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.

58

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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.