The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
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site maintained by the Florida
Cooperative Extension Service.
Copyright 2005, Board of Trustees, University
UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATION
Wilmon Newell, Director
A STUDY OF THE ROOT SYSTEMS
OF SOME IMPORTANT
By A. S. LAIRD
Bulletins will be sent free upon application to the
Agricultural Experiment Station
BOARD OF CONTROL
P. K. YONGE, Chairman, Pensacola
A. H. BLANDING, Leesbunrg
W. B. DAVIS, Perry
RAYMER F. MAGUIRE, Orlando
FRANK J. WIDEMAN, West Palm Beach
J. T. DIAMOND, Secretary, Tallahassce
STATION EXECUTIVE STAFF
JOHN J. TIGERT, M.A., LL.D., President
WILMON NEWELL, D. Sc., Director
S. T. FLEMING, A.B., Asst. Director
J. FRANCIS COOPER, M.S.A., Editor
R. M. FULGHUM, B.S.A., Asst. Editor
IDA KEELING CRESAP, Librarian
RUBY NEWHALL, Secretary**
K. H. GRAHAM, Business Manager
RACHEL McQUARRIE. Accountant
MAIN STATION-DEPARTMENTS AND INVESTIGATORS
W. E. STOKES, M.S., Agronomist
W. A. LEUKEL, Ph.D., Associate
G. E. RITCHEY, M.S.A., Assistant*
FRED H. HULL, M.S.A., Assistant
J. D. WARNER, M.S., Assistant
A. L. SHEALY, D.V.M., Veterinarian in
E. F. THOMAS, D.V.M., Asst. Veterinarian
R. B. BECKER, Ph.D., Associate in Dairy
W. M. NEAL, Ph.D., Assistant in Animal
C. R. DAWSON, B.S.A., Assistant Dairy
R. W. RUPRECHT, Ph.D., Chemist
R. M. BARNETTE, Ph.D., Associate
C. E. BELL, M.S., Assistant
H. L. MARSHALL, M.S., Assistant
J. M. COLEMAN, B.S., Assistant
J. B. HESTER, B.S., Assistant
W. A. CARVER, Ph.D., Assistant
E. F. GROSSMAN, M.A., Assistant**
RAYMOND CROWN, B.S.A., Field Assistant
C. V. NOBLE, Ph.D., Agricultural Economist
BRUCE McKINLEY, A.B., B.S.A., Associate
M. A. BROOKER, M.S.A., Assistant**
JOHN L. WANN, B.S.A., Assistant
OUIDA DAVIS ABBOTT, Ph.D., Head
L. W. GADDUM, Ph.D., Biochemist
C. F. AHMANN, Ph.D., Physiologist
J. R. WATSON, A.M., Entomologist
A. N. TISSOT, M.S., Assistant
H. E. BRATLEY, M.S.A., Assistant
A. F. CAMP, Ph.D., Horticulturist"
M. R. ENSIGN, M.S., Assistant
HAROLD MOWRY, B.S.A., Assistant'
G. H. BLACKMON, M.S.A., Pecan Culturist
W. B. TISDALE, Ph.D., Plant Pathologist
G. F. WEBER, Ph.D., Associate
A. H. EDDINS, Ph.D., Assistant
W. B. SHIPPY, Ph.D., Assistant
K. W. LOUCKS, M.S., Assistant
ERDMAN WEST, B.S., Mycologist**
BRANCH STATION AND FIELD WORKERS
R. R. KINCAID, M.S., Assistant Plant Pathologist (Quincy)
JESSE REEVES, Foreman, Tobacco Experiment Station (Quincy)
J. H. JEFFERIES, Superintendent, Citrus Experiment Station (Lake Alfred)
W. A. KUNTZ, A.M.,** Assistant Plant Pathologist (Lake Alfred)
B. R. FUDGE, Ph.D., Assistant Chemist (Lake Alfred)
GEO. E. TEDDER, Foreman, Everglades Experiment Station (Belle Glade)
R. V. ALLISON, Ph.D., Soils Specialist in charge Everglades Experiment Station (Belle Glade)
L. O. GRATZ, Ph.D., Associate Plant Pathologist (Hastings)
A. N. BROOKS, Ph.D., Associate Plant Pathologist (Plant City)
A. S. RHOADS, Ph.D., Associate Plant Pathologist (Cocoa)
STACY 0. HAWKINS, M.A., Field Assistant in Plant Pathology (Homestead)
L. R. TOY, B.S.A., Assistant Horticulturist (Homestead)
D. G. A. KELBERT, Field Assistant in Plant Pathology (Bradenton)
R. E. NOLEN, M.S.A., Field Assistant in Plant Pathology (Monticello)
FRED W. WALKER, Assistant Entomologist (Monticello)**
D. A. SANDERS, D.V.M., Associate Veterinarian (West Palm Beach)
M. N. WALKER, Ph.D., Associate Plant Pathologist (Leesburg)
C. C. GOFF, M.S., Assistant Entomologist (Leesburg)
*In cooperation with U. S. Department of Agriculture.
**On leave of absence.
A STUDY OF THE ROOT SYSTEMS OF SOME IMPORTANT
By A. S. LAIRD'
No other family of plants contributes to the wants of man more
than does the grass family (Graminaceae). To this family belong
the six cereal grains, sugar cane, sorghum, and a number of for-
age, ornamental and other plants. This family of plants alone
supplies over 64 percent of the total value of all farm crops in
According to their uses, grasses may be classified into three
major divisions: grains, forage plants, and lawn grasses; and
four minor divisions: ornamentals, sod-formers (soil binders),
sugar producing, and textile grasses. Only the sod-forming
grasses were used in this investigation, because their root systems
tend to bind the soil together, thus producing a turf of sod which
is suitable for putting greens, fairways, lawns and pastures. In
addition, these grasses will withstand close mowing, thereby
adding to their value for pasture, lawn, and putting green pur-
The published literature on the root systems of sod-forming
grasses seems to be rather limited. Weaver(15), Fitts(1), and
Ten Eyck(10), have contributed most of the printed information
dealing with this subject, so far as the writer is aware.
Weaver(15) and his co-workers report that the concentration
of the roots of most grasses was in the first 12 inches of soil,
although some of the roots of sod-forming grasses penetrated to
a depth of 7 to 8 feet.
Fitts(1) reports that the roots of sod-forming grasses tended
to concentrate in the surface few inches of a fertile soil. This
was particularly true when the soil was fertilized and the grass
Ten Eyck(11) found the roots of sod-forming grasses to be
concentrated in the first 12 inches of soil, with some of the roots
penetrating to a depth of 6 to 8 feet.
1Formerly Assistant Agronomist at the Florida Experiment Station; now
agent, Forage Crops Office, U. S. D. A.
2Figures in parentheses (italic) refer to citations in the list of references,
Florida Agricultural Experiiment Station
Due to the limited amount of information concerning the root
systems of these grasses, the present investigation was under-
taken to determine the influence of mowing, fertilizing and graz-
ing on the growth of the root systems of some important sod-
forming grasses under lawn, pasture, and putting green con-
METHODS OF GROWING GRASSES
The grasses selected for this investigation seem to be the most
outstanding sod-forming grasses for lawns, golf courses and
pastures in Florida, as well as in the Southeastern States. All
of these grasses are not suitable for the three purposes indicated,
as their adaptations vary, depending on the conditions under
which they are grown.
The grasses used were as follows: Bermuda grass (Capriola
dactylon (L.) Kuntze) ; carpet grass (Axonopus compressus
(Siv.) Beauv.) ; Bahia grass (Paspalum notatum Fluegge) ; Dal-
lis grass (Paspalum dilatatum Poir.) ; centipede grass (Eremoch-
loa ophiuroides (Munro) Hack.) ; blue couch grass (Digitaria
didactyla Willd.) ; St. Augustine grass (Stenotaphrum secunda-
tum (Walt.) Ktze.) ; and St. Lucie grass (Capriola dactylon var.
St. Lucie (L.) Kuntze).
These grasses were grown in the grass garden and pasture on
the University of Florida Experiment Station farm.
The grasses used for lawn and putting green studies were
grown in plots 10 feet wide and 25 feet long, while those for
pasture studies were grown in plots 4 feet wide and 50 feet long.
In addition, some small plots 5 feet wide and 7 feet long were
included for miscellaneous studies.
The grasses used for pasture and lawn studies were set during
the spring of 1922 and allowed to grow until the summer of 1926,
thus allowing them a growth of four years.
The grasses used for putting green and miscellaneous studies
were set in the spring of 1925 and allowed to grow through the
summer of 1926, thus giving them a period of one year's growth.
The grasses used for pasture studies were grown on Fellow-
ship sandy loam soil. The grasses for lawn and miscellaneous
studies were grown on Norfolk sand, and those for putting green
studies were grown on Norfolk sand, a portion of which had a
3-inch top-dressing of Fellowship clay loam.
Bulletin 211, Root Systems of Sod-Fi" ,,,iii Grasscs
The putting green grass plots were prepared by removing the
rubbish and a number of forage plants from the surface, and
then screening the first 12 inches of soil for nut grass. The soil
was then leveled and marked off into plots 10 feet wide and 25
feet long with a three-foot walk between each plot. The upper
three inches of soil from the west half of four of the plots was
removed. The excavated area of these plots was filled in with
Fellowship clay loam. The east half of all plots was allowed to
remain Norfolk sand. Of the plots receiving a top-dressing of
Fellowship clay loam one was set to Atlanta Bermuda grass, one
to St. Lucie and one to centipede grass.
All of the putting green plots were fertilized every two weeks
with ammonium phosphate at the rate of 1.7 ounces per 100
square feet, making a total application per acre per year of 1,000
pounds. Immediately after each application of ammonium phos-
phate the plots were watered liberally. In addition, each plot
was top-dressed three to four times per year with a soil similar to
that on which the grass was growing. The grasses were watered
and mowed daily in order to maintain a good putting condition.
The soil used for the lawn grass studies was prepared and
marked off into plots 10 feet wide and 25 feet long, with a three-
foot walk between the plots. After the rubbish had been removed
1 cubic yard of muck soil and one one-horse load of well-rotted
compost were thoroughly mixed with the soil in each plot. One
of these plots was then set to each of the following grasses: Ber-
muda, Bahia, centipede, Dallis and St. Augustine grasses. Vege-
tative parts of these plants were set 8 inches apart in 12-inch
rows. Commercial fertilizer was applied to each plot in the
spring and fall at such a rate as to give a total of 1,000 pounds
per acre per year. During the fall of 1923 and the fall of 1924
the west half of each plot was sown to Italian rye grass. Begin-
ning in the spring of 1925 each of these plots was fertilized once
a month with ammonium sulphate at such a rate as to give a total
application per acre per year of 1,000 pounds. The plots were
watered after each application of ammonium sulphate, and dur-
ing periods of dry weather. The grass was mowed every 7 to 10
days, throughout the growing season.
The soil used for the miscellaneous grass studies was cleared
of rubbish by flat hoeing, after which vegetative portions of the
plants were set 6 inches apart in 12-inch rows. Four plots each
were set to Bermuda, centipede and St. Augustine grasses. Two
Florida Agricultural Experiment Station
plots of each of these three grasses were mowed and never al-
lowed to mature seed while the other two plots were never mowed.
Small amounts of sodium nitrate were applied at varying inter-
vals. The grasses were watered after each application of sodium
nitrate and during periods of dry weather.
The preparatory soil work for the pasture grasses consisted of
plowing the soil just enough to make it workable, and then laying
off plots 4 feet wide and 50 feet long. Two plots each were set to
the following grasses: Bermuda, carpet, Bahia, centipede, blue
couch, and St. Augustine grasses. These grasses were set 6
inches apart in 24-inch rows and allowed to grow with no addi-
tional treatment except grazing daily during the growing period.
The soil on which these were growing is classified as Fellowship
sandy loam. It is not well drained. The water table stands ap-
proximately 2 feet below the surface. This type is underlaid with
a plastic clay at a depth of about 30 inches.
METHODS OF EXAMINING ROOT SYSTEMS
The problem of determining the position, extent, degree of
branching and other root characteristics is no easy task. One's
first thought might be to wash away the soil and thus uncover
the roots. Hays (5) was able to obtain useful information on the
development of the roots of corn by washing away the soil.
King(8) improved this method by isolating a prism of soil and
then placing a cage made of galvanized iron and poultrywire net-
ting around the prism of soil. When this cage was in place, sharp-
ened wires were pushed through the prism of soil in such a man-
ner as to hold the roots during washing. Plaster of Paris was
poured on the top surface to hold the plants in place. Weaver(15)
and his co-workers used the direct method of root examination.
For this method a trench is dug 8 to 12 inches from the plant to
be examined and as deep as necessary. The soil is then worked
away from the roots with a sharp-pointed hand pick.
None of these methods seemed adaptable to studies in this in-
vestigation, since this study dealt with a collection of plants mak-
ing a definite area of sod rather than individual plants. Besides,
neither method could be used successfully in the porous sands of
Florida. A different method was devised to study a given area
of sod and root system for each grass studied.
To obtain areas of sod with respective root system, perforated
iron cylinders 8 inches in diameter and 40 inches long were made
Bulletin 211, Root Systems of Sod-Forming Grasses 7
from 12-gage iron. An iron band 3/16 inch thick and 1.5 inches
wide was welded around the cylinder at the top, thus forming a
collar, which prevented the edges of cylinder from bending while
being driven into the soil. The bottom end of the cylinder was
slightly concaved and the edge sharpened to facilitate being
driven into the soil.
When a sample of roots was to be taken, the cylinder was placed
over the sod and a wooden block 10 inches high and 10 inches in
diameter was placed on top of the cylinder, which was then driven
into the ground with a sledge. A hole was then dug by the side
of the cylinder with a post-hole digger and by means of a hook
under the side, the cylinder, together with the sod, was lifted
out. The cylinder was then placed in a slanting trough and the
sandy soil washed from the roots, after which they were hung
on wires to dry. Photographs were made of each of the root sys-
tems thus obtained. The dry weights, zone of concentration and
maximum depth of the different root systems were recorded in
table form. The weight of tops includes the stolons and in the
case of Bermuda some of the underground stems, while root
weight refers, except in the case of Bermuda grass, exclusively
to fibrous roots.
A COMPARATIVE STUDY OF DIFFERENT GRASSES GROWN UNDER
The dry weights of the tops and roots, the depth and concen-
tration of roots of Bermuda, carpet, blue couch, St. Augustine,
centipede and Bahia grasses are shown in Table I, while the
respective root systems of these grasses are shown in Fig. 1.
Fig. 2 is a free-hand drawing to show the distribution of the root
systems of carpet, St. Augustine, centipede and Bahia grasses in
cross section of the sod under pasture conditions. These grasses
were grown in competition under pasture conditions. The results
show that Bahia grass produced the best and most vigorous root
system while centipede grass ranked a close second. However,
centipede grass produced the greatest amount of top growth.
Carpet grass ranked third in weight of root growth per unit area.
The concentration of the roots was practically the same for all of
the different grasses. The concentration of the roots extended
to a depth of five to eight inches. The results indicate that Bahia,
centipede and carpet grasses produced the best root growth under
Bermuda Carpet Blue Couch St. Augustine Centipede Bahia
Fig. 1. The root systems of grasses grown under pasture conditions.
Bulletin 211, Root Systems of Sod-Forming Grasses 9
From Fig. 2 it may be observed that the root systems of these
grasses extend below the water table. This property seems to be
rather common with many pasture and meadow plants.
DIFFERENT GRASSES GROWN UNDER LAWN CONDITIONS
The grasses for lawn studies were grown under as nearly
similar conditions as possible. Table II and Fig. 3 give the results
of these studies.
Under lawn conditions, centipede grass produced the best top
growth, with St. Augustine second, Bahia third, Dallis fourth and
Bermuda fifth. Although Dallis grass naturally has a bunch
habit of growth, it will produce a sod when mowed or grazed.
However, it does not have as smooth a sod as the other grasses
Fig. 2. Free-hand drawing of (left to right) Centipede, St. Augustine,
Carpet, and Bahia grass sods, showing the distribution of the root systems in
a soil profile. a-Water table-2 feet. b-Clay.
and hence is not as desirable for lawns. St. Augustine grass
grows rapidly and is generally used for lawns in the sandy sec-
tions of Florida. However its top growth is not as dense nor as
pleasing as that of centipede grass. St. Augustine grass also is
subject to attacks by the chinch bug (Blissus leucopterus Say.),
making it difficult to maintain a good sod.
Centipede grass seems to be superior to the other grasses for
lawns and fairways. It is thus far immune to brown-patch and
chinch bugs; grows well in shade, and spreads rapidly. This is
the only grass studied that does not have undesirable features.
Norton(14) states that centipede is the best lawn grass of
southeastern China. Throughout the clay region and the gravelly
TABLE I.-Dry weight of tops and roots, zone of maximum concentration of roots, and total depth of roots of Bermuda,
carpet, blue couch, St. Augustine, centipede and Bahia grasses under pasture conditions.
Dry wt. of unit area of sod Zone of maximum Length of roots-
Name of grass Photograph concentration Removed with
(Fig. 1) Tops Roots of roots 40" tube
gms. gms. inches inches
Bermuda* 22 38.9 8.4 0-8 35
Carpet 23 17.4 12.5 0-5 30
Blue couch 24 11.0 5.4 0-6 37
St. Augustine 25 18.7 9.4 0-5 35
Centipede 26 56.9 17.2 0-8 33
Bahia 27 21.9 22.4 0-7 35
*Age not known-miscellaneous sample removed from pasture. All other plants were four years old.
Bermuda Bahia Centipede Dallis St. Augustine
Fig. 3.-The root systems of different grasses grown under lawn conditions.
Florida Agricultural Experiment Station
sand-alluvian region, this is the dominant grass. He adds fur-
ther, "All the neglected fields and washed hillsides are covered
with it. It is valued in Kuliang and largely in Foochow as a grass
for lawns. If the lawns are mowed, clipped, or grazed, this is the
only grass which persists except Bermuda grass which sometimes
maintains itself along the edges of walks and paths. Centipede
grass in pure culture does not need to be mowed, as it grows only
3 to 4 inches high. It can be eradicated easily, as the runners are
on the surface; and it is easily propagated by pieces of runners,
turf or seed. It is the best grazing grass in this region, growing
with Lespedeza striata and allied forms over the fallow terrace
lands. The prime condition of the cattle grazing on these hills de-
pends on the prevalence of this grass and lespedeza. This is also
an excellent plant to prevent washing; the long runners stretch
out in every direction, root at every node and soon branch and
make cover. It can be grown even as far north as North Carolina,
it will solve the lawn difficulties of the Southeastern States, where
none of our grasses are satisfactory the year round."
The Bermuda grass produced a thin top growth, as shown in
Table II and Fig. 3, while Dallis grass produced an irregular sod
and top growth.
A study of the root systems of the grasses under lawn condi-
tions shows that although Bahia grass has a heavier root system
than centipede grass, yet the latter has a denser root system with
a heavier top growth. This is in accord with the results of
Fitts(6), who has shown in a study of golf green grasses that a
heavy root system is associated with a heavy top growth. From
Table II and Fig 3, it may be observed that the root system of
centipede grass has a weight of 20.6 grams per unit area with the
concentration of roots in the first 6 inches of soil and a maximum
depth of only 5 feet, 2 inches, while Bahia grass, the only one with
a heavier root system, has a weight of 24.4 grams per unit area
with a concentration in the first 10 inches and a maximum depth
of 7 feet, 8 inches. Although St. Augustine grass produced a
good top growth, its root system appears to be inferior to the
other grasses from the standpoint of density and weight per unit
area. Bermuda grass produced the least amount of top and root
growth. Dallis grass produced a good root growth, but its top
growth is too rough and bunchy to be of any marked value for
TABLE II.-Dry weights of tops and roots, zone of maximum concentration, length removed with 40" tube, and maximum
root depth of roots of Bermuda, Bahia, centipede, Dallis, and St. Augustine grasses under lawn conditions.
SDry wt. of unit area of sod Zone of maximum Total depth of
Name of grass Photograph concentration roots removed Maximum root
(Fig. 3) Tops Roots of roots with 40" tube depth
gins. gms. inches inches feet-inches
Bermuda 12 26.2 3 6 6 33 7-7
11 3I .7
%enupeue jermuaa St. Augustine
Fig. 4.-The root systems of different grasses under mowed and unmowed conditions.
Bulletin 211, Root Systems of Sod-Forming Grasses 15
To judge from the study of the root systems and top growth of
these grasses, it seems that centipede grass is the most outstand-
ing one for both pasture and lawn purposes. Although the weight
of its root system is not always the greatest, its habit of growth,
producing a concentrated root system near the surface, makes it
a better grass for both pasture and lawn purposes.
THE INFLUENCE OF MOWING ON THE DEVELOPMENT OF ROOT
SYSTEMS OF SOD-FORMING GRASSES
The results of a study of a series of samples removed from
mowed and un-mowed plots of Bermuda, centipede and St. Augus-
tine grasses are given in Table III and Fig. 4. The grasses were
grown under like conditions, with the exception of mowing.
The results show that mowing of centipede and Bermuda
grasses increased the root growth of these grasses and also in-
creased the concentration of the roots in the topmost portion of
the soil. This is not so pronounced with St. Augustine grass
(3a and 3b, Fig. 4). Mowing seemed to increase the rate of sod
formation. These grasses were not grown for a comparative
study as between species. However, it is interesting to note that
centipede grass has the greatest development of top and root
growth. St. Augustine grass ranks second, and Bermuda grass
From these studies it appears that mowing often enough to
prevent seed formation not only increases the root development,
but also produces a better sod than does non-mowing.
The samples for determining the weight of tops on the un-
mowed plots include the entire top growth, that is, stolons, rhi-
zomes in case of Bermuda, leaves and seed heads; while those
from the mowed area did not take into account the tops removed
DIFFERENT GRASSES GROWN UNDER PUTTING GREEN
THE INFLUENCE OF A 3-INCH TOP-DRESSING OF CLAY ON
NORFOLK SAND ON THE ROOT DEVELOPMENT OF SOD-
All of the grasses were grown under like treatment, with the
exception of clay top-dressing. Table IV and Fig. 5 show the
results of the root growth of Atlanta Bermuda, St. Lucie and
centipede grasses grown on Norfolk sand top-dressed with Fel-
TABLE III.-The influence of mowing on the root systems of Bermuda, centipede and St. Augustine grasses.
Name of grass Treatment Pho
St. Augustine early
St. Augustine Unmowed
*Tops refers to everything except fibrous roots.
Dry wt. of unit area of sod
29 3 3.2
Zone of r
Total Depth of
oot roots removed
ion with 40" tube
TABLE IV.-Dry weights of tops and roots, zone of concentration of the root systems, and depth of root penetration of
different grasses on Norfolk sand with and without a top-dressing of clay under putting green conditions.
A. Bermuda Norfolk sand alone
Norfolk sand with
A. Bermuda clay top-dressing
St. Lucie Norfolk sand alone
Norfolk sand with
St. Lucie clay top-dressing
Centipede Norfolk sand alone
Norfolk sand with
Centipede clay top-dressing
19 no clay
20 no clay
16 no clay
Dry wt. of unit area of sod
Zone of maxi- Total depth of
mum concen- roots removed
tration of roots with 40" tube
Name of grass
Atlanta Bermuda St. Lucie Centipede
Fig. 5.-The effect of top-dressings of clay on the root systems of grasses under putting green
conditions. (Cf. Fig. 6.)
Bulletin 211, Root Systems of Sod-Forming Grasses 19
From these results it may be seen that the root growth on the
soil top-dressed with clay are in every instance, except with cen-
tipede grass, heavier than are those grown on the sand alone.
This is probably associated with a greater content of plant nutri-
ents in the clay, especially as these grasses were not fertilized.
There is a 35 percent increase in the weight of the root system of
Atlanta Bermuda grass and 23 percent increase in St. Lucie grass
on Norfolk sand top-dressed with Fellowship clay over that grown
on Norfolk sand alone.
The root systems of the different grasses (except centipede)
were concentrated deeper when grown on the clay over the sand
than on sand alone. However, the top-dressing with the different
soils had no apparent effect on the maximum depth of root growth.
The centipede grass appears to be a rather shallow rooted grass,
while the other grasses grow to a considerable depth.
In order to determine the zone of greatest concentration of the
root systems of grasses in a rich and properly fertilized soil, a
number of areas of Bermuda grass sod were removed (method
previously described) from the fertilized portions of Norfolk
sand top-dressed with clay, and from Norfolk sand alone. The
dry weights of 4-inch sections of the root systems of this grass
at different depths is given in Table V. These results show that
the concentration of the roots is in the first eight inches of soil.
The sand with a clay top-dressing contained 70 percent of the
total.weight of roots in the first eight inches of soil-as compared
to 55 percent in the sand without clay (Table V and Fig. 5). This
is not entirely in accord with Fitts'(1) results with creeping bent
grass, as he reported the roots of this grass to be concentrated in
the first three or four inches of surface soil. This difference is
probably due to the open character of the Norfolk sand compared
to the heavier soil on which Fitts carried out his experiments.
These studies indicate that a top-dressing of clay on the sandy
soils of Florida would increase the development of the root system
of sod-forming grasses. The clay seems to make available a
greater and more constant supply of moisture and nutrient ma-
THE INFLUENCE OF AMMONIUM PHOSPHATE ON THE ROOT SYS-
TEMS OF SOD-FORMING GRASSES UNDER PUTTING GREEN
Table VI and Figs. 5 and 6 show the influence of bi-monthly
applications of ammonium phosphate on the development of the
root systems of grasses grown under putting green conditions.
TABLE V.-Weight in grams of consecutive 4" sections of Bermuda grass roots grown on Norfolk sand with and without a 3" top-
dressing of clay. The sod was one year old.
S 0"-4" 4"-8" 8"-12" 12"-16" 16"-20" 20"-24" 24"-28" wt. 0-28" .
Samples No No No No NNo o No No
Clay clay Clay clay Clay clay Clay clay Clay lay Clay lay Clay clay Clay clay
1 3.96 1.35 1.51 0.85 0.56 0.49 0.43 0.23 0.39 0.33 0.36 0.32 0.36 0.21 7.57 3.78
2 1.80 3.09 0.99 0.77 0.55 0.36 0 34 0.17 0.33 0.15 0.34 0.05 0.27 0.03 4.62 4.62
3 2.50 1.13 1.11 0.47 10.51 0.22 0.48 0.33 0.39 0.06 0.17 0.09 0.10 0.03 5.26 2.33
I I i.
4 2.82 1.69 1.66 0.70 0.93 0.61 0.57 0.43 0.34 0.23 0.26 0.35 0.22 0.39 6.70 4.40
,5 3.09 1.83 1.43 1.39 0.85 0.80 |0 57 0.45 0.49 0.38 0.38 0.28 0.32 0.13 7.13 5.26
Av. of -
Five 2.82 1.82 1.34 0.83 0.68 0.49 0.47 0.32 0.36 0.23 0.30 0.21 0.25 0.15 1 6.25 4.07 f
1 1 1111I
Atlanta Bermuda St. Lucie Centipede
Fig. 6.-The effect of ammonium phosphate and a top-dressing of clay on Norfolk sand on the root systems of
putting green grasses. All grasses were fertilized with ammonium phosphate. (Cf. Fig. 5.)
TABLE VI.-The effect of ammonium phosphate and a top-dressing of clay (on Norfolk sand) on the root systems of
different grasses under putting green conditions.
Name of grass dressing
A. Bermuda No clay 19
A. Bermuda No clay 19
A. Lucie NoBermuda Clay 20
St. Lucie No clay 20
St. Lucie Clay 2C
Centipede No clay 1(
Centipede Clay 1(
* no clay
6 no clay
Wt. of unit
area of roots
Zone of great-
tion of roots
4 no clay
5 no clay
18 no clay
Wt. of unit
area of roots
Zone of great-
tion of roots
Bulletin 211, Root Systems of Sod-Forming Grasses 23
These results show that ammonium phosphate increased the dry
weights and the development of the root systems of the different
grasses. Ammonium phosphate produced on Norfolk sand a
greater root growth than did a top-dressing of clay. However,
the root systems on the fertilized sand were not as good as they
were where the fertilizer and clay both were applied, with the
exception of the root system of St. Lucie grass. Frequent appli-
cations of ammonium phosphate produced almost as much root
growth on the sand as was produced on the sand with a top-dress-
ing of Fellowship clay (Fig 6).
The fertilizer on the sand alone had very little influence on the
depth of the zone of root concentration as compared to that of
sand top-dressed with clay.
It is interesting to note (Table II, Figs. 2, 3 and 4) that all of
the grasses studied produced larger and deeper root systems than
are ordinarily expected for sod-forming grasses. Fitts' results
with creeping bent grass on a fertile soil seem to indicate that
sod-forming grasses are rather shallow rooted plants. Close
observation (Figs. 2, 3 and 4) shows that the fibrous roots of some
grasses are much larger than those of others. This character,
together with the difference in size of both the surface and under-
ground stems, possibly accounts for the adaptation of the sod-
forming grasses to certain soil and climatic conditions. However,
the inherent characteristics of these grasses are very different
and should not be overlooked.
The largest and deepest root system of sod-forming grasses is
not necessarily associated with the best and most vigorous top
growth. However, in general this seemed to be true for most of
the grasses studied. Frequent mowing (two to three times per
week) seemed to bring about a more vegetative state with some
grasses than it did with others. This was particularly true with
centipede and Bermuda grasses. The top growth of the different
grasses and also the quality of the sods will be discussed with the
root systems wherever possible.
Of all the grasses studied Bermuda produced the most outstand-
ing sod under putting green conditions. However, the root system
of this grass was not as heavy as that of St. Lucie grass. On the
other hand, Bermuda grass produced a very poor top growth and
sod under lawn and pasture conditions, when compared to centi-
pede and Bahia grasses.
Florida Agricultural Experiment Station
Since Bermuda grass has rather small surface stems and also
underground stems, which are protected from the mower, the
excessive cuttings under putting green conditions would not likely
be so injurious as would be the case with grasses having larger
surface runners or stolons and no underground stems. This is
based on the assumption that the large surface stems or stolons
are struck by the mower blade. The size and position of the leaf
would no doubt be factors affecting the formation of carbohy-
drate material under putting green conditions. The excessive
mowings possibly reduced the carbohydrate formation to a greater
degree in centipede grass than in Bermuda grass. This seems to
account for the poor root growth of centipede grass under putting
green conditions, even though fertilizer and clay top-dressing
The small stems and fibrous roots of Bermuda grass as com-
pared with centipede and Bahia grasses, would not maintain very
much reserve food. Consequently this grass would not be ex-
pected to withstand conditions of low moisture and available food
supply in deep sandy soils. The results (Tables I and II, Figs.
2 and 3) show this to be true. The top-dressing of clay and fer-
tilizer increased the supply of available food and water which in
turn increased the root and top growth of Bermuda grass. This
substantiates the fact that this grass is more adapted to loams
and clay loams than to sandy soils.
The deep root system of all the grasses studied is partially
explained by the open textured soil used in this investigation.
The coarse sands have very little cohesive properties, thereby
making it difficult for the roots to bind this soil together. When
a clay top-dressing is applied to the soil the growth of roots is
increased, also a turf is more readily formed (Fig. 5). This was
particularly true with fine stemmed grasses having small fibrous
root systems. Since the soils used were not very fertile, ammon-
ium phosphate would be expected to stimulate the root growth of
all the grasses studied.
The large stolons and large fibrous roots of centipede and Bahia
grasses contain a greater supply of reserve foods than the roots
and stems of Bermuda grass, and hence the former would be more
able to withstand the low content of available moisture and soil
nutrients in the open sandy lands during dry seasons. Unpub-
lished data in the department shows that stolons and roots of
Bahia are high in content of hemicelluloses. A considerable por-
Bulletin 211, Root Systems of Sod-Forming Grasses 25
tion of these higher carbohydrates generally consist of pentosans.
This form of carbohydrate undoubtedly gives the plant greater
water binding capacity and thereby enables it to exist under
adverse soil moisture conditions. This greater imbibitional power
of plants through an increase in pentosan content was noted by
Spoehr in the cactus(13). McDougal considered this to be the
basis of Xerophytism(9). An increase in or change to pentosan
form of carbohydrate was found by Janssen(7) in wheat plants
grown in soils low in moisture. This apparent higher content of
these carbohydrates in Bahia and centipede grasses should enable
these grasses to overrun Bermuda, blue couch, St. Augustine, and
carpet grasses which appear to show less persistence under ad-
St. Augustine grass is one of the outstanding lawn grasses for
the sandy soils in the southeastern states. However, it does not
grow well under pasture conditions. This is possibly due to the
long internodes which seem to succumb readily to trampling. The
long internodes are not conducive to the formation of a compact
sod, even though the root fibres are somewhat large.
The root system of Dallis grass under lawn conditions was very
similar to that of Bahia grass, but the top is too rough and bunchy
for lawn purposes. Carpet grass is naturally adapted to moist
soils, but its fine root fibers render it unable to compete with the
larger roots of centipede and Bahia grasses, particularly on
Since the greater part of the soils of Florida are sandy they are
not very well adapted to the formation of good sods. However,
a top-dressing of clay and heavy applications of commercial fer-
tilizers seem to improve the quality of the sod and also increase
the concentration of the root system in the surface soil. Further-
more, the results indicate that a fertilizer carrying a high content
of nitrogen would produce a satisfactory sod on sandy soils.
The root systems of centipede, Bahia, Dallis, blue couch, Ber-
muda, St. Lucie and St. Augustine grasses were studied under
pasture, lawn and putting green conditions. The effect of a top-
dressing of clay and applications of ammonium phosphate on the
development of the root systems of these grasses were also in-
cluded in this investigation. The results of these studies are
given as follows:
Florida Agricultural Experiment Station
1. Bahia, centipede, St. Augustine, carpet, Bermuda and blue
couch grasses were grown in competition on Fellowship sandy
loam soil under pasture conditions. Centipede grass produced
the best top growth and second best root growth, while Bahia
grass produced the best root system.
2. Bermuda, Bahia, centipede, Dallis and St. Augustine grasses
were grown on Norfolk sand under lawn conditions. Here, centi-
pede grass produced the best top growth and second best root
growth, while Bahia again produced the best root growth. The
other grasses produced good root growth, with the exception of
Bermuda. The root systems of all the grasses extended to a
depth of six to eight feet.
3. Mowing sufficiently to prevent seed formation produced
better developed root systems with Bermuda and centipede
grasses than did non-mowing. However, this was not the case
with St. Augustine grass.
4. A 3-inch top-dressing of clay on Norfolk sand produced a
better root system with Bermuda, St. Lucie and centipede grasses
than did the Norfolk sand alone, when no ammonium phosphate
was applied. But when the ammonium phosphate was applied
the growth of the roots on both soils was about the same.
5. A top-dressing of clay and an application of ammonium
phosphate very greatly increased the concentration of the root
systems of all the grasses in the first eight inches of surface soil.
Over 50 percent, by weight, of the roots recovered were found in
the first eight inches of soil.
The writer wishes to take this opportunity to express his appre-
ciation and thanks to Mr. W. E. Stokes, under whose direction
the experimental work was conducted; to Dr. O. C. Bryan of the
College of Agriculture for helpful criticism and suggestions dur-
ing the preparation of.this manuscript; to Dr. R. M. Barnette for
helpful assistance in arranging the date and to Dr. W. A. Leukel
for information on the root growth of plants.
Bulletin 211, Root Systems of Sod-Forming Grasses 27
1. FITTS, O. B.: A preliminary study of the root growth of fine grasses
under turf conditions. Bulletin, Green Section, U. S. Golf Association,
V: 3:58-62. 1925.
2. GRAVER, S.: Alfalfa root studies. U. S. D. A. Dept. Bulletin 1087. 1922.
3. GARICKE, W. F.: Investigations of physiological processes related to
root systems of plants. Cal. Agr. Expt. Station, Rept. 1922: 116-117.
4. GOFF, E. S.: The resumption of root growth in spring. Wis. Agr. Exp.
Sta. Rept. 15:220-228. 1898.
5. HAYS, W. M.: Corn, its habits of root growth, methods of planting and
cultivating, notes on ears and stools or suckers. Minn. Agr. Exp. Sta.
Bul. 5:5-33. 1889.
6. HITCHCOCK, A. S.: A textbook of grasses. MacMillan. 1914.
7. JANSSEN, GEO.: Effect of seeding winter wheat on plant development
and its relationship to winter hardiness. Jour. Am. Soc. Agron. 21:4.
8. KING, F. H.: Natural distribution of roots in field soils. Wis. Agr. Exp.
Sta. Rept., 1892: 112; also 1893: 160.
9. McDOUGAL, D. T., RICHARDS, H. M., AND SPOEHR, H. A.: Basis of
succulence in plants. Bot. Gaz. 67: 405-416. 1919.
10. TEN EYCK, A. M.: A study of the root systems of cultivated plants
grown as farm crops. N. D. Agr. Exp. Sta., Bulletin 43. 1900.
11. : Roots of plants. N. D. Agr. Exp. Sta., Bulletin 36. 1899.
12. --- : The roots of plants. Kans. Agr. Exp. Sta., Bulletin 127. 1905.
13. SPOEHR, H. A.: Carbohydrate economy of cacti. Pub. 287, Carnegie
Inst., Washington. 1919.
14. VINALL, H. N. AND REED, H. R.: Centipede Grass. Office of Forage
Crops, Bureau of Plant Industry, U. S. D. A. Aug. 13, 1926. [Mimeo-
15. WEAVER, JOHN E.: Root development of field crops. McGraw-Hill.
INTRODUCTION ............................... ....... .. ...... 3
EXPERIMENTAL WORK ...................... ................ ....... 4
Methods of Growing Grasses .................................. 4
Methods of Examining Root Systems. ........................... 6
A Comparative Study of Different Grasses Grown Under Pasture
Conditions ................ .............................. 7
Different Grasses Grown Under Lawn Conditions ................ 9
The Influence of Mowing on the Development of Root Systems of
Sod-forming Grasses ........................................ 15
Different Grasses Grown Under Putting Green Conditions ........ 15
The Influence of a 3-inch Top-Dressing of Clay on Norfolk
Sand on the Root Development of Sod-forming Grasses..... 15
The Influence of Ammonium Phosphate on the Root Systems of
Sod-forming Grasses Grown Under Putting Green Conditions 19
D ISCUSSION ............ ................................. ......... 23
SUMMARY .............. ... .................. ........ ............ 25
REFERENCES ............. ......................................... 27