Group Title: Effects of amendments on soil properties and on growth of bermuda grass on putting greens /
Title: Effects of amendments on soil properties and on growth of bermuda grass on putting greens
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 Material Information
Title: Effects of amendments on soil properties and on growth of bermuda grass on putting greens
Physical Description: x, 176 leaves : ill. ; 28 cm.
Language: English
Creator: Smalley, Ralph Ray, 1919-
Publication Date: 1961
Copyright Date: 1961
 Subjects
Subject: Bermuda grass   ( lcsh )
Soils   ( lcsh )
Soil physics   ( lcsh )
Soil Science thesis Ph. D
Dissertations, Academic -- Soil Science -- UF
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Thesis: Thesis (Ph. D.)--University of Florida, 1961.
Bibliography: Includes bibliographical references (leaves 170-175).
Additional Physical Form: Also available on World Wide Web
General Note: Typescript.
General Note: Vita.
Statement of Responsibility: by Ralph Ray Smalley.
 Record Information
Bibliographic ID: UF00097989
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: alephbibnum - 000407902
oclc - 36814095
notis - ACF4225

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EFFECTS OF AMENDMENTS ON SOIL

PROPERTIES AND ON GROWTH

OF BERMIUDAGRASS ON

PUTTING GREENS









By
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
June, 1961













ACKNOIWLEDGMUENTS


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.











11


Ir P IK3













TABLE OF CONTENTS



A.CKNOWLEDC24ENT...... .......


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 ................


Page
ii


. .V


. ix














. 14


. 18


Green Construction and Turf Planting
Maintenance of the Green ......
Purf Evaluations ..........
Soil Measurements .........
Statistical Analysis ........


RESULTS AND DISCUSSION............


Purf Evaluations..........


. .
. .
. .
. .
. .


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 . . .. .
Penetrability .....
Compactability .............
Porosity . . . .
Hydraulic conductivity.........
Retention and availability of soil water


. .35


. .37
. .41
. .42
. .44
. .46















TABLE OF CONTENTS--( continued)


Page
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


Table Page
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)


Table Page
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

vi












LIST OF TABLES--(continued)


Table Page
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)


Table
42.


Page


Analyses of variance for the effects of time on the
extractable calcium and magnesium in soil
mixtures and the subsoil, 1959 and 1960. ...


167


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.


168


.. 169


viii












LIST OF FIGURlES


Figure
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. .. ..


Page


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,


.. 55


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.


per-
con-


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)


Figure Page
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











INTRODUCTION


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,
Fla. 1960.












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

materials.

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
Their Properties

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,

59).

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

floricultural uses.

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


rnl




iice


upon


to


- .er ar. ai

cf the sand

that th~e ch

is dependent

th sc i .


; r


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iayt il-

inerez

j tl;ad


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sist cor

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from e.


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, littl 1 tu


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Jct- s

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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

sandy soils.

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

ratio.



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

removed.

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,

and plants.

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
silt silt


Arredondo loamy
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.

18


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.
Material
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

soil amendments:

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

erosion.

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

planting.

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.


Turf Evaluations

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

scale:

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 .


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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


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rOOtS, ar

rlot, r;cre


ipr su-


aI ;"surements


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ct-ivel .







Lr ar a


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t~oi


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In nini.: rlol.


randorl


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T"CI-~Clri rOr


CILL",











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 '


the~ i











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

studies.

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.











Statistical Analysis

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

putting greens.

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.


Turf Evaluations

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
production

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.


























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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

penetration.


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.





4_0

















24

10fg Colloidal phos.





~a20


20 5% Colloidal phos.



TI I
0 10 20
Vermiculite (percent)

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
after
S *-,r1 r r-t armor tment 011:-i
O E 1 ?







.r o











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





1. 6"


3





a
a,
M
m 2
E
co
a L
t,
c
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o
k
a
1


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.





























P eat


10% Peat


3CI


Fired Clay (percent)


Figure 4--Average seedhead prevalence of
dagrass grown on soil mixtures
volume varying levels of fired
1960.


Tifgreen bermu-
containing by
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

conditions.


Bulk density

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




Penetrability

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.


Compactability

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%
























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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.





















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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.


Porosity

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

amendment.

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







60











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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

particles.

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

colloids (65).


Hydraulic conductivity

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

turf growth.

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,






64












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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

distribution.

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

soil mixtures.


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






68
























a~O










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.


Phosphorus

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




























6




Soo


QO








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

(figure 14).

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







75











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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
1960
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

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
1960
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

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
1960
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.


Magnesium

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,

respectively.











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

(table 12).
















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
1960
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

greens.


Soil pH

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

soil mixtures.

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

of decomposition.

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.



































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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

of turf.

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.




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