY AND CUTTING HEIGHT STUDIES
Mature Sod Experiment: Merion Kentucky bluegrass sod was

 

obtained from the Michigan State University Muck Experimental
Farm and transplanted into greenhouse flats. The sod was
harvested at a 1.0 inch depth. The flats measured 14 inches
by 20 inches by 3 inches deep. A loamy sand soil of pH 6.9
was placed in the flats prior to transplanting the sod at a
depth that allowed the soil surface of the sod pieces to be

35

flush with the tOp of the flats.

The sod was allowed to root for two months following
transplanting. The treatments were arranged in a split-block
design of six replications. TwO nitrogen fertility levels
were applied across five cutting height treatments. The cut-
ting heights were randomly assigned to flats of sod. The sods
were out three times weekly with the clippings removed.

The nitrogen fertility treatments were applied monthly
with the first application made at the time the sod was trans-
planted. Ammonium nitrate was applied using water as the
carrier at rates of 0.43, or 1.72 gms per flat. This was
equivalent to 0.5 and 2.0 # of actual N/lOOO sq. ft., reSpec-
tively. The treatments were applied in 20 inch strips across
the cutting height treatments. The sod was allowed to root
under greenhouse conditions of daily irrigation and a soil
temperature of 70°F. The day length during this study averaged
9-10 hours without additional artificial lighting.

Following a two-month period for rooting of the sod and
acclimation to the cultural treatments, annual bluegrass seed-
lings were transplanted into the Merion Kentucky bluegrass
sods. The seedlings were transplanted at the 2-leaf stage of
develOpment. Two seedlings were transplanted per flat. Sod
cores, 2.0 inches in diameter, were removed from the Merion sod
growing in the flats. The resulting holes were filled with
soil identical to the soil used in establishing the sod. The
annual bluegrass seedlings were then transplanted into the

bare soil of the flats.

36

The annual bluegrass seedlings were removed from the sod
flats after a two month treatment period. Measurements made
on the seedlings included: (1) tiller number; (2) Shoot dry
weight; and (3) root organic matter. These measurements were
used in comparing the effects of the five cutting heights and
two nitrogen fertility treatments on the growth of an annual
bluegrass plant in a Merion Kentucky bluegrass stand. The
treatment effects were compared statistically using an analysis
of variance and the Duncan's Multiple Range Test.

Tiller counts for each annual bluegrass plant were made
first. The roots were then washed gently to remove the soil
particles. The roots and shoots were separated at the crown
meristem of the plant. They were then dried for 48 hours at
2l2oF. After drying, shoot dry weights were recorded. The
dried roots were weighed in crucibles and then ashed at 1000°F
overnight. The crucibles and contents were reweighed after
ashing to determine the root organic matter.

Annual Bluegrass Monostand Experiment: Monostands of annual

 

bluegrass were established from seed in 4.25 inch diameter by
3.0 inch deep waxed cups. The soil used was a loamy-sand of
pH 6.9. A complete Heagland's nutrient solution (20) was added
to the cups once weekly during the experiment. Cutting height
treatments were applied to the monostands beginning three

weeks after establishment. The five cutting heights used were
0.5, 1.0, 1.5, 2.0, and 2.5 inches. The cups were clipped
three times weekly with the clippings removed. Cardboard

collars similar to those mentioned earlier were used to assure

37

a uniform cutting height. Clippings were removed by use of
hand clippers having a metal basket attached. The soil temper-
atures of the plugs averaged 75°F during the 45 day treatment
period. The photoperiod was twelve hours involving both
natural and artificial illumination. Daily irrigation was
applied to the turfgrass plugs to prevent wilt.

A randomized block design with three replications was
used. The study was conducted over a 45 day period after which
shoot density counts were made. These data were used in de-
termining the optimum cutting height for annual bluegrass when

grown in a monostand.

ROOT GROWTH AND DEVELOPMENT STUDIES

Specially constructed root observation boxes were used
throughout these studies. The boxes measured 10 inches square
at the tOp with one side being a glass plate. The glass was
slanted toward the rear at a 23° angle. Each box measured 17
inches in height and contained 0.6 cubic foot of soil (Figure
2.). Black plastic and wooden covers were used to exclude
light from the glass face. This was done to minimize light
influences on root growth. The rooting boxes were first de-
scribed by Beard and Daniel (10).

Root growth of the three turfgrasses was compared using
the root observation boxes. Plants of each Species were es-
tablished in 20 x 14 x 3 inch deep greenhouse flats containing
a loamy sand soil of pH 6.9. Staggered seed germination dates

were again used as discussed in a previous section. When the

38

Figure 2. Root observation box with slanting glass face used
for observation of root growth and develOpment.

 

39

plants reached the 3-1eaf stage of develOpment they were trans-
planted into the rooting boxes. A single plant was placed in
the middle of the box 1.0 inch behind the glass plate. The
soil in the boxes was a loamy sand having a pH of 6.9. The
transplanted plants were irrigated daily and received a com-
plete Heagland's (20) nutrient solutiOn weekly. The plants
were grown under a twelve hour photOperiod using both natural
and artificial light.

The effects of two heights of out were compared during
this study. One set of plants of the three species remained
uncut while the other set was clipped three times weekly at a
height of 1.0 inch. Both sets of plants were arranged in a
randomized block design of three replications. As the roots
elongated, they would come into contact with the glass plate.
Wax crayons were used to mark each day's root growth on the
glass face. The root elongation was marked at 1:00 p.m. Soil
temperature measurements were made at the two inch soil depth
using a weston Model 4200 thermometer.

The original study was conducted over a period of 30 days.
A shorter study was suggested by observations of the root
growth patterns during the first study. Therefore, a second
study of 15 days duration was also conducted. The procedure
for the 15-day study was the same as previously described for
the 30-day study. Both clipped and unclipped plants were used.

The plants were removed from the loamy sand greenhouse
soil at the conclusion of both studies. After being separated

from the plants, the roots were washed to remove the adhering

4O

soil. Screens were used to collect all roots. Following
washing, the roots were dried at 212°F for 48 hours. The
roots were then placed in crucibles, weighed, and ashed at
1000°F overnight. The crucibles and their contents were then
reweighed to determine the total root organic matter produced
by each plant.

Root depth was also used as a measurement of root growth.
The rooting depth of each plant was determined by measuring
the deepest penetration of the visible roots on the glass face.
This determination was made on the final day of each study.
An analysis of variance and a Duncan's Multiple Range Test
were conducted to compare the root organic matter production

and rooting depths of the three species.

RESULTS AND DISCUSSION

TEMPERATURE-GROWTH RELATIONSHIPS

Phenological Observations

 

1971 Observations: The phenological observations of annual

 

bluegrass during the spring of 1971 suggested several temper-
ature-growth relationships. The first of these involved the
initiation of shoot growth. New shoot growth and develOpment
occurred at soil temperatures above 55°F at four of the obser-
vation sites. Subsequent shoot growth ceased at soil tempera-
tures below 55°F. This was true even for short low temperature
exposure periods of 48 hours. The one exception to this was
the annual bluegrass plant growing on the edge of a bentgrass
putting green. The plant was growing in bare soil at this
location and the 1.0 inch soil temperature was already above
60°F when readings were begun in mid-April. For this reason
it was not possible to determine when annual bluegrass growth
was initiated at this site.

The second general observation concerning annual bluegrass
growth dealt with seedhead production. The first seedheads
develOped after the soil temperature had surpassed 60°F. The
lowest recorded mean soil temperature at which seedheads were
produced was 60.3°F. All seedheads were removed at each site

in mid-JUne. New seedheads were produced within one to two

41

42

weeks. Some seedheads were present on the plants through the
first frost in October. Seedhead production was most intense
on the sports turf. The least seedheads were produced by the
annual bluegrass plant growing on the golf tee.

The seedhead observations further suggested the presence
of the subspecies annua_and reptans, on the Sports turf and
golf tee, respectively. A plug of annual bluegrass was removed
from'the golf tee. Close examination of this plug revealed a
stoloniferous growth habit of the annual bluegrass. This sub-
stantiated the earlier suggestions (16) that the perennial
subSpecies would be dominant on the golf tee. By comparison,
the plant in the Sports turf remained bunch-type in nature
throughout the summer. The plant died in early July. This
appeared to be a result of drought stress. The plant had
survived a single day's soil temperature of 91.3°F in late
May. Hewever, when the soil temperature remained above 80°F
for an extended period the plant died. Death was probably
influenced by the lack of supplemental irrigation.

1972 Observations: Observations made during the early spring

 

of 1972 concurred with the previous year's findings. Again it
was observed that annual bluegrass initiated new shoot growth
at soil temperatures above 55°F. Annual bluegrass plants
growing over steam lines on the Michigan State University
campus were also observed. Soil temperatures were taken at
this location to compare with the defoliated area being ob-
served. The annual bluegrass was already green and producing

seedheads. The 1971 findings were again substantiated since

to

soil temperatures over the steam lines were above 60°F.

In comparison with annual bluegrass, the defoliated areas
of Kentucky bluegrass and creeping bentgrass were observed to
begin shoot growth earlier. Plants of the latter two species
began growing at soil temperatures between 50° and 55°F. An
exact soil temperature could not be determined due to inter-
mittent snow covers during the observation period. Kentucky
bluegrass regrowth proceeded at the most rapid rate, reaching
a height of 1.0 inch five days after beginning growth. Creep-
ing bentgrass regrowth was quite slow by comparison having
only attained a height of 0.25 inch. All three species initi-
ated spring green-up at about the same time on the observation
area that was not defoliated.

Controlled Climate Growth Chamber Studies

 

Study I: The results of the sand culture study are presented
in the form of temperature-growth reSponse curves. The Shoot
growth responses are presented in Figure 3 and the root growth
responses in Figure 4. The mean comparisons, by Duncan's
Multiple Range Test, for the study are presented in the Appendix.
All plants of the three species died during the two-week
stabilization period at 110°F. Light and moisture were not
limiting. Therefore death was the result of direct high tem-
perature kill. These results agreed with the findings of
Fischer (15) that temperatures as low as lO4°F could cause
direct high temperature kill. Some plants of all three Species
survived through day 15 at the 100°F temperature treatment.
Hewever, the remaining plants were killed before day 30.

44

Fischer (15) reported similar findings concerning high temper-
ature kill. He showed that the longer a plant was grown under
high temperature stress, the lower the killing temperature.
There was essentially no root and shoot growth at 100°F
as shown by the lack of significance between days 0 and 15.
The most significant amount of root and shoot growth at 40°,
50°
shoot growth was negligible between days 0 and 15 at these

, and 90°F was produced between days 15 and 30. Root and

three temperature treatments. In the middle temperature range
(60°, 70°, and 80°F) all three Species matured faster with the
growth patterns becoming evident by day 15.

Hawes (19) had previously reported that annual bluegrass
plants grown at soil temperatures of 85° and 95°F matured
quickly and died. However, in this study the annual bluegrass
plants matured most quickly at 80°F. Seedhead production was
used as a measure of maturity. Seedheads were present on
plants at day 30 of the 60°, 70°, and 90°F treatments but none
were observed at day 15. In addition, seedhead production was
also evident at day 15 at the 80°F temperature. NO seedheads
were produced at 40°, 50°, or 100°F. This agreed with the
phenological (field) observations in which seedhead production
of annual bluegrass was not observed until the soil temperature
at a one inch depth surpassed 60°F.

Another indication of plant maturation is the root color.
AS root systems mature and begin to die they turn brown. The
root systems of all three Species in this study had begun
turning brown by day 30 when grown at 80°F.

45

The plants of all three species were held longer in the
greenhouse prior to being placed in the 40°F temperature treat-
ment. hTherefore, the plants were better develOped initially.
In addition, the temperature in the chamber was not constant.
It rose to 60°F for a period of two days until the malfunction
was corrected. These factors combined to give inconsistent
results at 40°F. All three Species were affected Similarly.
These two variable inputs did not reoccur at the six higher
temperature treatments.

All three Species produced the maximum shoot growth at
60°F. Penncross creeping bentgrass produced significantly
greater shoot growth than either Merion Kentucky bluegrass or
annual bluegrass after 30 days at all temperatures except 50°
and 60°F where annual bluegrass Shoot growth was comparable.
Annual bluegrass shoot growth was significantly greater than
Merion Kentucky bluegrass except at the extreme temperatures
of 40° and 90°F where there was no significant difference.

In earlier investigations (4, 7, 12) annual bluegrass was
found to be less heat and cold tolerant than Penncross creeping
bentgrass or Merion Kentucky bluegrass.

The results of the 40°F treatment show that both Penncross
creeping bentgrass and Merion Kentucky bluegrass produced more
root and shoot dry weight than annual bluegrass. This in con-
junction with the 1972 phenological observations suggest that
these two species begin active shoot growth at a lower tempera-
ture than annual bluegrass. This is contrary to the earlier

report of Sprague and Burton (34) who observed that annual

46

Figure 3. Shoot growth responses of three turfgrass species
to seven constant temperature treatments.

SHOOT DRY WEIGHTS (mg)

 

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47

bluegrass was among the first grasses to resume growth in the
spring. The difference may be due to differences in the annual
bluegrass species. The spring green-up rate of the annual sub-
species may differ from the green-up rate of the perennial sub-
Species.

The root growth responses to temperature are depicted in
Figure 4. Again, Penncross creeping bentgrass demonstrated a
wider range of temperature adaptability with significantly
higher root production than the other two species at 40° and
90°F. Root growth of annual bluegrass was significantly greater
at the other five temperature treatments. The optimum root
growth of annual bluegrass and Merion Kentucky bluegrass was
achieved at 70°F. In contrast, Penncross creeping bentgrass
root growth reached its maximum at 60°F. These results were
quite significant since Beard (6) reported that the Optimum
root growth temperature is more important to the turfgrass
plants' total growth than is the optimum temperature for shoot
growth.

The phenological observations and sand culture study are
very important for the professional turf manager. These results
give an indication of the competitive ability of the three
species in response to temperature. Annual bluegrass is least
able to compete with Penncross creeping bentgrass and Merion
Kentucky bluegrass at the temperature extremes of 40° and 90°F.
This suggests that an early spring application of a water sol-
uble nitrogen fertilizer would favor the Penncross creeping

bentgrass and Merion Kentucky bluegrass. Annual bluegrass was

48

Figure 4. Root growth responses of three turfgrass species
to seven constant temperature treatments.

 

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49

better able to compete at the higher temperatures than would
normally be expected from previous general observations.
Cockerham and Whitworth (13) reported injurious effects to
annual bluegrass plants grown at 80° to 90°F temperatures for
18 hours per day. However, annual bluegrass still competed
quite well at 80°F in this study. Annual bluegrass root pro-
duction was also superior to the other two species at 80°F.

Study II: Clipping yields were also used as a measure of shoot

 

growth as influenced by temperature. Annual bluegrass and
Merion Kentucky bluegrass were compared in this manner. The
mean comparisons are presented in Table 2. No clipping yields
are reported at 90°F due to death of the plugs during the sta-
bilization period.

There was no significant difference among annual bluegrass
clipping yields within the 40°, 50°, 80°, and 100°F treatments.
The shoot growth rate was equal throughout the 30 day study.
There were no clippings obtained after day 15 at 100°F due to
death of the plugs. Significant differences in the clipping
yields of annual bluegrass were observed within the 60° and 70°F
treatments. The mean dry weights increased from day 5 to day
30 in both cases. This Showed that the 60° and 70°F temperatures
were most favorable for the shoot growth of annual bluegrass.
This confirms the sand culture study in which maximum annual
bluegrass shoot growth was attained at 60°F.

The Merion clipping yields were Significant within each
of the temperatures observed. At 40° and 100°F the clipping

yields decreased from day 5 to day 15, and then remained con-

stant through day 30 in both cases. Harrison (18) reported

50

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51

very little recovery of Kentucky bluegrass after cutting at
100°F. He reported essentially no new shoot growth after the
second cutting. The results were the same at 100°F in this
study. The shoot growth rate at 80°F increased through day 15
and then held constant through the remaining 15 days. Clipping
yields tended to increase throughout the 30 day period at both
60° and 70°F. Clipping yields of Merion Kentucky bluegrass
tended to increase throughout the study at 50°F although there
was no significance from days 20 to 30. These results also
show that Merion Kentucky bluegrass produces greater shoot
growth during the initial 15 days at the low (40°F) temperature
than annual bluegrass. This was also observed during the 1972
phenological observations. These results point up the fact
that temperature-growth measurements should not be made at
only one point in time since the responses varied with the
exposure time.

Study III: The seed germination percentages of annual blue-

 

grass as affected by the seven temperatures are shown in Table
3. There was no statistical significance in the annual blue-
grass germination at 40°, 50°, 60°, or 70°F. The lowest per-
centage among these temperatures was 73.7%. The seed germina-
tion of annual bluegrass at 80°F was significantly decreased.
A further significant decrease occurred at 90°F. This data
further delineates the findings of Engel (13) who reported
severe reductions in annual bluegrass seed germination at con-
tinuous 86°F temperatures. Based on these findings it can be
seen that annual bluegrass germinates best in Spring and fall

as Opposed to mid-summer.

52

TABLE 3. Annual bluegrass seed germination as influenced by
six temperature treatments.

 

 

TEMIEEIRATURE GERMINAgION (l)
40 83.3 a (2)
50 78.3 a
70 77.0 a
60 73.7 a
80 49.7 b
90 21.0 c

 

(1) values given are the means of three replications.
(2) Means in the column followed by the same letter are

not significant at the 5% level of the Duncan's
Miltiple Range Test.

CUTTING HEIGHT AND NITROGEN FERTILITY STUDIES
Mature Sod Experiment: The cutting height treatments signifi-

 

cantly influenced the tillering and shoot dry weights of the
annual bluegrass plants. HOwever, root organic matter produc-
tion was not affected by cutting height. All nitrogen fertility
level-cutting height interactions were found to be non-signifi-
cant. The mean shoot dry weights resulting from the five cut-
ting height treatments are shown in Table 4. The mean shoot dry
weight ranked highest at the 1.0 inch cutting height; although
not significantly different from the 1.5 or 2.0 inch cutting
heights. The lowest shoot dry weight occurred at the 0.5 inch

53

cutting height. This is of particular interest in view of the
many reports of favorable annual bluegrass growth at a 0.25
inch cutting height. Apparently annual bluegrass has a better
ability to compete at short cutting heights than do the other
turfgrass species. Although annual bluegrass possesses this
ability, it is even better adapted to a higher cutting height

of 1.0 inch or more.

TABLE 4. The influence of five cutting heights on the shoot
dry weights of individual annual bluegrass plants
grown in a mature Merion Kentucky bluegrass sod.

 

 

Cutting Height Shoot Dr Weights (1)
(inches) (mg)
1.0 26.7 a(2)
1.5 24.0 a b
2.0 23.4 a b
2.5 18.7 b c
0.5 16.4 c

 

(1) values given are the means of 12 replications across
two nitrogen fertility levels.

(2) Means in the column followed by the same letter are

not significant at the 5% level of the Duncan's
Multiple Range Test.

Another component of a plant's competitive ability is
tillering. The more tillers a plant produces the denser the

turfgrass sward will be. As with the shoot growth responses,

54

the 1.0 inch cutting height resulted in the greatest tillering
for individual annual bluegrass plants growing in a Kentucky
bluegrass stand (Table 5). The 1.5 inch cutting height ranked
second and was not significantly different from the 1.0 inch
height. HOwever, the tiller production at the 0.5 inch cutting
height was superior to the 2.0 and 2.5 inch heights. The lack
of tillering by the more diminutive annual bluegrass plants at
these higher cutting heights could be the result of shading by
the Merion Kentucky bluegrass plants. The plants were more

Spindly at the higher cutting heights.

TABLE 5. The influence of five cutting heights on the tillering
of individual annual bluegrass plants grown in a
mature Merion Kentucky bluegrass sod.

 

 

Cutting Height Tiller Number (1)
(inches)
1.0 3.0 a (2)
1.5 2.4 a b
0.5 2.3 b
2.0 1.8 b c
2.5 1.3 c

 

(1) values given are the means of 12 replications across
two nitrogen fertility levels.

(2) Means in the column followed by the same letter are
not Significant at the 5% level of the Duncan's
Multiple Range Test.

55

Annual Bluegrass Monostand: A dense, healthy turfgrass sward

 

is the primary defense against weed invasions. Cutting height
is one of the cultural practices influencing the shoot density
of turf. The effects of five cutting height treatments on the
shoot density of an annual bluegrass monostand are shown in
Table 6. As in the previous studies, the most influencial
cutting height is 1.0 inch. The number of shoots per square
inch were significantly higher at the 1.0 inch height. No
significant differences were observed among the other four

cutting height treatments.

TABLE 6. The influence of five cutting heights on the shoot
density of annual bluegrass plants grown in a mono-

 

 

stand.
Cutting Height Shoot Density (1)
(inches) (shoots/sq. in.)

(2)

1.0 32.1 a

0.5 24.1 b

1.5 23.3 b

2.5 22.9 b

2.0 22.2 b

 

(1) values are the means of three replications.

(2) Means in the column followed by the same letter are
not significantly different at the 5% level of the
Duncan's Multiple Range Test.

56

Based on the results of these studies it can be concluded
that the Optimum cutting height for annual bluegrass is 1.0
inch. Most fairways in Michigan are mowed at a height of 0.75
to 1.0 inch. The optimum cutting height for Kentucky bluegrass
is 1.5 to 2.0 inches. Therefore, a stress is placed on the
Kentucky bluegrass while annual bluegrass is favored when a
Kentucky bluegrass fairway is cut at 0.75 to 1.0 inCh.

The two nitrogen fertility levels used in this study did
not influence (at the 5% level of Significance) the root
organic matter, shoot dry weight, or tiller number of the
annual bluegrass plants grown in a mature Merion Kentucky blue-
grass sod. However, the root organic matter production of
annual bluegrass under the two nitrogen fertility treatments
approached significance (14.7% level) with the higher level
(2 # N/lOOO sq. ft. per month) causing a reduction in the root
organic matter production (Appendix Table 8). This is similar
to Harrison's (l8) findings with Kentucky bluegrass. He re-
ported greater root and rhizome weights without nitrogen. The
lack of significance at the 5% level could have been due to
the short-term nature of this study. Root growth may have been
further restricted under the influence of a long-term fertility

program.

ROOT GROWTH.AND DEVELOPMENT
The rooting depths within cutting heights of annual blue-
grass, Merion Kentucky bluegrass, and Penncross creeping bent-

grass were not significantly different 30 days after transplanting.

57

This response was similar for both the uncut and cut plants.
The data supports the earlier findings of Sprague and Burton
(34) and Wilkinson and Duff (38). Annual bluegrass and Penn-
cross creeping bentgrass exhibited a reduction in rooting
depth when clipped three times weekly at 1.0 inch (Table 7).
Beard and Daniel (10) observed similar results during their
study of bentgrass rooting. The rooting depth of Penncross
creeping bentgrass was more severely reduced by cutting than

the root depths of annual bluegrass.

TABLE 7. The rooting depths of three turfgrass Species grown
under two cutting treatments for 30 days after trans-

 

 

 

planting.
Rooting Depth (1)
(inches)
Turfgrass Species Uncut Cut 3 times weekly
at 1.0 inch

(2) ,
Annual bluegrass 10.3 a 6.4 b c
Merion Kentucky bluegrass 7.3 a b c 4.6 c d
Penncross creeping bentgrass 8.7 a b 3.3 d

 

(1) values are the means of three replications.
(2) Means in the column followed by the same letter are

not significantly different at the 5% level of the
Duncan's Multiple Range Test.

The root organic matter produced during the 30-day period
was also not Significantly different among the three turfgrass

58

species. HOwever, there was a high degree of variability
between replications within each treatment (S i = 47.3).
Annual bluegrass ranked highest in the amount of root organic
matter under both the cut and uncut conditions. Penncross
ranked second with Merion producing the least amount. This
was consistent with the results obtained in the controlled
climate growth chamber study under similar temperature con-
ditions.

The mean soil temperature during the 30-day period was
72°F. This is slightly higher than earlier reports concerning
the Optimum root growth temperature of annual bluegrass (5,
19), but is similar to the Optimum root growth temperature
observed in the sand culture study.

Visual observations indicated that the annual bluegrass
roots develOped at a more rapid rate during the early phases
of this study. later in the 30-day study it appeared that
the Penncross and Merion plants became more competitive in
root growth and develOpment. This response occurred during
the third week. For this reason a l5-day study was conducted
to confirm these observations.

Again, as in the earlier study there were no significant
differences in the rooting depths of the three species. This
was true for the plants cut at 1.0 inch as well as those that
were uncut. Under the uncut conditions annual bluegrass again
ranked highest in terms of root depth. However, Merion Kentucky
bluegrass ranked highest when out at 1.0 inch. The effect of

cutting at 1.0 inch on rooting depth was not as pronounced

59

during the 15-day study. No significant differences were
detected between cutting height treatments (Table 8).

TABLE 8. The rooting depths of three turfgrass species grown
under two cutting heights for 15 days after trans-

 

 

 

planting.
Root Depth (1)
(inches)
Turfgrass Species Uncut Cut 3 times weekly
at 1.0 inch
(2)
Annual bluegrass 8.0 a 4.5 a
Merion Kentucky bluegrass 7.2 a 4.8 a
Penncross creeping bentgrass 6.3 a 3.0 a

 

(1) values are the means of three replications.
(2) Means in the column followed by the same letter are

not significantly different at the 5% level of the
Duncan 3 Multiple Range Test.

The root organic matter produced by each Species during
the 15-day period is shown in Table 9. Analysis of variance
Showed that the root organic matter production among species
approached Significance. The uncut plants were significantly
different at the 5.5% level and the cut plants were significantly
different at the 7% level. The annual bluegrass root organic
matter production was not significantly different from Merion
Kentucky bluegrass when left uncut. However, Penncross creeping

bentgrass rooting differed Significantly from annual bluegrass

60

under these conditions. The Opposite results occurred when

the plants were out three times weekly at 1.0 inch. Penncross
creeping bentgrass and annual bluegrass were non-significant
but annual bluegrass rooting was significantly different from
Merion Kentucky bluegrass. This suggests that cutting at 1.0
inch causes annual bluegrass and Penncross to initiate addi-
tional roots instead of producing deeper roots. The root
systems of the three Species are shown in Figure 5. The figure
shows greater numbers of roots being initiated by the Penncross

creeping bentgrass and annual bluegrass plants.

TABLE 9. The root organic matter produced by three turfgrass
species when grown under two cutting treatments for
15 days after transplanting.

 

Root Organic Matter (1)

 

 

(mg)
Turfgrass Species Uncut Cut 3 times weekly
at 1.0 inch
(2)
Annual bluegrass 83.3 a 13.7 a
Merion Kentucky bluegrass 50.4 a b 5.0 b
Penncross creeping bentgrass 31.8 b 5.8 a b

 

(1) values are the means of three replications.

(2) Means in the column followed by the same letter are
not significantly different at the 5% level of the
.Duncan's Multiple Range Test.

61

Figure 5. Rooting of three turfgrass species 15 days after
transplanting. Left to right: Merion Kentucky
bluegrass, annual bluegrass, and Penncross creeping

bentgrass.

 

CONCLUSIONS

The following conclusions may be drawn from this investi-

gation:

l.

Penncross creeping bentgrass and Merion Kentucky bluegrass
initiated new shoot growth earlier in the spring than
annual bluegrass. Penncross and Merion initiated growth
between 50° and 55°F while established plants of annual
bluegrass did not initiate new Spring growth until the
soil temperatures exceeded 55°F.

Penncross creeping bentgrass produced maximum root growth
at 60°F while Merion Kentucky bluegrass and annual blue-
grass produced maximum root dry weights at 70°F.

All three Species produced maximum shoot growth at 60°F.
Penncross creeping bentgrass is adapted to a wider range
of temperatures in terms of producing superior root and
shoot dry weights than Merion Kentucky bluegrass and
annual bluegrass at the extreme temperatures of 40° and
90°F. ’

A 1.0 inch cutting height produced the highest tiller
numbers, shoot dry weights, and shoot density counts for
annual bluegrass in both mono- and polystands.

Rooting depths were similar for all three species.

Annual bluegrass possessed a more extensive, branched

62

63

root system thereby resulting in greater root dry weights
than Merion Kentucky bluegrass.

The rooting depths of all three species were reduced by
clipping three times weekly at 1.0 inch. Penncross

creeping bentgrass was the most severely effected.

BIBLIOGRAPHY

10.

11.

12.

BIBLIOGRAPHY

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Arber, A. 1934. The Gramineae. Cambridge University
Press, Iondon, England. pp. 480.

 

Beard, J. B. 1959. The growth and develOpment of
Agrostis palustris roots as influenced by certain environ-

 

annua. USGA Green Section Record 68(7):10-12.

mental factors. M.S. Thesis, Purdue University. pp. 75.

Beard, J. B. 1966. Direct low temperature injury of
nineteen turfgrasses. Michi an Agricultural Experiment
Station Quarterly Bulletin 4 (3):377-383.

Beard, J. B. 1968. Effect of temperature stress on Poa

Beard, J. B. 1968. Low temperatures and Poa annua. USGA
Green Section Record 68(11):lO-11.

Beard, J. B. 1970. An ecological study of annual blue-
grass. US A Green Section Record 8(2):l3-l8.

Beard, J. B. 1970. The plant characteristics, dissemina-
tion, environmental adaptation, and cultural requirements
of Poa annua L. Rasen Turf Gazon 2/70:33-35.

Beard, J. B. and C. R. Olien. 1963. low temperature
injury in the lower portion of Poa annua L. crowns. CrOp

Science 3(4):362-363. ‘__-

Beard, J. B. and W. H. Daniel. 1965. Effect of tempera-
ture and cutting on the growth of creeping bentgrass
(Agrostis palustris HUds.) roots. Agronomy Journal 57:

2W

Brobrov, R. A. 1955. The leaf structure of Poa annua

with observations on its smog sensitivitg in Los Angeles
county. American JOurnal of Botany 42:4 7-474.

 

 

 

 

Carroll, J. C. 1943. Effects of drought, temperature
and nitrogen on turfgrasses. Plant Physiology 18:19-36.

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65

Cockerham, S. T. and J. W. Whitworth. 1967. Germination
ggdlgoRgrol of annual bluegrass. The Golf Superintendent

Engel, R. E. 1967. Temperatures required for germination
of annual bluegrass and colonial bentgrass. The Golf
superintendent 35:20_28.

Fischer, J. A. 1967. An evaluation of high temperature
effects on annual bluegrass (Poa annua In). M.S. Thesis,

Michigan State University. pp. 42.

Gibeault, v. A. 1970. Pereniality in Poa annua L. PhD
Thesis, Oregon State University. pp. 125.

Gibeault, v. A. 1971. Agronomic factors in irrigation
design. TUrf-Grass Times 7(4):17.

Harrison, 0. M. 1934. Responses of Kentucky bluegrass
to variations in temperature, light, cutting and fertil-
zing. Plant Physiology 9:87-106.

Hawes, D. T. 1965. Control of annual bluegrass. Thrf
Conference Proceedings, University of Massachusetts.

pp. 5-10.

HOagland, C. R. and D. I. Arnon. 1950. The water culture
method for growing plants without soil. California
Agricultural Experiment Station Circular 347. pp. 32.

 

HOvin, A. W. 1957. variations in annual bluegrass.
Golf Course Reporter 25(7)l8-19.

Jackson, N. 1959. Evaluation of some grass varieties.
Journal of the Sports Thrf Research Institute 10(35):l3-28.

Jackson, N. 1964. Further notes on the evaluation of some
grass varieties. Journal of the Sprots Tarf Research
Institute 40:67-75.

JUhren, M., W. Noble and F. W. Went. 1957. The standard-
ization of Poa annua as an indicator of smog concentrations.
1. EffectS‘O? temperature, photOperiod, and light inten-
;%gysggring growth of test plants. Plant Physiology 32:

Juska, F. v. and A. A. Hanson. 1969. Nutritional require-
ments of Poa annua L. Agronomy Journal 61:466-468.

Kerr, C. F. 1968. Thrf enemy No. 1 - Poa annua. weeds,
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Keshy, T. K. 1968. Evolutionary origin of Poa annua L.

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Keshy, T. K. 1969. Breeding systems in annual bluegrass,
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langvad, B. 1969. Turfgrasses in Sweden. Proceedings
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p. 13.

Lynch, R. I. 1903. Poa annua not a self fertilizer. The
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Monteith, J. 1931. Experimental results at Miami Beach
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Renney, A. J. 1964. Preventing Poa annua infestations.

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Robinson, 0. S. 1969. Greenkeeping problems in New
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Sprague, H. B. and G. W. Burton. 1937. Annual bluegrass
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Targeon, A. J. 1971. The role of 7-oxabicyc1e (2.21)
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APPENDIX

APPENDIX

Appendix Tables 1-7 present the data from which the tem-
perature-growth response curves were drawn. The data is pre-
sented as mean comparisons of the root and shoot dry weights
at each temperature. The treatment symbols used on the Tables
are as follows:

P/30 - Penncross creeping bentgrass plants removed at day 30.

M/30 - Merion Kentucky bluegrass plants removed at day 30.

A/30 - Annual bluegrass plants removed at day 30.

P/15 - Penncross creeping bentgrass plants removed at day 15.

M/15 - Merion Kentucky bluegrass plants removed at day 15.

A/15 - Annual bluegrass plants removed at day 15.
P/O - Penncross creeping bentgrass plants removed at day 0.
M/O - Merion Kentucky bluegrass plants removed at day 0.

A/O - Annual bluegrass plants removed at day 0.

Appendix Table 8 presents the data from the nitrogen fer-
tility level-cutting height study. The data shown deal with
the reduced rooting of annual bluegrass when grown at the higher
nitrogen fertility level (2 # N/lOOO sq. ft. per month).

67

68

APPENDIX TABLE 1. The root and shoot dry weights of three

turfgrass Species grown at a constant 40°F

 

 

 

temperature.
Treatment Root dry weights (1) Shoot d weights
(species/date) (mg) (m23
P/3O 241.8 a (2) 835.0 a
M/30 139.3 b 443.5 b
A/30 116.3 b c 332.5 b
A/15 39.8 c d 86.5 c
P/15 39.5 c d 79.0 c
M/15 28.0 d 79.3 c
A/O 9.0 d 7.5 C
P/O 8.8 d 12.5 c
M/O 7.0 d 9.3 c
(1) values given are the means of four replications.

(2)

Means in the column followed by the same letter are
not significant at the 5% level of the Duncan's
Miltiple Range Test.

69

APPENDIX TABLE 2. The root and shoot dry weights of three

turfgrass species grown at a constant 50°F

 

 

 

temperature.
Treatment Root dry weights (1) Shoot dry weights
(Species/date) (mg) (mg)
A/30 169.3 a (2) 465.5 a
P/30 116.8 b 453.3 a
W30 64.3 c 182.8 b
A/15 24.0 d 50.0 c
M/15 14.8 d 32.3 c
P/15 11.5 d 30.3 c
A/O 5.3 d 7.8 c
M/O 3.8 d 6.0 c
P/O 2.0 d 4 .5 c
(1) values given are the means of four replications.

(2)

Means in the column followed by the same letter are
not significant at the 5% level of the Duncan's
Multiple Range Test.

70

APPENDIX TABLE 3. The root and Shoot dry weights of three
turfgrass species grown at a constant 60°F

 

 

temperature.
Treatment Root dry weights (1) Shoot dry weights

(species/date) (mg) (mg)

A/3O 947.5 a (2) 2084.0 a

P/30 621.5 b 2204.3 a

M/3O 252.5 c 849.0 b

P/15 149.0 c d 406.8 c

A/15 96.3 c d 234.0 c d

M/15 32.8 c d 109.5 d

A/O 11.8 d 22.8, d

P/O 4.5 d 14.3 d

M/O 4.0 d 13.8 d

 

(1) values given are the means of four replications.

(2) Means in the column followed by the same letter are
not significant at the 5% level of the Duncan's
Multiple Range Test.

71

APPENDIX TABLE 4. The root and shoot dry weights of three
turfgrass species grown at a constant 70°F

 

 

temperature.
Treatment Root dry weights (1) Shoot dry weights

(Species/date) (mg) (mg)

A/30 1043.8 a (2) 1364.8 b

P/30 483.5 b 1564.0 a

M/3O 302.0 c 697.5 c

A/15 223.0 c d 404.0 d

P/15 108.8 d e 295.5 e

M/l5 49.8 e 139.8 f

A/O 9.8 e 18.8

P/O 7.8 e 16.8

M/O 5.3 e 10.0

 

(1) values given are the means of four replications.

(2) Means in the column followed by the same letter are
not significant at the 5% level of the Duncan's
Multiple Range Test.

72

APPENDIX TABLE 5. The root and shoot dry weights of three

turfgrass species grown at a constant 80°F

 

 

temperature.
Treatment Root dry weights (1) Shoot dry weights

(species/date) (mg) (mg)

P/30 132.8 b (2) 993.5 a

A/30 199.5 a 791.8 b

M/30 147.8 b 693.3 c

P/ 15 109.5 b 396.3 d

A/l5 138.0 b 367.3 d

M/15 21.0 c 80.0 e

A/0 9.5 c 22.3 e

P/O 7.0 c 22.0 e

M/O 2.8 c 6.5 e

 

(l)
(2)

values given are the means of four replications.

Means in the column followed by the same letter are
not significant at the 5% level of the Duncan's
Multiple Range Test.

73

APPENDIX TABLE 6. The root and shoot dry weights of three 0
turfgrass species grown at a constant 90 F

temperature.

 

 

 

(2)

Treatment Root dry weights (1) Shoot dry weights
(species/date) (mg) (mg)
P/30 109.5 a (2) 492.3 a
A/30 62.0 b 329.5 b
M/30 45.0 b C 242.8 b c
A/15 33.0 C 89.3 C d
P/15 24.0 c d 90.8 c d
M/l5 20.0 c d 82.3 c d
A/0 5.3 d 19.3 c d
M/O 5.0 d 22.5 d
P/O 4.8 d 17.0 d
(1) values given are the means of four replications.

Means in the column followed by the same letter are
not significant at the 5% level of the Duncan's
Multiple Range Test.

74

APPENDIX TABLE 7. The root and shoot dry weights of three
turfgrass Species grown at a constant
100°F temperature.

 

 

Treatment Root dry weights (1) Shoot dry weights
(species/date) (mg) (mg)
M/15 1.3 a (2) 8.8 a
P/l5 1.3 a 6.0 a
A/l5 1.0 a 5.0 a
M/O 1.5 a 4.5 a
A/O 1.0 a 4.3 a
P/O 1.3 a 3.3 a

 

(1) values given are the means of four replications.

(2) Means in the column followed by the same letter are
not significant at the 5% level of the Duncan's
Multiple Range Test.

Note: Death occurred between days 15 and 30.

75

APPENDIX TABLE 8. The influence of two nitrogen fertility
levels on the root organic matter produc-
tion of annual bluegrass plants grown in
a mature Merion Kentucky bluegrass sod.

 

 

Fertility level Cutting height Root organic matter (1)
(# N/lOOO sq. ft/mo.) (inches) . (mg)
0.5 34.5 a (2)
1.0 34.2 a
0.5 1.5 22.7 a
2.0 30.8 a
2.5 21.3 a
0.5 9.6 a
1.0 20.6 a
2.0 1.5 24.5 a
2.0 10.2 a
2.5 23.7 a

 

(1) values given are the means of six replications.

(2) Means in the column followed by the same letter are
not significant at the 5% level of the Duncan's
Multiple Range Test.

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