EFFECTS OF AMENDMENTS ON SOIL
PROPERTIES AND ON GROWTH
OF BERMIUDAGRASS ON
RALPH RAY SMALLEY
A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL OF
THE UNIVERSITY OF FLORIDA
IN PARTIAL FULFILLMENT OF THE REQUIREMlENTS FOR THE
DEGREE OF DOCTOR OF PHILOSOPHY
UNIVERSITY OF FLORIDA
The author wishes to extend his sincere appreciation to his
major professor, Dr. Wv. L. Pritchett, for his suggestions during these
investigations, and for his guidance and constructive criticisms of
the manuscript. Appreciation is also expressed to Dr. G. C. Horn,
Dr. W. O. Ash, Dr. L. C. Hammond,and Dr. F. B. Smith for many helpful
suggestions during the course of this work and constructive criticisms
of the manuscript.
Sincere appreciation is expressed to Mr. Dewain Railey, field
assistant, for his help in establishing and maintaining this experi-
ment and to members of the soil testing laboratory for soil analysis.
The writer wishes to extend his appreciation to Dr. F. B. Smith
and the Soils Department of the University of Florida for granting a
research assistantship, thereby making possible the continuation of
graduate studies. Appreciation is also extended to the Golf Course
Superintendents Association of America whose research grant helped
finance this study. Also, thanks are extended to LonCala Phosphate
Company, High Springs, Fla., Wyandotte Chemicals Corporation, Wyandotte,
M~ich., and Zonolite Company, Travelers Rest, S. C., for amending
materials used in this experiment.
Ir P IK3
TABLE OF CONTENTS
LIST OF TABLES . . . . .
LIST OF FIGURES . . . . .
INTRODUCTION . . . . .
REVThIEWOF LITERATURE .
Physical Soil Conditioning Materials and
Their Properties ............
Use and Effects of Physical Soil Am~endmhents
upon Soil . . . .
Soil Structure and Plant Growth ......
MATERIALS AND METHODS ................
Green Construction and Turf Planting
Maintenance of the Green ......
Purf Evaluations ..........
Soil Measurements .........
Statistical Analysis ........
RESULTS AND DISCUSSION............
Yield of bermudagrass .........
Bermudagrass root development in soil
mixtures . . . .
Soil coverage by bermudagrass .....
Quality of bermudagrass ........
Drought resistance of benrudagrass ...
Seedhead prevalence of benmudagrass ..
Physical Soil Evaluations..........
Bulk density . . .. .
Porosity . . . .
Retention and availability of soil water
TABLE OF CONTENTS--( continued)
Chemical Soil Evaluations .. .. .. 66
Organic matter content .. .. .. .. .. .. 67
Cation exchange capacity .. .. .. 69
Phosphorus . . . . .. 70
Potassium . . . . .. 75
Calcium . . . 77
Magnesium . . . . .. 80
Soil pH . . 83
Soil Properties and Turf Growth 84
Pore space and turf growth ........... 85
Available soil water and turf growth ...... 87
Permeability and turf growth .. .. 89
Penetrability and turf growth ., 1
Nutrient content and turf growth ., 9
SUEPE~RY ,, ., 4
CONCLUSIONS .. .. ... .. .. .. .. .. 101
APPEN\DIX .. .. .. .. .. .. .. .. 105
LITERATURE CITED .. .. .. .. .. . 170
BIOGRAIPHY .. .. .. ... .. .. .. ... .,. .. .. 176
LIST OF TABLES
1. Particle size distribution of Arredondo loamy fine
sand and colloidal phosphate as determined by
the hydrometer method. .. .. .. .. .. 18
2.Sieve analyses of the sand fraction of Arredondo
loamy fine sand and of fired clay. .. .. .. .. 19
5. Volume of vermiculite, colloidal phosphate, fired
clay, peat.and soil utilized in sub-plot treatments. 21
4. Relative dry matter production, quality, seedhead
prevalence, and drought resistance of Tifgreen ber-
mudagrass grownm on 56 soil treatments; treatment
0-0-0-0 equals 100%. ... .. .. .. .. ... 34
5. Average effects of various amendments upon the yield
of Tifgreen bermudagrass roots in the top 3 inches
of soil mixtures; g. per 547 cc., 1960. .. .. .. .. 39
6. Average effects of various amendments upon the percent
coverage of soil mixtures by Tilgreen bermudagrass
at 4 and 6 weeks after sprigging, 1959. ... .. 41
7. Average bulk density of soil mixtures containing
various soil amendments, 1960. .. .. .. .. .. 49
8. Average hydraulic conductivity of soil mixtures con-
taining various levels of amendments, 1960. .. .. 62
9. Average extractable phosphorus, P205, content of soil
mixtures containing various level of amendments,
1959 and 1960. .. ... .. .. .. .. .. .. 74
10. Average extractable potassium, K20, content in soil
mixtures containing various levels of amendments,
1959 and 1960. .. .. ... .. .. .. ... 76
11. Average extractable calcium, Ca0, content in soil
mixtures containing various levels of amendments,
1959 and 1960. .... ... .. ... .. 78
12. Average extractable magnesium, MIg0, content in soil
mixtures containing various levels of amendments,
1959 and 1960. .. .. .. .. .. .. .. .. .. 82
LIST OF TABLES--(continued)
15. Average daily growth in grams of dry matter per
100 square feet of Tifgreen bermudagrass. .. .. 107
14. Dry weight of Tifgreen bermudagrass roots in the
top 3 inches of soil mixtures, 1960. . .... 115
15. Maximum depth of rooting of Tifgreen bermudagrass
in soil mixtures, 1960. .. ... .. .. .. 114
16. Coverage by Tifgreen bermudagrass at 4 and 6 weeks
after ;prigging, 1959. ... .. .. .. .... 115
17. Quality ratings of Tifgreen bermudagrass grown on
soil mixtures, 1959. .. .. .. .. .. ... 117
18. Drought resistance of Tifgreen bermudagrass grown
on soil mixtures, 1960. .. .. .. .. ... 119
19. Seedhead prevalence of Tirgreen bentudagrass grown
on soil mixtures, 1960. .. .. ... .. .. 120
2C. Bulk density of soil mixtures, 1960. .. .. .. .. 121
21. Pounds of force required for penetrating soil mixtures
with the Cornell penetrometer at 0- to 1-, 2- to 4-,
and 7- to 10-inch depths, 1960. .. .. ... 122
22. Bulk density of soil mixtures compacted at increasing
moisture content, 1960. ... ... .. .. 125
23. Noncapillary pore space of soil mixtures, 1960. .. 129
24. Capillary pore space of soil mixtures, 1960. ... 150
25. Total pore space of soil mixtures, 1960. .. ... 151
26. Hydraulic conductivity of soil mixtures, 1960. .. 152
27. Intrinsic permeability of soil mixtures, 1960. .. 133
28. Water retained in soil mixtures at 50 cm. water
tension and 5 and 15 atn. tension, 1960. .. .. 134
29. Water retained in pore spaces of soil mixtures
between 50 cm. water tension and 15 atn. tension
and between 50 cm. water tension and 5 atm.
tension, 1960. ... .. .. .. .. .. .. .. 157
LIST OF TABLES--(continued)
30. Organic matter content of soil mixtures,
1959 and 1960. .. .. ... .. .. .. ... 139
51. Cation exchange capacity of soil mixtures,
1959 and 1960. .. ... .. .. .. .. ... 141
32. Extractable phosphorus, potassium, calcium, and
magnesium of soils mixed to 0 to 6 and 0 to 12
inches, and of subsoil samples taken from 6 inches
below respective mixtures, 1959 and 1960. .. .. 143
33. The pH of soils mixed to 0 to 6 and 0 to 12 inches,
and of subsoil samples taken from 6 inches below
respective mixtures, 1959 and 1960. .. .. .. 155
34. Analyses of variance for yield of Tifgreen bermudagrass,
soil water available between 50 cm. water tension
and 15 atm. tension, and hydraulic conductivity for
soil mixtures, 1960. .. .. .. ... .. .. 159
35. Analyses of variance for coverage and quality of
Tifgreen bermudagrass, 1959. .. .. .. ... 160
36. Analyses of variance for seedhead prevalence, drought
resistance, and depth and weight of roots of
Tifgreen bermudagrass, 1959. .. ... ... 161
37. Analyses of variance for bulk density and total and
capillary pore space of soil mixtures, 1960. .. 162
38. Analyses of variance for cornell penetrometer readings
at three depths in soil mixtures, 1960. .. .. 163
39. Analyses of variance for extractable phosphorus and
potassium in soil mixtures and in the subsoil,
average 1959 and 1960. .. ... .. .. 164
40. Analyses of variance for the effects of time on the
extractable phosphorus and potassium in soil
mixtures and in the subsoil, 1959 and 1960. .. 165
41. Analyses of variance for extractable calcium and
magnesium in soil mixtures and in the subsoil,
average 1959 and 1960. .. .. .. . .. 166
LIST OF TABLES--(continued)
Analyses of variance for the effects of time on the
extractable calcium and magnesium in soil
mixtures and the subsoil, 1959 and 1960. ...
45. Analyses of variance for pH, exchange capacity,
and organic matter content of soil mixtures,
and pH of subsoil, average 1959 and 1960. ..
44. Analyses of variance for the effects of time on pH,
exchange capacity, and organic matter content of
soil mixtures, and pH of subsoil, 1959 and 1960.
LIST OF FIGURlES
1. Effects of vermiculite and fired clay on percent
change in daily yields of Tifgreen bermudagrass
from yields at the zero level of these materials,
1959 and 1960. .. ..
2. Average depth of rooting of Tifgreen bennudagrass in
soil mixtures containing by volume various levels
of vermiculite and colloidal phosphate, 1960. .. 40
3. Average drought damage to Tifgreen bermudagrass growJn
on soil mixtures containing by volume 0, 5, and
10% colloidal phosphate mixed to 6 and 12? inches,
1960. .. .. .. ... .. .. .. 45
4. Average seedhead prevalence of Tilgreen bermudagrass
grown on soil mixtures containing by volume vary-
ing levels of fired clay and peat, 1960. .. .. .. 47
S. Force required for penetration by Cornell penetron-
eter at varying depths in unamended soil and in a
soil mixture containing by volume 20;% vermiculite,
5% colloidal phosphate, 10% fired clay, and 10$
peat, mixed to 6 and 12 inches, 1960. ... .. 51
6. Changes in bulk density
centages of moisture
training by volume 0,
7. Changes in bulk density
centages of moisture
gaining by volume 0,
1960. . .
by compaction at various per-
content of soil mixtures con-
10, and 20% vermiculite, 1960.
by compaction at various per-
content of soil mixtures con-
5, and 10% colloidal phosphate,
8. Changes in bulk density by compaction at various
centages of moisture content of soil mixtures
training by volume 0 and 10% fired clay, 1960.
9. Changes in bulk density by compaction at various per-
centages of moisture content of soil mixtures con-
taining by volume 0 and 10% peat, 1960. .....
10. Average percent total, capillary, and noncapillaryl
pore space of Arredondo loamyr fine sand and of soil
mixtures containing by volume O, 10, and 20% ver-
miculite, 0, 5, and 10% colloidal phosphate, O and
10% fired clay, and 0 and 10% peat, 1960. ....
LIST OF FIGURES--(continued)
11. Average percent moisture by volume held at 50 cm.
water tension and 3 and 15 atm. tension, by
Arredondo loamy fine sand and by soil mixtures
containing by volume 0, 10, and 20$ vermiculite,
0, 5, and 10% colloidal phosphate, O and 109 fired
clay, and O and 10% peat, 1960. .. ... ... 64
12. Organic matter content (1959 and 1960) of soil mix-
tures receiving by volume 0 and 10%9 peat in 1959. .. 68
13. Cation exchange capacity of unamended Arredondo
loamy~ fine sand and soil mixtures (average of all
mixtures) in 1959 and 1960. .. ... .. .. .. 71
14. E~xtractable phosphorus (P205) in soil mixtures con-
taining by volume 0, 5, and 10% colloidal phos-
phate, 1959 and 1960. ... .. .. ... 73
15. Extractable calcium (Ca0) in soil mixtures contain-
ing by volume 0, 5, and 10% colloidal phosphate,
1959 and 1960. ... .. .. ... . 79
16. Regression of the yield-quality index of Tifgreen
bermudagrass on percent capillary and noncapil-
lary pore space in soil mixtures, 1960. .. .. .. 86
17. Regression of the yrield-quality index of Tifgreen
bermudagrass on the percentage of readily avail-
able water, held between 50 cm. waater tension and
5 atm. tension, and on the percentage of total
available water, held between 50 cm. water ten-
sion and 15 atm. tension, in soil mixtures, 1960. .. 88
18. Regression of the yield-quality index of Tifgreen
bermudagrass on hydraulic conductivity of soil
mixtures, 1960. .. ... .. .. .. . 90
19. Regression of the yield-quality index of Tifgreen
bermudagrass on the penetrability of the 2- to
4-inch depth of soil mixtures as measured by the
Cornell penetrometer, 1960. .. .. .. .. ... 92
20. Experimental layout. ... .. .. .... .. 106
The favorable subtropical climate of Florida is a prime force
in the rapid population growth and industrial development of the state.
It also permits year-round golfing, a sport which has become increas-
ingly popular with both residents and tourists. As a result of the
demand for these recreational facilities, Florida has more than 225
operating golf courses, requiring an estimated 10 million dollars
annually for maintenance.6
W~ith the increased popularity of the game, golf superintend-
ents are finding it difficult to maintain good vegetative cover and
putting surfaces on their greens. The Florida peninsula has predom-
inantly sandy soils and amendments must be added to produce good,
durable putting surfaces on greens.
Many different types of soil mixtures have been used for golf
greens construction. The types and amounts of amendments used have
often depended upon availability of amendments and preference of golf
course architects. These prepared soils, however, have usually con-
sisted of a mixture of sand, peat, and a soil containing a high percent-
age of clay. Some mixtures have produced good greens throughout the
years, while others have failed within a short period of time. A num-
ber of the failures can be attributed to poor greens maintenance,
~Unpublished report. Florida Turf Association, Bradenton,
while others appear to be caused by factors such as compaction, water-
logging, and improper construction.
Man has been more successful in controlling the chemical prop-
erties of soils than the physical ones. This has been especially true
of golf greens which are usually subjected to frequent watering, there-
by enhancing soil compaction and resulting in grass with a limited
root system. Player traffic and high speed, vibrating maintenance
equipment tend to quickly destroy desirable soil structure unless the
soil has inherent resistance to compaction.
The addition of organic matter to soil and the resultant bio-
logical and chemical decomposition of this material tends to improve
structure and decrease the rate of physical deterioration of the greens
soil. Organic matter, however, has a short life in the sandy soils of
Florida. This is especially true in golf greens where high rates of
fertilizer applications accelerate biological decomposition of organic
The relatively high rate of rainfall, long growling season,
and high temperatures in Florida cause rapid leaching of certain
plant nutrients from sandy soils. There are, however, drought periods
during which irrigation is necessary in order to maintain desirable
grass growth on putting greens. Because of the limited ability of
sandy soils to hold water, greens are watered frequently and often
excessively. This not only increases leaching of plant nutrients but
adds greatly to costs of maintaining a golf course.
It appears, therefore, that the ideal physical additives for
sandy soils used for golf greens should be materials that resist bio-
logical decomposition and compaction. They should increase the ability
of the soil to hold plant nutrients and to release them as they are
needed for plant growth. Furthermore, they should increase the reten-
tion of available soil water and, at the same time, allow comparatively
rapid infiltration and percolation of water.
In order to study and evaluate changes occurring in prepared
greens soils, an experiment was conducted utilizing Arredondo loamy
fine sand in combination wiith various levels of one organic and three
nonorganic amencduents. The objectives of the experiment were to eval-
uate the amendments; first, by measur-ing turf response by visual means,
clipping weights, and root development; secondly, by studying physical
and chemical soil conditions produced by the amendments; and finally,
to evaluate the aforementioned soil conditions in relation to their
effect on the growth of turf.
REVIEW OF LITERATURE
One of the fundamental axioms of soil science is that all
soils differ, not only in chemical composition but in physical prop-
erties. Buckm~an and Brady (7) described mineral soils as the "upper
and biologically weathered portion of the regolith" composed of a
mixture of broken and weathered minerals plus decaying organic matter.
They added that this mixture supports plant life when it contains
proper amounts of air, water, and plant nutrients.
The components of the mineral fraction having diameters of
less than 2 mm. are referred to as soil separates (7). The individ-
ual separates are classified in relation to their diameters in milli-
meters as follows: very coarse sand, 2.0 to 1.0; coarse sand, 1.0 to
0.5; medium sand, 0.5 to 0.25; fine sand, 0.25 to 0.10; very fine sand,
0.10 to 0.05; silt, 0.05 to 0.002; and clay, below 0.002 (58). Seldom
will a soil consist entirely of one separate and it is usually a com-
bination of sand, sil4 and clay.
Physical Soil Conditioning Materials and
The purpose of soil amendments is to change either the physical
or chemical properties of soil in a way that will benefit the growth
of plants. Grau (19) stated, "Sand added to clay is an amendment.
Clay added to sand is an amendment." He concluded that any material
added to a soil to improve either the physical or chemical properties
of the soil is an amendment thereof. He cited a long list of materials
that have been used for amending golf green soils.
Several writers (16, 19, 23, 24, 30, 35, 39) stressed the im-
portance of sand in maintaining good structure in putting-green soils
and have suggested that a relatively high percentage of sand should be
used in the construction of greens. Holmes (25) referred to sand as
the "skeleton" of a greens soil. Buckmran and Brady (7) noted that
sand grains may be rounded, angular, or even flat. They added that
when these grains are not coated with clay and silt they have no cohe-
sive properties; therefore, infiltration and percolation are rapid,
aeration is good to excessive, and nutrient and water-holding capac-
ities are low.
Silt is composed of irregular particles which are seldom smooth
and are between clay and sand in size. Its water-holding capacity is
high, infiltration and percolation rates are slow, and nutrient-holding
capacity is low (75). Jamison and Kroth (28), also, noted that avail-
able water-holding capacity increased in a soil as its silt content
increased. Several workers (23, 24, 29, 35, 39), however, recommended
that the content of fine sand and silt should be low in soil mixrtures.
The need for anall amounts of clay, or other colloidal materi-
als, in greens soils has been recognized by a number of workers (23, 24,
29, SO, 35). Clay particles are mica-like in shape with small dimen-
sions (7). These particles often expand on wetting, are very plastic
and sticky wchen w~et, and have considerable water-holding capacity (73).
The surface areas of clay particles are large in relation to diameter
and because of their ionic structure, they carry a negative charge.
As a result of negative charges, cations swarm around these particles
and it is this phenomenon that is called cation exchange (7).
Several writers (16, 19, 23, 24, 30, 55, 39, 59) have recommended
soils high in clay, but low in fine sand and silt, as sources of clay
to be added to sandy soils for golf greens. Another source of colloidal
material that has been used in greens construction, but not properly
evaluated, is waste pond phosphate. Sauchelli (55) stated that this
material is sold under trade names of calphos, longphoska, colloidal
phosphate vitaloids, and possibly others. It is a mixture of finely
divided rock phosphate containing a considerable amount of clay (55).
It was reported that waste pond phosphate contains 18 to 23$ calcium
phosphate, of which 2 to 38 is available P205 (8).
Another source of colloidal material in golf greens is humus,
which is organic matter in an advanced stage of decomposition. If the
organic materials are sufficiently intact to allow identification, it
is called peat. However, if it has undergone sufficient decomposition
for identification to be impossible, it is called muck. Peat is
classified according to origin into five general classes: woody,
fibrous, moss, sedimentary, and colloidal (58). Buckmnan and Brady (7)
divided peat into three classes: sedimentary, fibrous, and woody.
They reported peat to have a bulk density of 0.20 to 0.30 g. per cc.
and surface soils a bulk density of 1.25 to 1.45 g. per cc.
Since densities of peat vary greatly, rates of application
should be measured by volume rather than by weight for research
purposes (11). Richer et al. (50) found that a mixture of peat and
sand containing 14$ peat on a dry-weight basis gave a mixture that was
approximately 35% peat by volume. The water-holding and nutrient-
holding capacities of organic matter wrere reported to be high (1, 39,
It was reported that sedimentary and colloidal peat have high
moisture capacities, hold water tightly, and dry out slowly. W~hen dry,
they absorb water slowly, remain in a hard and lumpy condition, and even
small amounts added to other soils produced undesirable soil conditions
(7). Undecomposed, fibrous, and woody peats are often used as soil
additives and it was reported that mucks have been employed with
satisfactory results (7, 25, 59, 50).
There has been increasing interest during recent years in
materials to replace or supplement organic material in soils for golf
greens. One of these materials is exfoliated vermiculite.
Ciw-inn (20) defined vermiculite as hydrated magnesium silicates
formed by hydro-thermal alteration of biotite and phlogophyte mica.
He reported that this material expanded up to 20 times its original
volume upon heating and that exfoliation was produced most success-
fully between 1600 and 20000 F. Exposure of the ground vermiculite
ore to heat of the above temperature for periods longer than 4 to 8
seconds removed the combined water and produced a material that was
permanently brittle. Expanded vermiculite has considerable exchange
capacity and excellent water-holding ability (15). Bulk density
ranges from 6 to 10 pounds per cubic foot writh the finer grades having
the highest densities. Friedmann~(15) gave an excellent review of the
development of the vermiculite industry and its non-agricultural and
Another material that can be used as a soil amendment or top
dress for golf greens is crushed, fired clay. Very little popular or
technical data concerning this material as a soil conditioner have been
published. Investigations are now being conducted at Purdue University
in which fired clays are being studied as soil additives and soil sub-
stitutes for golf greens (69). In a Wyandotte Chemicals Corporationf
brochure, it is reported that this material, granulated calcined
montmorillonite, holds and releases both nutrients and water, has
penaanent structure, and is not toxic. In an extensive study of the
physics and chemistry of clays, Searle and Grimshaw (56) explained that
clays are calcined by heating to a red color or beyond and that this
process changes the structure, volume, density, strength, color, and
other physical or chemical characteristics of the clay.
A number of other materials that have been used as soil amend-
ments are spent mushroom soil and cocoa shells (2, 50), wood chips (SS),
sawdust (2, 33), corn hulls and corn gluten feed (70), perlite (21),
carbon black (10), and fused cinders (39).
bChemical and physical properties of vermiculite. G-81,
Zonolite Company, Chicago, Ill. 14 pp. 1954.
Turface, soil supplement for golf course use. Bul. S-31,
W~yandotte Chemicals Corporation, J. B. Ford Division, Wyr~andotte,
M*ich. 5 pp. 1959.
Use and Effects of _'-2-17' S il
Amnenim~ents uFO n Cil
In or or to maintain a vigorous turf under here~- traffic,
putt'r *- greens are usually constructed of specially prep re- cils
S-e 1scl normally ar marle r t-: one or more min ral r
r trial into tile native soi. It is -, r 2 ~y
role of sand in a gren nixtur is to incres caLr in 11 .i~on
Sr tion, aeration, and to Cecrea~se Soil. c~pGte (, ,
Lunt ( ) stac t.a r~
in .. need 'oy the 'icle sit
cf scil. iFurt .aermore, he nct -
be uc, in a putting- I ?en mix
dr in :~ se: 1 rl;ir
3t~~ ;1 :ii~ n oio wn: r-he:
Dr~icle sie der sn. In d
\;.,ir to o ..t we -' r
compaction is mini- : .:.en
mixture r.. in particle siz
- .er ar. ai
cf the sand
that th~e ch
th sc i .
v of "c,-a
aeti n. It
to O.. a
. n r~
Sit sinould mu
, littl 1 tu
capaci +y ann re luces
tia s v 10~-m isture
JIL ? a
nL (2 i:
particle size fractions should be coarse silt > fine silt > clay
> fine sand > coarse sand. Tanner and Mamaril (62) of Wisconsin found
that animal traffic caused no significant compaction of a coarse silt
soil. They added, however, that this soil wras normally of poor struc-
ture and without aggregation.
Golf green mixtures that contained 2 to 4$ clay by weight
compacted less and were superior to mixtures containing larger percent-
ages of clay (24, 29). Howard (24) of Texas found that montmorillonite
sources of clay in putting-green mixtures produced higher clipping
weights and a better quality bentgrass than either illite or kaolinite
sources. Montmorillonite and illite clays are expanding clays that
have greater cation-adsorption capacities than kaolinite (7). Lutz
and Leamer (56) studied the effect of swelling of colloids on perme-
ability and found that expanding colloids may decrease permeability
by clogging the soil pores. This was confirmed by Jamison and Kroth
(28), who noted that clay added to sandy soils increased both total
and available water, but the addition of clay to silt reduced the per-
centage of available water in the latter.
The use of colloidal phosphate and ground rock phosphate as
soil amendments has been limited. Both materials reduced wetting time
of Florida sandy soils more effectively than sources of clay (26).
HowJever, a minimum of 5 tons per acre of either material was required
and 25 tons gave the most satisfactory results.
Investigations by Westveld (71) indicated that application of
colloidal phosphate up to 25 tons per acre had no significant effect
on the exchange capacity of a sandy soil, but did increase the milli-
equivalents of exchangeable bases present. The addition of 5 tons per
acre of colloidal phosphate caused the greatest increase in large
pores but none of the applications increased total pore space. Colloi-
dal phosphate had a definite buffering action upon the sandy soil and
increased the pH slightly. Furthermore, it was noted that the moisture
equivalent was raised nearly 24 by the addition of the colloidal phos-
phate and that response of pine seedlings to fertilizer treatment was
greater where colloidal phosphate or peat was present.
A study of more recent literature indicated that the presence
of 7 to 209 by volume of a coarse organic material in greens mix pro-
duced better greens than higher additions of this material (16, 24,
29, 55). Garman (16) found that a soil-sand-peat mixture containing
209 peat by volume and 8.29 clay by weight had a hydraulic conductivity
of 0.8 inches per hour. He felt that this value, which was four times
that of the 1-1-1 volume-ratio mixture, was satisfactory for golf
greens. It has been found that excessive use of peat for greens
construction causes soils to be soggy and to lose their resiliency.
Furthermore, it was noted that as decomposition of the peat progressed,
a tight, gummy, almost water-tight structure developed (39).
Sprague and Marrero (59) conducted a greenhouse experiment to
evaluate the relative value of several types of organic matter for the
growth of bentgrass. They found that, on sandy soils, European peat
resulted in greater increase in water-holding capacity and pore space
than the other sources of organic matter tested. European peat decayed
more rapidly than peat from cultivated fields, spent mushroom soil,
Michigan peat, or well-rotted manure. Best results on New Jersey sandy
soils were obtained w~ith cultivated peat and spent-mushroom soil.
In 1956, Feusted and Byers (11) concluded that imported sphagnum peat
conserved water better than sedge peat or cultivated reed peat in
putting-greens soils. However, they did not recommend the use of peat
as a soil amendmtent for the sole purpose of conserving a supply of
available moisture. This was in agreement with Jamison (26) who found
little relationship between percentage of available water and organic
matter content of soils low in clay. He noted that anyr small benefit
such as source of nutrients or structural improvement may be more than
offset by a decrease in wettability of the soil mix.
Free et al. (14) reported that the least compaction occurred
in cultivated plots containing the most organic matter. It was noted
also that soils containing more organic matter compacted at a higher
moisture percentage than those lower in organic content.
Friedmnann(15) reported that Florahome peat from Florida had a
total base exchange capacity of 200.0 me. per 100 g. Buckmnan and
Brady (7) showed a range of 183.8 to 265.1 me. per 100 g. exchange
capacity for woody peat. The nutrient content of organic matter varied
with the type and source of material (2, 7).
Sawdust applied at 150 tons per acre to coarse-textured soils
decreased soil-moisture fluctuations, but failed to increase corn
yields during a 4-year study (9). Lunt (35) compared the use of a
number of sources of sawdust and wood chips and found the latter to
be slightly more effective than sawdust as a soil conditioner for
Friedman?(15) reported on the use of vermiculite as a soil
conditioner. He found that this material increased exchange capacity,
exchangeable magnesium, the moisture equivalent, and the potassiun
content of the soil mix. No change was noted in pH or exchangeable
calcium by the addition of as much as 50% vermiculite by volume.
He found that the vermiculite used in his experiment had an exchange
capacity of 34.2 me. per 100 g. Th~e Zonolite Company,a however,
reported their vermiculite to have an exchange capacity of 19.4 to
22.4 me. per 100 g., depending upon source. It was noted that the
total amount of water held by venticulite ranged from 23 to 41$ by
volume, with the finer material holding the most water. Hagan and
Stockton (21) stated that vermiculite held more water than other
inorganic amendments studied, but that its mechanical strength was low.
They added that if it were kept wet, vermiculite would soon slack to
a "pasty mess. Garman (16) noted that a mixture containing 20% ver-
miculite by volume and less than 95 clay by weight produced a favorable
greens mix. In addition, he found that a vermiculite-soil-sand mix-
ture in a 1-1-1 volume ratio showed higher permeability and more
resistance to compaction than a peat-soil-sand mixture in the same
AChemical and physical properties of vermiculite. G-81,
Zonolite Company, Chicago, Ill. 14 pp. 1954.
Information is very limited concerning the use of fired clay
materials in soil mixtures. Wya-ndotte Chemicals Corporationa recom-
mended the use of their material at the rate of 50 pounds per cubic
yard of soil as a soil conditioner for golf green mixtures. They
reported that granular fired clay improves aeration, water infiltra-
tion and percolation, and reduces compaction.
Soil Structure and Plant Growth
In attempts to maintain the productivity of greens soils, many
soil amendments have been utilized. The primary purpose of these amend-
ments has been to prevent soil compaction which occurs in the upper
1 1/2 inches of greens soils (54). Kunze (29) and Howard (24) studied
the effect of mechanical compaction upon physical soil conditions and
upon growth of fine turf grasses. They both noted significant positive
correlations between noncapillary porosity and weight of clippings
A study of the effect of mechanical impedance and aeration on
the growth of seedling roots of barley showed that reduction of oxygen
reduced the rate of root growth of confined and unconfined roots, and
that impedance caused macroscopic deformation of roots (17). Taylor
(63) showed conclusively that oxygen diffusion is strongly affected by
the degree of compaction and by the moisture content of the soil.
Baver and Farnsworth (4) reported sugar beet losses of nearly 50% on
6Turface, soil supplement for golf course use. Bul. S-31,
Wy~andotte Chemicals Corporation, J. B. Ford Division, Wyandotte,
Mich. 5 pp. 1959.
soils in which noncapillary porosity was less than 2% and normal pro-
duction where the air capacity was 8;g or above.
Page and Bodman (42), in an excellent review of the mechanics
of soil aeration and its effects on root growth and nutrient uptake,
noted that deficient oxygen in soil limits normal plant growth, exten-
sion of roots, development of root hairs and, hence, affects the up-
take of nutrients. Peterson (45) and Russell (53) have written exten-
sive reviews concerning the relationships between soil air, roots,
Favorable air and water movement through soil is required for
the growth of good turf (39). Permeability of soil is related to the
pores drained at the flex point, the tension at the flex point, the
size distribution of the pores, and the continuity of the pore space
(40). When oxygen is limiting, water transmission characteristics of
soil affect root growth and the effect is most pronounced in the 1 to
3 atmosphere (atm.) tension range (18). Wilcox (72) reviewed factors
affecting moisture-hc~ding capacity and stated that a pore 10 microns
in diameter is the largest that will normally hold water and that the
depth of the column of soil above the water table is important.
Russell (54) hypothesized that most water use by plants occurs
at continuously decreasing soil-moisture percentages which are inter-
rupted by sudden returns to field capacity or above. Stanhill (60)
reviewed 80 papers concerned with soil moisture. He found plant growth
responses to differences in soil moisture in 66 of the papers, and with
one exception, greatest yields were associated with the wettest regimes.
Lawton (31), however, found that an increase of moisture content to
a high level caused a reduction of both tops and roots of corn in a
greenhouse experiment and a decrease in the percentage of potassium,
nitrogen, calcium, magnesimm and phosphorus in the plant. He found
that a reduction of pore space through compaction reduced root growth
and decreased potassium and phosphorus in the plant. Compaction
resulted in a greater reduction of plant growth than did high soil
moisture. It has been reported that compaction produced greater
reduction of aggregation than waterlogging (25).
The most immediate effect of either lack of aeration or com-
paction is the physical restriction of root growth. Bryant (6) grew
barley plants in Hoagland solution and found that roots were longer and
slimmer with aeration than without and although lack of aeration
resulted in a greater number of short leaves, its greatest effect was
upon roots. These findings generally agreed with those of Loehwing (32)
who grew soybeans and sunflowers in continuously aerated sand and soil
cultures. He noted that aeration produced fibrous root systems,
increased the uptake of nutrients and produced smaller top-root ratios
than non-aerated soils. Too rapid aeration, however, caused a depres-
sion in plant growth.
Veihmeyer and Hendrickson (67) obtained results which indicated
that soils resisted the penetration of sunflower roots into layers
compacted to relatively high densities. Although density varied be-
tween soils, in no case did they find roots entering soils of bulk
density greater than 1.9 g. per cc. They added that the limiting
factor was the size of the pores rather than the total porosity.
Flocker et al. (12, 15) grew tomatoes and potatoes on Yolo fine sandy
loam and found that roots in non-compacted plots penetrated the layer
from 18 to 50 inches more extensively than roots in compacted areas.
As the bulk density of the soil increased from 1.0 to 1.6 g. per cc.,
yields decreased steadily and shallowa-rooted plants were more severely
affected than deeper-rooted ones. Kunze et al. (3C), however, found
bulk density to be an unsatisfactory measure of grass-producing poten-
tial of soil mixtures for golf greens. They indicated that noncapil-
lary pore space is a better gauge of productivity and that 10 to 15%
noncapillary pore space measured at 40 cm. tension is sufficient for
good grass growth.
This study was initiated in June, 1959, on the turf research
area of the Florida Agricultural Experiment Station at Gainesville.
Four materials were selected as soil amendments for this investigation:
Number 2 vermiculite (TPerra-lite6), colloidal phosphate (Lonfosco ),
crushed calcined montmorillonite clay (Turface ), and European peat.
Hereafter, Terra-lite will be referred to as vermiculite, Lonfosco as
colloidal phosphate, Turf ace as fired clay, and European peat as peat.
These amendments were mixed with Arredondo loamy fine sand, the
native soil of the turf area. The particle size distribution of this
soil and that of colloidal phosphate, as determined by the hydrometer
method (5), is shown in table 1. Sieve analysis of the sand fraction
of the Arredondo soil is shown in table 2.
Table 1--Particle size distribution of Arredondo loamy fine sand
and colloidal phosphate as determined by
the hydrometer method.
MIaterial Sand Coarse Fine Clay
fine sand 88.00 3.95 0.45 7.60
Colloidal phos. 5.50 44.00 16.70 34.00
BSupplied by Zonolite Company, Travelers Rest, S. C.
Supplied by LonCala Phosphate Company, High Springs, Fla.
Supplied by Jyandotte Chemicals Corporation, RJyandotte, MIich.
MATERIALS ANTD METHODS
Number 2 expanded vermiculite has a density of 4 1/2 to
7 pounds per cubic foot and 20 to 80$ is retained on an 8-mesh sieve,
75 to 994 on a 16-mesh sieve, and 90 to 100% on a 50-mesh sieve.a
The density of the fired clay was 38.5 pounds per cubic foot and sieve
analysis of this material is shown in table 2.
Table 2--Sieve analyses of the sand fraction of Arredondo
loamy fine sand and of fired clay.
Particle size distribution in mm.
5-2 -11-0.5 0.5-0.25 < 0.25
Sand 0.0 0.6 7.9 39.9 51.6
Fired clay 15.1 47.9 30.5 8.4 0.5
The total exchange capacities of the materials used in the
soil-amendment mixtures, in milliequivalents per 100 g., were as
follows: venniculite 57.46, colloidal phosphate 8.24, fired clay 19.81,
and peat 107.80.
A split-plot design with two replications was selected.
Depths to which treatments were mixed into the soil, O to 6 inches
and 0 to 1;2 inches,formaithe main-plots. Materials and rates, in a
3 by 5 by 2 by 2 factorial arrangement formed the sub-plots.
Chemical and physical properties of vermiculite. G-81,
Zonolite Company, Chicago, Ill. 14 pp. 1954.
The following percentages of materials by volume were utilized as
Vermi-ulite O, 10, and 20%
Colloidal phosphate O, 5, and 109
Fired clay O and 10%
Peat 0 and 10%
A complete description of the 36 sub-plot treatments, with codings,
is given in table 3.
& The total experiment, covering an area 148 feet long and
70 feet wide, was divided into tw~o equal blocks separated by a 2-foot
alley. Each block was split into two main-plots, 36 by 70 feet in
size, separated by a 1-foot alley and randomized for depth of mixture
treatments. For convenience of construction and maintenance of the
sub-plots, each main-plot was divided into three panels, 18 by 36 feet
in size, with an 8-foot drive between panels. Each of the panels was
then divided into twelve 6 by 9-foot sub-plots. Amendmnent treatments
were randomized within each main-plot utilizing Snedecor's (57) ran-
domly assorted digits. The complete plot layout for this experiment
is shown in figure 20, appendix.
-p~reen Construction and Turf Planting
Before staking of the plots, the entire area was plowed with
a tractor-draw~n, three-bottom, moldboard plow to a depth of 6 inches.
Then the upper 6 inches of soil was removed from the 12-inch depth
treatment area by use of a scraper attached to the rear of a Model 350
Table 3--'!oliure nf ver ieul ite, crllab21a rAcemate, fire cl: ,
peat, and soil utr1i ;ec in sui-CIn t~reatmentr.
Treatment Verric- Coll ida1 Fired :
1 C- O- 0- i. C 0 .
2 1 C- C- 1 rl
5 I1 5- "- 1 ,
8 ~ 1 -1 1 ~ l
i -1 ii- O1.Ci
10 0- -1C -; 10
11 1 C-1 `- G 113~
12 : i -1
13 c- E -1 1 5
ii LC~1- E-i-1 0 -5
1_7 ~1 -1 -1- i Cl1
ii-i -1C- -1 "
S- C- -1C 0o'
2 ~ 5- -10 ~
-1. -3_' C-1C Ii.1
-1 --. 23ie
2 I:- -1 -I -i1
S -$ -1~ -';
O- t -1CI -
32 1 -
21- 8-13i -' I
-1 1il -b ;
International tractor. This soil was stockpiled until it could be
used to refill the excavated area.
Following hand-leveling of the bottom of the excavated area
with shovels, the soil was loosened an additional 6 inches with a
24-inch Howaard Gem Rotovator. Sub-olots were then staked for the
application of amendment treatments.
When a treatment involved the use of two or more amendments,
they were thoroughly mixed before application. It was necessary to
shred the peat in order to facilitate the mixing with the soil and
other amendments. Superphosphate was added at the rate of 1 ton per
acre to all sub-plots, except those receiving colloidal phosphate.
The analysis of the colloidal phosphate was guaranteed at 18% total
phosphoric acid and not less than 2% available phosphoric acid. These
phosphorus materials presumably supplied adequate amounts of this
nutrient for good growth of grass in all plots.
The amending treatment wJas spread evenly over the specific
sub-plot area. Then the dry amendments were thoroughly mixed into the
moist native soil by rototilling twice to a depth of 6 inches.
Upon completion of the mixing of the lower half of the 12-inch
main-plot treatment, the entire experimental area was leveled by adding
soil to the excavated area. Dolomitic limestone was applied at a rate
of 1/2 ton per acre and disked into the surface 2 inches of soil.
Amendments were incorporated into the upper 6 inches of all
main-plots in the same manner as previously described for the 12-inch
main-plots. After all treatments had been completed, 9-inch strips
of building paper were placed along the plot borders across the slope
to a depth of 6 inches in order to separate the plots and prevent
Prior to the addition of amendments, laboratory examination of
a composite sample of the native soil for nematodes showed a low to
moderate number of sting nematodes. Since all the amending materials
were sterile, the experimental area was not sterilized preceding
From July 2 to 7, 1959, the sub-plots were sprigged with
Tifgreen (Tifton 528) bermudagrass. This grass has been described as
best of several Fl hybrids, involving Charlotte bermudagrass (Cynodon
dactylon) and African bermudagrass (Cynodon transvaalensis) (22).
Maintenance of the Green
The maintenance practices were those generally used in the
maintenance of putting greens of golf courses. They consisted of
frequent mowing, regular applications of fertilizer, chemical weed
control, use of insecticides for armywJorms and webworms, and renova-
tion. After the grass was established, watering was usually limited
to rainfall and irrigation directly following fertilizer applications.
The first broadcast application of fertilizer was made July 27,
1959, and-consisted of 44 pounds each of N and K20 per acre. The source
of N was ammonium nitrate and potassium sulfate was used as a source
of K and S. Thereafter, fertilizer was applied at approximate, 17-day
intervals with alternate application of ammonium nitrate and 15-0-15
fertilizer. This provided, during a period of 1 year, 914 pounds of
N and 491 pounds of K20 per acre. All fertilizer applications were
made with a hand-operated, 36-inch Gandy fertilizer spreader.
The experimental green was first mowed on August 17, 1959.
Thereafter, it was mowed regularly on a 2 to 3 day schedule unless
unfavorable weather conditions reduced the growth of grass. After the
first mowing at a 5/8-inch clipping height, the height of cut was
reduced to 3/8 inch for a month and then lowered to 1/4 inch. With
few exceptions, mowing was done with a 20-inch gasoline-powered,
Model W~P2, West Point Atco putting-green mower. All clippings were
removed from the plot area.
To control crabgrass and broadleaf weeds, a mixture of di-
sodium methyl arsonate (Di-Met) at 6 quarts per acre and 2,4-D at
1 pound of active ingredients per acre was applied on July 27, August 3,
September 4 and 10, 1959. Because of the deposition of weed seeds by
winds during the winter months, it was necessary to treat the entire
area with 2,4-D to control broadleaf weeds on Miarch 24, 1960. The plots
were treated for sod webworms on October 7 and 30, 1950 and for army-
worms on June 7, July 5, August 12 and 15, 1960.
The plot area was renovated on July 20, 1960, to remove the
1/2- to 3/4-inch thatch that had developed. Approximately 20 cubic
yards of thatch were removed. The renovated area was not topdressed
and although the plots were brown, the loosened, amended soils gave a
satisfactory putting surface. Eight days following completion of
renovation, coverage by grass was nearly complete and clipping weights
were taken on August 4.
Grass samples were collected, oven dried and weighed for yield
determinations on each of the following dates: October 2=, November 5
and 23, 1959, April 26, May 12, June 1 and 27, and August 4, 1960.
After cutting 10-inch borders from the ends of the sub-plots, samples
were collected from 20 by 88-inch center areas of each sub-plot.
The clippings from each plot were oven dried at 1800 F. and weighed to
the nearest 0.1 g.
The rate of coverage of soil mixtures by bermudagrass was
determined on August 18 and 29, 1959, by the Double-Quadrat (D-Q)
method as devised by Nutter et al. (41). Values obtained from lateral
extension and density were given equal weight and combined into a
single growth-index value.
Purf quality evaluations were made August 25 and December 29,
1959. Both density and color were considered and combined to give
single values. Because of uniformity of appearance, quality evalua-
tions were very difficult to make. The rating scale used for the
August 25 evaluations w~as as follows:
1 Very poor condition 4 Good condition
2 Poor condition 5 Very good condition
3 Fair condition 6 Excellent condition
It was possible to use only four values in the December 29 evaluation
and they were:
1 Poor condition 3 Good condition
2 Fair condition 4 Very good condition
Each time turf quality or other visual data were taken, ratings
were determined by first selecting the best and poorest sub-plots.
Values, the highest and lowest, respectively, were assigned to these
sub-plots and the remaining sub-plots were given intermediate values
between these extremes.
Drought resistance ratings were taken May 19, 1960, 16 days
after a 1-inch rain and 7 days after a light irrigation. Also, plots
had received 44 pounds of N per acre 1 week preceding rating. Evalua-
tions by three individuals were made and averaged, using the following
1 Severe damage 3 Slight damage
2 Moderate damage 4 No damage
Seedhead prevalence was evaluated on June 1, 1960, and the
rating scale used was as follows:
1 Very many 4 Few
2 Many 5 Very few
3 Some 6 None
Total weight of bennudagrass roots in 347 cc. of the top
3 inches of amended soil was obtained by using a core sampler similar
to the one described by Uhland (66). The roots were separated from the
mix by gently sieving through a 4.76 mm. sieve. They were then allowed
re scci < Io
trater a tP .
-- -- ,ly urs in, I
o: th~e neares
diepth in the various miixt
10 tubCe incePs intio t~h
mi. bec 'crr fille
i writh! t:p
ulreS was evaiil
g~anic tnd nuitrient
t soil .i~SS ,~
Icr~ ~~ to tiell,
to 6 inc!
i been a
yea 1 r.
inei~ in 1
ea~ich 4- e
~i u- "
.oi ri 3
Lr ar a
In nini.: rlol.
:s ~ 1 I;r ard
rr. sit i ::e n ~
phosphorus and potassium.~
Total exchange capacity was determined on soil mixtures and
amendments by the ammonium acetate (pH 6.8) method as described by
Russel and Stanford (51) and modified by distilling the ammonia into
4% boric acid solution containing mixed indicators.
Organic matter evaluations of 1959 and 1960 samples were made
using a modification of the method proposed by Walkley and Black (68).
One-gram samples were oxidized with potassium dichromate in the presence
of sulfuric acid. The excess dichromate was titrated against standard
N ferrous sulfate using orthophenanthroline as the indicator, in the
presence of phosphoric acid.
Compaction tests were made on mixtures from composites of six
individual staples taken from each sub-plot of the first replication.
Samples were taken with a 4-inch putting-cup hole cutter and compacted
at different moisture percentages. The samples were compacted in a
cylinder having a 4-inch inside diameter and a 4.58-inch height with a
5.5-pound rammer dropped from a height of 12 inches (1). Bulk densi-
ties and moisture percentages for compaction evaluations are reported
on an oven-dry weight basis.
Zones of soil compaction were determined with the Cornell
penetrometer (64). Three probes per sub-plot were made and the read-
ings averaged. Readings for maximum force needed for penetrating
BIreland, H. L. Methods of analysis used in soil testing.
Dept. of Soils Mimeo Report No. 58-3, Florida Agr. Exp. Sta. Gaines-
ville, Fla. 24 pp. 1957.
0 C"c '
Percolation rates were determined by removing the soaked core
samples from the vacuum dessicators and placing them on a permeameter
rack. WJater was maintained over the samples at a 1-inch depth until
permeability studies were completed (66). Percolation for each core
was evaluated twice for a period of 10 minutes and the temperature and
the amount of leachate recorded. The results of the two observations
were averaged and hydraulic conductivity calculated according to
Darcy's law (46). Intrinsic permeability, also, was calculated from
these data (46).
A pressure plate apparatus and procedures similar to those
described by Richards (48) were used to determine the moisture re-
tained in the samples at 50 cm. of water tension. Capillary and non-
capillary porosity determinations were made on a volumetric basis.
Separation of the two was made on the basis of the amount of water
retained by a sample subjected to 50 cm. of water tension (52). Total
pore space percentages were obtained by sunrming the percentage of
capillary and noncapillary pore space. Procedures, as described by
Uhland (66), were used to obtain noncapillary pore space, which is the
difference in weights of the cores saturated and when at equilibrium
with 50 cm. of water tension. The difference in weights of soil mix-
tures when dry and at equilibrium: :ith 50 cm. of water tension was
used as a measure of capillary pore space.
Following removal from the pressure plate the samples were
weighed and an aliquot of each sample was oven dried at 1050 C. in
order to find the percentage of moisture that the mixture held at 50 cm.
of water tension and to calculate bulk density. It was necessary to
multiply all moisture data by bulk density to obtain pore space and
moisture percentages on a volume basis. After removal of the aliquot,
samples were sieved through a 4.76 mm. sieve to remove bermudagrass
roots and, then, stored in plastic bags for further moisture retention
The disturbed samples from the sieved cores were placed on the
pressure membrane apparatus (47) where water retention percentages at
5 and 15 atm. levels were measured.
The percentage of available wJater for plant growth was found
by subtracting the percentage of water held at 15 atm. pressure from
the amount held at 50 cm. of water tension. These two latter values
represent pennanent wrilting point and field capacity, respectively.
Thne relationship between yield and quality of Tifgreen
bermudagrass was evaluated and found to be positive. Then, these two
measurements w~ere combined into a yield-quality index. To obtain this
index, yields and quality ratings of the 36 soil treatments were con-
verted to relative values based upon the assigned yield and quality
ratings of 100 for turf grown on the native soil plots. These two
values were then summed and divided by two, to give an average yield-
quality index for each plot. O~nly soil properties which appeared to
have an effect on the growth of turf under the conditions of this
experiment were selected for regression studies.
Data for turf evaluations, clipping weights, and physical and
chemical soil determinations were punched on cards and IBMI equipment
was used for the computation of sums and sums of squares for the analysis
of variances. The format for analysis where time was not involved was
standard for a split-plot experiment (57). However, when treatments
were averaged for two years in the analysis of variances, the format
was as described by Steel and Torrie (61) for split-plot experiments
in time and space. As the mean square for each single degree of free-
dom in the analysis of variance for experimental data w~as available,
each was evaluated for significance and discussed where pertinent.
The relationship between yield and quality of Tifgreen bermudagrass
was established by correlation,while the dependence of the yield-quality
index upon soil conditions was evaluated by regression procedures (57).
RESULTS AN~D DISCUSSION
Field and laboratory data collected throughout the year of
experimentation are grouped and discussed according to the type of
measurement and presented in the following order: effects of soil
amendments on quantitative and qualitative turf evaluations and on
physical and chemical properties of the soil, and the effects of
selected soil properties upon growth and quality of bermudagrass on
Basic data and analyses of variance tables are found in the
appendix, starting wJith table 13. Effects that are statistically
significant are hereafter referred to as follows: significant, 0.05
level of probability; highly significant, 0.01 level of probability;
and very highly significant, 0.001 level of probability.
The relative comparisons of 35 soil mixtures to the native
soil for dry matter production, quality, seedhead prevalence, and
drought resistance of Tifgreen bermudagrass are sho~n? in table 4.
Since Arredondo loamy fine sand, which was used as the basic soil
for this experiment, is a better than average soil for putting greens,
the bermudagrass grew exceptionally wJell on all plots. Thus, eval-
uation of the effects of soil amendments on turf growth and quality
was exceedingly difficult. The relative advantages of treatment
combinations were less apparent than they would have been if builders
Table 4--Relative dry matter production, quality, seedhead prevalence,
and drought resistance of Tifgreen bermudagrass grown on
36 soil treatments; treatment 0-0-0-0 equals 1008.
Treatment Dry Quality$ Least Drought
codel matter seedheads4 resistance
0- 0- 0- O 100 100 100 100
10- 0- 0- O 103 115 150 175
20- 0- 0- O 108 95 130 275
0- 5- 0- O 102 110 170 275
10- 5- 0- O 106 105 180 350
20- 5- 0- O 105 100 180 275
0-10- 0- O 106 115 190 325
10-10- 0- O 103 105 160 300
20-10- 0- O 116 115 180 300
0- 0-10- O 91 85 90 175
10- 0-10- O 104 110 130 225
20- 0-10- O 101 110 140 250
0- 5-10- O 101 105 180 275
10- 5-10- O 98 105 170 275
20- 5-10- O 99 95 150 275
0-10-10- O 94 75 120 225
10-10-10- O 94 100 140 275
20-10-10- O 102 105 130 500
0- 0- 0-10 94 80 110 175
10- 0- 0-10 106 100 120 275
20- 0- 0-10 104 120 140 225
0- 5- 0-10 101 95 140 250
10- 5- 0-10 102 120 200 300
20- 5- 0-10 98 130 200 325
0-10- 0-10 99 110 190 325
10-10- 0-10 110 125 170 275
20-10- 0-10 111 130 170 300
0- 0-10-10 102 100 110 250
10- 0-10-10 96 105 130 200
20- 0-10-10 99 110 110 275
0- 5-10-10 96 100 120 500
10- 5-10-10 103 125 140 300
2C- 5-10-10 103 115 150 350
0-10-10-10 97 105 110 300
10-10-10-10 106 120 100 300
20-10-10-10 106 110 120 250
Vermiculite-colloidal phosphate-fired clay-peat; percent
added by volume.
2Eight clipping periods.
43uality; August 5 and December 29, 1959.
:Increasing values represent less seedheads.
'Increasing values represent better drought resistance.
sand or a nore sandy soil had been used as the basic material for
constructing the green.
Yield of bermudagrass
Yield data in table 15 indicate that variations in yields at
the eight clipping dates were greater because of seasonal conditions
than because of treatment. As shown in table 54, both vermiculite
and fired clay had highly significant effects on the total yield of
bermudagrass. Vermiculite produced an average 5% yield increase.
The 10k level of vermiculite was nearly as effective as the 20% in
this respect. The response to fired clay was surprisingly poor,
resulting in a decrease of 6$ in total dry matter yield of bermuda-
grass clippings for the eight sampling periods. It was observed that
plots containing fired clay had their lowest yield in the spring months,
while those containing venticulite gave a better than average increase
in yield during the same period (figure 1).
It appeared that 20% vermiculite in soil fixtures was superior
to 10% in increasing yields of bermudagrass during periods of soil-
moisture deficiencies. However, under standard irrigation practices
for putting greens, there appears little advantage in utilizing over
1QC vermiculite in soilmixtures to increase yield of bermudagrass.
Plots containing fired clay gave lowest yields during the drought
period but improved under higher moisture regimes. After renovation,
their average yield was higher than that of other plots. These re-
sults indicate that bermudagrass made a more rapid recovery on plots
containing fired clay than on those not containing this material.
I Qc CO
4 O c
O1 k 0 *H
k *8 ,0 k
r- H H I O MO,
o a I *He I I+- r
*H *H( 'O Q, H E
H n I H O
(?ua3ed) ~aT~ y e~aq*H
Examination of the single degrees of freedom for the inter-
action between depth and treatments in the analysis of variance for
yield (table 54), showed that a significant three-factor interaction
existed between depth, vermiculite, and peat. It was indicated that
mixtures containing peat and venticulite yielded better at the 12-inch
depth of mixing than they did at the 6 inch. At the 6-inch depth of
mixing, the addition of peat to mixtures containing vermiculite gener-
ally reduced the tendency of venticulite to increase yield over that
of plots not containing vermiculite. However, at the 12-inch mixing
depth, vermiculite in soil mixtures gave a lower yield than plots not
containing this amendment, unless peat was included in the mixture.
This latter combination of materials produced yields equal to, but no
better than, those from mixtures which contained neither vermiculite
nor peat at the 12-inch depth. With the exception of the aforemen-
tioned interaction, there was no significant difference in yields
from plots mixed at the two depths.
Bermudagrass root development in soil mixtures
Most plants develop extensive root systems, with the depth of
rooting and the concentration of roots in a given volume of soil de-
pendent upon soil conditions, as well as the genetic nature of the
plant. It has been noted that grasses grown on putting greens usually
have shallow roots (39). Therefore, it was deemed desirable to in-
vestigate effects of various soil mixtures on the quantityr of ro ts in
the top 3 inches of soil and the maximum rooting depth of Tifgreen
bermudagrass. Data for root weight and depth of rooting are reported
in tables 14 and 15, respectively, while analyses of variance for
these twro variables are found in table 56.
The mean root weight in the top 5 inches of soil was 0.56 g.
per 347 cc., which is equivalent to 0.54 ton per acre. Only colloidal
phosphate had a highly significant effect on root weight in this zone.
This linear effect may have resulted from the fact that increments of
colloidal phosphate increased capillary pore space and correspond-
ingly decreased noncapillary pore space (figure 10). This would
increase the water-holding capacity of the soil mixture and cause
some concentration of roots near the soil surface. Also, the increased
wettability of soils containing colloidal phosphate (26) could have
produced favorable moisture conditions for root development in the top
3 inches of soil. Samples for root-weight studies were taken during,
and immediately following, a period of less than normal rainfall,
supplemented by a minimum of irrigation.
Vermiculite, fired clay, and peat produced no significant root
depth response. However, with the exception of peat, each tended to
increase root content in the top 3 inches of soil (table 5).
Bermudagrass root penetrations were deeper in plots in which
the amendments were mixed to the 12-inch depth than in plots in which
they were mixed only 6 inches deep, with an average penetration of
25.1 and 18.4 cm., respectively. There was a trend for vermiculite
and peat to limit root penetration, while fired clay and colloidal
phosphate tended to increase depth of rooting. It w~as of interest to
note that the 5$ level of colloidal phosphate resulted in better root
penetration than the 10% level. This indicated that additions of
more than 5$ by volume of this material would likely reduce root
Table 5--Average effects of various amendments upon the yield
of Tifgreen bermudagrass roots in the top 5 inches
of soil mixtures; g. per 347 cc., 1960.
Dry weight of roots
Amendment Percent amendment added
O 5 10 20
g. g. g. g.
Vermiculite 0.54 0.60 0.56
Colloidal phos. 0.49 0.56 0.64
Fired clay 0.56 0.57
Peat 0.59 0.54
The depth of rooting response of bermudagrass to vermiculite
and colloidal phosphate varied as these two amendments were combined
in mixtures at different levels (figure 2). In the highly significant
interaction, mixtures containing 5$ colloidal phosphate and 20% vermic-
ulite produced the deepest rooting, while mixtures containing 5$ col-
loidal phosphate and 10$ vermiculite produced the shallowest rooting.
Treatments containing 10$ colloidal phosphate had deeper rooting than
those containing 5$, only when each was included in mixtures with
10% vermiculite (figure 2). It appeared that for maximum root pene-
tratSon of Tifgreen bermudagrass, colloidal phosphate and vermiculite
should be combined with caution.
10fg Colloidal phos.
20 5% Colloidal phos.
0 10 20
Figure 2--Average depth of rooting of Tifgreen bermudagrass
in soil mixtures containing by volume various
levels of vermiculite and colloidal phosphate,
19 60 .
I' r-id notlalis'r int of grass on putli.. gr in -"v
dsir .10 i. or ar to 3rLe th r< ~ O h ~il-- ;
frcr t i.. anc wfr :rsirn ,$i .O. iillii n -?l I;i
4 and 61 wesaftr.rl I .. aa c'r i ar FF1Ld :.
percent t 1a cover in :c'~l 1 and ~n ls of vaiarc n i
1k~ p ,rid are --- ... in t-l
iil Gc' r. grer n : .
of 493 and G b et viTrae at *:. *n G -.iks r tivei-
'JecTiculite3 and r--- t bt siffni 10 'ly in r / n orceni cc
at the 4-w~eek eval w ion oario a r effee ss of' aenrned
are sbo n in table G
--i 1 effect eS fa ricu ar FI l-ts un t -ii -r '1i
co of" scl rixt:re `''i? 1 -e r:
at 4; anc : .eks a:' ar 1
t'acks rnenc~ment F -rcen coverage of nihturnr
S *-,r1 r r-t armor tment 011:-i
O E 1 ?
By the end of 6 weeks, bermudagrass on the vermiculite and
fired clay plots showed very highly significant increases in percent
coverage, when compared to plots not containing these amendments.
However, bermudagrass response to the 10$ level of vermiculite was
nearly as great as to the 20$ level (table 6). Colloidal phosphate
gave a highly significant increase in percent coverage, while peat
had little effect. There was a significant interaction between fired
clay and colloidal phosphate. The inclusion of fired clay with 5k
colloidal phosphate increased percent coverage, but it was ineffective
when mixed with 10$ colloidal phosphate. Thus, in terms of rate of
coverage, there would seem to be no advantage in combining 10% col-
loidal phosphate and 10k fired clay in soil mixtures. Also, a signif-
icant interaction existed at the 6-week evaluation period between
vermiculite, fired clay, and peat, which indicated that fired clay
and vermiculite more effectively increased percent coverage in the
presence of peat than in its absence.
Quality of bermudagrass
Since yield and coverage present only a partial picture of
turf performance, turf quality ratings were also used as a means of
evaluation. These evaluations were made to estimate turf quality
during the periods of normal summer and winter growth.
Data for the estimated quality of bermudagrass during both a
summer and winter period are presented in table 17 and statistical
evaluations for the two periods are presented in table 35. Quality of
individual plots varied between the two seasons and several evalua-
tions probably should be made before establishing the superiority of
a treatment in regard to quality of turf production. Relative compar-
isons of 35 soil mixtures to the native soil for quality of Tirgreen
bermudagrass are shown? in table 4.
Vermiculite treatments produced a very highly significant
278 increase in quality during the summer evaluation period. However,
they had little effect upon winter quality. It should be pointed out
that during the summer period, 10% venriculite treatments were equal
to the 2056. Colloidal phosphate at the 5 and 10$ rates significantly
increased quality during the summer by 10 and 20%, respectively.
However, there was a trend for colloidal phosphate, at the 10$ level,
to decrease turf quality during the winter period.
While fired clay produced a significant 9%6 increase in quality
during the summer, it caused a very highly significant 24% quality
decrease during the winter period. Peat had a slightly positive
effect during both periods, and when present in mixtures with vermic-
ulite and/or fired clay, turf quality during the winter period was
considerably better than it was in its absence. The quality response
of bermudagrass to fired clay indicated that yield and quality of turf
are closely associated, since fired clay increased percent yield of
bermudagrass only when growing conditions were favorable.
Drought resistance of bermudagrass
The proper use of water on golf-course turf depends upon an
understanding of the water requirements of grass and the ability of
soil to supply water. Wihen surface soil is allowed to dry out to a
depth of 2 to 3 inches, grass roots tend to penetrate deeper into the
soil. Evaluation of grass quality was made in M~ay, 1960, after the
green had not been watered for 1 week. Data for the effects of soil
treatments on drought resistance of bermudagrass are shown in table 18.
During this period of comparatively high soil-moisture stress,
a mixture of 20% vermiculite, 5% colloidal phosphate, 10% fired clay,
and 10% peat was found to be superior to all other treatments. The
relative comparisons of 35 soil mixtures to the native soil for drought
resistance of Tifgreen bermudagrass are shown in table 4. Although
vermiculite gave a significant 4$ increase in quality, colloidal phos-
phate was much more effective in maintaining quality turf during the
drought period. The very highly significant 21% increase in turf
quality showed that colloidal phosphate could be a valuable amendment
in greens mixtures, either when irrigation facilities are limited or
as a means of reducing the need for frequent irrigation. Furthermore,
it was indicated that 5% colloidal phosphate by volume was as effec-
tive as the 10$ level under drought conditions. Peat and fired clay
were ineffective in maintaining turf quality during this period.
Statistical analysis for drought resistance is shown in table 36.
Depth of mixing influenced the response to all materials,
except vermiculite, and the 0- to 6-inch depth of mixing generally
Colloidal Phosphate (percent)
Figure 5--Average drought damage to Tifgreen bermudagrass
grown on soil mixtures containing by volume 0,
5, and 10$ colloidal phosphate mixed to 6 and
12 inches, 1960.
~1- severe damage, 2 moderate damage, 5 slight damage.
produced better quality turf than the 0- to 12-inch depth. In the
highly significant interaction between colloidal phosphate and depth
(figure 5), the curvilinear effect of the former was more pronounced
at the 0- to 6-inch treatment depth than at the 0- to 12-inch depth.
Seedhead prevalence of bermudagrass
Seedhead prevalence of bermudagrass on a putting green is a
detriment to a good playing surface. The development of seedheads of
Tilgreen bermudagrass was most noticeable during late spring and early
summer. Evaluations were made in early June, 1960, to determine whether
or not soil mixture treatments were effective in reducing seedheads.
Results are presented in table 19 and the statistical analysis of var-
iance for seedhead prevalence of bermudagrass is shown in table 36.
The relative comparisons of 35 soil treatments to the native soil for
seedhead prevalence of bermudagrass are shown in table 4.
Vermiculite tended to reduce the number of seedheads per plot,
but plots containing fired clay and peat had numerous seedheads. Col-
loidal phosphate, at the 5k level, gave a highly significant 24%
decrease, while the 10k was ineffective.
The combination of peat and fired clay resulted in a very
highly significant interaction which greatly increased development
of seedheads (figure 4). Peat, in the absence of fired clay, slightly
reduced seedhead numbers. Although fired clay increased seedhead
development, fewer seedheads were produced on plots containing fired
clay in the absence of peat than in its presence.
Fired Clay (percent)
Figure 4--Average seedhead prevalence of
dagrass grown on soil mixtures
volume varying levels of fired
clay and peat,
1l very many, 2 many, 5 some, 4 few, 5 very fewJ,
and 6 none .
Physical Soil Evaluations
Soil is the home of turf roots and the physical well-being
of grass greatly depends upon physical soil conditions. For roots
to be healthy, soil must be porous and well drained, but have good
water-storage capacities. Physical studies were made of the soil
treatments in an attempt to determine the effectsof vermiculite, col-
loidal phosphate, fired clay, and peat upon various physical soil
Perhaps as much as any other single factor, soil structure
determines the bulk density of soils of similar mineral and organic
composition. However, when amendments which have different specific
gravities and physical stabilities are added in comparatively large
quantities to a mineral soil, bulk density measurements alone are
likely to be misleading as a measure of soil structure.
All of the amendments, with the exception of colloidal phos-
phate, decreased bulk density. Bulk density data for treatments are
presented in table 20 and the significance of the effects of amend-
ments is shownm in table 37.
The 4 and 6% decreases in bulk density, resulting from the
inclusion of 10 and 20$ vermiculite in soil mixtures, were very highly
significant, but considerably less than the original bulk density of
vermiculite would indicate. Thus, it appeared that the physical struc-
ture of exfoliated vermicul-ite was not stable and that, in timne, the
internal pore space of this material collapsed.
Although the increase in bulk density in colloidal phosphate
mixtures was statistically significant, it was very slight. Both fired
clay and peat produced a very highly significant decrease in bulk den-
sity, wiith the former being slightly more effective in this respect
(table 7). Since fired clay has a low bulk density (0.60 g. per cc.),
the observed decrease in bulk density of mixtures containing fired clay
was of expected magnitude. In addition, it appeared that little phys-
ical deterioration of this material occurred. Although peat was found
to decompose rapidly during a 1-year period (figure 12), it continued
to decrease the bulk density of mixtures in which it was present.
Thus, it may be theorized that it had a tendency to stabilize aggre-
gation and improve soil structure.
Table 7--Average bulk density of soil mixtures containing
various soil amendments, 1960.
Amendment Average bulk density
Percent amendment added
O 5 10 20
g./cc. g./cc. g./cc. g./cc.
Vermiculite 1.47 1.41 1.37
Colloidal phos. 1.42 1.43 1.43
Fired clay 1.48 1.36
Peat 1.45 1.38
The most severe compaction in greens frequently occurs in the
top 2 inches of soil. A Cornell penetrometer was used to obtain infor-
mation concerning resistance to soil-mixture penetration at various
depths. Data for pounds of force required to penetrate soil mixtures
are reported (table 21) as maximum force needed at the 0- to 1-inch
depth and the average force needed at the 2- to 4-inch and the 7- to
10-inch depths. Analysis of variance for the force required at each
depth is shown in table 38. In figure 5, an example of the change in
penetrability writh depth for native soil and an amended soil is illus-
trated. The relative force required for penetration of the two treat-
ments reflects differences in both compaction and inherent moisture
content of the mixtures.
Although there was a 20% difference in the maximum force re-
quired for the easiest and the most difficult penetrations at a depth
of 0 to 1 inch, there were no statistically significant differences
due to treatment. This indicated that the four amendments used in
this experiment had limited value in decreasing the force required
for penetration of the surface of the native smady soil.
At the 2- to 4-inch depth, venriculite and peat produced a
very highly significant positive effect upon penetrability, while col-
loidal phosphate and fired clay caused no significant change. As
penetrability obtained by use of the Cornell penetrometer indicates
ease of root penetration, it would seem desirable to use those mix-
tures that can be penetrated with a minimum force.
Both vermiculite and fired clay were very highly effective in
increasing penetrability at the 7- to 10-inch depth. One-half of the
plots were mixed to a depth of 12 inches and the evaluation at this
depth w~as made to determine the effect of depth of treatment on
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penetrability. Several highly significant interactions were found
between depth and materials, which showed easier penetration in the
presence of soil mixtures than in their absence. Figure 5 shows that
native soil was more resistant to penetration than a mixture of 20$
vermiculite, 5$ colloidal phosphate, 10% fired clay, and 10$ peat.
It was of interest to note that disturbed native soil had greater
resistance to penetration than the undisturbed soil, while the oppo-
site was true of soil mixtures.
Bulk density and penetrometer studies indicated that campac-
tion had occurred in the 1-year period due to normal maintenance
practices. It is likely that they compacted less under the condi-
tions of this experiment than they would have under normal player
traffic of a golf course. Therefore, all mixtures were subjected to
compactability tests at varying moisture levels as described in the
section, MATERIALS AND METHODS. Because of the varying specific
gravities and physical stabilities of the amendments, the difference
between bulk density of mixtures (table 20) and the bulk density of
compacted mixtures (table 22), was used to estimate the campactabil-
ity'of mixtures, instead of absolute bulk density.
Mixtures containing 10 and 209 vermiculite compacted slightly
more than those without vermiculite. Those containing 0 and 10% ver-
miculite had the greatest change in bulk density at approximately the
same moisture content (figure 6). Although mixtures containing 20%
,C O ,D
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O *8l v00
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vermiculite had a slightly greater change in bulk density than either
the 0 or 10% level, they were at a 4$ higher moisture level at maximum
change in compaction. As the 20% vermiculite mixtures would less
likely be subjected to moisture conditions optimum for maximum com-
paction, they might compact less under player traffic than mixtures
containing less than 20%.
The changes in bulk density at different moisture levels of
soil mixtures containing colloidal phosphate are shown in figure 7.
The 0 and 5% levels of colloidal phosphate were very similar in their
tendencies to compact, while mixtures containing 10%g colloidal phos-
phate had a somewhat greater change in bulk density at a slightly
higher moisture content. Compaction tendencies of mixtures contain-
ing colloidal phosphate, which is high in silt, partially supports the
beliefs of several wYriters (16, 19, 55, 59), who reported that silt in
greens mixtures provides little protection against compaction.
The mixing of 10% fired clay into sandy soils resulted in no
change in bulk density (figure 8). Mixtures containing fired clay
compacted at a 4% higher moisture content than those without this
material, with no change in bulk density. This indicated that this
material may have some value in preventing compaction of greens soils.
Soil mixtures containing peat compacted more readily at com-
parably higher moisture contents than those lacking this amendment
(figure 9). Peat, at higher rates than 209 by volume, has been found
unsatisfactory in preventing soil compaction on putting greens (16, 39).
However, at the 10$ level, it had little effect upon compaction.
*H 0 0
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As soil compaction of putting greens occurs with time, it is
possible that future penetrometer studies of these soil mixtures will
produce results similar to those found in compaction studies.
Pore space, that portion of soil occupied by air and water,
is a result of the interrelated influences of texture, compaction, and
aggregation. Total pore space is the simplest characterization of the
soil pore system. Although, in itself, total pore space is a poor
measure of soil aeration and water-holding capacities, the distribu-
tion of its components, capillary and noncapillary pore space, has
been successfully used in evaluating soil structure (52).
Average total pore space for individual mixtures varied from
42.8 to 54.7%. Complete data for noncapillary, capillary and total
pore space are presented in tables 23, 24, and 25, respectively.
Analyses of variance for total and capillary pore space are shown
in table 37.
The sum of capillary and noncapillary pore space equals total
pore space. Therefore, it is important to know the individual effect
of each component upon total pore space. Figure 10 shows the average
effect of each soil amendment upon the components, as well as total
pore space. In this figure, soil is treatment 0-0-0-0, while the 0%
level of an amendment indicates that the specific amendment was
absent from mixtures.
Vermiculite in soil mixtures produced a very highly signi'-
icant increase in total and capillary pore space. It is shown (fig-
ure 10) that 10% vermiculite slightly decreased noncapillary pore
space, while the 20$ level gave a slight increase. However, 10% ver-
miculite increased capillary pore space from 46.5 to 48.5%, while the
20% level was only 0.6% higher than the 10$ level of this amendment.
As expanded vermiculite makes an increased void volume without sig-
nificantly changing the size of platelets (20), it is believed that
the noted increase in capillary pore space and its effect upon total
pore space were primarily due to the physical presence of this
Colloidal phosphate gave a very highly significant increase
in capillary pore space, with only a significant increase in total
pore space. It is shown (figure 10) that each increment of colloidal
phosphate gave nearly a 2k increase in capillary pore space. However,
this amendment caused a decrease in noncapillary pore space from 11.39
to 9.3 and 9.1F%, at the 5 and 10% levels, respectively. It is hypoth-
esized that colloidal phosphate was effective in producing the change
in pore space in two ways: first, addition of colloidal phosphate
greatly increased the number of colloidal particles in soil mixtures,
which would favor aggregation; and secondly, the silt fraction from
this amendment probably filled some of the macro voids of the sandy
soil, thereby reducing noncapillary pore space.
Fired clay in soil mixtures produced a very highly significant
increase in both capillary and noncapillaryr pore space. Mixtures
.i : : : .. i: : .: : 0
HQ 0 r
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containing this amendment had 2.6% higher capillary pore space and
1.9% higher noncapillary pore space than mixtures which did not con-
tain fired clay. Because of the increase in both capillary and non-
capillary pore space, mixtures containing fired clay had the highest
average total pore space (figure IC). Fired clay, wJhich is compara-
tively large in size (0.25 to 5 mm. in diameter) and high in internal
pore space, was physically stable. Therefore, its effect was pri-
marily due to its physical presence and not to aggregation of soil
Peat was very highly effective in increasing total and
capillary pore space. Mixtures containing peat had 2.4 and 0.2$ higher
capillary and noncapillary pore space, respectively, than mixtures
which contained no peat (figure 10). It is hypothesized that the
effect of peat on pore space of soil mixtures was due to aggregation
and not to its physical presence. It is thought that saprophytic
organisms, wJhich live upon soil organic matter, physically bind soil
particles together, while biological decomposition of proteinaceous
material results in chemical bonding of organic materials and soil
Hydraulic conductivity is the ratio of the flow velocity to
the driving force for the viscous flowJ of water under saturated con-
ditions in the soil (5). Since this permneability or transmission
constant is a function of soil properties, particularly particle size
and the amount and nature of pore space, it has considerable value in
soil mixture evaluations. The rate of water flow through soil cores
was studied in July, 1960. Hydraulic conductivity and intrinsic per-
meability data are reported in tables 26 and 27, respectively. As the
same basic data were used for determining both variables, only hydrau-
lic conductivity was statistically analyzed (table 34).
Although increments of colloidal phosphate had a very highly
significant negative effect upon the rate of water flow, the 10% level
restricted the rate only slightly more than the 5% level. It was
noted that a difference of 2$ in noncapillary pore space in mixtures
containing 0 and 5% colloidal phosphate (figure 10) reduced water
transmission over 4 inches per hour (table 8).
Table 8--Average hydraulic conductivity of soil mixtures
containing various levels of amendments, 1960.
Amendments Hydraulic conductivity
Percent amendment added
0 5 10 20
in./hr. in./hr. in./hr. in./hr.
Vermiculite 7.39 6.83 6.62
Colloidal phos. 10.01 5.86 5.12
Fired clay 5.98 8.00
Peat 7.03 6.95
Venticulite and peat decreased permeability only slightly.
However, fired clay was very highly effective in increasing the rate of
water transmission through mixtures. This was as expected because soils
containing high percentages of coarse separates allow rapid percolation
of water. The inclusion of fired clay in soil mixtures tended to
increase the proportion of coarse material in mixtures.
It was noted that in the experimental area, where a perched
water table existed for 24 to 48 hours after heavy rain, the mixtures
containing colloidal phosphate and/or vermiculite had a tendency to
have slow percolation rates. This showed that these materials, espe-
cially the latter, when used either on w~et sites or under excessive
irrigation practices, could produce unfavorable conditions for good
The average rate of water flow through all experimental plots
was good and in many cases, exceptionally rapid. It appeared that
lack of internal drainage of water from soil mixtures was not a limit-
ing factor for bermudagrass growth in this experiment.
Retention and availability of soil water
The principal factors affecting water-holding capacity of an
undisturbed soil are texture, structure, organic matter content, and
boundary conditions. To study the effects of amendments upon soil
water, necessary measurements for moisture retention characteriza-
tions were made in July, 1960, for each soil mixture used in this
study. Data for water retention in soil mixtures at 50 cm. of water
tension and 3 and 15 atm. tension are reported in table 28.
Values shown in figure 11 are useful in characterizing the
average effects of the use of the four amendments studied. The differ-
ence between the percent water held in soil at 50 cm. water tension,
AI C I a
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cOE O co
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a measure of field capacity (5;2), and at 15 atm. tension, or permanent
w~ilting point, is an estimate of total available moisture for turf
growth. The difference between 50 ca. water tension and 3 atm. tension
represents the readily available moisture for turf growth. It is with-
in the latter range that putting greens are usually maintained. Data
for the percentage of available water between the given tensions are
presented in table ;29, while analysis of variance for total available
water is shown in table 34.
The percentage of water retained at all tensions generally
increased as the amount of amendments in soil mixtures increased.
Fired clay in mixtures caused little change in the percentage of water
retained at 50 cm. of water tension, but increased the retention at
3 and 15 atm. tension, respectively. The incorporation of the other
amendments into soil mixtures increased the percentage of moisture
retained at 50 cm. water tension and 3 and 15 atm. tension, respec-
tively. This was as expected, since the tension writh which water is
held within a soil is a function of pore space and particle size
Increments of vermiculite produced a very highly significant
increase in available water, while fired clay caused a significant
decrease. Peat was more effective in increasing available water than
might have been expected, considering the rapid decomposition of this
material in mixtures. Ten percent peat in mixtures was as effective
in increasing available water as 20% vermiculite.
It was surprising to find that colloidal phosphate had no
significant effect upon the percentage of available water in nixtures,
since it was very highly effective in preventing damage of bermuda-
grass during a period of minimum watering of the experimental green.
However, it did enter into a significant interaction with peat.
Increments of colloidal phosphate tended to reduce the ability of peat
to increase the percentage of available water in mixtures. It is
believed that small particles of this phosphatic material either
blocked or filled pore space in mixtures, which would normally hold
available water for plant growth.
Total available water appeared to be a useful tool in eval-
uation of soil mixtures for growing good turf. The effects of ver-
miculite and fired clay upon turf yield were apparently associated
w~ith the available-moisture capacities of these twJo amendments in
Chemical Soil Evaluations
The production of good turf depends upon the proper supply of
plant nutrients in the presence of favorable soil air and water condi-
tions, so that the grass can make the most efficient use of these
nutrients. Although chemical fertilizers were applied uniformly to
all plots, some amendments supplied additional nutrients and resulted
in changes in the exchange capacity and water relations, which affect
the accumulation of nutrients in the soil. Therefore, chemical analy-
ses wrere made of the amended soils to measure the effects of
vermiculite, colloidal phosphate, fired clay, and peat upon the
nutrient status of the soil.
Organic matter content
The primary source of soil nitrogen is organic matter. The
end products of aerobic decomposition of organic residues are carbon
dioxide, water, ammonium compounds, and other mineral salts. It has
been shown previously that peat effectively influences pore space and
available water in soil mixtures. To study the effects of the amend-
ments on the organic matter content of soil mixtures, samples were
taken at the initiation of the experiment and 1 year later. Data from
the analysis of these samples are shown in table 50.
As was expected, only peat proved to have a very highly sig-
nificant positive effect upon percent organic matter content. Statis-
tical analyses for the average effects of amendments on organic matter
content of soil mixtures, and the change in content in a 1-year period,
are shown in tables 45 and 44, respectively.
Although peat produced a positive effect in 1959 and 1960,
there was a net decrease in the percent organic matter content of all
plots during this period (figure 12). This was primarily due to the
high rate of nitrogen fertilization, which stimulated the activity of
soil organisms that are responsible for organic decomposition. Also,
it was noted that the addition of 10$ peat produced only 0.3 and 0.2%
increases in organic matter content in 1959 and 1960, respectively.
The organic matter content of plots containing fired clay and
peat differed in 1959 from that of 1960. In 1959, the soil mixtures
Fiur 12-Ogncmte co ntn (15 and 1960) of
soi mixure reevn by voue n
100/ pea in199
were higher in organic matter content in the presence of fired clay
than in its absence and the opposite was true in 1960. It is hypoth-
esized that the initial effect of fired clay was an indirect one
resulting from a reduction in sample weight, thus increasing percent
organic matter content on a dry-weight basis. However, the tendency
of fired clay to reduce organic matter content after 1 year was real
and perhaps of greater magnitude than indicated. This might be ex-
pected, since this material increased noncapillary pore space, which
is closely associated with aeration, and, thus, resulted in increased
biological decomposition of organic matter.
Cation exchange capacity
The exchange capacity of soils is primarily dependent upon
the amount and particle size distribution of the colloidal fraction,
the chemical nature of the colloids, and the physical structure of
the colloid. Exchange capacity is an important consideration, not
only in respect to nutrients already present in soils, but also in
relation to those applied in the form of commercial fertilizer.
Samples taken in 1959 and 1960 for organic matter content
evaluations wrere tested for exchange capacity (table 31). Statistical
analyses for the average effects of amendments upon this variable and
the change during the 1-year period of the test are shown~ in tables
43 and 44, respectively.
Although no material increased the exchange capacity as much
as 1 me. per 100 g., all except peat produced a very highly significant
increase. However, the utilization of amendments solely to increase
exchange capacity of the soil is a questionable practice, since the
difference between the rather low value obtained for native soil and
the highest value for the treatment containing 50$ by volume of
combined amendments was only 2.62 me. per 100 g.
It was of interest to note that little change occurred in the
exchange capacity of the native soil between 1959 and 1960. However,
during the same period, there was a considerable decrease in the
average exchange capacity of soil mixtures. The effect of time upon
the exchange capacity of native soil and soil mixtures is shown in
figure 15. Calculated on the basis of 2 me. of exchange capacity
for each 1% change in organic matter content, the decrease in ex-
change capacity of mixtures can be accounted for by the loss of organ-
ic matter content during this period. Consequently, it is believed
that organic matter decomposition was the major contributing factor
in the net decrease in exchange capacity during the 1-year period.
Although phosphorus may be held as an exchangeable anion by
clays, the major source of phosphorus for plant growth is the weather-
ing of soil materials, decomposition of organic matter, and commercial
fertilizer. However, the amount of phosphate in the soil solution at
any one time is extremely small and in most soils, it will be less
than a pound per acre of P205 (43). Evaluations of the phosphorus
content of soil mixtures and the native soil beneath them were made
tue (aerg of all mitrs in 195
W. ~ ~ n 1960.I l
at the initiation of the experiment and again 1 year later. Data for
these evaluations are reported as parts per million (ppm.) of extract-
able P205 (table 32). Statistical analyses for the average effects
of soil amendments upon extractable phosphorus content and the change
in content during the 1-year period of test are shown in tables 39
and 40, respectively.
The average content of extractable phosphorus in soil mixtures
containing various levels of amendmrents is shown in table 9. The fact
that all amended mixtures were high in extractable phosphorus was not
surprising, since Arredondo loamy fine sand is a phosphatic soil and,
in addition, large quantities of phosphorus were incorporated into the
soil at the time of establishment of the green. However, it was
interesting to note that the application of approximately 45 and 86
tons per acre of colloidal phosphate, which represented the 5 and 10%
levels, respectively, was much less effective in increasing the ex-
tractable phosphorus levels than 1 ton per acre of superphosphate
Although statistically significant, neither the slight increase
in phosphorus caused by fired clay nor the numerous interactions in-
volving fired clay, vermiculite, and colloidal phosphate were of
agronomic importance. From figure 14, it appears that phosphorus from
colloidal phosphate became more available with time, while there was
a considerable decrease in extractable phosphorus in plots containing
superphosphate. All1 plots received superphosphate, except the plots
amended with colloidal phosphate. The noted decrease in extractable
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phosphorus in plots receiving superphosphate was probably associated
wsith the fixation of phosphorus at the soil surfaces and not with
plant use or leaching (37). In figure 14, it is also shown that the
very highly significant effect of colloidal phosphate was curvilinear.
Table 9--Average extractable phosphorus, P205, cneto
soil mixtures containing various levels
of amendments, 1959 and 1960.
Year Amendment Extractable P205
Percent amendment added
0 5 10 20
1959 ppm. ppm. ppm. ppm.
Vermiculite 54.6 35.5 34.5
Colloidal phos. 45.8 28.9 30.2
Fired clay 34.0 55.9
Peat 54.6 55.4
Vermiculite 52.5 52.6 32.2
Colloidal phos. 38.5 29.6 30.5
Fired clay 52.0 52.8
Peat 32.9 52.0
The phosphorus content of the undisturbed soil beneath mixtures
containing colloidal phosphate was lower than that of soil beneath
mixtures containing superphosphate. Vermiculite significantly de-
creased phosphorus content of subsoil, but this decrease of less
than 3 ppm. was too small to be agronomically important. The tendency
of soil mixtures and subsoils to decrease in phosphorus content only
5 ppm. in 1 year showed that for turf, it is not necessary to apply
this nutrient frequently.
Potassium is one of the bases held in exchangeable form by
mineral and organic colloids. It is quite mobile as a cation in the
soil, but when combined as part of a crystal structure, it is highly
imnobile and resistant to weathering processes. Evaluations of the
potassium content of the soil mixtures and the subsoil beneath these
mixtures were made at the initiation of the experiment and 1 year
later. Data for these evaluations (table 32) are reported as parts
per million of extractable K20. Statistical analyses for the average
effects of soil amendments on ex',ractable potassium content and on the
change in content during the 1-year period are shown? in tables 39
and 40, respectively.
Although all clippings were removed from the green, there was
a net average increase in K20 content of 43 ppm. in the 1-year period,
indicating that the high rate of potassium fertilization w~as more than
that required for good grass growth. The average effects of the amend-
ments upon extractable potassium content of soil mixtures in 1959 and
1960 are shown in table 10.
Colloidal phosphate and venniculite slightly increased the
amount of extractable potassium held in mixtures, while additions of
peat seemed to decrease the ability of mixtures to supply potassium?.
The very highly significant increase in extractable potassium in soil
mixtures containing fired clay was due initially to the potassiurm-
supplying ability of this amendment, and later to its ability to hold
and release larger quantities of this element than the other amendments.
Year Amendment Extractable K20
Percent amendment added
O 5 10 20
1959 ppn~. ppm. ppm. ppm.
Vermiculite 74.7 85. 0 95.5
Colloidal phos. 87.7 81.4 86.2
Fired clay 67.1 105.1
Peat 84.9 85.3
Vermiculite 117.9 155.1 157.2
Colloidal phos. 125.0 150.1 152.5
Fired clay 105.7 151.8
Peat 130.7 126.5
Table 10--Average extractable potassium, K20, content in
soil mixtures containing various levels
of amendments, 1959 and 1960.
Extractable potassium content of the subsoil indicated that
colloidal phosphate reduced the downward movement of potassium, while
subsoils of plots beneath mixtures containing fired clay or vermiculite
had a considerable increase in potassium. The net average increase in
extractable potassium of the subsoil from 1959 to 1960 was 17 ppm.
This was about 40% of the increase in surface soil mixtures. Of
interest was the tendency for extractable potassium to accumulate more
rapidly in the subsoil beneath plots containing vermiculite than
beneath plots containing fired clay.
These evaluations indicate that the extractable potassium
content of soil mixtures can be greatly increased. In addition, it
was found that monthly application rates of 44 pounds per acre of K20
were higher than was necessary to maintain soil potassium levels for
vigorously growing turf.
Calcium occurs largely in the exchangeable form and as un-
decomposed minerals in acid, humid-region soils. If the activity of
calcium in the soil solution is suddenly increased or decreased, there
tends to be an opposing shift of equilibrium, with subsequent adsorp-
tion or release of calcium by the exchange complex. Chemical analysis
of the leachate obtained by treating a 5-g. soil sample with 25 ml. of
ammonium acetate (pH 4.8) gave an estimate of exchangeable calcium in
the soil mixtures, as well as extractable calcium. Data for the soil
mixtures and subsoil samples taken in 1959 and 1960 are reported in
table 52 as parts per million of Ca0. Statistical analyses for the
average effects of soil amendments upon extractable calcium content
and the change in content during the 1-year period are shown in
tables 41 and 42, respectively.
The very highly significant negative response obtained from
colloidal phosphate was quite unexpected. It was expected that, after
the application of approximately 45 and 86 tons per acre of this mater-
ial, which represented the 5 and 10% levels of colloidal phosphate,
respectively, and reported to be 27% Ca0 by weight, a decided increase
in the content of extractable calcium would occur. Contrary to this,
in 1959, there was actually a decrease (table 11). Apparently the
gypsum (CaSO4) in superphosphate, which was applied at 1 ton per acre
to plots not receiving colloidal phosphate, increased exchangeable
Analysis of Soft Phosphate with Colloidal Clay. LonCala
Phosphate Co., Hligh Springs, Fla. 1956.
calcium more than high rates of colloidal phosphate. Superphosphate
is 27% Ca0 equivalent (8). However, at the 1960 evaluation, mixtures
containing superphosphate were lower in exchangeable calcium than
those containing colloidal phosphate. The change in effect of col-
loidal phosphate from 1959 to 1960 upon extractable calcium of soil
mixtures is shown in figure 15. This very highly significant inter-
action between colloidal phosphate and time indicated that biological
activity and chemical weathering must occur in such mixtures before
calcium is released from this amendment.
Table 11--Average extractable calcium, Ca0, content in
soil mixtures containing various levels
of amendments, 1959 and 1960.
Year Amendment Extractable Ca0
Percent amendment added
0 5 10 20
1959 ppm. ppm. ppm. ppm.
Vermiculite 750 754 767
Colloidal phos. 791 682 758
Fired clay 705 782
Peat 752 735
Vermiculite 592 621 651
Colloidal phos. 507 625 711
Fired clay 560 668
Peat 615 616
Venticulite and peat produced no significant effect upon the
extractable calcium content of soil mixtures. However, fired clay
gave a very highly significant increase. The cause for this increase
appeared related to the high amount of extractable Ca0 (2250+ ppm.)
contained in this material.
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There was an average decrease of 130 ppm. of extractable Ca0
in the mixtures from 1959 to 1960, with a corresponding 55 ppm. increase
in the subsoil. This indicated that calcium moved downward in the pro-
file. However, there was no significant effect of the amendments upon
the subsoil except that a significant interaction of colloidal phos-
phate writh time showed that, in 1959, there was less extractable cal-
cium in the subsoil beneath plots containing this material than beneath
those containing other amendments. However, in 1960, the extractable
calcium content of subsoil beneath colloidal phosphate mixtures wras
equal to that beneath those not containing this amendment.
The amount of calcium in all mixtures was high to very high
and, consequently, the differences in calcium levels probably had
little effect upon turf growth.
Available soil magnesium is considered to be in the exchange-
able and water-soluble form. The behavior of magnesium in soils is
similar to that of calcium. Data on extractable magnesium in samples
taken in 1959 and 1960 from soil mixtures and the native soil beneath
them are reported as parts per million of Mg0 in table 32. Statistical
analyses for the average effects of amendments on extractable magnesium
content of soil mixtures and the change in the extractable magnesium~
levels during the 1-year period are shownm in tables 41 and 42,
At the time of establishment of the green, all plots received
dolomitic limestone at the rate of 1/2 ton per acre. Although no ad-
ditional magnesium was added during the period of investigation, the
decrease in extractable magnesium during this time was considerably
more than expected. From an average of 166 ppm. of extractable Mg0
in all plots in 1959, there was a significant decrease to an average
of 84 ppm. in 1960.
Despite the noted decrease in extractable magnesium between
1959 and 1960, all amendments had a highly or very highly significant
positive effect in 1959 and produced conditions leading to increased
availability of magnesium in 1960. The order of the average effect on
extractable magnesium obtained from the various anendnrents was:
fired clay > colloidal phosphate > vermiculite > peat. The average
extractable magnesium content in 1959 and 1960 of soil mixtures con-
taining various levels of anendnents is shownm in table 12.
The change in effect of colloidal phosphate between 1959 and
1960 on extractable magnesium from soil mixtures was interesting.
In 1959, the 5% level of this amendmrent raised the extractable mag-
nesium content of soil mixtures nearly as much as the 10% level.
By 1960, however, the 5% level was only approximately 50% as effective
as the 10% level in increasing the extractable magnesiumn content
Year Amendment Extractable Mg0
Percent amendment added
O 5 10 20
1959 ppm. ppm. ppm. ppm.
Vermiculite 146 168 183
Colloidal phos. 152 171 174
Fired clay 142 189
Peat 159 172
Vermiculite 75 84 95
Colloidal phos. 59 89 105
Fired clay 62 106
Peat 81 87
Table 12--Average extractable magnesium, Mg0, content in
soil mixtures containing various levels
of amendments, 1959 and 1960.
Mixing depth had a slight effect upon the conservation of
extractable magnesium in soil mixtures. At the end of the 1-year
period, it was found that 50 ppm. less Mg0 were leached, or utilized
by plants, in the 0- to 12-inch depth than in the 0- to 6-inch depth.
It appeared that part of this noted change was due to leaching, since
in the same period, the average increases in extractable Mg0 content
of the native soil beneath the two depths were 8 and 18 ppm. for the
12- and 6-inch mixing depths, respectively.
There was significantly greater movement of magnesium into the
subsoil from mixtures that contained either colloidal phosphate or
fired clay than from mixtures which did not contain these amendments.
This can be explained by the fact that the inclusion of these two
amendments in soil mixtures greatly increased the amount of leachable
magnesium in the mixtures.
At the end of the 1-year period, the soil containing no amend-
ments had a lowJ level of 32 ppm. of extractable Mg0, while the treat-
ment containing 209 vermiculite, 5% colloidal phosphate, 10% fired
clay, and 10% peat had a high level of 152 ppm. It is possible that
low magnesiurm content of some mixtures could have lowered both quality
and yield of turf.
This study had its greatest importance in showing the need for
frequent inclusion of magnesium in the soil-fertility program of golf
A marked change in pH undoubtedly indicates a radical modifi-
cation of soil environment, especially in respect to the availability
of plant nutrients. Some grasses tolerate a wide range of pH, while
others do well only within a narrow range.
Data for pH of samples taken in 1959 and 1960 of soil mixtures
and of native soil beneath them are reported in table 33. Statistical
analyses for the average effects of amendments on pH of soil mixtures
and the change in pH during the 1-year period are shown in tables 45
and 44, respectively.
There was a very highly significant average increase in pH of
0.3 of a unit in plots receiving colloidal phosphate. It was antic-
ipated that the large additions of this material would cause a greater
increase than that encountered. There was little or no change of pH
due to additions of either venriculite or fired clay to the soil.
Peat produced a very highly significant average decrease in pH of
Colloidal phosphate and fired clay entered into a highly
significant interaction. However, resulting pH changes were too
small to be of agranomic importance. Colloidal phosphate was a little
more effective in increasing the pH in 1959 than in 1960 and the
opposite was true for fired clay. Peat caused less reduction in. ?H in
1960 than in 1959, which indicated that it was in an advanced stage
The only subsoil samples which showed a significant increase
in pH were those from beneath colloidal phosphate mixtures and, sur-
prisingly, the greatest increase was found for the initial sampling
period. It is hypothesized that since this material was 45%9 clay, the
finer colloidal particles, high in exchangeable bases, rapidly moved
into the subsoil and produced the initial 0.2 of a unit increase in pH.
However, as these mixtures became more settled, there was less down-
ward movement of clay particles and,thus, little change in pH.
Soil Properties and Turf Growth
In the preceding discussion, the effects of amendments upon
physical and chemical properties of soil mixtures have been considered.
In some cases, there was indication that these properties influenced
the growth of turf. Therefore, in order to evaluate these observed
soil properties, without reference to amendments, it was necessary to
measure the effect of soil conditions upon the growth and quality
responses of turf.
i i r .i
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noncapillary pore space was above 10% and decreased at lower percent-
ages. The differences in response found from the above studies and
those from soil mixtures of this experiment cannot be explained solely
by methods of analysis, as procedures were similar. Therefore, the
use of noncapillary pore space as a criterion for greens soils is only
feasible when data can be compared to results obtained from testing
similar mixtures under uniform conditions of compaction.
Available soil water and turf growth
It has been indicated that all moisture held in the range of
the previously described tensions for "available" water is not equally
available to plants and that growth of plants decreases progressively
as the moisture stress increases (49).
The response of bermudagrass to readily available water in
soil mixtures, held between 50 cm. water tension and 3 atm., was not
significant. However, the linear dependency of the yield-quality
index of Tirgreen bermudagrass on total available water, held between
50 cm. water tension and 15 atm. tension, was significant within the
limits of the analyzed data (figure 17). This was explained by the
fact that some mixtures contained proportionally smaller pores than
others, which decreased the slope of the moisture tension curve be-
tween 3 and 15 atm. Although slight, this decrease in slope resulted
in a small but important increase in water available to turf at higher
moisture tensions, which would be most noticeable in improving yrield
and quality during drought periods.
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It appeared that yields and quality of turf improved rapidly
as total available water increased from 22 to 324 by volume (figure 17).
However, these findings are related to soil conditions produced by
specific amendments and values would vary writh materials.
Permeability and turf growth
Since hydraulic conductivity is a function of noncapillary pore
space and is particularly related to the size and continuity of the
macropore space of soil, it should be associated with yield and quality
A very highly significant negative regression coefficient was
found for the response of Tifgreen bermudagrass to the permeability of
soil mixtures (figure 18). The yield and quality of bermudagrass de-
creased as the permeability of soil mixtures increased from 3 to 10
inches per hour. Under the experimental conditions of this investiga-
tion, turf yield and quality decreased when either noncapillary pore
space or permeability increased. This was to be expected since these
two soil factors are closely related.
Although the best yield and quality of turf occurred when the
hydraulic conductivity was near 5 inches per hour, it should not be
assumed that the response of turf from soil mixtures having much lower
rates than this would be favorable. Furthermore, on golf courses, it
would be desirable to have fairly rapid water movement into and through
soil, so that play could be quickly resumed after heavy rains. Also,
if infiltration and percolation rates are slow, rapid watering of the
green would result in runoff and a loss of water.