GROWTH OF ROOTS, RHIZOMES, AND TILLERS OF KENTUCKY BLUEGRASS (Poa .l?.ratensis L.) CULTIVARS AND GENOTYPES AS AFFECTED BY
FERTILITY LEVEL, CUTTING HEIGHT, AND SEASON
by
Frank Edward Smith
Thesis submitted to the Graduate Faculty of the
Virginia Polytechnic Institute and State University
in partial fulfillment of the requirements for the degree of
MASTER OF SCIENCE
in
Agronomy
Approved:
Dr. R. E. Schmidt, Chairman
Dr. D. c. Martens
March 1973
Blacksburg, Virginia
ACKNOWLEDGMENTS
The author is indebted to Dr. R. E. Schmidt for serving as chairman
of his committee. Special appreciation is extended to Drs. R. E. Blaser,
D. C. Martens, and J, M. Byrne for serving on the graduate committee.
Gratitude is also extended to Drs. G. W. Brown, E. R. Edmondson, and
J. L. Jones for helping with the computer analysis, to other staff
members and fellow graduate students for their suggestions, and to
Miss Suella Robinson for typing the manuscript.
The greatest appreciation is expressed to the author's wife,
Susan, for her help, endurance, and encouragement throughout the study
and preparation of this manuscript.
TABLE OF CONTENTS
ACKNOWLEDGMENTS
LIST OF TABLES.
LIST OF FIGURES
INTRODUCTION .•.
LITERATURE REVIEW Seasonal Growth. Nitrogen Fertility . Cutting Height . . . . • . Carbohydrate Content .
MATERIALS AND METHODS - UNDISTURBED UNDERGROUND GROWTH OF VARIOUS CULTIVARS AND GENOTYPES • • • • • • •
RESULTS - UNDISTURBED UNDERGROUND GROWTH OF VARIOUS CULTIVARS AND GENOTYPES . • . • • • . • . •
Root Elongation. Total Roots •...•• White Roots .• Average Total, Brown, and White Roots .. Rhizomes .•. Tillers .... Disease Incidence. Turf Cover . . . •
MATERIALS AND METHODS - CUTTING HEIGHT EFFECT ON UNDISTURBED UNDERGROUND GROWTH OF VARIOUS CULTIVARS AND GENOTYPES . ,
RESULTS - CUTTING HEIGHT EFFECT ON UNDISTURBED UNDERGROUND GROWTH OF VARIOUS CULTIVARS AND GENOTYPES .
Total Roots. White Roots. Rhizomes ... Plant Height .
MATERIALS AND METHODS - ROOT STRENGTH STUDIES OF VARIOUS CULTIVARS AND GENOTYPES FROM FIELD GROWN SOD .•.•••
RESULTS - ROOT STRENGTH STUDIES OF VARIOUS CULTIVARS AND GENOTYPES FROM FIELD GROWN SOD.
Root Strength. • Rhizomes . • . Plant Height • •
iii
ii
v
• vii
1
2 2 5 6 7
11
15 15 17 17 21 21 21 25 25
28
30 30 30 34 34
38
40 40 44 44
iv
TABLE OF CONTENTS (Cont.)
DISCUSSION.
SUMMARY AND CONCLUSIONS •
LITERATURE CITED.
VITA.
Page
49
54
56
61
LIST OF TABLES
Table 1. Origin or source of Kentucky bluegrass (Poa pratensis L.) cultivars and genotypes. • • • • • • • • • • • 12
Table 2. Composition of nutrient solution used for growing turfgrasses. . . • • • . • • • . • . • • • • • 13
Table 3. Root elongation (cm/data period) of 24 Kentucky bluegrasses at six dates • • • • • • • • • • • 16
Table 4. Total number of roots of 24 Kentucky bluegrasses at 20 cm depth at four dates. . • • • • • • 18
Table 5. White roots of 24 Kentucky bluegrasses at 20 cm depth at four dates. • • . • • . . • • • • 20,
Table 6. Rhizomes of 24 Kentucky bluegrasses at four dates • 23
Table 7. Turf cover of 24 Kentucky bluegrasses at four dates 27
Table 8. Total number of roots of 8 Kentucky bluegrasses for two cutting heights (1.3 cm-low, 5 cm-high) at three da.tes • 31
Table 9. Number of white roots of 8 Kentucky bluegrasses for two cutting heights (1.3 cm-low, 5 cm-high) at two dates 33
Table 10. Number of rhizomes of 8 Kentucky bluegrasses for two cutting heights (1.3 cm-low, 5 cm-high) at two dates 35
Table 11. Foliar regrowth of 8 Kentucky bluegrasses at two cutting heights (1.3 cm-low, 5 cm-high) for two periods (original cutting height subtracted) • • • • • • • • , , 36
Table 12. Root strength* of 30 Kentucky blu.egrasses after three growth periods (averaged for two fertility levels) and percentage change from previous period • • • • . • 41
Table 13. · Root strength* of 30 Kentucky bluegrasses after three growth periods averaged for t~q fert~lity levels 43
Table 14. Root strength* of 30 Kentucky bluegrasses after three growth periods and two fertility levels (low-0.5 kg N/200m2, high-1.0 kg N/200m2) • • • • . • • • • 46
Table 15. Height of 30 Kentucky bluegrasses at two periods for two fertility levels • • • • • . • • • • • • • 47
v
vi
LIST OF TABLES (Cont.)
Table 16. Height of 30 Kentucky bluegrass sods after three growth periods and two fertility levels (0.5 kg N/200m2, 1. 0 kg N/ 200m2) • • , • • • • • • • • • • • • • • • , , • 48
LIST OF FIGURES
Figure 1. Root development at 20 cm depth of 24 Kentucky bluegrasses (August 8, 1971) ••••••
Figure 2. Total, brown, and white roots at 20 cm depth of 24 Kentucky bluegrasses at four dates ••••••
19
22
Figure 3. Tillers of 24 Kentucky bluegrasses (August 8, 1971) .• 24
Figure 4. Relative disease incidence of 24 Kentucky bluegrasses (September 15, 1971) . • . • • • . • • . • • 26
Figure 5. Decrease of roots at 20 cm depth of 8 Kentucky bluegrasses clipped at 1.3 cm as compared to those grasses clipped at 5 cm (June 22, 1972). , • , ..•...••• 32
Figure 6. Differences in top regrowth of 8 Kentucky bluegrasses clipped at 1.3 cm as compared to those grasses clipped at 5 cm (June 22-July 25, 1972) •.•••.•.•.•••• , • 37
Figure 7. Emerged rhizomes 15 weeks after the sod of Kentucky bluegrasses had been removed from field plots on April 20, 1972 .••.•.••.••••••••
vii
45
INTRODUCTION
In the past few years, many new Kentucky bluegrass cultivars have
been released for various regions of the country and for many truf grass
uses. Many more cultivars will be released since Dr. C. Reed Funk of
Rutgers has developed a technique to hybridize apomitic Ky. bluegrasses.
The new cultivars released have undergone only limited evaluation;
nevertheless, certain cultivars have been sold for use in many unadapted
areas. The golf course superintendent, sod producer, and home owner
should have information on performance of these new cultivars to make
wise selections.
Various experiments conducted under different field conditions with
some cultivars have often produced conflicting data. Also, data from
experiments measuring underground growth have also been limited because
of difficulty in technique. Many experiments have been conducted on the
effects of fertility and cutting height on underground growth, but in-
most cases the cultivars were disturbed before the end of the growing
season or not observed throughout the growing season.
In this thesis the objectives were to study effects of fertility
level and cutting height on underground growth of various Kentucky
bluegrasses during various seasons and develop a technique for measuring
underground growth without disturbing the cultivars and genotypes,
1
LITERAIURE REVIEW
Seasonal Growth
It has been shown that root initiation of temperate grasses occurs
primarily during late winter until early spring $prague, 1933; Stuckey,
1942; Etter, 1951; Troughton, 1951, 1957; Jacques and Edmonds, 1952;
Roberts and Bredakis, 1960; Hanson and Juska, 1961; Powell, Blaser, and
Schmidt, 1967; Garwood, 1967). During the late spring and sununer, few
new bluegrass roots are initiated and elongation is confined to the
lower soil horizons (Troughton, 1951; Jacques and Schwass, 1956;
Garwood, 1967). Temperate grass root initiation increases in autumn
and root elongation decreases (Troughton, 1951; Jacques and Schwass,
1956; Garwood, 1967). Troughton (1951) and Stuckey (1942) indicated
that temperate grass root elongation increases slowly during winter,
continues to increase throughout the spring and early summer, decreases
at early root initiation and beginning of flowering, and declines
steadily after June. This trend may be altered in mild climates where
root growth may also occur in summer and winter.
Decay of old roots sometimes masks the growth of new roots in
temperate grasses. Numerous investigations indicated that root growth
occurred during harsh environmental periods if adjustments for the decay
of old roots were made (Troughton, 1957). Decay of old roots begins
during flowering and continues until early winter. The decaying is
enhanced during high temperature, especially under heavy irrigation
(Troughton, 1951; Stuckey, 1942; Brown, 1943).
2
3
Time of root initiation influences root morphology and longevity.
Roots produced in the autumn live longer than those initiated in the
spring (Troughton, 1951; Garwood, 1967). Etter (1951) has reported
that roots produced in the summer were thin and wiry as compared to
those produced in the spring or autumn. Cell division has been found
to occur during temperatures of 32F, and cessation of root growth
occurred at summer temperatures (Stuckey, 1942; Brown, 1943).
Maximum root and shoot growth of temperate grasses does not occur
at the same time (Stuckey, 1942; Troughton, 1951; Jacques and Edmonds,
1952, 1956; Roberts and Bredakis, 1960; Youngner, 1969). Maximum root
growth occurs either before or after shoot growth (Stuckey, 1942;
Troughton, 1951).
Roots of Poa pratensis L. were reported to function more than one
year (Stuckey, 1942). Sprague (1933) and Roberts and Bredakis (1960)
found that about half of this species' root system is regenerated each
spring.
Environmental conditions are different for maximum top growth and
root growth in temperature grasses (Youngner, 1969). Light intensity
has more effect on root growth while soil water has more effect on top
growth (Troughton, 1960). Temperate grass root growth is higher at
lower temperatures than foliage growth (Beard and Daniel, 1965).
Initiation of Kentucky bluegrass rhizomes peaks in late spring and
early surraner (Evans and Ely, 1935; Evans and Watkins, 1939), being
three times higher in spring than in fall (Evans and Watkins, 1939).
4
The amount of buds producing ~illers in the fall affects rhizome
number since the same buds produce both tillers and rhizomes. Rhizomes
produced in sunnner are responsible for the next year's inflorescence.
Rhizome development is favored by winter, spring, and summer fertiliza-
tion (Etter, 1951).
It was shown that day length affected elongation, flowering, and
type of growth of Kentucky bluegrass (decumbent, erect, etc.) (Evans
and Watkins, 1939). Evans and Watkins (1939) reported more rhizome
initiation during short day lengths; however, Moser, Anderson, and
Miller (1968) reported that long day lengths promoted initiation and
growth of rhizomes.
A tiller originates from an axillary bud. Roots emerge from the
crown node of each tiller causing it to be independent from the parent
plant. The major amount of tiller initiation occurs during early fall
to late winter (Etter, 1951). Environmental conditions favoring blue-
grass tiller initiation are short day lengths, adequate fertilization,
a lack of shade and weeds, close fall mowing, and irrigation (Harrison,
1934; Etter, 1951).
The greatest initiation of new bluegrass shoots occurred from
August or September until the end of the growing season, and again from
April to early May (Evans and Ely, 1935; Brown, 1943). With long days
there was no elongation of internodes, no inflorescence, and a decum-
bent to semi-decumbent growth habit. Short days produced elongation of
internodes, production of inflorescence, and upright growth (Evans and
Watkins, 1939; Peterson and Loomis, 1949).
5
Nitrogen Fertility
For temperate grasses added increments of nitrogen cause the growth
of grass roots to increase and finally to decline with additional
applications of nitrogen (Powell et al., 1967; Harrison, 1934; Juska
et al., 1955; Auda et al., 1966; Goss and Law, 1967; Schmidt, 1967).
Date of applying nitrogen influences root growth. Nitrogen applied in
fall increased temperate grass root production (Hanson and Juska, 1961;
Powell et al., 1967); however, early spring applications decreased
temperate grass root growth (Schmidt and Blaser, 1969). Low nitrogen
fertility causes low metabolic activity and decline in temperate grass
root growth (Powell et al., 1967). Excessive nitrogen fertility stimu-
lates cell division and respiration (Alberta, 1966; Schmidt and Blaser,
1967; Goss and Law, 1967).
Harrison (1934) reported Kentucky bluegrass rhizomes left uncut
receiving liberal amounts of nitrogen fertility emerged from the soil
in the late fall. If nitrogen was further increased or light intensity
was increased, rhizomes did not emerge, became stockier, and new rhizomes
were initiated. He also found that at 60F without nitrogen increased
root initiation and decreased rhizome emergence as compared to Ky.
bluegrass fertilized lightly with nitrogen. However, Juska et al.,
(1955) reported excess nitrogen fertility decreased rhizome number and
initiation, and Auda et al. (1966) reported increased tiller initiation
and stimulated growth for orchardgrass with nitrogen applications.
Numerous experiments cited increased nitrogen enhanced top growth
as compared to root growth yields (Harrison, 1931; Ahlgren, 1938;
6
Juska et al., 1955; Troughton, 1956; Madison, 1962b; Pellet and Roberts,
1963; Alberta, 1966; Goss and Law, 1967; Schmidt and Blaser, 1967;
Monroe, Coorts, and Skogley, 1969; Youngner, 1961).
Cutting Height
A completely new root system is generally produced in closely mowed
turf of cool season grasses each spring. Decline in root growth occurs
as cutting height is lowered (Weaver, 1930; Harrison, 1931, 1934;
Gernert, 1936; Harrison and Hodgson, 1939; Kennedy and Russell, 1948;
Jacques and Edmonds, 1952; Roberts and Bredakis, 1960; Madison, 1962a;
Beard and Daniels, 1965; Goss and Law, 1967; Hanson and Juska, 1961;
Schmidt and Blaser, 1969; Watson, 1969). Close clipping reduces root
number and weight (Youngner, 1969; Harrison, 1931), depth and length of
life (Harrison, 1931; Troughton, 1957). Thus close clipping will pro-
duce a thin sod with a shallow root system.
The number, growth, and weight of rhizomes are decreased when blue-
grass is mowed (Harrison, 1934; Harrison and Hodgson, 1939; Gernert,
1936; Kennedy and Russell, 1948; Goss and Law, 1967; Schmidt and Blaser,
1969; Youngner, 1969). Brown (1943) found that clipping affects
rhizomes more than roots,
More .top growth occurs with high cutting height when compared to
low cutting height (Harrison, 1931, 1934; Gernert, 1936; Ha~rison and
Hodgson, 1939; Kennedy and Russell, 1948; Roberts and Bredakis, 1960;
Goss and Law, 1967; Schmidt and Blaser, 1969; Watson, 1969; Youngner,
1969).
7
Merion Kentucky bluegrass produced a better root system than connnon
Kentucky bluegrass under a 1.9 cm cutting height regime (Roberts, 1958).
The Kentucky bluegrass cultivars, Merion, Windsor, Cougar, Fylking, and
Prato tolerated a lower cutting height than Park, Delta, Newport, or
Connnon (Watson, 1969). Wood and Burke (1961) ranked Merion first,
Newport and Park second, Delta and Common third or last in turf density
when mowed at 1.3 cm. Merion was rated first when averaged over three
cutting heights (1.3 cm-2.5 cm-3.2 cm) with Common and the others second.
An increase in cutting height will increase grass vigor, wear
resistance, and reduce weed encroachment (Schmidt and Blaser, 1969;
Juska, Tyson, and Harrison, 1956). Severe defoliation may mask seasonal
variations in growth (Troughton, 1957).
Carbohydrate Content
"Reserve carbohydrates are non-structural materials that may be
stored in various plant tissues and later utilized in respiration and
growth" (Youngner, 1969). Reserve carbohydrates consist of sugars,
fructosans, and starch (Youngner, 1969). Oligosaccharides are the
dominant form of reserve carbohydrate in Kentucky bluegrass (Green and
Beard, 1969). Reserve carbohydrates are stored in roots, rhizomes,
crowns, and stolons of Kentucky bluegrass (Brown, 1943).
The reserve carbohydrates are utilized when growth demands for
energy exceed that supplied by photosynthesis and stored when photo-
synthesis exceeds requirements for growth (Juska et al., 1955; Brown and
Blaser, 1965). Also, reserve carbohydrates provide energy for recovery
from injury, temperature, and moisture stress, as well as tiller
8
initiation (Youngner, 1969; Peterson and Loomis, 1949). May (1960)
stated that utilization of carbohydrates by plants depends more on
mobilization and translocation than the amounts stored. Mobilization
may be affected by a hormone or an auxin. Translocation is affected by
concentration gradients caused by temperature, oxygen, and water.
Low carbohydrates appears to be the limiting factor in the growth
of roots (Youngner, 1969). Low carbohydrates in temperate grasses
reduces root and rhizome development (Schmidt and Blaser, 1967; Juska
and Hanson, 1961). Weaver (1930) reported that grasses in the
Andropogen genera with a poor root system and little stored food
reserves are less resistant to winterkilling.
Nitrogen fertilization, moisture, temperature, light, cutting
height, and growth period are the major environmental factors influencing
carbohydrate reserves (Carroll and Welton, 1938; Brown, 1939; Sullivan
and Sprague, 1943, 1953; May, 1960; Brown and Blaser, 1965; Zanoni,
Michelson, Colby, and Drake, 1969; Waite and Boyd, 1953; Green and
Beard, 1969; and Youngner, 1969).
The largest period of carbohydrate storage in temperate grasses
occurs in autumn, declining slowly during winter. In early spring there
is a brief period of carbohydrate accumulation with a sharp decline
during rapid top growth. A slow decline of carbohydrate levels contin-
ues throughout the summer until accumulation begins again in the
autumn (Brown, 1943; Youngner, 1969). During maximum vegetative growth,
Colby, Drake, Field, and Kreowski (1965) found fructosan to decrease in
orchardgrass.
9
Excessive nitrogen rates and favorable environment for rapid growth
cause stored carbohydrates to be used for top growth (Balser, 1969).
The rate of regrowth in Lolium perenne L. and Dactylis glomerata L.
was influenced by the decreasing of soluble carbohydrates caused by
nitrogen fertilization as growth requirements increased relative to rate
of photosynthesis (Jones, Griffith, and Walters, 1965; Ward and Blaser,
1961). With autumn-winter nitrogen fertilization, root growth does not
decline because tempeJ'.'atures inhibit top growth. Nitrogen applied
during favorable temperatures causes low carbohydrate reserves because
of rapid top growth (Schmidt, 1969; Schmidt and Blaser, 1969).
Cutting of temperate grasses reduces carbohydrate reserves in
grasses (Weaver, 1930; Harrison, 1931; Burkey and Weaver, 1939; Sullivan
and Sprague, 1943; Troughton, 1957; Roberts and Bredakis, 1960; Ward and
Blaser, 1961). Defoliation of a plant causes mobilization and translo-
cation of reserve carbohydrates from storage areas to shoot tissue for
rapid regrowth (Troughton, 1957). Reducing the photosynthetic area by
mowing decreases root and rhizome production and ca~bohydrate storage
(Harrison, 1931; Juska et al., 1955).
When perennial ryegrass with high and low non-structural carbo-
hydrates was cut, the plants with high carbohydrates produced twice as
many leaves. The final total weight of the plants was greater in plants
with high carbohydrates (Alberta, 1966). Sullivan and Sprague (1943)
reported that after partial defoliation the water soluble carbohydrates
(glucose, fructose, sucrose, and fructosan) decreased rapidly for
several weeks and then increased. When placing plants in darkness,
10
soluble carbohydrates decreased almost to exhaustion and some hydrolysis
of protein occurred. The higher the percentage of stored fructosan and
sucrose, the greater the decrease of carbohydrates after clipping
(Sullivan and Sprague, 1950).
Nitrogen causes increased top growth, thereby reducing carbohydrates,
and mowing enhances this response (Youngner, 1969). Johnson and Dexter
(1939) reported on several occasions the stimulation of growth in
quackgrass with nitrogen applications followed by removal of top growth
caused the plant to rely upon its stored carbohydrates for growth.
Eventual starvation and death of plants occurred following these
treatments.
More carbohydrate reserves were found at low temperatures (7C
night-16C day) than high temperatures (21C night-27C day) in Merion,
Fylking, and Newport varieties of Kentucky bluegrass. Newport had the
most carbohydrates at all temperatures (Youngner and Nudge, 1968).
MATERIALS AND METHODS
UNDISTURBED UNDERGROUND GROWTH OF VARIOUS CULTIVARS AND GENOTYPES
Twenty-four Kentucky bluegrass (Poa pratensis L.) cultivars and
genotypes were obtained from the Virginia Polytechnic Institute and
State University turfgrass research center at Blacksburg, Virginia. The
cultivars and genotypes obtained were as follows: Fylking, Pennstar,
Geary, Cougar, Kenblue, Newport, Windsor, Delta, Arista, Merion, BA6124,
Minnesota 6, PPl, K107, P5, Belturf, Southport, Nugget, Palouse, Park,
A34, Campus, Baron, and KllO (Table 1).
Ten bluegrass clones of each cultivar and genotype were trans-
planted into frames (5 cm x 30 cm wide x 60 cm deep) with 30 cm x 60 cm
clear plastic fronts filled with a 2.5 cm thick 90% crystallized shale
and 10% peat mixture growing medium on July 12, 1971. A 0.63 cm section
of exterior celotex was placed over the recessed transparent plastic
front to exclude light. Underground organs were forced toward the
plastic by tilting the frames fifteen degrees. The window frames with
sod were placed in six rows in a randomized block design into an
insulated container in the field and grown during four seasons. A
modified complete nutrient solution as described by Hoagland and Arnon
(1950) was applied in like amounts through plastic tubing to each frame
twice each day for 15 minutes (Table 2). Approximately 1800 cc was
applied to each sod frame each day.
All but four tillers were removed from each frame at the end of_
the first week. The cultivars were clipped at 5 cm so that no more
than one-half of the leaf area was removed at any one cutting.
11
12
Table 1. Origin or source of Kentucky bluegrass (Poa pratensis L,) cultivars and genotypes.
Selection Origin or Selection Origin or source source
Fylking Sweden Palouse Alaska Penns tar Pennsylvania Park Minnesota Geary Jacklin Seed Co. A34 Warrens Cougar Washington Campus W.R. Grace Campus Netherlands Baron New Jersey Kenblue Kentucky KllO Pennsylvania
Newport Washington S. Dakota S. Dakota Windsor Ohio-0.M. Scott WK411 Sweden Delta Canada WK412 Sweden Arista w. R. Grace Adelphi New Jersey Merion Maryland-USDA P35 New Jersey BA6124 Ohio-0.M. Scott Pll5 New Jersey
Minnesota 6 Minnesota Pll4 New Jersey PPl Rhode Island Sod co Minnesota Kl07 Pennsylvania Primo Indiana PS New Jersey P56 New Jersey Bel turf Maryland-USDA K8144 Northrup King Southport w. R. Grace K8146 Northrup King Nugget Alaska
13
Table 2. Composition of nutrient solution used for growing turfgrasses.
Salt mmoles/L. Salt mmoles/L.
Ca(N03) 2 'H20 5.400 KN03. 2.70000
MgS04 1.400 ZnS04 •7H20 0.000310
KH2Po4 1.900 CuS04 •SH2o 0.000310
H3Bo3 0.018 H2Mo04 °H2o 0.000044
MnC12·4H20 0.0037 EDTA-Feso4 •7H2o 0.02700
14
Underground measurements were made without disturbing the plant
by horizontally marking five 10-cm intervals beginning at the soil
surface on the clear plastic. All roots were counted before October 5,
1971, and white roots were distinguished from brown roots after that
date.
Periodically grease pencil marks were made on the clear plastic
opposite active root tips in order to measure root growth during a
certain period. Tillers and rhizomes were counted at varying dates.
Soil cover with turf, and disease were rated visually (10-best, 1-worst).
All data were subjected to analyses of variance and Duncan's
Multiple Range Test was used to separate the means.
RESULTS
UNDISTURBED UNDERGROUND GROWTH OF VARIOUS CULTIVARS AND GENOTYPES
Root Elongation
Root elongation of the 24 cultivars and genotypes averaged tended
to be rapid for the first two months after transplanting, and remained
quite high during the fall until May 15 (Table 3). There was little
elongation between May 15 and June. 22, 1972, and none between June 22
and July 25, 1972 (the latter data not shown).
Differences between cultivars and genotypes occurred at the 5%
level during only two periods (July 22-29, 1971 and March 30-May 15,
1972). The root elongation of BA6124, Minnesota 6, Cougar, Merion,
Palouse, and Park was more than the average of all bluegrasses for each
of the two periods. Among the cultivars· and· genotypes, only Merion,
BA6124, Minnesota 6, Park, Kenblue, Newport, Delta, PPl, Kl07, Belturf,
Southport, Campus, and KllO showed some root elongation after May 15,
1972.
Pennstar, Newport, Kl07, Southport, A-34, Campus, and Baron had
less root elongation than the average of all cultivars and genotypes for
both of the two periods (July 22-29 and March 30-May 15). Fylking, Arista,
PPl, and Nugget showed less root elongation rates than the average for
all bluegrasses during July 22-July 29, 1971, but had higher than average
for March 30-May 15, 1972. On the other hand, root elongation of Geary,
Kenblue, Windsor, Delta, PS, Belturf, and KllO was better than average
during July 22-July 29, 1971 and less than average of all bluegrasses
during March 30-May 15, 1972.
15
Table 3. Root elongation (cm/data period) of 24 Kentucky bluegrasses at six dates.
Cultivar
Fylking Penns tar Geary Cougar Kenblue Newport Windsor Delta Arista Merion BA6124 Minnesota 6 PPl Kl07 PS Bel turf Southport Nugget Palouse Park A34 Campus Baron KllO Mean
Periods July 22 '71 Aug. 16 '71 Oct. 5 '71 Dec. 16 '71 Mar. 30 '72 May 15 '72
to to to to to to July 29 '71 Aug. 28 '71 Dec. 16 '71 Mar .. 30 '72 May 15 '72 June 22 '72
Growth rate (cm/data period)
l.8d* 6.4 3.7 6.7 4.7abcdef 4.8abc 7.8 2.0 4.7 l.8ef 6.5abc 8.3 3.3 6.0 3.0bcdef 7.2a 9.5 2.7 6.0 5.7abcde 6.0abc 9.2 2.0 2.0 2.7bcdef 4.9abc 8.3 2.7 3.3 3.8abcdef 6.Sabc 7.3 2.0 3.0 3.8abcdef 6.5abc 6.3 3.3 2.7 2.0def 4.9abc 5.3 2.7 5.7 4.3abcdef 5.6abc 7.7 2.7 2.7 6.3abcd 6.7ab 9.3 3.3 6.3 7.0ab 6.6abc 7.1 5.7 6.3 7.7a 4.3bc 7.9 6.0 8.7 5.3abcde 4.Sabc 9.0 4.0 5.7. 3.2bcdef 6.3abc 9.7 3.3 5.3 O.Sf 6.0abc 8.7 4.3 5.0 3.2bcdef 4.8cd 7.3 4.7 4.3 3.0bcdef 3.9abc 9.5 4.3 5.3 4.3abcdef 6.2abc 10.3 2.3 3.0 5.0abcdef 5.8abc 8.4 3.0 4.7 6.7abc 4.3abc 6.1 4.0 7.0 3.7abcdef 4.Sabc 6.9 3.3 5.3 3.3abcdef 5.0abc 7.1 3.0 2.3 2.3cdef 6.9ab 8.7 2.0 3.3 4.0abcdef 5.5 8.0 3.3 4.8 4.1
0.0 0.0 o.o 0.0 0.3 2.0 o.o 0.3 0.0 0.3 0.7 1.0 1.3 0.3 o.o 1.3 0.7 o.o 0.0 0.7 OJ) 1.0 o.o 1.0 0.5
*Values with a letter in common do not differ significantly from each other: Duncan's Multiple Range run only on parameters with significant ANOVA (5%).
I-'
°'
17
Total Roots
The average number of roots growing to the 20 cm depth tended to
increase from December 16, 1971 to May 15, 1972 and then decline
(Table 4).
BA6124 consistently had the most roots, but not significantly more
than for some of the cultivars and genotypes. Merion and Minnesota 6 also
produced large numbers of roots throughout the four dates.
Fylking, Kl07, and PPl were among the bluegrasses with the lowest
number of roots at 20 cm after the late summer transplanting (Figure l);
however, values for these three were above the average of all bluegrasses
by the spring, 1972 (Table 4).
Baron, Delta, Arista, Nugget, and Pennstar tended to produce fewest
roots when considering all dates (Table 4). Geary, Windsor, KllO had
more roots during the December 16 period than the average for all culti-
vars and genotypes, but less than average during the next July. On
December 16 Fylking, Cougar, PPl, Park, and A34 had less roots at a 20 cm
depth than the average of all bluegrasses, but above-average values by
May 15 (Table 4).
White Roots
The number of white roots at the 20 cm depth differed significantly
during the autumn and spring, the periods when most of the white roots
were produced (Table 5). No white roots appeared after June 22, 197.2
(data not included). Fylking, Minnesota 6, Park, and Campus produced more
white roots than the average of the bluegrasses during December 16 and May
15. Delta, PPl, Kl07, PS, Southport, Nugget, and A34 tended to have more
18
Table 4. Total number of roots of 24 Kentucky bluegrasses at 20 cm depth at four dates.
Dates Cultivar Dec. 16, 1971 Mar. 30, 1972 May 15, 1972 July 25, 1972
Fylking Penns tar Geary Cougar Ken blue Newport
Windsor Delta Arista Merion BA6124 Minn6
PPl Kl07 PS Bel turf Southport Nugget
Palouse Park A34 Campus Baron KllO
Mean
20.-3cde* 20. 3cde 34.0bcd 27.3cde 33.0bcde 29. 3bcde
34.7bcd 18.7de 12.0e 34.7bcd 63. 7a 49.3ab
33.0bcde 40.3bcd 32. 7bcde 41.7bc 47. Obed 25.0cde
29.0bcde 30.0bcde 22. Ocde 37.7bcde 25.0cde 35.7bcd
31.5
31.0cde 37.3bcde 44.0abcde 44.7abcde 38.0bcde 36. Obcde
41.7bcde 27.0de 21.3e 52.3abc 66.0a 65.7a
38.7bcde 51.0abcd 32.3cde 60.0ab 39.7bcde 23.3e
30.7cde 37.3bcde 26.3e 29.0cde 26.7de 29.}bcde
39.2
Roots
Number
55.0ab 35.3bc 42.3bc 40.0bc 39.7bc 42.3bc
36.3bc 32.3bc 32.3bc 45.3bc 72.3a 73.0a
43.0bc 57.0ab 23.3c 52.7ab 39.3bc 32.0bc
35.0bc 42.0bc 42.3bc 36.7bc 20.()c 34. Obc
41.8
41.3bcd 19.0ef 24.3def 33.0cde 21. 7def 30.3cdef
31).3cdef 19.0ef 19. 7def 40.0bcde 61. 7a 59.0ab
26.3cdef 47.7abc 18.3ef 37.3cde 32.0cde 26.7cdef
3rJ.Ocdef 30.0cdef 30.3cdef 30.0cdef 8.7f 29.7cdef
31.1
*Values with a letter in conunon do not differ significantly from each other: Duncan's Multiple Range run only on parameters with significant ANOVA (5%).
{/) .w 0 0
14 1,.o ·~
13
12
11
10 ~
9
u ,.Cl
C\1 ...... u
,.0
19
-H 8 ~ 0
H Q)
,.0 E: g
...-! C\1 .w 0
E-1
7
6
5
4
3
Q) Q) Q) "d "d "d u u u
..a ..a ..a ~ Q)
"d ~ ~ u Q) Q) ...O"d"d~~ r- u u Q) Q)
.0 ..a "d "d ..... r- u u
,.0 ,.0
~ Q)
"d u ~ ..a Q) "d u ~
Q) "d
Figure 1. Root development at 20 cm depth of 24 Kentucky bluegrasses (August 8, 1971). Values with a letter in common do not differ significantly from each other: Duncan's Multiple Range run on parameters with significant ANOVA (5%).
20
Table 5. White roots of 24 Kentucky bluegrasses at 20 cm depth at four dates.
Cultivar
Fylking Penns tar Geary Cougar Kenblue Newport
Windsor Delta Arista Merion BA6124 Minn6
PPl Kl07 PS Bel turf Southport Nugget
Palouse Park A34 Campus Baron KllO
Mean
Dates Dec. 16, 1971 Mar. 30, 1972 May 15, 1972 June 22, 1972
Roots
4.3bc* 0.7c 1. 7c 2.0c 0.7c 0. 7c
0.7c 3.0bc 1.0c 2.0c 1. 3c 6.7b
10.3a 4.7bc 4.3bc 2.0c 4.0bc 4.7bc
1. 7c 3.7bc 3.0bc 4.7bc 1.0c 1.0c
2.9
6.3 5.7 2.7 3.3 o.o 0.3
1.0 o.o 3.3 o.o 0.0 1.3
4.3 1.0 0.7 0.7 1.0 o.o o.o 1.0 1.3 1.0 1.0 1.0
1.5
Number 8.0a 0.3de 0.7cde 5.0abcde l.Ocde 2.3abcde
l.Ocde 0.7cde 2.3abcde 3.3abcde 6.3abcd 7.7ab
2. 7abcde 2.0abcde O.Oe 1. Ocde 1. Ocde 2.7abcde
5.0abcde 7.3ab
. 1. 7bcde 6.7abc O.Oe 3.0abcde
3.0
o.o o.o o.o o.o 0.0 0.7
o.o 0.3 o.o o.o o.o o.o 0.7 0.0 o.o o.o 0.3 o.o 0 ,() 0.3 o.o 0.7 o.o 0.0
0.1
*Values with a letter in common do aot differ significantly from each other: Duncan's Multiple Range run only on parameters with significant ANOVA (5%).
21
white roots than the average of all bluegrasses in the autumn, while
Cougar, Merion, BA6124, and Palouse more white roots than the average on
May 15 (Table 5). Although Pennstar had few white roots on December 16
and May 15, it tended to have the most white roots on March 30.
Total, Brmvn, and White Roots
There were few white roots; hence brown and total roots had similar
growth patterns during the year (Figure 2). The largest number of brown
and total roots occurred during March and May. The average number of white
roots was largest during December and May. No white roots appeared
during July 1972. Total and brown roots declined during July.
Rhizomes
Fylking, Pennstar, Cougar, Arista, Campus, and A34 had more rhizomes
than the average of all cultivars and genotypes for December, March, and
June (Table 6). Geary, Newport, Windsor, Delta, Minnesota 6, PS, Palouse,
Park, Baron, and KllO had less rhizomes than the average values for the
bluegrasses for the same three periods.
Kenblue, Merion, and BA6124 had more rhizomes than the average of
all grasses in December and March; and PPl and Southport had higher
than average numbers of rhizomes in March. Kl07 was the only cultivar
or genotype with below average values for rhizomes in December and March,
but above the average of all values in June.
CJ) .µ
45
40
35
g 30 ,._.
4-l 0
Dec. 16, 1971
n . 1 :i j l ' '
22
Mar. 30, 1971
Dates
Fl ' : ! l
! ! f.
c:::::J Total roots
r:~l Brown roots
CZ:zl White roots
f·l ~: I
J 1 1 I
July 25, 1972
Figure 2. Total, brown, and white roots at 2n cm depth of 24 Kentucky bluegrasses at four dates.
23
Table 6. Rhizomes of 24 Kentucky bluegrasses at four dates.
Cultivar
Fylking Penns tar Geary Cougar Ken blue Newport
Windsor Delta Arista Merion BA6124 Minn6
PPl Kl07 PS Bel turf Southport Nugget
Palouse Park A34 Campus Baron KllO
Mean
Dates Dec. 16, 1971 Mar. 30, 1972 May 15, 1972 June 22, 1972
Rhizomes
15.7bcdefgh* 21.3abc 11. 7defghi 25.0a 20.3abcde 9.7hi
9.7hi 5.0i
20.7abcd 19. 7abcdefg 22.3ab 12.3cdefghi
10.7ghi 13. 7bcdefghi 9.3hi
12.0defghi 12.3cdefghi 14.0bcdefghi
12.0defghi 12.7cdefghi 17.0abcdefgh 20.0abcdef ll.3efghi 11.0fghi
14.6
Number 17.3abcde 17.7abcde
4.7f 21. 7abc 14.3bcdef
9.0def
11.0cdef 5.7f
26.0a 15.3bcdef 18.3abcd ll.3bcdef
15.3bcdef 11. 3bcdef
7 .3ef 14.0bcdef 16.7abcde 14.0bcdef
10. 7def 12.0bcdef 22.0ab 18.7abcd 13.3bcdef
9 .Odef
14.0
11.0 20.3 9.0
20.3 14.7
9.0
6.0 3.3
14.0 11. 7 14.3
6.7
9.7 11.0
6.7 8.3
10.0 7.3
7.0 8.0
13.3 15.0
9.3 5.3
10.5
32.3a 22.0abc 7.3def
21.7abc 8.3def
13 .Ocdef
9.7cdef 2.0f
26.0ab 9.3cdef
13.0cdef 13.3cdef
12.7cdef 15.3bcde
4. 7ef 12.0cdef 12.0cdef 13.3cdef
7. 7def 13.3cdef 26.3ab 19.3bcd
8. Odef ll.3cdef
13. 9-
*Values with a letter in common do not differ significantly from each other: Duncan's Multiple Range run only on parameters with significant ANOVA (5%).
Num
ber
of
till
ers
0 t-
' N
00
i=;:=::=!:====~====~====~-=-==~=-===-==~~~~~~~~~--
Bar
on
a 1-------------------~----------~
:.--:B~e~l~t~u~r~f __
__
__
__
__
__
__
__
__
__
__
__.a
b
H_e_r_i_o_n_~-----
------------~_.]bc
~~~~--~~~~~~~~~~~~~
I W
inds
or
bed
t~ou.!
hP...:
..o~r"
""t _
__
__
__
__
__
_ __
,j cd
e
buoz
1
cdef
I Min
n6
: ]
cdef
g
r- l K
llO
I c
def
g
~nst
ar
J cd
efg
h
~-A_r:i,
..s;_ta
lcde
fgh
i Pal
~mse
ld
efgh
l--,,,--~------------
~Q_Q
11_g
_a r
:J d
efg
hi
t-"P
ark
I ef
gh
i
t A34
ef
gh
ij
( K
enbl
ue
l efg
hij
r F:v
llgg
g --, e
fgh
ij k
p.8-
6124
fg
hij
k
b?-~
J:Y
] fgh
i_ik
LN
ewg_
Q_r
_t__
J
gh
ijk
! lg
hi]
'k
illl.P
.VJ>
c..
.---
----
-'-
~P~P'"""l"'---------'hij k
t-'
0
2S
Tillers
Among the highest number of tillers group, Baron and Belturf
tended to produce more tillers than Merion and Windsor during three weeks
after transplanting (Figure 3). PS, Delta, Nugget, and PPl were among
the cultivars and genotypes with the lowest number of tillers
Disease Incidence
On September lS, 1971, Delta and KllO had more Helminthosporium
leaf spot than other cultivars and genotypes with Palouse being next
(Figure 4). Other cultivars and genotypes had small amounts of disease.
Turf Cover
Fylking provided excellent turf cover in December, May, and June
(Table 7). Turf cover of Cougar, BA6124, Minnesota 6, Kl07, A34, and
Campus was above average cover for all cultivars and genotypes for the
same dates. Pennstar, Arista, and Merion generally had about average
turf cover values on these three dates. Delta, Kenblue, PS, Nugget,
Park, Newport, and KllO gave an unsatisfactory turf cover for December,
May, and June, while Southport, Palouse, Windsor, Belturf, and Baron were
unsatisfactory during May and June (Table 7).
1:l n f a
a a a a a a a - - - - - ~ - a a a - - - ab ab ab ab -·--·- ab ab ab ab - - - ~
8r ,,-... 7 I
! J w I
b_c;.
c --
I '
c
[fJ 5:
! J 00 i:: ·rl w ci;J 3
. 2
1
0
,._.
i~·~l ~j~i C!l C!l I -c:i:: :_ ~L "°
J I
~ 4-1 w ,._. tir [fJ ~I C!l•
w
, ~11~1 01
21 cu ooj
~I ~ i:: ~I
~ '° w ;::l ,...jl
~I r-- 01 i:: ~ Ill 0. ..ol 0 .-! o1 b()l -<t ,._.,
-~I i::
~l ·rl E! d .-!
P-< HI .If)
r~l ;@j M ~1 0 C!l, C!ll , ·rl ,._. cu' C!lj .-! 11; ~ 'i:i.; <:t:: ?'. <:t:: ~
i I u 1"°! zl ::s:, ul j~j 11;1 I I j ill
Figure 4. Relative disease incidence of 24 Kentucky bluegrasses (September 15, 1971). Values with a letter in common do not differ significantly from each other: Duncan's Multiple Range run on parameters with significant ANOVA (5%).
N
°'
27
Table 7. Turf cover of 24 Kentucky bluegrasses at four dates.
Cul ti var
Fylking Penns tar Geary Cougar Kenblue Newport
Windsor Delta Arista Merion BA6124 Minn6
PPl Kl07 PS Bel turf Southport Nugget
Palouse Park A34 Campus Baron KHO
Mean
Dec. 16, 1971
9.3ab* 9.3ab 8. 7ab 8.7ab 8.3ab 8. 7ab
9.0ab 6.3c 9.0ab
10.0a 9.7ab
10.0a
8.3ab 9. 7ab 8.0bc 9.3ab
10.0a 8.0bc
9.0ab 8.7ab 9.7ab 9. 7ab
10.0a 8.0bc
9.0
Mar. 30, 1972 Rating
5.0 3.0 6.0 4.3 1.3 2.7
1. 7 2.0 3.7 2.3 3.0 4.0
2.7 3.0 1.0 2.7 2.0 1. 7
3.3 2.7 2.7 3.3 2.0 3.0
2.9
Dates May 15,
1972 (10 best-1 worst)
10.0a 5. 7bcdef 5.3bcdefg 8.0ab 1. 7gh 4.3bcdefgh
3.7defgh 1. 7gh 6.3abcde 5.0bcdefg 7.7abc 7.3abcd
6.3abcde 6. 7abcd l.Oh 4.3bcdefgh 4.0defgh 4. Odefgh
3.7defgh 4.0defgh 8.0ab 6.7abcd 2.3fgh 2.7efgh
s.o
June 22, 1972
10.0a 5.3d 5.7d 9.3a 1. 7g 3.3g
3.3g l.Ohi 7.7b S.7d 7.3bc 8.0b
5.0de 6. 7c 0.3i 4.3ef 3.3g 3.7fg
3.7fg 3.7fg 8.0b 7.3bc l.3g 3.0g
4.9
*Values with a letter in common do not differ significantly from each other: Duncan's Multiple Range run only on parameters with significant ANOVA (5%).
MATERIALS AND METHODS
CUTTING HEIGHT EFFECTS OF UNDISTRUBED UNDERGROUND GROWTH OF VARIOUS CULTIVARS AND GENOTYPES
Sod strips (1/3 cm x 5 cm wide x 2.5 cm deep) of eight Kentucky
bluegrass cultivars and genotypes were obtained from field trials at
Virginia Polytechnic Institute and State University turf grass research
center at Blacksburg, Virginia on April 12, 1972. The bluegrass
obtained was as follows: BA6124, Pennstar, A34, Merion, Nugget, PPl,
Windsor, and Fylking (Table 1).
The sod strips were placed in plywood boxes (15 cm top tapering to
7.5 cm bottom x 25 cm wide x 45 cm deep) with 25 cm x 45 cm plastic
fronts filled to within 2.5 cm of the top with an 80% crystallized
shale and 20% peat mixture growing medium.
A 0.63 cm section of exterior celotex was placed over a transparent
plastic front to exclude light. The boxes were arranged in a split plot
design with cutting height as the main plot and cultivars and genotypes
as subplot and placed in an insulated container in the field. There
were three replications. 2 One kg/200 m of nitrogen from an ammonium nitrate source was
applied on May 24, 1972, and 1 kg/200 m2 of nitrogen from a 10-10-10
fertilizer source was applied June 30, 1972. Irrigation was utilized
as needed.
Measurements of underground organs were made without disturbing the
plant. The boxes were divided horizontally into three 10-cm intervals
from the soil surface on the clear plastic. The number of total, brown,
28
29
and white roots was measured at each 10-cm interval. Periodically a
grease pencil mark was made on the clear plastic opposite active root
tips in order to measure the root growth during a certain period, The
number of rhizomes was counted at varying time periods. Foliar regrowth
was obtained when marking the underground organ measurements.
All data were subjected to analyses of variance, and Duncan's
Multiple Range Test was used to separate the means.
RESULTS
CUTTING HEIGHT EFFECTS ON UNDERGROUND GROWTH OF VARIOUS CULTIVARS AND GENOTYPES
Total Roots
There was a larger number of roots on June 22 than for the other
dates. Nugget, Merion, Pll, and Pennstar tended to produce the largest
number of roots at the 20 cm depth at three dates, while Windsor and
A34 tended to have the least roots (Table 8). BA6124 increased total
roots from May 15 into the summer.
The cultivars and genotypes tended to produce more roots at the
high cutting height (5 cm) than at the low cutting height (1.3 cm)
(Table 8). On June 22, the influence of low cutting height on root
development tended to be least with Fylking and BA6124, and most with
A34 and Nugget (Fig. 5).
White Roots
PPl, Fylking, and Nugget tended to have the most and BA6124 and
Windsor tended to have the least white roots on May 18 at 20 cm depth
(Table 9). But by June 22, BA6124 produced the largest number of roots,
and the other cultivars did not differ significantly. When averaging all
cultivars there were 5-fold more white roots on May 18 than on June 22.
No cultivars had white roots on July 25. High cutting height tended
to give more white roots on May 18 than the low cutting height (Table 9).
30
Table 8. Total number of roots of 8 Kentucky bluegrasses for two cutting heights (1.3 cm-low, 5 cm-high) at three dates.
Dates - 1972 ~18 June 22 July 25
Cultivar Cutting height Cutting height Cutting height Low High Average Low High Average Low High Average
Roots (Number)
BA6124 3.0 4.3 3.7c* 11.0 12.0 ll.5bc 12.0 11.0 11.5abc Penns tar 7.7 9.0 8.3ab 12.7 17.0 14.8ab 11.0 16.3 13. 7ab A34 6.0 5.0 5.5bc 5.3 12.3 8.8c 7.3 11. 7 9.5bc Merion 8.7 12.3 10.5a 12.3 17.0 14.7ab 16.0 16.3 16.2a Nugget 9.7 11.0 10.3a 13.7 19.7 16.7a 11.0 18.3 15.2ab PPl 8.0 14.7 11.3a 13.7 17 .3 15.5ab 12.0 16.3 14.2ab Windsor 1.3 6.3 3.8c 6.7 9.0 7.8c 5.0 10.7 7.8c Fylking 7.0 12.0 9.5ab 11.7 12.7 12.2abc 6.7 8.0 7.3c
Mean 6.4 9.3 7.9 10.8 14.6 12.8 10.1 13. 7 11.9
Cutting Height Significant
* at .05 N .S. N .S.
*Values with a letter in common do not differ significantly from each other: Duncan's Multiple Range run on parameters with significant ANOVA (5%).
w ,_.
32
-----..-
-n
H cu .µ i::: .µ UJ 0 (!) i::: •r-1 t>() i::: H cc .q (!) (j) ::l M
p._, ~ z <i:
Figure 5. Decrease of root number at 2n cm denth of 8 Kentucky bluegrasses clipned at 1.3 cm as comnared to those grasses clipped at 5 cm (June 22, 1972).
33
Table 9. Number of white roots of 8 Kentucky bluegrasses for two cutting heights (1. 3 cm-low, 5 cm-high) at two dates.
Dates - 1972 May 18 June 22
Cul ti var Cutting height Cutting height Low High Average Low High Average
Roots (Number)
BA6124 2.3 3.3 2.8d* 1.3 1.0 l.2a
Penns tar 4.3 4.3 4.3bcd 0.3 0.3 0.3b
A34 4.3 4.3 4.3bcd 0.3 o.o .0.2b
Merion 4.3 7.3 5.8bc o.o 0.7 0.3b
Nugget 6.0 6.3 6.lb 0.3 0.3 0.3b
PPl 6.0 12.3 9.la o.o .o.o O.Ob
Windsor 1.3 5.0 3.2cd 0.3 o.o 0.2b
Fylking 5.0 7.0 6.0b 0.0 o.o O.Ob
Mean 4.2 6.3 5.3 0.3 0.3 0.3
Cutting Height Significant at .05 * N .S.
*Values with a letter in common do not differ significantly from each other: Duncan's Multiple Range run on parameters with significant ANOVA (5%).
34
Rhizomes
No rhizomes were observed before May 18 (Table 10). A34, Fylking,
Windsor, and Nugget had more rhizomes than the other Kentucky bluegrasses
on June 22. On July 25, Merion had the smallest rhizome number and the
other cultivars did not differ sig~ificantly. Average rhizome number
observed on July 25 was greater than the number observed on June 22.
Most cultivars had similar or more rhizomes at the high than at the low
cutting height during both periods (Table 10). Fylking and Merion
tended to produce more rhizomes at the low than at the high cutting
height on both dates (Table 10).
Plant Height
Nugget produced the least top growth (height) during June 15-22; and
Pennstar, Merion, and Nugget had lower values than BA6124 and PPl on
July 18-25 (Table 11). For all cultivars and genotypes, plants were
taller during July 18-25 than other dates. When top growth was compared
for the cutting heights (1.3 cm and 5 cm), the heights of Fylking and
Pennstar decreased the least as cutting height was lowered; however, as
compared to these bluegrasses, BA6124, PPl, and Windsor were among those
with the sharpest decrease (Figure 6).
35
Table 10. Number of rhizomes of 8 Kentucky bluegrasses for two cutting·heights (L3 cm-low, 5 cm-high) at two dates.
Dates - 1972 June 22 July 25
Cultivar Cutting height Cutting height Low High Average Low High Average
Roots (Number)
BA6124 0.3 0.7 O.Sb* 2.0 1.7 L8a
Penns tar 1.3 1.3 1.3b 1.3 4.0 2.7a
A34 0.7 7.7 .4.2a 1.0 7.0 4.0a
Merion 0.7 o.o 0.3b LO 0.7 O.Bb
Nugget 1.0 3.3 2.2a 3.0 5.0 4.0a
PPl 1.0 0.7 0.8b 1. 7 2.3 2.0a
Windsor 1.0 4.0 2.Sa 4.3 3.7 4.0a
Fylking 5.3 2.7 4.0a 5.7 1.7 3.7a
Mean 1.4 2.5 2.0 2.5 3.3 2.9
Cutting Height Significant at .05 N. S. N. S.
*Values with a letter in connnon do not differ significantly from each other: Duncan's Multiple Range run on parameters with significant ANOVA (10%) •
36'
Table 11. Foliar regrowth of 8 Kentucky bluegrasses at two cutting heights (1.3 cm-low, 5 cm-high) for two periods (original cutting height subtracted).
Dates - 1972 Cultivar June 15-June 22 July 18-July 25
Cutting height {cm} Cutting height {cm} Low High Average Low High Average
BA6124 4. s- . 3.7 4.la 5.0 6.0 5.5a
Penns tar 4.3 3.2 3.7a 4.9 3.7 4.3b
A34 4.8 4.3 4.6a 5.8 5.3 5.6a
Merion 4.4 3.3 3.9a 4.1 4.2 4.2b
Nugget 3.3 1.5 2.4b 4.5 4.2 4.3b
PPl 4.6 3.9 4.2a 5.1 5.6 5.4a
Windsor 3.4 4.3 3.9a 4.4 4.9 4.7ab
Fylking 4.1 3.8 4.0a 5.9 4.3 5.2ab
Mean 4.2 3.5 3.8 4.9 4.8 4.9
Cutting Height Significant at .05 * N.S.
*Values with a letter in common do not differ significantly from each other: Duncan's Multiple Range run on parameters with significant ANOVA (5%).
,,...... 8 (.)
'--'
.IJ .c bt
•rl (I) .c .IJ r::: ell
...-! P-<
37
3.5 - ---
3.0 -
2.5
-2, I)
1. 5
1.0 - I I I
H bt (\j
(). 5 ,... r::: .IJ •r-1 (I)
..Y! r:::
...-! r::: ;>-, (I)
0 l'r.; p..
H I .IJ r::: 0 -..:1° (I) 0 (I) "I b.( .IJ '""Cl ...-!
I bi) -..:1° H r::: ...-! \.C ::J ("} (I) •rl p.. <r: z <r: ~ I ::s: p.. P'.'.l
Figure 6. Differences in top regrowth of 8 Kentucky bluegrasses clipped at 1.3 cm as comnared to those grasses clipped at 5 cm (June 22-July 25, 1972),
MATERIALS AND METHODS
ROOT STRENGTH STUDIES OF VARIOUS CULTIVARS AND GENOTYPES FROM FIELD GROWN SOD
Sods 2.5 cm thick of thirty three-year-old Kentucky bluegrass
cultivars and genotypes were obtained on April 20, 1972 from plots at
The Virginia· Polytechnic Institute and State University turf grass
research center at Blacksburg, Virginia and p~aced into flats 30 cm wide
x 45 cm long x 2.5 cm deep) with 0.63 cm wire mesh bottoms. The culti-
vars and genotypes obtained were as follows: South Dakota, Newport,
Windsor, Delta, Arista, Merion, BA6124, WK.412, WK.411, PPl, Kl07,
Adelphi, P35, PS, Southport, Nugget, A34, Campus, Pll5, Fylking, Pennstar,
Cougar, Pll4, Sodco, Primo, P56, Kenblue, K8144~ A20, and K8146 (Table 1).
Prior to cutting the sod ammonium nitrate was used to apply 1 kg/
200 m2 of nitrogen to high nitrogen fertility plots of each of the blue-
. grasses on October 20, 1971 and January 28, 1972. A 10-10-10 fertilizer
source was used with 1 kg/200 m2 of nitrogen was applied over high and
low nitrogen plots on November 8, 1971.
Immediately after the sods were placed in the wire mesh bottom
flats, the flats were placed in a well-prepared seedbed of Frederick
silt loam. The area had a 3% slope that was tilled to a uniform grade.
Soil analyses indicated the soil had a pH of 6.5 with medium to high P
and K levels. A split plot field design was utilized with nitrogen
fertility levels as the main plot and cult.ivars and genotypes as the
subplots. The cultivars and genotypes were assigned at random within
three replications.
38
39
After leaving the flats in place for a root growth period of five
weeks, the amount of energy required to remove the sodded frames from
the soil was measured with an apparatus similar to that reported by
King and Beard (1969), except that a spring-scale hung from a tripod
between a pulley and a winch.
The sodded frames were transplanted a second time on May 26-30,
1972. High fertility plots received 1 kg/200 m2 and low fertility
plots received 0.5 kg/200 m2 of nitrogen from a 10-10-10 fertilizer
source on June 7, 1972. After another 5-week root growth period,
rooting was again measured, and the sodded frames were again trans-
planted on July 1-3, 1972. The same amounts and kind of fertility as
described was applied on July 17, 1972. After a 6-week root growth
period, the same root lifting procedure was followed, and the sodded
frames were transplanted on August 12-14, 1972. Height of foliar
growth was measured before each lift was made.
Areas where the sod of each cultivar and genotype was originally
cut were cleared to a depth of 10 cm and replaced with a rhizome-free
soil. The number of rhizomes developing iri the rhizome-free soil from
each cultivar was obtained by counting new plants on August 14, 1972.
All data were subjected to analyses of variance, and Duncan's
Multiple Range Test was used to separate the means.
RESULTS
ROOT STRENGTH STUDIES OF VARIOUS CULTIVARS AND GENOTYPES FROM FIELD GROWN SOD
Root Strength
The root strength of all bluegrass cultivars and genotypes was
higher for the first period (April 20 to May 29) than for the other two
periods (Tables 12 and 13). K8146, WK411, and Nugget had the largest
percentage decrease while Pennstar and Fylking had the least (Table 12).
Although most cultivars and genotypes continued to decrease in
root strength to the end of the third period (late summer), several
cultivars and genotypes increased in root strength over the previous
growth period. BA6124 had the largest percentage increase from the
second to the last period followed by Sodco, K8144, Kenblue, Primo,
Arista, S. Dakota, Campus, and Nugget, respectively.
A20 had the greatest root strength during the first two periods, but
had a 99% decrease from the second to last period. BA6124 was inter-
mediate in root strength rank during the first two periods, but during
the third period root strength was 31% lower than its first period root
strength. It ranked highest, though not significantly, during the last
period (Table 12).
Although K8144 and Arista had a large percentage increase from the
second to the last period, they still had very weak root strength during
the last period. The two nitrogen fertility levels did not cause signifi-
cant differences in root strength among the bluegrasses during any of
the three dates (Table 14).
40
Table 12. Root strength* of 30 Kentucky bluegrasses after three growth periods (averaged for two fertility levels) and percentage change from previous period.
Period-1972 Period-1972 Period-1972 April _20~May 29 n_M~_29-_July 4 July 4-August 14
% % Rank Cul ti vars Root Root Iner. (+) Root Iner. (+)
strength strength or strength or (lbs.) (lbs.) Deer. (-) (lbs.) Deer. (-)
1 A20 197.7 A20 88.7 -55 BA6124 98.5 +67 2 PPl 178.8 Delta 81.0 -47 Sod co 86.0 +so 3 Adelphi 176.6 P35 80.6 -52 S. Dakota 79 .3 +16 4 Merion 171.4 Kl07 78.9 -46 Campus 74.7 +10 5 P35 168.5 Penns tar 71.3 -57 Newport 72.2 + 5 6 Penns tar 165.3 Newport 69.8 -32 Ken blue 72.2 +33 7 Fylking 161.4 Cougar 68.6 -33 Prime 72.2 +24 8 A34 159.4 S. Dakota 68.6 -51 Cougar 65.8 - 4 9 Delta 153.7 Campus 67.7 -5S P35 65.7 -18
10 Campus 152.1 Merion 67.7 -61 K8144 65.3 +35 11 Sodco 151.3 Pll5 65.1 -47 Merion 64.7 - 4 12 Southport 149.7 WK411 64.3 -54 PS 63.8 + 5 13 Pll4 147.1 Fylking 62.0 -62 WK411 63.2 - 2 14 Kl07 144.9 Pll4 61.3 -58 Pll5 63.0 - 3 15 P56 144.0 PS 61.0 -45 Arista 60.3 +25
*Pounds required to lift a flat of sod (1200 cm2) after a five-week rooting period (first two periods) and a six-week rooting period (last period).
~ ~
Table 12. (Continued).
Period-1972 Period-1972 Period-1972 AEril 20-May 29 May 29-July 4 July 4-August 14
% % Rank Cultivars Root Root Iner. (+) Root Iner. (+)
strength strength or strength or (lbs.) (lbs.) Deer. (-) __ (lbs.) D~er._ (_-)
16 BA6124 142.0 BA6124 60.1 -58 Delta 59.3 -27 17 WK411 140.6 PPl 59.3 -67 Nugget 52.2 + 9 18 S. Dakota 138.7 Windsor 58.9 -40 Pl14 51.8 -15 19 Nugget 127.7 Adelphi 58.2 -67 Windsor 51.0 -13 20 Pll5 122.7 Primo 57.4 -48 Fylking 50.0 -19 21 Kenblue 114.2 Sodeo 57.4 -62 K8146 47.8 -16 22 PS 110.3 A34 55.5 -65 Adelphi 47.5 -2() 23 Primo 109.4 Ken blue 54.6 -52 Kl07 45.0 -43 ~
24 Cougar 102.5 Southport 53.9 -64 A20 40.8 -57 N
25 Newport 102.2 WK412 50.3 -47 PPl 39.3 -34 26 Windsor 98.0 Arista 48.1 -50 Penns tar 36.5 -49 27 Arista 96.5 Nugget 47.7 -63 WK412 34.8 -31 28 WK412 95.1 K8146 41.2 -48 P56 31.8 -23 29 K8146 78.5 P56 41.2 -71 Southport 29.7 -44 30 K8144 75.3 K8144 41.0 -46 A34 26.8 -51
Mean 135.8 61.4 57.l --
*Pounds required to lift a flat of sod (1200 em2) after a five-week rooting period (first two periods) and a six-week rooting period (last period).
43
Table 13. Root strength*of 30 Kentucky bluegrasses after three growth periods averaged for two fertility levels.
Periods-1972 Cultivars April 20-May 29 May 29-July 4 July 4-August 14
South Dakota Newport Windsor Delta Arista Merion BA6124 WK412 WK411 PPl Kl07 Adelphi P35 PS Southport Nugget A34 Campus Pl15 Fylking Penns tar Cougar Pll4 Sodco Primo P56 Kenblue K8144 A20 K8146
Mean
Root strength (lbs.)
138. 7abcdefgh** 102.2efghi
98.0fghi 153.7abcdefg
96.Sfghi 171.4abcd 142.0abcdefg
95.lghi 140.6abcdefg 178.8ab 144.9abcdefg 176.6abc 168.Sabcd 110.4defghi 149.7abcdefg 127.7bcdefghi 159.4abcdef 152.labcdefg 122.7bcdefghi 161.4abcde 165.3abcd 102.Sefghi 141.labcdefg 151.3abcdefg 109.4defghi 144.0abcdefg 114.2cdefghi 75.3i
197.6a 78.Shi
135.8
68.6abcd 69.8abcd 58.9abcd 81.0ab 48.lcd 67.7abcd 60.labcd 50.3bcd 64.3abcd 59.3abcd 78.8abc 58.labcd 80.6ab 61.0abcd 53.9bcd 47.7cd 55.5bcd 67.7abcd 65.labcd 62.0abcd 71.3abcd 68.6abcd 61.3abcd 57.4abcd 57.4abcd 41.2d 54. 6bcd 41.0d 88.7a 41.2d
61.4
79.3abc 73.2abcd 51.0bcdefgh 59.3bcdefgh 60.3bcdefgh 64. 7abcdefg 98.5a 34.8fgh 63.2bcdefg 39.3defgh 45.0cdefgh 47.Scdefgh 65. 7abcdef 29.7gh 63.8bcdefgh 52.2bcdefgh 26.8h 74.7abcd 63.0bcdefg 50.0cdefgh 36.Sefgh 65.8abcdef 51.8bcdefgh 86.0ab 71.2abcde 31.8fgh 72.5abcd 65.3abcdef 40.8defgh 47.8cdefgh
57.1
*Pounds required to lift a flat of sod (1200 cm2) after a five-week rooting period (first two periods) and a six-week rooting period (last period).
**Values with a letter in common do not differ significantly from each other: Duncan's Multiple Range run only on parameters with significant ANOVA (5%).
44
Rhizomes
A20 had the most rhizomes by nearly 2-fold more than competitors,
PPl and P56 which ranked second and third (Fig. 7). The smallest number
of rhizomes occurred with Arista and Campus. The number of rhizomes
ranged from 0.3 to 15.3 per.bluegrass strain, the average number of rhi-
zomes for all grasses being 4.3.
Plant Height
Cougar, A34, and Merion were among the tallest, while Arista was
among the shortest during the second and third periods (Table 15).
Although not significant, Arista, Nugget, and K8144 were taller at the
low than at the high nitrogen fertility. Bluegrasses with high nitrogen
fertility tended to be tallest during the July 24-August 14 date (Table
16).
co Q)
5 N -n ..c::: 1-l
44 0
1-l Q)
,.0 s z
15
14 13
12 11 10
9 8
7 6
5 4
3
2
1 0
t\'l
,.0
cl L iN !P... < ,p...,
(.) ,.0 '"d
(.) ,.0
Q) Q) '1:1 "Cl (.) (.) Q) 44
..0 ,.0 '"d Q) (.) '"d
,.0 (.) .c.
.jJ 1-l
44 44 44 O 1-l aJaJaJ4444 P.O 'O'"d"t:i Q) Q) ..c::: co (.) (.) (.) '"d "Ci 44 .µ '"d ,.0,.0,.0 (.)(.)al ::l i:::
.µ 1-l 0 P. ::: Q)
1-l ~ ctt co ctt N .µ ::l b.() .-l co r::.. ::l \0 Lt) •rl 13 0 < C""l 1-l ctt ,.0 ,.0 '"d 44 44 0 •rl z u n '"d'O Q) Q)
Ii - '"d '"d
til .jJ
I~ ~I ~1~
---~ n(.) Q) aJ4444 m:::;;:
I I~ I 11~1 l,..I l I l .. 11 l i·~l I In ....... Q) Q) 4aJ 4aJ
~ p., < u
U) eLt..Lf'. .-Ji !~l P'! !~l jool j_Qll I@! F111.21 l~l l~! l"8U IJ l al !ll[l[]4Qj 4aJ 44 44 P...J Pl ~ill_. ~Lb 1:2 LtJJ.:.Ll~.L~l.E ._.L _ ~ -r::=w=t
Figure 7. Emerged rhizomes 15 weeks after the sod of Kentucky bluegrasses had been removed from field plots on April 20, 1972. Values with a letter in common do not differ significantly from each other: Duncan's ~ultinle Range run on parameters with significant ANOVA (5%).
.i::--lJl
46
Table 14. Root strength* of 30 Kentucky bluegrasses after three growth periods and two fertility levels (low-0.5 kg N/200m2, high-1.0 kg N/200m2).
Period-1972 AEril 20-May 29 May 29-July 4 July 4-August 14
Cul ti vars Fertility level Low High Low High Low High
Root strength (lbs.)
S. Dakota 131.6 145.9 53.9 83.4 73.3 85.3 Newport 99.6 104.8 64.4 75.3 92.0 54.3 Windsor , 81.9 113. 9 58.2 59.6 49.7· 52.3 Delta 137.3 170.2 68.6 93.4 31.0 87.7 Arista 95.3 97.7 54.8 41.5 65.3 55.3 Merion 156.8 185.9 54.3 81.0 75.3 54.0 BA6124 140.1 144.0 62.9 57.2 85.7 111.3 WK412 82.5 107.7 46.7 53.9 33.3 36.3 WK411 129.2 152.1 67.7 61.0 67.7 58.7 PPl 195.9 161. 6 68.6 50.1 37.3 41.3 Kl07 151.1 138.7 75.3 82.5 56.7 33.3 Adelphi 204.0 149.2 59.6 56.7 56.3 38.7 P35 144.0 193.1 51.5 109.6 70.7 60.7 PS 117.3 103.4 55.3 66.7 62.0 65.7 Southport 148.2 151.1 55.8 52.0 28.7 30.7 Nugget 144.9 110.6 47.7 47.7 47.3 57.0 A34 144.4 174.5 66.7 44.3 34.7 19.0 Campus 135.9 168.3 52.9 82.5 71.0 78.3 Pll5 120.1 125.4 56.7 73.4 69.3 56.7 Fylking 161.6 161.1 60.1 63.9 43.3 56.7 Penns tar 160.2 170.4 61.5 81.0 39.7 33.3 Cougar 77. 7 127.3 52.4 84.8 57.0 74.7 Pl14 146.8 147.3 65.3 57.2 52.0 51. 7 Sodco 142.0 160.6 50.5 64.4 92.0 80.0 Primo 107.3 111.5 42.9 72.0 77.7 64.7 P56 136.3 151. 6 43.4 39.1 36. 7 27.0 Ken blue 105.3 123.0 52.0 57.2 71.7 73.3 K8144 64.8 85.8 38.6 43.4 69.3 61.3 A20 212.1 183.0 95.3 82.0 52.0 29.7 K8146 70.1 86.9 29.1 53.4 39. 7 56.0
Mean 131.5 140.2 57.1 65.6 57.9 56.1
Fertility significant at .05 N.S. N. S. N.S.
*Pounds required to lift a flat of sod (1200 cm2) after a five-week rooting period (first two periods) and six-week rooting period (last period).
47
Table 15. Height of 30 Kentucky bluegrasses at two periods for two fertility levels.
Periods-1972 Cul ti vars May 29-July 4 July 24-August 14
Height (cm)
S. Dakota 9.8abcdef* 13. 2abcde Newport 9.5bcdefg 12.3abcdefg Windsor 10.5abcde ll.8bcdefg Delta 10.8abcde 12. 7abcdef Arista 7.3h 10.0g Merion ll.5ab 13.2abcde BA6124 9.3cdefg 13. 7abc WK412 9.5bcdefg ll.5bcdefg WK411 9.8abcdef 12.7abcdef PPl 10.0abcdef 12. Obcdefg Kl07 ll.2abc 12.8abcdef Adelphi 9.5bcdefg 10.5fg P35 10.2abcdef 13.8ab PS 8.2fgh 11. 7bcdefg Southport 10.9abcde 11. 8bcdefg Nugget 8.8efgh ll.5bcdefg A34 11. 7a 13.5abcd Campus 7.0h 12.0bcdefg Pll5 9.Sbcdefg ll.3cdefg Fylking 11.0abcd 12.3abcdefg Penns tar 10.5abcde 12.3abcdefg Cougar 11. 2abc 14. 7a Pl14 10.7abcde 12.5abcdefg Sodco 9.7abcdefg 13.2abcde Primo 10.3abcde 14.0ab P56 8.9defgh 11.0defg Ken blue 9.8abcdef 12.3abcdefg K8144 7.8gh 11. 7bcdefg A20 11.3abc 12. 5abcdefg K8146 8.8efgh 10.Sefg
Mean 9.8 12.3
*Values with a letter in common do not differ sig-nificantly from each other: Duncan's Multiple Range run only on parameters with significant AlilOVA (5%),
48
Table 16. Height of 30 Kentucky bluegrass sods after three growth periods and two fertility levels (0.5 kg N/200m2, 1.0 kg N/200m2).
Periods-1972 May 29-July 4 July 24-August 14
Cul ti vars
S. Dakota Newport Windsor Delta Arista Merion BA6124 WK.412 WK.411 PPl Kl07 Adelphi P35 PS Southport Nugget A34 Campus Pll5 Fylking Penns tar Cougar Pll4 Sodco Primo P56 Kenblue K8144 A20 K8146
Mean
Fertility significant at .05 *
Fertility level Low High Low High
9.7 9.0
10.0 10.7
7.5 9.7 9.0 8.7 9.3
10.0 10.3
9.3 9.0 8.0
10.3 9.7
11.0 7.3 8.0
10.7 10.0 10.3 10.7 8.3 9.7 8.2 9.3 7.8
11.0 8.3
10.5
N.S.
10.0 10.0 11.0 11.0
7.2 13.3
9.7 10.3 10.3 10.0 12.0
9.7 11.3
8.3 11.5 8.0
12.3 6.7
11.0 11.3 11.0 12.0 10.7 11.0 11.0
9.7 10.3
7.7 11.7
9.3
10.3
Height (cm)
12.7 11.3 10.3 11.0
9.7 12.0 12.6 10.3 11.6 10.6 12.0 10.3 13.3 10.0 10.7 11.3 12.7 11.0 10.7 12.0 11.3 12.7 12.3 11. 7 13.0
9.3 10.7 11.0 11.0
9.7
11.3
*
13. 7 13.3 13.3 14.3 10.3 14.3 14.7 12.7 13.7 13.3 13.7 10.7 14.3 13 .3 13.0 11. 7 14.3 13.0 12.0 12.7 13.3 16.7 12.7 14.7 15.0 12.7 14.0 12.3 14.0 12.0
13.3
DISCUSSION
Watschke, Schmidt, and Blaser (1970) observed that root develop-
ment among Kentucky bluegrasses varied under high temperatures.
However, this study was conducted in growth chambers with water cul-
tures. Water cultures do not evaluate the abrasive action associated
with soil. An attempt was made in these studies to evaluate root
development under near normal field conditions by growing the cultivars
in a mini-rhizotron (window boxes) and in wire mesh bottom flats under
normal field environment.
The first two experiments with two types of window boxes made it
possible to observe root development without disturbing the turf. An
indirect method of measuring root development of cultivars and geno-
types was investigated by growing the grasses in wire mesh bottom flats
placed on the soil surface. Measuring the energy required to lift the
frames after a rooting period was assumed to correlate with root
development.
None of the techniques used was completely satisfactory. The
window boxes utilized in the undisturbed underground growth experiment
were more accurate than those used in the cutting height experiment.
The boxes were tilted 15 degrees, forcing all roots to the front of the
box in the undisturbed growth experiment, while the boxes were cut at a
15 degree angle allowing only the front 4.5 cm of root to be observed in
the cutting height experiment. It was very difficult to distinguish
between active and non-active roots when the experiments exceeded three
months.
49
50
In the root strength study, the cutting of the sod apparently
stimulated new roots which might not have occurred if left undisturbed.
The ability of the cultivars to regenerate a new root system was measured
in this study. It may be assumed that the larger the energy required to
lift a wire mesh bottom flat the more roots and greater the depth of root
penetration. However, the root strength experiment gave invaluable
information on the performance of cultivars after injury during various
seasons of the year, especially for injury from divots, aeration, insects,
or for sod cutting and subsequent establishment.
In the experiment of undisturbed growth with no cutting treatment,
it was observed that most bluegrass cultivars and genotypes initiated
new roots in late winter and spring. Those cultivars which produced
more roots in spring tended to have more roots later in the year.
Based upon knowledge obtained from this experiment, the cultivars may
be grouped into four categories which are as follows:
1. Cultivars and genotypes with predominantly fall and winter
root development - P-5, Belturf, Baron, and KllO.
2. Cultivars and genotypes with predominantly winter and early
spring root development - Fylking, Geary, Merion, Kl07, Cougar.
3. Cultivars and genotypes with predominantly spring root
development - Nugget, Campus, Park, Newport, Arista, Kenblue,
A34, PPl.
4. Cultivars and genotypes that produce roots continuously from
fall to late spring - Windsor, BA6124, Minn 6, Palouse.
51
In the cutting height experiment, the low cutting height reduced root
number in all cultivars and genotypes, except A34 in the spring and
BA6124 in the sllltliller (Table 8). Cultivars and genotypes with high root
number at low cutting heights also had high root number at high cutting
heights, indicating that cultivar and genotype was a more important
variable than cutting height.
BA6124 and Merion maintained many roots during July, while
Windsor and A34 had relatively few roots at this date for the cutting
height study (Table 8) and other experiments. Although Fylking, A34, and
Windsor had a large number of roots in spring, rooting decreased by
summer. Similar data were recorded in the undisturbed underground growth
experiment. Even though Pennstar, PPl, and Nugget generally maintained
their summer roots in the cutting height experiment, these results did
not correlate with the undisturbed underground growth experiment with no
cutting height treatment.
Cultivars and genotypes had the greatest root strength in the spring
and decreased as the year progressed into summer in the root strength
experiments. This may be attributed to decreased adventitious root
primordia, but it is more likely that adverse environmental conditions,
reduced carbohydrates, and inherent root development could also be
contributing factors. The fact that BA6124, Sodco, South Dakota, Campus,
Kenblue, and Primo decreased from May 29 to July then increased from
July to August in root development indicates that there were adequate
adventitious root primordia and some other factor such as environmental
aspects influenced root development.
52
The root strength of BA6124 and Merion was better than the average
of all cultivars and genotypes during the sununer (Table 12). Fylking
and PPl had better-than-average root strength in spring but poorer-than-
average in the summer. A similar trend was found in the undisturbed
underground growth and cutting height experiments. These results may
indicate why some sod producers have difficulty with Fylking knitting
(producing roots) in the summer. Other cultivars and genotypes which
may have the similar phenomena as Fylking include Windsor, A34, Adelphi,
Pennstar, PPl, and A20.
There was no consistency in rhizome development in the undisturbed
underground growth experiment. Kenblue, Merion, BA6124, Pennstar,
Campus, Arista, and A34 produced more rhizomes than the average of all
cultivars and genotypes in the fall. During the winter PPl, Southport,
Pennstar, Campus, Arista, and A34 had more rhizomes than the average of
all cultivars and genotypes. In the spring, Fylking, Pennstar, Cougar,
Kl07, Arista, and A34 were higher in rhizome number than the average of
all cultivars and genotypes.
Rhizome number tended to be reduced under low as compared to high
cutting height. Fylking, the only exception, produced many rhizomes in
all three experiments. This could be an important consideration for the
golf course superintendent who needs grasses which have the ability to
quickly replenish divotal areas.
Under different environments and using different techniques,
experimental results can be reversed. Moser et al. (1968) observed that
Windsor produced more rhizomes than Merion, and Merion produced more
53
tillers than Windsor. This work was accomplished in the greenhouse
under ideal conditions. Under field conditions as in this experiment,
Windsor had less rhizomes and more tillers than Merion.
SUMMARY AND CONCLUSIONS
The objective of this study was to investigate the effects of
fertility level and cutting height on the underground growth of various
Kentucky bluegrasses during various seasons and develop a technique for
measuring underground growth without disturbing the grasses.
Since no one cultivar or genotype had the largest amount of under-
ground growth throughout all parameters studied, blending the best
cultivars under various conditions should result in a desirable turf-
grass. By blending such cultivars as Merion, Fylking, and BA6124, the
desired bluegrass turf under changing environments will be created.
During certain periods common bluegrass such as Kenblue and South Dakota
Certified produced large amounts of underground growth. Because these
common cultivars can be obtained in some areas easily and with less cost,
the cultivars could also be included in blends.
The undisturbed underground growth experiment revealed that most
root growth occurs in late winter and spring. Little or no root growth
occurred in the summer. Decay of old roots also occurred at a maximum
during the summer. Those cultivars with high root numbers in the spring
tended to maintain these during the summer. Cultivars that have a high
amount of roots in late spring have a better chance of survival with
less maintenance during the summer.
The cutting height experiment indicated such cultivars as Fylking
can survive low cutting heights better than other cultivars and geno-
types. Also in the undisturbed underground growth experiment, BA6124
produced more roots in summer than spring, and Fylking produced more
roots in spring than summer.
54
55
The root strength experiment revealed.that some cultivars and
genotypes such as BA6124, Campus, and Primo had ability to produce more
new adventitious roots du1:ing the summer than Fylking, PPl, and Adelphi,
but the latter cultivars had more root strength in the spring. This
phenomena may explain the sod producer's problem of Fylking's slow
knitting in the summer.
From the experiments concluded it is known which cultivar and geno-
type performs the best under different cutting height, different fertility
and various seasons, but it is not known which cultivar and genotype
performs best under all three treatments combined. An additional
experiment is needed in which the same, or more, cultivars and genotypes
are tested for root strength at different seasons. Improved techniques
such as more peat in the growth medium, experiments of short duration,
few cultivars, and more replications per experiment would improve studies
involving underground growth during various seasons. Findings from such
short duration experiments would then be evaluated under field environ-
ments with cutting height and fertilization variables over long-term
periods. Analyses for water soluble carbohydrates, nitrogen, phosphorus,
and potassium would help substantiate data such as those for the experi-
ments reported in this thesis.
LITERATURE CITED
Ahlgren, H. L. 1938. Effect of fertilization, cutting treatments, and irrigation on yield of forage, and chemical composition of the rhizomes of Kentucky bluegrass (Poa pratensis L.). J. Amer. Soc. Agron. 30:683-691.
Alberta, T. H. 1966. The influence of restKVe substance on dry matter production after defoliation. Proc. x~ Inter. Grassl. Cong. pp. 140-147.
Auda, H., R. E. Blaser, and R.H. Brown. 1966. Tillering and carbo-hydrate contents of orchardgrass as influenced by environmental factors. Crop Sci. 6:139-143.
Beard, J. B., and W. H. Daniel. 1965. The effect of temperature and cutting on the growth of creeping bentgrass (Agrostis palustris Huds.) roots. Agron. J. 57:249-250.
Blaser, R. E. 1969. Soil and air temperatures and fertilizing turf. Proc. Ohio Turfgrass Conf. pp. 45-49.
Brown, E. M. 1939. Some effects of temperature on the growth and chemical composition of certain pasture grasses. Mo. Agri. Exp. Sta. Res. Bull. 299:1-76.
1943. Seasonal variations in the growth and chemical composition of Kentucky bluegrass. Res. Bull. 360, Mo. Agri. Exp. Sta. p.76.
Brown, R.H., and R. E. Blaser. 1965. Relationships between reserve carbohydrate accumulation and growth rate in orchardgrass and tall fescue. Crop Sci. 5:577-582.
Burkey, F. s., and J.E. Weaver. 1939. Effect of frequent clipping on the underground food reserves of certain prairie grasses. Ecology 20:246-252.
Carroll, J. C., and F. A. Welton. 1938. Effect of heavy and late applications of nitrogenous fertilizer on the cold resistance of Kentucky bluegrass. Plant Physiol. 14:297-308.
Colby, W. H., M. Drake, D. L. Field, and G. Kreowski. 1965. Seasonal pattern of fructosan in orchardgrass stubble as influenced by nitrogen and harvest management. Agron. J. 57:169-173.
Etter, A. G. 1951. How Kentucky bluegrass grows. Ann. Mo. Bot. Gardens 38:293-375.
56
57
Evans, M. W., and J.E. Ely. 1935. The rhizomes of certain grass species. J. Amer. Soc. Agron. 27:791-797.
~~~~~~' and J. M. Watkins. 1939. The growth of Kentucky blue-grass and Canada bluegrass in late spring and in autumn as affected by length of day. J. Amer. Soc. Agron. 31:767-774.
Garwood, E. A. 1967. Seasonal variation in appearance and growth of grass roots. Brit. Grassl. Soc. J. 22(2):121-130.
Gernert, W. B. clipping.
1936. Native grass behavior as affected by periodic J. Amer. Soc. Agron. 28:447-455.
Goss, R. L., and L. G. Law. 1967. Performance of bluegrass varieties at two cutting heights and two nitrogen levels. Agron. J. 59: 516-518.
Green, D. G., and J.B. Beard. 1969. Seasonal relationships between nitrogen nutrition and soluble carbohydrates in the leaves of Agrostis palustris Huds., and Poa Pratensis L. Agron. J. 61:107-111.
Hanson, A. A., and F. V. Juska. 1961. Winter root activity in Kentucky bluegrass (Poa pratensis L.). Agron. J. ,53:372-374.
Harrison, C. M. 1931. Effect of cutting and fertilizer applications on grass development. Plant Physiol. 6:669-684.
1934. Responses of Kentucky bluegrass to variations in temperature, light, cutting, and fertilizing. Plant Physiol. 9: 83-106.
~~~~~~
, and C. W. Hodgson. 1939. Response of certain perennial grasses to cutting treatment. J. Amer. Soc. Agron. 31:418-430.
Hoagland, D.R., and D. I. Arnon. growing plants without soil.
1950. The water-culture method for Calif. Agr. Exp. Sta. Cir. 347.
Jacques, W. A., and D. B. Edmonds. 1952. Root development in some common New Zealand pasture plants. V. The effects of defoliation and root pruning on cocksfoot (Dactylis glomerata) and perennial ryegrass (Lolium perenne). New Zealand J. Sci. and Tech. 34: 231-248.
~~~~~~
, and R. H. Schwass. 1956. Root development in some common New Zealand pasture plants. VII. Seasonal root replacement in perennial ryegrass (Lolium perenne), Italian ryegrass (1,. multi-florum), and tall fescue (Festuca arundinaceae). New Zealand J. Sci. and Tech, 37:569-583.
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The vita has been removed from the scanned document
GROWTH OF ROOTS, RHIZOMES, AND TILLERS OF KENTUCKY BLUEGRASS
(Poa Pratensis L.) CULTIVARS AND GENOTYPES AS AFFECTED BY
FERTILITY LEVEL, CUTTING HEIGHT, AND SEASON
by
Frank E. Smith
(ABSTRACT)
Field experiments were established on July 12, 1971, and April 12
and April 20, 1972, by transplanting various cultivars and genotypes of
Kentucky bluegrass (Poa pratensis L.). Objectives were to study effects
of fertility level and cutting height on underground growth of various
Kentucky bluegrasses during various seasons and develop a technique for
measuring underground growth without disturbing the cultivars and
genotypes.
Most root growth occurred in late winter and spring, and cultivars
and genotypes with high amount of roots in late spring tend to have a
better chance of survival with less maintenance during the summer.
Fylking produced more roots in spring and survived under low cutting
height better than other cultivars and genotypes. BA6124 produced more
roots in summer than any other cultivar and genotype. No cultivar and
genotype had the largest underground growth throughout all parameters
studied; therefore, blending is recommended to create a desirable blue-
grass turf. Techniques used in experiments were adequate.