Group Title: Bulletin - University of Florida. Agricultural Experiment Station ; 396
Title: Types and distribution of microorganisms in some Florida soils
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Permanent Link: http://ufdc.ufl.edu/UF00026419/00001
 Material Information
Title: Types and distribution of microorganisms in some Florida soils
Series Title: Bulletin University of Florida. Agricultural Experiment Station
Physical Description: 41, 2 p. : ; 23 cm.
Language: English
Creator: Smith, F. B ( Frederick Burean )
Gall, O. E ( Owen E )
Publisher: University of Florida Agricultural Experiment Station
Place of Publication: Gainesville Fla
Publication Date: 1944
 Subjects
Subject: Soil microbiology -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Bibliography: p. 40-41.
Statement of Responsibility: by F.B. Smith and Owen E. Gall.
General Note: Cover title.
 Record Information
Bibliographic ID: UF00026419
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 000925202
oclc - 18231860
notis - AEN5848

Full Text





HISTORIC NOTE


The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
(EDIS)

site maintained by the Florida
Cooperative Extension Service.






Copyright 2005, Board of Trustees, University
of Florida







Bulletin 396


January, 1944


UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATION
HAROLD MOWRY, Director
GAINESVILLE, FLORIDA










TYPES AND DISTRIBUTION OF

MICROORGANISMS IN SOME

FLORIDA SOILS

By
F. B. SMITH
Professor of Soils, University of Florida College of Agriculture, and
Microbiologist, Florida Agricultural Experiment Station

and
OWEN E. GALL

Formerly Research Assistant in Soils, Florida Agricultural Experiment
Station










Single copies free to Florida Residents upon request to.
AGRICULTURAL EXPERIMENT STATION
GAINESVILLE, FLORIDA










BOARD OF CONTROL

H. P. Adair, Chairman, Jacksonville
N. B. Jordan, Quincy
T. T. Scott, Live Oak
Thos. W. Bryant, Lakeland
M. L. Mershon, Miami
J. T. Diamond, Secretary, Tallahassee

EXECUTIVE STAFF

John J. Tigert, M.A., LL.D., President of the
University8
Harold Mowry, M.S.A., Director
L. 0. Gratz, Ph.D., Asst. Dir., Research
W. M. Fifield. M.S., Asst. Dir., Admin."
J. Francis Cooper, M.S.A., Editor8
Clyde Beale, A.B.J., Assistant Editors
Jefferson Thomas, Assistant Editor3
Ida Keeling Cresap, Librarian
Ruby Newhall, Administrative Managers
K. H. Graham, LL.D., Business Managers
Claranelle Alderman, Accountants

MAIN STATION, GAINESVILLE

AGRONOMY

W. E. Stokes, M.S., Agronomist1
Fred H. Hull, Ph.D., Agronomist
G. E. Ritchey, M.S., Agronomist2
W. A. Carver, Ph.D., Associate
Roy E. Blaser, M.S., Associate
G. B. Killinger, Ph.D., Agronomist
H. C. Harris, Ph.D., Associate
R. W. Bledsoe, Ph.D., Assistant
Fred A. Clark, B.S., Assistant

ANIMAL INDUSTRY

A. L. Shealy, D.V.M., An. Industrialist' 8
R. B. Becker, Ph.D., Dairy Husbandman8
E. L. Fouts, Ph.D., Dairy Technologista
D. A. Sanders, D.V.M., Veterinarian
M. W. Emmel, D.V.M., Veterinarians
L. E. Swanson, D.V.M., Parasitologist4
N. R. Mehrhof, M.Agr., Poultry Husb.3
T. R. Freeman, Ph.D., Asso. in Dairy Mfg.
R. S. Glasscock, Ph.D., Asso. An. Husb.
D. J. Smith, B.S.A., Asst. An. Husb.3
P. T. Dix Arnold, M.S.A., Asst. Dairy Husb.3
G. K. Davis, Ph.D., Animal Nutritionist
C. L. Comar, Ph.D., Asso. Biochemist
L. E. Mull, M.S., Asst. in Dairy Tech.4
O. K. Moore, M.S., Asst. Poultry Husb.3
J. E. Pace, B.S., Asst. An. Husbandmans
S. P. Marshall, M.S., Asst. in An. Nutrition
C. B. Reeves, B.S., Asst. Dairy Tech.

ECONOMICS, AGRICULTURAL

C. V. Noble, Ph.D., Agr. Economist'1
Zach Savage, M.S.A., Associate
A. H. Spurlock, M.S.A., Associate
Max E. Brunk, M.S., Assistant


ECONOMICS, HOME

Ouida D. Abbott, Ph.D., Home Econ.'
Ruth 0. Townsend, R.N., Assistant
R. B. French, Ph.D., Biochemist


ENTOMOLOGY

J. R. Watson, A.M., Entomologist'
A. N. Tissot, Ph.D., Associates
H. E. Bratley, M.S.A., Assistant



HORTICULTURE

G. H. Blackmon, M.S.A., Horticulturist'
A. L. Stahl, Ph.D., Asso. Horticulturist
F. S. Jamison, Ph.D., Truck Hort.
R. J. Wilmot, M.S.A., Asst. Hort.
R. D. Dickey, M.S.A., Asst. Hort.'
J. Carlton Cain, B.S.A., Asst. Hort.'
Victor F. Nettles, M.S.A., Asst. Hort.'
Byron E. Janes, Ph.D., Asst. Hort.
F. S. Lagasse, Ph.D., Asso. Hort.2
H. M. Sell, Ph.D., Asso. Horticulturists



PLANT PATHOLOGY

W. B. Tisdale, Ph.D., Plant Pathologist'
Phares Decker, Ph.D., Asso. Plant Path.
Erdman West, M.S., Mycologist
Lillian E. Arnold, M.S., Asst. Botanist


SOILS


R. V. Allison, Ph.D., Chemist'1
Gaylord M. Volk, M.S., Chemist
F. B. Smith, Ph.D., Microbiologists
C. E. Bell, Ph.D., Associate Chemist
L. E. Ensminger, Ph.D., Soils Chemist
J. R. Henderson, M.S.A., Soil Technologist
L. H. Rogers, Ph.D., Associate Biochemist'
R. A. Carrigan, B.S., Asso. Biochemist6
G. T. Sims, M.S.A., Associate Chemist
J. N. Howard, B.S., Assistant Chemist
T. C. Erwin, Assistant Chemist
H. W. Winsor, B.S.A., Assistant Chemist
Geo. D. Thornton, M.S., Asst. Microbiologist
R. E. Caldwell, M.S.A., Asst. Soil Surveyor'
Olaf C. Olson, B.S., Asst. Soil Surveyor



SHead of Department.
2 In cooperation with U. S.
3 Cooperative, other divisions, U. of F
SIn Military Service.
SOn leave.















BRANCH STATIONS
NORTH FLORIDA STATION, QUINCY

J. D. Warner, M.S., Vice-Director in Charge
R. R. Kincaid, Ph.D., Plant Pathologist
V. E. Whitehurst, Jr., B.S.A., Asst. An. Hush.4
W. C. McCormick, B.S.A., Asst. An. Husb.
Jesse Reeves, Asst. Agron., Tobacco
W. H. Chapman, M.S., Asst. Agron.4
R. C. Bond, M.S.A., Asst. Agronomist

Mobile Unit, Monticello
R. W. Wallace, B.S., Associate Agronomist

Mobile Unit, Milton
Ralph L. Smith, M.S., Associate Agronomist

CITRUS STATION, LAKE ALFRED

A. F. Camp, Ph.D., Vice-Director in Charge
V. C. Jamison, Ph.D., Soils Chemist
B. R. Fudge, Ph.D., Associate Chemist
W. L. Thompson, B.S., Entomologist
W. W. Lawless, B.S., Asst. Horticulturist4
R. K. Voorhees, Ph.D., Asso. Plant Path.
C. Stearns, Jr., B.S.A., Asso. Chemist
H. 0. Sterling, B.S., Asst. Horticulturist
T. W. Young, Ph.D., Asso. Horticulturist
J. W. Sites, M.S.A., Asso. Horticulturist


EVERGLADES STA., BELLE GLADE

J. R. Neller, Ph.D., Vice-Director in Charge
J. W. Wilson, Sc.D., Entomologist4
F. D. Stevens, B.S., Sugarcane Agron.
Thomas Bregger, Ph.D., Sugarcane
Physiologist
G. R. Townsend, Ph.D., Plant Pathologist
R. W. Kidder, M.S., Asst. An. Husb.
W. T. Forsee, Jr., Ph.D., Asso. Chemist
B. S. Clayton, B.S.C.E., Drainage Eng.2
F. S. Andrews, Ph.D., Asso. Truck Hort.4
R. A. Bair, Ph.D., Asst. Agronomist
E. C. Minnum, M.S., Asst. Truck Hort.
N. C. Hayslip, B.S.A., Asst. Entomologist


SUB-TROPICAL STA., HOMESTEAD

Geo. D. Ruehle, Ph.D., Vice-Director in
Charge
S. J Lynch, B.S.A., Asso. Horticulturist
P. J. Westgate, Ph.D., Asso. Horticulturist


W. CENT. FLA. STA., BROOKSVILLE

Clement D. Gordon, Ph.D., Asso. Poultry
Geneticist in Charge2

RANGE CATTLE STA., ONA

W. G. Kirk, Ph.D., Vice-Director in Charge
E. M. Hodges, Ph.D., Asso. Agron., Wauchula
Gilbert A. Tucker, B.S.A., Asst. An. Husb.4


FIELD STATIONS

Leesburg
M. N. Walker, Ph.D., Plant Path. in Charge"
E. M. Andersen, Ph.D., Asso. Hort. in Charge

Plant City
A. N. Brooks, Ph.D., Plant Pathologist

Hastings
A. H. Eddins, Ph.D., Plant Pathologist
E. N. McCubbin, Ph.D., Truck Horticulturist

Monticello
S. 0. Hill, B.S., Asst. Entomologist2 4
A. M. Phillips, B.S., Asst. Entomologist2

Bradenton
J. R. Beckenbach, Ph.D., Horticulturist in
Charge
E. G. Kelsheimer, Ph.D., Entomologist
F. T. McLean, Ph.D., Horticulturist
A. L. Harrison, Ph.D., Plant Pathologist
David G. Kelbert, Asst. Plant Pathologist
E. L. Spencer, Ph.D., Soils Chemist

Sanford
R. W. Ruprecht, Ph.D., Chemist in Charge
J. C. Russell, M.S., Asst. Entomologist

Lakeland
E. S. Ellison, Meteorologist2"
Warren O. Johnson, Meteorologist"

SHead of Department.
In cooperation with U. S.
SCooperative, other divisions, U. of F.
SIn Military Service.
On leave.


















CONTENTS

Page

INTRODUCTION ................. ...--- -- --- .......- 5
THE MICROBIAL POPULATION OF THE SOIL AND CONDITIONS AFFECTING
THE GROWTH OF SOIL MICROORGANISMS -................--...----...-.. .. 6
Bacteria ................... .................................. 6
Actinomyces .................... ............. .............. 7
M olds ................ ........................ 8
Algae ........... ................. ..... ................... 9
PLAN OF INVESTIGATION ............. ....... --- ..----- --...........---- ..-- 10
The Numbers of Microorganisms in Seven Soil Types................... 10
The Numbers of Microorganisms in Arredondo Fine Sand Under
Different Cropping Systems ................-.. ......-.....-- 17
The Numbers of Microorganisms in Norfolk Loamy Fine Sand
Cropped to Corn and Peanuts, and Land Resting............... 20
The Numbers of Microorganisms in Norfolk Loamy Fine Sand
at Different pH Levels ........................-.------------...... 26
The Numbers of Microorganisms in Norfolk Fine Sand Under
Pineapple Orange Grove ....................-..---- ----........... 30
The Numbers of Microorganisms in the Profile of a Leon Fine
Sand .......... .... -........... ..... ............. --...... 34
The Algal Flora of a Leon Fine Sand ...._....... --.......--.....--.--.... 37
DISCUSSION AND SUMMARY ........,............................... 38
LITERATURE CITED ............. ...... .......... .................. ...... 40








TYPES AND DISTRIBUTION OF MICROORGANISMS
IN SOME FLORIDA SOILS

F. B. SMITH and OWEN E. GALL

INTRODUCTION

An inventory of the microbial population and the biological
characteristics of a soil are just as essential to'the complete char-
acterization of a soil type as certain of the physical and chemical
properties commonly employed to differentiate one type from
another. Certainly this information is desirable if soil manage-
ment practices are to be developed on a soil type basis.
An appreciation of the importance of microbiological action in
soils has developed within recent years and the biological char-
acteristics of soils have been accepted quite generally as one of
the main groups of factors governing soil fertility. However,
the very close relationship that exists between the microorgan-
isms and the growth of the higher plants does not seem to be so
generally appreciated. When the essentiality of the microorgan-
isms for plant growth has been fully recognized, new and im-
proved soil management practices based on the needs of the
microorganisms may be developed.
No extensive investigations of the micro-flora of Florida soils
have been published. The soil conditions are peculiar to the State
for the most part and many soil types found in Florida are not
developed elsewhere. The numerous publications on numbers
and kinds of microorganisms in other soil types are not applicable
to Florida conditions. Also, many of the previous investigations
along this line were made before quantitative methods for deter-
mining the numbers of microorganisms in the soil had reached
their present degree of accuracy. There is still much to be de-
sired in methods for investigating problems of this nature but
recent advances by James and Sutherland (3) (4) 1 indicate that
by refinements of the technique the dilution plate method may
be used to show differences not detectable by the procedures com-
monly followed in many of the earlier investigations. Much addi-
tional information may be obtained by a repetition of some of

SFigures (Italic) in parentheses refer to Literature Cited.






Florida, Agricultural Experiment Station


the older studies and the results obtained on one soil type need
confirmation on others before generalizations can be drawn.
The purpose of the work reported here was to make an inven-
tory of the microbial population of some of the main soil types
and to study the influence of climate, cropping systems and fer-
tilizer treatments on the numbers and types of microorganisms
in some Florida soils.

THE MICROBIAL POPULATION OF THE SOIL AND CONDI-
TIONS AFFECTING THE GROWTH OF SOIL MICROOR-
GANISMS
The microbial population of the soil is composed of organisms
representing both the plant and animal kingdoms. Under ordi-
nary circumstances the members of the plant world are in the
majority in the normal, well-drained soil. The microscopic plants
found in the soil are represented by the algae, fungi and bacteria.
The term fungi is used in a general way to denote yeasts, yeast-
like molds, molds and the fleshy-fungi or mushrooms. Another
group, the actinomyces, is generally classed with the bacteria.

BACTERIA
The bacteria are the most numerous of the soil microorganisms
generally, though not always. Presumably they are the most
important, considered on the basis of their activities. The num-
ber of bacteria in the soil varies widely with conditions of tem-
perature, moisture, reaction and food supply. A fertile silt loam
may contain 20 million pet gram as determined by the dilution
plate method. Generally, fertile soils contain larger numbers of
bacteria than unproductive soils. Some barren soils have been
found to be practically sterile. This implies a rather fundamental
relationship between the occurrence and action of microorgan-
isms in the soil and soil fertility.
For convenience of discussion the soil bacteria may be divided
into 2 groups on the basis of their physiology. In 1 group, char-
acterized by the ability to secure their growth energy from the
oxidation of simple, inorganic compounds, belong the Nitrobacter,
Nitrosomonas and Nitrosococcus. These are the organisms re-
sponsible for the changing of nitrogen, after it has been liberated
by the decay organisms, into the nitrate form. The process is
referred to as nitrification and the bacteria are called the nitri-
fiers. In this group also are the sulfur-oxidizing bacteria. The
process of sulfur oxidation is referred to as sulfofication and the






Types and Distribution of Microorganisms


bacteria are known as the sulfofiers. The importance of these
2 groups of bacteria to soil fertility can hardly be overestimated,
since all of the nitrogen and sulfur in plant materials must be
transformed before it is again available for plant use. The other
group of bacteria, those that require organic matter as a food
substance, may be subdivided into 2 smaller groups based on
their nitrogen requirements. One is capable of utilizing atmos-
pheric nitrogen, usually referred to as the nitrogen-fixing bac-
teria, and the other requires fixed nitrogen. The nitrogen-fixing
bacteria are of 2 general classes, the non-symbiotic or free-living,
as the Azotobacters, and the symbiotic or root-nodule bacteria of
legumes.
The process of nitrogen fixation probably has been studied
more extensively than any other microbiological activity, yet
there are still many mysteries concerning the process. It has not
yet been found feasible to inoculate soils with the free-living
nitrogen-fixing bacteria. Legume inoculation, one of the oldest
practical applications of soil microbiology, is a well established
practice wherever legumes are grown and yet results have not
been uniformly successful on all soil types and under all climatic
conditions. The bacteria requiring fixed nitrogen make up the
bulk of the soil bacteria and are those developing on the agar
plate commonly used in counting soil bacteria. This group of
bacteria is generally referred to as general purpose bacteria,
mainly because no special functions have been attributed to them.
The general purpose bacteria are active in the decomposition of
all forms of organic matter. As a consequence, when nitrogenous
organic matter is decomposed numerous bacteria liberate the
nitrogen in excess of their requirements as ammonia and the pro-
cess is called ammonification. Since the nitrogen requirements of
the bacteria are higher than those of the molds and actinomyces,
the ammonia and nitrate-nitrogen are quickly immobilized when
large quantities of available carbonaceous organic matter are
present in the soil. The liberation of ammonia, the production
of carbon dioxide, the transformation of mineral plant food nutri-
ents into available forms and the formation of humus are all
important processes brought about by the so-called general pur-
pose bacteria. Biological interactions not yet known are undoubt-
edly common among this group of bacteria.
ACTINOMYCES
Physiologically the actinomyces resemble the bacteria and for
this reason they are generally classed with the bacteria. Mor-






Florida Agricultural Experiment Station


phologically they resemble the molds and are often classed with
the fungi. The microorganisms in this little known group grow
slowly, which probably accounts for the lack of knowledge con-
cerning the soil forms, and are more sensitive to acidity than the
bacteria and molds. They require complex forms of nitrogen,
are resistant to drying, apparently are able to remain active at
low moisture levels, and are capable of decomposing humus. The
actinomyces not only decompose the unaltered organic matter,
liberating ammonia and carbon dioxide, but are capable of reduc-
ing further the organic matter left by other microorganisms.
They require proportionately less nitrogen than the other decay
organisms for the decomposition of highly carbonaceous organic
matter and consequently there is less likelihood of nitrogen im-
mobilization by these organisms than by the bacteria and molds.
They are universally present in soils and appear to be more abun-
dant in proportion to the bacteria and molds in tropical and sub-
tropical soils, especially in locations where the seasons are alter-
nately wet and dry. In Louisiana and Florida soils 40 to 85
percent of the colonies developing on the agar plate may be
actinomyces, whereas in more northerly latitudes they rarely
exceed 15 percent of the total microbial population. The actual
numbers may vary widely with conditions from a few hundred
to several million per gram of soil.

MOLDS
The molds are the filamentous fungi with a branched mycelium
which extends in all directions ramifying through the soil inter-
stices and the organic matter upon which they feed. The molds
are active in the decomposition of both nitrogenous and non-
nitrogenous materials. Since only 1 part of nitrogen is required
by the molds for about 30 parts of carbon utilized, large amounts
of ammonia are liberated when they decompose nitrogenous sub-
stances. The molds are active in ammonification. On the other
hand, most molds are able to assimilate large quantities of am-
monia and nitrate-nitrogen when an abundance of carbonaceous
organic matter is available. The nitrogen is immobilized and
certain crops growing in the soil at such times may suffer from
nitrogen starvation unless adequate nitrogen for both the micro-
organisms and the crops is applied. Molds tolerate more strongly
acid soil conditions than the bacteria and actinomyces. Conse-
quently, acid soils usually have a higher proportion of molds to
bacteria and actinomyces than less acid soils. Since the molds






es and Distribution of Microorganisms
Types and Distribution of Microorganisms


require large amounts of organic matter, their activity is natur-
ally limited in soils of low organic matter content. A rich loam
containing as much as 10 percent organic matter may have as
many as 1,000,000 per gram, whereas a fine sand as low as 1
percent in organic matter may contain less than 10,000 per gram.
Most of the molds in the soil are beneficial, reducing organic mat-
ter to humus, liberating ammonia and carbon dioxide and render-
ing available plant food nutrients. A few of the species, however,
are parasitic, causing much damage in plant disease. Some of
the saprophytic forms are highly antagonistic to the parasitic
forms. For example, it has been found that one of the common
yellowish-green molds, Trichoderma lignorum, (Tode) Harz, has
decided fungicidal properties. Allen and Haenseler (1) reported
on the antagonistic effect of this organism on rhizoctonia and
other soil fungi. This is just another instance of the importance
of microbiological interrelationships in the soil about which we
know very little.

ALGAE

The Algae are commonly regarded as water plants, living in
ponds, lakes, rivers and the ocean. However, many forms are
common in the surface layers of the soil, and they have been
reported to depths as great as 70 cm. (5). The numbers found
in soils vary from a few hundred to 500,000 per gram. Larger
numbers have been reported (7) in limed soil than in unlimed
soil. Smith and Ellis (6) found 17 species of the Myxophyceae
in the surface of a poorly drained Portsmouth fine sand. Six of
these species were also found in the surface of a Norfolk fine
sand, a soil that is excessively drained and relatively dry. The
Norfolk fine sand contained 9 species of Myxophyceae not found
in the Portsmouth fine sand. Certain of the algae are chloro-
phyll-bearing plants and have the ability to synthesize organic
matter from the carbon dioxide of the atmosphere. It has been
definitely established (2) that certain of the Myxophyceae have
the ability to utilize atmospheric nitrogen. The economic impor-
tance of these 2 processes in soils is not known but the implica-
tions are that they may be factors worth reckoning with, espe-
cially in sandy soils low in organic matter and nitrogen. There
are many such soils in Florida and the problem seems worthy of
very careful consideration from a purely practical standpoint.






Florida Agricultural Experiment Station


PLAN OF INVESTIGATION
Since the purpose of this work was to obtain a broad, general
view of the microflora of Florida soils under various conditions
of climate, soil type, cropping systems and soil treatment, soil
samples were taken at regular intervals for a determination of
the numbers of molds, bacteria and actinomyces, and in one
instance of the kinds of algae in the profile of a virgin soil.
The numbers of molds, bacteria and actinomyces in the surface
soils were determined at monthly intervals, except as noted, in:
1. Seven soil types, both virgin and cultivated areas.
2. Arredondo fine sand under different cropping systems.
3. Norfolk loamy fine sand cultivated and resting, and with
crop residues burned and plowed under in each case.
4. The numbers of molds, bacteria and actinomyces in Norfolk
fine sand at different pH levels were determined in June and
October, 1938, and in February and April, 1939.
5. The average numbers of microorganisms in Norfolk fine
sand under Pineapple orange groves at Palm Harbor, Florida,
were determined in March, April and May, 1940, and at Winder-
mere, Florida, in April and May, 1940.
6. The numbers of molds, bacteria and actinomyces, and the
kinds of algae were determined in the different horizons of a
virgin Leon fine sand profile at monthly intervals from January
to August, 1940.
The procedure followed in all these investigations consisted
essentially in the determination of the numbers of the different
groups of organisms by the dilution plate method as recom-
mended by James and Sutherland (3, 4). The details are given
under the different experiments.

THE NUMBERS OF MICROORGANISMS IN SEVEN SOIL TYPES
Seven soil types in the vicinity of Gainesville were selected
for this study. The soils were all of the same textural grade,
namely fine sand, and represented the different conditions of
drainage from the deep sands on the ridges to the low marshy
areas. The series represented were Norfolk, Blanton, Hernando,
Gainesville, Orlando, Leon and Portsmouth. For a complete
characterization of these soils see Station Bulletin 334. Two
representative virgin areas of each type and 2 areas of each type
under cultivation were sampled at monthly intervals from June,
1938, through June, 1939. The virgin areas of all types were
sampled at 1 time during the first week of the month and the






Types and Distribution of Microorganisms


samples from the cultivated areas were taken during the latter
part of the month.
The samples were taken aseptically from the surface 0 to 6
inches of the soil, brought into the laboratory and thoroughly
mixed and dilution plates were poured the same day of sampling.
The moisture content of the soil was determined by drying in an
oven 5 hours at 1100C. A quantity of moist soil equivalent to 50
grams of dry soil was placed in 500 cc. of sterile tap water in 1
liter Erlenmeyer flasks and shaken vigorously for approximately
1 minute. After the sand had settled 10 cc. of the suspension
were transferred to 90 cc. of sterile tap water in 250 cc. Erlen-
meyer flasks by means of a sterile 10 cc. pipette. This process
was repeated until a total of 5 dilutions had been made. Approxi-
mately 25 cc. of the first dilution (1:10 soil-water suspension)
were taken for pH determinations by the quinhydrone electrode
method. One cc. aliquots were taken from the third dilution for
molds and from the fifth dilution for bacteria and actinomyces.
Five plates were poured from each dilution. Synthetic acid agar,
pH 4.0, was used for the determination of molds, and egg albu-
men agar for bacteria and actinomyces. The plates were incu-
bated at room temperature, 250 to 300C., and the molds were
counted after 2 days. The bacteria and actinomyces were usually

TABLE 1.-AVERAGE NUMBERS OF MOLDS IN 7 SOIL TYPES.
(Thousands per gram of dry soil)
SOIL TYPE
Nor- Blan- Her- Gaines- I Ports-
folk ton nando ville Orlando Leon mouth
Mo. Fine Fine Fine Fine Fine Fine Fine Mean
Sand Sand Sand Sand Sand Sand Sand
June 42 58 65 50 68 431 30 50.85
July 50 108i 55 31 146k 65 53 72.57 //
Aug. 46 44 33 37 51 49 47 43.85
Sept. 50 73 54 I1, 59 58 41 57.00
Oct. 48 40k 49 4:' 63 61 24?. 47.2N
Nov. 44 49 50 20& 74 59 4: 48.71
Dec. 51 90 48 32 88 67W I,4 62.85
Jan. 48 60 53 40 97 64 !!.- 59.14
Feb. 45 84 62 41 99 53 52 62.28
Mar. 32 1 99 92.- 32 80 51 64H 64.28
Apr. 69 65 4' 32 65 62 43 55.00
May 46 65 25k 27 67 52 40 46.00 L-
June 80 I 71 54 27 67 50 41 55.71

Mean 50.07 69.69 53.00 36.84 78.76 5(.46 45.92
d I I







Florida Agricultural Experiment Station


counted after 4 to 6 days. The results obtained are presented in
Tables 1 to 5.
There were no significant differences between the mean num-
bers of microorganisms in the samples of soil from the same soil
type at different locations, according to the method of analysis
of variance. Therefore, the results are presented as averages for
each soil type at each sampling.
Table 1 gives the average numbers of molds in the 7 soil types.
The largest number was found in the Orlando fine sand and the
smallest number in the Gainesville fine sand. The average num-
ber of molds in all soils varied from month to month, the largest
numbers being obtained during July. There were no significant
differences between the numbers of molds in the same soil type
at different locations, and the mean difference between the differ-
ent soil types was not significant because of the failure of the
numbers in each soil type to vary the same at the different loca-
tions. The distance between the areas of the same soil type and
the local nature of the rainfall were undoubtedly fact rs contrib-
uting to the large interaction between location and, soil type.
The-ifferences between the numbers of molds in the virgin and
cultivated soils were not significant and possibly the slight dif-
ference in time of sampling the soils under the 2 conditions was
a complicating factor.


Mo.

June
July
Aug.
Sept.
Oct.
Nov.
Dec.
Jan.
Feb.
Mar.
Apr.
May
June

Mean


TABLE 2.-AVERAGE NUMBERS OF BACTERIA IN 7
(Thousands per gram of, dry soil)
SOIL TYPE
Nor- Blan- Her- Gaines-[
folk ton nando ville Orlando Leon
Fine Fine Fine Fine Fine Fine
Sand Sand Sand Sand Sand Sand

426 528 580 558 866 116
272 348 371 528 969 230
258 422 387 404 476 249
180 164 390 382, 242 197
495 321 354 859 355 624
1,137 814 572 1,040 1,062 2,237
614 1,268 620 1,438 1,702 433
1,194 1,401 1,192 3,423 1,404 1,073
930 1,424 600 2,080 1,558 824
869 1,400 870 2,243 1,193 456
1,149 916 890 2,399 1,091 673
1,019 984 729 1,137 826 425
1,044 705 715 3,031 1,142 481

737.5 823.0 636.2 1,501.7 952.8 616.8


SOIL TYPES.


Ports-
mouth
Fine
Sand

342
576
480
280
486
656
1,030
1,088
4,708
1,398
928
1,086
968

1,078.9


Mean

416.6
470.6
382.3
262.1 -
499.1
1,074.0
1,015.0
1,539.3
1,732.0 r
1,204.1
1,149.4
886.6
1,155.1


Least Significant Difference between Means of Months, P = 5%. 733.2.


I







Types and Distribution of Microorganisms


Table 2 gives the average numbers of bacteria in the 7 soil
types. The numbers of bacteria in the different soil types were
not significantly different because of the relatively large inter-
action between location and soil types. The Gainesville fine sand
contained the largest number of bacteria and the Leon fine sand
the smallest number. There were no significant differences in
the numbers of bacteria under virgin and cultivated conditions.
There was, however, a significant difference in the numbers of
bacteria at the different samplings. The smallest numbers of
bacteria were obtained during September and the largest num-
bers during February. In general, the numbers of bacteria were
high in all soils during November, December, January, February,
March and April, and low during May, June, July, August, Sep-
tember and October. The numbers of bacteria in all soils were
lower in June, 1938, than in June, 1939. No doubt these differ-
ences reflect differences in soil temperature and soil moisture
conditions during the 2 months.
The numbers of actinomyces in the 7 soil types are presented
in Table 3. There was a significant difference in the numbers of
actniomyces in the different soil types. The Gainesville fine sand
contained the largest number of actinomyces and the Leon fine
sand the smallest number. The smallest number of actinomyces

TABLE 3.-AVERAGE NUMBERS OF ACTINOMYCES IN 7 SOIL TYPES.
(Thousands per gram of dry soil)

SOIL TYPE
Nor- Blan- Her- Gaines- I Ports-
Mo. folk ton nando ville Orlando I Leon mouth
Fine Fine Fine Fine Fine Fine Fine Mean
_( Sand Sand Sand Sand Sand Sand Sand
June 1,106 993 1,486 1,539 992 322 635 996.1
'July 967 1,196 1,331 1,638 2,164 557 852 1,243.6
Aug. 600 786 786 942 953 442 704 744.7 L
Sept. 1,031 706 1,318 1,479 1,246 526 710 1,002.3
Oct. 1,360 890 1,035 1,703 1,468 618 562 1,090.9
Nov. 1,339 1,084 970 1,442 1,685 424 600 1,077.7-
Dec. 1,031 1,100 900 1,634 1,552 416 502 1,019.3
Jan. 1,168 1,191 1,054 1,632 1,266 351 561 1,031.9.
Feb. 951 996 843 2,140 1,048 366 529 981.9
Mar. 1,352 935 949 1,224 1,272 444 597 967.6
Apr. 1,444 634 842 1,355 809 459 454 856.7'
May 1,377 952 1,191 1,300 1,224 554 561 1,022.7
June 1,826 988 1,360 2,541 1,140 614 732 1,314.4

Mean 1,196.3 950.1 1,081.9 1,582.2 1,293.8 468.7 615.3

Least Significant Difference between Means of Soil Type. P = 5%, 453.4.






Florida Agricultural Experiment Station


in all soils was obtained in August, 1938, and the largest number
in June, 1939. The numbers of actinomyces were high in all soils
during July, September, October, November, December, January,
May and June, 1939. During several months of the year the num-
bers of actinomyces were larger than the numbers of bacteria.
The largest numbers of bacteria and actinomyces occurred in
the Gainesville fine sand. The total number of organisms in this
soil was 3,120,740 per gram, of which 1 percent were molds, 48
percent were bacteria and 51 percent were actinomyces. The
smallest average numbers of microorganisms occurred in the
Leon fine sand. The average total number of microorganisms
in the Leon fine sand was 1,141,960 per gram. The proportion
of molds, bacteria and actinomyces in this soil was about 5, 54,
and 41 percent, respectively. The Orlando fine sand contained
the largest average number of molds. The average total number
or organisms in this soil was 2,325,260 per gram. The average
number of molds in the Orlando fine sand was 78,760 per gram.
The total number of organisms in the soils at the July
sampling was 1,786,770 per gram, of which 72,570 or 3 percent
were molds. Bacteria made up 25 percent of the total population
and actinomyces 72 percent at this sampling. At the September
sampling actinomyces composed 75 percent of the total popula-
tion. The average total number of organisms in the soils at the
February sampling was 2,776,180 per gram. Bacteria composed
62 percent of the total population.at that time. At the June,
1939, sampling the average total number of organisms was 2,-
525,210 per gram, of which 53 percent were actinomyces.
These data are of special interest in the characterization of
these soils. The low mold content reflects the low organic matter
content of all these soils. The high proportion of actinomyces
in the total microbial population indicates the nature of the
organic matter and the soil moisture relations. Ordinarily, acti-
nomyces rarely exceed 15 percent of the total population of the
average loam. However, in these soils the proportion of acti-
nomyces to the total number of microorganisms was frequently
higher than this. The actinomyces are able to withstand drying
conditions and are capable of decomposing the most resistant
fractions of organic matter. On account of the coarse texture,
long periods of low rainfall and relatively high temperatures,
these soils support a vigorous flora of the actinomyces which
decompose the organic matter rapidly and completely. In order
to maintain an adequate supply of organic matter in these soils







Types and Distribution of Microorganisms


short rotations with an annual green manure crop should be
practiced.
Table 4 gives the percent moisture in the soils at the monthly
samplings. The data show that the Portsmouth fine sand was
the wettest of the 7 soils. The moisture content of this soil was
higher than that of any other soil at every sampling during the
year, except March, when the Orlando fine sand contained slightly
more moisture. The field moisture capacity of the Portsmouth fine
sand was not determined but it was undoubtedly lower than the
moisture content of the soil a greater part of the year. The rela-
tively low numbers of molds in the Portsmouth fine sand were
undoubtedly caused by an excess of moisture. The Leon fine sand
becomes very dry during periods of drought and very wet during
prolonged rainy seasons because of a hardpan which occurs at
about 30 inches below the surface. The moisture content of this
soil was 16.1 percent at the October sampling. The rainfall for
October was 9.13 inches (see Table 6). The percentage moisture
at the November and December samplings was 11.3 and 7.3,
respectively, with rainfall of 0.74 inches for November and 0.53
inches for December. The Norfolk and Blanton fine sands are
excessively drained and consequently relatively dry, even during
periods of high rainfall. The Orlando fine sand is usually well
drained and with a relatively high organic matter content condi-
tions are generally favorable for mold development. The clay
underlying the Hernando and Gainesville fine sands influences


TABLE 4.-THE MOISTURE CONTENT OF 7 SOIL TYPES (Percent).

SOIL TYPE
Her- Gaines- Ports-
Norfolk Blanton nando ville Orlando Leon mouth
Month Fine Fine Fine Fine Fine Fine Fine
Sand Sand Sand Sand Sand Sand Sand
June 6.0 7.2 8.3 8.5 7.2 8.7 17.7
July 6.1 6.1 7.7 12.4 8.4 8.2 15.2
Aug. 2.8 8.3 1.7 3.8' 10.2 2.9 21.8
Sept. 6.6 4.0 7.2 9.3 4.8 7.1 17.0
Oct. 8.1 3.4 7.1 11.8 5.3 16.1 18.5
Nov. 5.3 5.9 3.8 8.3 7.2 11.3 21.3
Dec. 4.2 5.7 5.1 6.3 6.6 7.3 16.2
Jan. 7.3 4.6 7.4 7.2 7.1 10.3 18.6
Feb. 7.6 6.5 7.5 9.7 8.9 9.5 18.6
Mar. 4.9 7.1 6.1 7.1 8.9 6.6 8.6
Apr. 6.0 4.8 8.1 10.0 7.2 6.3 17.8
May 3.4 5.3 4.0 6.3 7.0 5.6 20.0
June 8.6 6.9 8.0 11.5 8.0 16.9 15.9








Florida Agricultural Experiment Station


TABLE 5.-THE PH OF 7 SOIL TYPES.


.SOIL
SHer-
Norfolk Blanton nando
Month Fine Fine Fine
Sand Sand Sand


June
July
Aug.
Sept.
Oct.
Nov.
Dec.
Jan.
Feb.
Mar.
Apr.
May
June


TABLE 6.-MEAN MONTHLY 1
GAINSVILLE DISTRICT, Ji

Month

June ......-...........................
July ........... ............. ..... ........
August .................. .............
Septem ber ....................................
October ......................................
November ......................................
Decem ber ...................... ............
January -....---. ...........-...................
February ....................................
M arch ........ .. .......... ...........
April ................ ................
M ay ........................................ ....
June .... ............................... .......


tEMPERATURE AND TOTAL PRECIPITATION,
UNE, 1938, THROUGH JUNE, 1989.
Temperature Total Rainfall
Degrees F. Inches

78.1 9.63
79.2 5.11
81.7 5.95
77.7 4.61
68.7 9.13
65.9 0.74
56.0 0.53
59.1 1.81
65.4 5.70
66.8 1.00
69.5 4.51
74.5 3.77
80.4 10.45


the moisture content of these soils. The moisture content of all
soils varied considerably and in addition to indicating differences
in physical properties of the different soils it emphasizes the local
nature of- rainfall (see Table 6).
Leon and Portsmouth fine sands were strongly acid. Orlando,
Blanton and Norfolk fine sands were of medium acidity. Hernando
and Gainesville fine sands were medium to slightly acid in reac-
tion. The pH of the latter 2 soils reflects the influence of lime-
stone in the parent materials of these soils. The less acid condi-
tion of the Gainesville fine sand was undoubtedly a factor in the
development of higher numbers of bacteria and actinomyces than
in any other soil, (see Table 5).


TYPE
Gaines-
ville
Fine
Sand

5.73
5.60
5.75
5.87
5.73
5.75
5.72
5.88
6.00
6.00
6.00
5.65
5.85


Orlando
Fine
Sand

5.37
5.66
5.50
5.31
5.76
5.38
5.40
5.48
5.74
5.69
5.45
5.65
5.65


Leon
Fine
Sand

4.40
4.42
4.52
4.78
4.45
4.51
4.36
4.47
4.64
4.65
4.25
4.50
5.00


Ports-
mouth
Fine
Sand

4.67
4.83
4.79
4.67
4.75
4.91
5.09
5.41
5.45
5.77
5.00
5.10
5.15







Types and Distribution of Microorganisms


Table 6 gives the mean monthly temperature and total precipi-
tation in the Gainesville district for the months corresponding
to the sampling periods. The lowest average monthly tempera-
ture was 560F. and was recorded in December. The highest mean
monthly temperature was 81.70F. and was recorded in August.
The average monthly temperature was below 700F. during Octo-
ber, November, December, January, February, March and April.
The highest total monthly rainfall, 10.45 inches, occurred in
June, 1939, and the lowest, 0.53 inches, in December. November,
December, January and March were relatively dry. The total
rainfall for the year was 52.39 inches.

THE NUMBERS OF MICROORGANISMS IN ARREDONDO FINE SAND
UNDER DIFFERENT CROPPING SYSTEMS 2
The "Land Resting Experiment" conducted by the Agronomy
Department (8) in 1933 was sampled at monthly intervals from
June, 1938, through May, 1939, for a determination of the num-
bers of molds, bacteria and actinomyces. This experiment, de-
signed to compare the effects of continuous cropping, "resting"
the land and native cover with leguminous cover crops on crop
yields, consists of 4.replicated blocks, each block consisting of 5
plots 35 feet wide and 760 feet long. The 5 plots were cropped
as follows:
Plot 1. Continuous corn and peanuts.
Plot 2. Continuous corn and peanuts with species of crotalaria at last
cultivation, oats between corn and peanuts in fall.
Plot 3. Corn and peanuts alternating with year of crotalaria.
Plot 4. Corn and peanuts alternating with year of rest.
Plot 5. Corn and peanuts alternating with 2 years of rest.
Five samples of soil were taken aseptically from the surface 6
inches in each plot, brought into the laboratory and composite.
Moisture determinations were made on the soils of each compo-
site sample and a quantity of moist soil equivalent to 50 grams
of dry soil was weighed into 500 cc. of sterile tap water in 1-liter
Erlenmeyer flasks. pH determinations were made and dilution
plates poured from the 1:10 soil-water suspension. Thejplates
were incubated and the counts of microorganisms made in the
usual manner. The results obtained are presented in Tables 7, 8
and 9. The pH and moisture contents are given in Appendix I.
At the June sampling the moisture content of the soils varied
from 10.4 percent to 12.7 percent and the pH varied from 5.75
2 The authors are indebted to Mr. W. E. Stokes, Head, Department of
Agronomy, Agricultural Experiment Station, for permission to sample these
and other experimental plots.













TABLE 7.-AVERAGE NUMBERS OF MOLDS IN ARREDONDO FINE SAND UNDER DIFFERENT CROPPING SYSTEMS.
(Thousands per gram of dry soil)


Month



June .....................-.
July ..........-..........
August ............
September .............
October ................-
November ..............
December ...........
January ................
February ..............
March ..........-.
April .................
May .....................--


Mean


Continuous
Corn and
Peanuts


41
56
26
40
38
52
101
47
54
50
42
41

49.0


Continuous Corn]
and Peanuts Crotalaria 1
with Summer Year. Corn and
Cover of Peanuts 1 Year
Crotalaria


56
52
27
33
34
74
100
65
62
54
54
46

55.5


62
66
321.-
51
35
84
104
69
53
64
68
51

61.5


Native Cover
1 Year. Corn
and Peanuts
1 Year.

35
43
24
35
51
61
103
47
39
61
45
32

48.0


Native Cover
2 Years. Corn
and Peanuts
I Year.

44
52
29 '


Mean



47.6
53.8
27.6
38.2
37.8
66.0
99.0
54.8
50.4
57.0
53.0
39.0


Least Significant Difference between Means of Cropping Systems, P = 5%, 9.3; 1%, 12.7.
Least Significant Difference between Means of Months, P = 5%, 9.5; 1%, 13.9.


I
--------------..~







Types and Distribution of Microorganisms


to 6.08 (Appendix I). The number of molds in the soil under
continuous corn and peanuts was 41,000 per gram of dry soil.
The average number of molds in the soil in the plots under corn
and peanuts with a summer cover crop of crotalaria was 56,000
per gram of dry soil; it was 62,000 per gram in the soil under
crotalaria 1 year and corn and peanuts 1 year. With native cover
1 year and corn and peanuts 1 year the numbers of molds aver-
aged 35,000 per gram. In the plots under native cover 2 years
and corn and peanuts 1 year, the numbers of molds averaged
44,000 per gram.
The numbers of molds were slightly larger in all the soils at
the July sampling, except in the case of soils under continuous
corn and peanuts with summer cover of crotalaria. The average
number of molds in the soil of these plots was 52,000 per gram.
At the August sampling the average number of molds in the
soil under continuous corn and peanuts was 26,000 per gram,
under corn and peanuts with summer cover of crotalaria 27,000,
and under corn and peanuts alternated with crotalaria the num-
ber was 32,000 per gram of dry soil. There were only 24,000
molds per gram of dry soil under native cover 1 year and 29,000
in the soil under native cover 2 years. The average number of
molds at the August sampling was lower than at any other
sampling.
The number of molds in the soil under continuous corn and
peanuts was higher than that under continuous corn with pea-
nuts and a summer cover of crotalaria at the September sam-
pling, and the number of molds in the soil under corn and peanuts
alternated with crotalaria was higher than the number in any
other soil.
At the November sampling the soils under continuous corn
and peanuts with a summer cover of crotalaria contained an
average of 74,000 molds per gram, whereas the soils under crota-
laria 1 year and corn and peanuts 1 year contained an average
of 84,000 per gram.
The number of molds in the soil planted to corn and peanuts
1 year and rested 2 years was lower than that of any other soil at
the December sampling. There was a marked increase in the
numbers of molds in all soils at that sampling, the average being
99,000 per gram.
The numbers of molds declined sharply at the January sam-
pling, the average numbers being 54,800 per gram. The numbers
of molds in the soils under continuous corn and peanuts with







Florida Agricultural Experiment Station


summer cover of crotalaria were higher than those of any other
soil at the February sampling, but at the March, April and May
samplings the numbers of molds in the soil alternated with crota-
laria 1 year and corn and peanuts 1 year were higher than in
the soil under any other treatment.
There were no significant differences between the average
numbers of molds in the soils under continuous corn and peanuts,
land rested 1 year or that rested 2 years. There was a significant
increase in the numbers of molds in the soil under crotalaria
1 year and corn and peanuts 1 year. This soil contained the
largest number of molds, averaging 61,500 per gram. The mean
differences in numbers of molds in the soils under different
cropping systems were highly significant.
The numbers of bacteria and actinomyces did not vary signifi-
cantly in the soils under the different cropping systems. How-
ever, the differences between the monthly means of both groups
of organisms were highly significant. The smallest numbers of
bacteria were obtained in August. The average number of bac-
teria for this month was 321,000 per gram of dry soil. There
was a gradual increase in the numbers of bacteria in soil from
August until January, when the average number was 4,489,200
per gram. The largest numbers of actinomyces were obtained in
July and the smallest numbers in August. The average numbers
of actinomyces in the soil in July and August were 3,087,000 and
1,367,400 per gram, respectively. The proportion of molds, bac-
teria and actinomyces to the total population in the soils were
molds, 1.4 percent, bacteria 22.1 percent and actinomyces 76.5
percent for July. For August the percentages were 1.3, 26.2, and
72.5 for molds, bacteria and actinomyces, respectively.

THE NUMBERS OF MICROORGANISMS IN NORFOLK LOAMY FINE
SAND CROPPED TO CORN AND PEANUTS, AND LAND RESTING
The numbers of molds, bacteria and actinomyces were deter-
mined in unfertilized plots of Norfolk loamy fine sand at monthly
intervals from August, 1938, to March, 1939, inclusive. The soil
samples were taken from an experiment conducted by the
Agronomy Department and designed to study the effects of burn-
ing crop residues on crop yields compared with plowing the resi-
dues under in a system of alternate cropping to corn and peanuts
and "resting" or "laying' out." The experiment consisted of 4
3 By courtesy of Mr. W. E. Stokes, Head, Department of Agronomy,
Florida Agricultural Experiment Station, Gainesville, Florida.











TABLE 8.-AVERAGE NUMBERS OF BACTERIA IN ARREDONDO FINE SAND UNDER DIFFERENT CROPPING SYSTEMS.
(Thousands per gram of dry soil)
CROPPING SYSTEM
Continuous Corn
Continuous and Peanuts Crotalaria 1 Native Cover Native Cover
Month Corn and With Summer Year. Corn and 1 Year. Corn 2 Years. Corn Mean
Peanuts Cover of Peanuts 1 Year and Peanuts and Peanuts .
Crotalaria 1 Year 1 Year _

June ..................... 757 624 799 788 898 773.2
July .. .......... 1,269 1,254 1,242 961 847 1,114.6 g.
August ......... 329 456 324 278 218 321.0
September .............- 602 489 490 529 397 501.4
October .... .........--- 1,191 1,233 1,289 1,046 896 1,131.0
November -..........| 1,505 1,649 1,851 1,475 1,447 1,585.4
December ............ 3,347 2,770 3,496 2,408 2,893 2,982.8
January --......- 3,876 5,070 5,094 3,989 4,417 4,489.2 "
February ..---........ I 3,578 4,368 3,211 2,554 3,395 3,421.2 Q
March ........... 2,904 4,592 4,265 3,680 5,772 4,242.6 0
April .---.. .......... 2,731 3,907 3,134 2,691 2,594 3,011.4
May .............. ... 5,862 2,397 3,275 2,052 1,847 3,086.6

Least Significant Difference between Means of Months, P 5%, 2,634.6; 1%, 3,833.0.














TABLE 9.-AVERAGE NUMBERS OF ACTINOMYCES IN ARREDONDO FINE SAND UNDER DIFFERENT CROPPING SYSTEMS.


Month


June ............- ..
July ......................
August .......-.....
September .....---
October .... .........
November ..........
December ......
January .................
February .....---.....
March ....-
April ................
May .......-.........


Continuous
Corn and
Peanuts


2,299
2,696
1,731
2,217
2,393
1,825
2,513
1,962
2,084
2,141
2,267
2,605


(Thousands per gram of Dry Soil)
CROPPING SYSTEM
Continuous Corn
and Peanuts Crotalaria Native Cover Native Cover
With Summer 1 Year. Corn 1 Year. Corn 2 Years. Corn Mean
Cover of and Peanuts and Peanuts and Peanuts
Crotalaria 1 Year 1 Year 1 Year

2,875 2,775 2,814 2,655. 2,683.6
3,386 3,554 3,038 2,761 3,087.0
1,620 1,575 1,006 905 1,367.4
2,308 2,352 2,085 1,737 2,139.8
2,536 2,358 2,471 2,146 2,380.8
2,135 2,132 2,158 2,322 2,114.4
1,964 2,425 2,213 2,563 2,335.6
1,957 2,396 2,067 2,161 2,112.6
2,056 2,213 2,117 2,104 2,114.8
2,282 2,678 2,261 2,218 2,316.0
2,065 2,480 2,286 2,137 2,247.0
2,575 2,445 2,292 2,042 2,391.8


Least Significant Difference between Means of Months, P = 5%, 359.0; 1%, 522.3.


-~--~






Types and Distribution of Microorganisms


randomized blocks, 2 planted to corn and peanuts in alternate
years and 2 lying out while supporting a growth of native weeds
and grasses. Each block was divided into 16 plots 27 feet wide
and 140 feet long. The residues on 8 plots in every block were
burned in the early spring before preparation of the seedbed for
planting and the residues on the other 8 plots in each block were
turned under. Two plots in each block were unfertilized and
served as a check. The other 14 plots in each block were treated
with different fertilizers. The 8 check plots were sampled each
month, 4 on which the residues had been burned and 4 on which
the residues had been plowed under.
Samples were taken aseptically at 5 locations on the plot at
intervals approximately 25 feet part. All samples from each
plot were mixed thoroughly in the laboratory. Moisture deter-
minations were made on the composite samples and dilution
plates poured for numbers of microorganisms in the usual man-
ner. The pH was determined on the 1:10 soil-water suspension
used for the dilution plates by the quinhydrone electrode. The
results obtained are presented in Tables 10, 11 and 12 and Ap-
pendix II.
The data show that the moisture content of these soils was
never high and the reaction varied between pH 5.79 and 6.45
(Appendix II). There were no significant differences in the num-
ber of microorganisms in the burned and unburned areas of this
soil. There was a significant difference in the number of molds
in the soil cultivated to corn and peanuts and in the soil resting.
TABLE 10.-NUMBERS OF MOLDS IN NORFOLK LOAMY FINE SAND CULTI-
VATED AND RESTING.
(Thousands per gram of dry soil)

S CULTIVATED RESTING I
Month -I Mean
__ Replications II Replications
I 1 2 3 4 1i 1 2 3 4_
August 76 21 38 21 32 28 36 27 34.8
September 15 32 38 6 19 11 23 15 19.8
October 46 40 79 42 29 29 23 27 39.3
November 88 59 58 45 24 27 51 24 47.0
December 57 34 62 46 34 19 42 23 39.6
January 112 64 72 58 59 80 59 43 68.3
February 49 44 54 32 44 33 32 27 39.3
March 93 53 58 45 56 37 49 40 53.8
Mean 51.1 34.4

Least Significant Difference between Means of Treatments. P = 5%, 9.7.
Least Significant Difference between Means of Months, P = 5%, 11.3; P = 1%, 15.7.















TABLE 11.-AVERAGE NUMBERS OF BACTERIA IN NORFOLK LOAMY FINE SAND CULTIVATED AND RESTIN
(Thousands per gram of dry soil)


CULTIVATED


1 2

August 1,271 497
September 356 362
October 851 691
November 2,302 1,677
December 1,514 1,178
January 1,860 1,732
February 2,562 3,279
March 1,784 2,580


1,562.5 1,499.5


1,155
209
769
2,094
1,729
2,666
2,787
2,574


1,747.8


I 1


1,160 1,271
212 212
781 670
1,241 1,779
1,283 1,492
1,116 2,599
3,409 1,982
3,122 8,119


1,540.5 2,265.5


RESTING


]Iplaln


Reliaton


953 841 870
129 64 278
419 562 607
1,514 1,695 1,295
1,110 1,378 1,089
1,174 1,681 1,902
1,576 1,996 1,277
5,330 8,572 5,408

1,525.6 2,098.6 1,590.7


Least Significant Difference between Means of Months, P = 5%, 416.6; P = 1%, 578.2.


G.



Mean

< .
902.2
227.7
668.7
1,699.6
1,346.6
1,841.2
2,358.5
4,686.1


Z2-
--



Month


Replications


Mean


.


I


Least Significant Difference between Means of Months, P 5%, 416.6 ; P = 1%, 578.2.


I


I


Kepllcations


3 4













TABLE 12.-THE AVERAGE NUMBERS OF ACTINOMYCES IN NORFOLK LOAMY FINE SAND CULTIVATED AND RESTI:
(Thousands per gram of dry soil)


Month

1

August 3,363
September 1,164
October 1,912
November 2,407
December 1,872
January 1,647
February 2,534
March 958

Mean 1,982.1


CULTIVATED

Replications


3


2

1,411
1,960
1,969
1,864
2,040
1,626
1,667
1,808

1,793.1


4


2,468 2,439
479 530
416 2,173
2,644 2,402
1,896 1,914
1,891 1,541
1,677 2,153
1,212 2,455

1,585.3 1,950.8


2,304
934
1,885
1,807
2,773
1,527
2,120
1,265


RESTING

Replications
2 3


1,986
665
2,206
1,620
1,613
1,761
1,993
1,439


1,826.8 1,660.3


2,156
956
1,748
1,907
1,983
1,494
1,762
1,698


4


2,400
791
1,738
1,586
1,717
1,489
1,440
1,432


1,713.0 1,574.1


2,

1,
2,(
1,i
1,;
1,
1,i


NG.




Mean



315.8
934.8
755.8
029.6
976.0 -
622.0
918.2
533.3

-b


Least Significant Difference between Means of Months, P = 5%, 492.9; P = 1%, 684.1.






Florida Agricultural Experiment Station


The average number in the cultivated soil was 51,100 per gram,
whereas the average number in the resting soil was 34,400 per
gram. The mean differences between months were highly signi-
ficant. The lowest numbers were present in September and the
highest numbers in January.
The mean differences between the numbers of bacteria in the
soil cultivated to corn and peanuts and those in the resting soil
were not significant. There was a highly significant difference
between the mean numbers of bacteria found in these soils at the
different months. The number for September averaged 227,700
and that for March 4,686,100 per gram of dry soil.
The number of actinomyces in the soil varied widely in August
and September, the numbers being 2,315,800 and 934,800, re-
spectively. The average numbers at the other samplings ranged
from slightly over 1.5 million to a little more than 2.0 million
per gram. These differences were highly significant. The differ-
ences between the mean numbers of actinomyces in the culti-
vated soil and the resting soil were not significant.
At the September sampling 79.0 percent of the total population
of microorganisms were actinomyces, 19.3 percent were bacteria
and 1.7 percent were molds. At the March sampling 74.7 percent
of the total population were bacteria, 24.4 percent actinomyces
and 0.9 percent were molds. The average total number of organ-
isms in the soils at the September sampling was 1,182,300 per
gram. At the March sampling the average total number of
organisms in the soil was 6,273,200 per gram.
The low initial organic matter content of these soils and the
small amount of residues that were burned previous to the sam-
pling probably account for the absence of any significant differ-
ence in the numbers of microorganisms in the burned and un-
burned soils. The small proportion of molds and large proportion
of actinomyces to the total microbial population indicate a soil of
low organic matter content and low microbiological activity.

THE NUMBERS OF MICROORGANISMS IN NORFOLK LOAMY FINE
SAND AT DIFFERENT pH LEVELS
The effect of soil reaction or pH on the numbers of molds,
bacteria and actinomyces in a Norfolk loamy fine sand was stud-
ied at seasonal intervals during the latter part of 1938 and the
first part of 1939. A series of plots referred to as the "Reaction
Plots" treated according to the outline shown in Table 13 was
used. These plots were established in 1926. Two plots were







Types and Distribution of Microorganisms 27

treated in duplicate with different amounts of sulfur to produce
varying degrees of acidity. Duplicate plots were left untreated
and served as checks. Three plots were treated in duplicate with
different amounts of calcium limestone. The plots were laid out
15 feet wide and 1041/2 feet long. The plots were separated
by 14 gauge steel plates 12 inches wide stood on edge between the
plots and extended about 4 inches above the surface of the
ground.

TABLE 13.-OUTLINE OF SOIL TREATMENTS IN REACTION PLOTS ON NORFOLK
LOAMY FINE SAND.

Plot i Pounds per 2,000,000 Pounds of Soil
No. Material I 1926 1931 1935 | 1937 I 1938
1 Sulfur ............... 1,000 900 500 500 500
2 Sulfur ............. 500 450 250 250 250
3 Check .-.......-- -
4 Limestone ........ 1,000 450 500 500 500
5 Limestone ........ 2,000 900 1,000 1,000 1,000
6 Limestone ........ 4,000 1,800 2,000 2,000 2,000
7 Sulfur ............... 1,000 900 500 500 500
8 Sulfur.............. 500 450 250 250 250
9 Check ............... -
10 Limsetone ........ 1,000 450 500 500 500
11 Limestone ....... 2,000 900 1,000 1,000 1,000
12 Limestone ....... 4,000 1,800 2,000 2,000 2,000


The soils were sampled aseptically in June and October, 1938,
and February and April, 1939, for the determination of numbers
of microorganisms by the usual methods. The percent moisture,
pH, and numbers of molds, bacteria and actinomyces at the vari-
ous samplings are given in Tables 15, 16, 17 and 18. The soils
were sampled in November, 1939, for a determination of calcium,
magnesium, and phosphorus soluble in 0.1 N HC1. Official meth-
ods were used in the analysis of these extracts. The results ob-
tained are presented in Table 14.
The data in Table 14 show that sulfur was effective in lowering
the pH of this soil. The calcium had leached from the surface of
the acid soils and the contents of magnesium and phosphorus
were lower in the check and sulfur-treated soils than in the
limed soils.
At the June sampling the sulfur-treated soils, pH 5.21 or be-
low, contained a higher average mold content than the limed
soils and a markedly lower content of bacteria and actinomyces.
The average mold count was 75,250 per gram in soils below pH
5.30 and 60,666 per gram in soils above pH 6.55. The average







Florida Agricultural Experiment Station


TABLE 14.-THE PH, AND CALCIUM, MAGNESIUM AND PHOSPHORUS SOLUBLE
IN 0.1 N HCL IN NORFOLK LOAMY FINE SAND. (November 1939.)

Pounds per 2,000,000 Pounds of Soil
Plot pH I
No. Ca Mg P

1 3.88 0 10 208
7 3.74 0 10 166
2 4.08 0 10 208
8 4.16 0 10 160
3 5.13 400 10 200
9 5.06 350 10 200
4 5.82 700 26 208
10 5.74 750 26 200
5 6.33 1,000 30 228
11 6.23 1,000 30 210
6 6.87 1,900 40 294
12 6.79 2,000 40 294


TABLE 15.-PERCENT MOISTURE, pH AND NUMBERS OF MOLDS, BACTERIA
AND ACTINOMYCES PER GRAM OF DRY SOIL IN NORFOLK LOAMY FINE SAND,
JUNE 3.
Plot Percent I
No. Moisture pH Molds 1 Bacteria Actinomyces

1 4.3 4.03 92,000 167,000 648,000
7 3.8 4.27 71,000 Z 166,000 166,000
2 4.5 5.30 65,000 524,000 524,000
8 4.5 5.21 73,000 314,000 314,000
3 4.3 6.25 63,000 982,000 1,024,000
9 4.8 6.58 80,000 1,155,000 861,000
4 4.5 6.55 88,000 1,089,000 1,361,000
10 4.2 6.75 46,000 1,226,000 1,879,000
5 4.3 7.10 / 94,000 1,149,000 1,609,000
11 4.6 7.23 L44,000 786,000 1,169,000
6 4.5 7.55 46,000 1,257,000 963,000
12 4.3 7.38 46,000 1,515,000 1,306,000


numbers of bacteria in these soils were 292,750 and 1,170,333
per gram, respectively. The average numbers of actinomyces
were 413,000 and 1,381,333 per gram, respectively. This rela-
tionship persisted at the other samplings and was the most out-
standing feature of the experiment. There was a considerable







Types and Distribution of Microorganisms


TABLE 16.-PERCENT MOISTURE, pH AND NUMBERS OF MOLDS, BACTERIA
ANID ACTINOMYCES PER GRAM OF DRY SOIL IN NORFOLK LOAMY FINE SAND,
OCTOBER 14.


pH

4.11,
4.49
4.6
5.43
5.30
5.85
5.81
6.49
6.56
7.00
7.16


Molds

162,000
125,000
155,000
96,000
99,000
100,000
112,000
67,000
/226,000
'56,000
67,000
.. 58,000


Bacteria

133,000
/ 27,000
348,000
452,000
642,000
793,000
1,066,0)00
i 1,452,000
1,226,000
1,122,000
719,000
690,000


Actinomyces

319,000
/ 265,000

589,000
585,000
1,151,000
1,070,000
1,839,000
I 2,189;000
1,919,000
1,870,000
1,917,000
1,168,000


TABLE 17.-PERCENT MOISTURE, pH AND NUMBERS OF MOLDS, BACTERIA
AND ACTINOMYCES PER GRAM OF DRY SOIL IN NORFOLK LOAMY FINE SAND,
FEBRUARY 21.
Plot Percent
No. Moisture pH Molds Bacteria Actinomyces

1 3.0 3.95 103,000 361,000 284,000
7 2.8 3.83 85,000 1 179,000 t 283,000
2 3.0 4.01 1' 124,000 575,000 361,000
8 3.2 4.29 116,000 671,000 775,000
3 3.1 4.94 83,000 877,000 593,000
9 3.5 5.56 47,000 1,166,000 725,000
4 3.3 5.72 59,000 1,396,000 1,577,000
10 3.7 6.35 47,000 1,428,000 1,817,000
5 3.5 6.25 83,000 / 2,306,000 1,579,000
11 3.7 6.65 57,000 1,298,000 1,376,000
6 3.6 7.06 39,000 1,789,000 1,037,000
12 5.4 7.25 4. 26,000 1,480,000 1,136,000


increase in the average numbers of molds in the soil at the Octo-
ber and February samplings compared with the counts at the
June and April samplings, especially in the more strongly acid
soils. This seasonal fluctuation in numbers of microorganisms
was not so noticeable in the bacteria and actinomyces.
The higher average numbers of molds in the strongly acid


Plot
No.


Percent
Moisture






Florida Agricultural Experiment Station


TABLE 18.-PERCENT MOISTURE, pH AND NUMBERS OF MOLDS, BACTERIA
AND ACTINOMYCES. PER GRAM OF DRY SOIL IN NORFOLK LOAMY FINE SAND,
APRIL 11.
Plot Percent
No. Moisture pH Molds Bacteria Actinomyces
1 2.9 3.90 98,000 103,000 232,000
7 2.8 3.60 12,000 26,000 128,000
2 3.1 3.90 64,000 387,000 490,000
8 3.1 3.90 13,000 566,000 722,000
3 3.4 5.20 67,000 1,242,000 957,000
9 3.1 5.90 90,000 1,367,000 748,000
4 3.1 6.30 101,000 1,857,000 1,986,000
10 3.7 6.00 67,000 2,440,000 1,583,000
5 3.4 6.60 31,000 1,553,000 957,000
11 3.7 7.00 44,000 2,284,000 1,350,000
6 3.6 6.70 49,000 1,487,000 1,035,000
12 3.5 7.20 47,000 1,502,000 1,259,000


soils of this series than in the less acid or neutral soils does not
indicate a higher organic matter content in the soils of low pH
but reflects the extreme sensitiveness of the bacteria and acti-
nomyces to strongly acid conditions. In other words, the molds
are about the only organisms that can tolerate these conditions
of acidity. The check soils and the soils treated with sulfur,
usually below pH 5.0, contained extremely small total numbers
of microorganisms compared with the limed soils, even though
the acidity of the soil in every case was not completely neutral-
ized, pH 6.0-6.5. Presumably, microbioloogical activity in these
strongly acid soils was at a low ebb. The deleterious effect of
strong acidity on the chemical composition and loss of nutrients
through leaching of this soil is indicated in the analyses pre-
sented, Table 14. These data, both chemical and biological,
emphasize the need for lime on acid soils and the fundamental
nature of lime in maintaining permanent soil fertility.

THE NUMBERS OF MICROORGANISMS IN NORFOLK FINE SAND
UNDER PINEAPPLE ORANGE GROVE

The number of molds, bacteria and actinomyces in the soil
under Pineapple orange groves were determined at 3 samplings
during March, April and May, 1940, at Palm Harbor and at 2
samplings during April and May, 1940, at Windermere (9). Four







Types and Distribution of Microorganisms


plots of the Nitrogen Fertilizer Experiment 4 laid out in 1937
and a virgin area of the Norfolk fine sand in the vicinity of the
Fertilizer Experiments were sampled at each location. Each
plot consisted of 16 trees planted 25 x 25 feet, the soil samples
being taken from around the periphery of the 4 trees in the
center of the plot. All plots received the same basic 0-8-8 fer-
tlizer. The nitrogen and mineral supplements applied to the
soils of the different plots sampled in these studies were as
follows:
Plot No. Source of Nitrogen
1 1/ organic
14 nitrate of soda
%4 sulfate of ammonia
2 Same as treatment 1 plus copper,
zinc and manganese supplement.
3 % uramon
14 nitrate of soda
1/ sulfate of ammonia
4 Same as treatment 3 plus copper,
zinc, and manganese supplement.
5 Virgin
The nitrogenous fertilizers at the Palm Harbor grove were
applied December 19, 1939, at the rate of 12 pounds of 4-8-8
mixture per tree and March 14, 1940, at the rate of 3 pounds
of a 16-0-0 per tree. The mineral supplement was applied March
12, 1940, at the rate of 11/2 pounds per tree. The nitrogen ferti-
lizers at the Windermere grove were applied November 18, 1939,
at the rate of 15 pounds of a 4-8-8 mixture per tree and March
19, 1940, at the rate of 5 pounds of 16-0-0 per tree. The mineral
supplement was applied March 11, 1940, at the rate of 11/2 pounds
per tree. Five samples of soil were taken at random from the
0 to 6 inch depth from each plot and brought to the laboratory
in Gainesville where the determinations were made immediately,
in every case within 24 hours after the sample had been taken.
The pH determinations were made by the glass electrode and the
numbers of microorganisms were determined by the dilution
plate method in the usual manner. The results obtained are
presented as averages in Tables 19, 20, 21, 22, and 23.
At the March sampling of the soil in the Palm Harbor grove

The samples were supplied from this experiment through the courtesy
of Mr. Eugene Borda, formerly Graduate Assistant in Soils. Thanks are
also due Mr. Borda for help in making the determinations.







Florida Agricultural Experiment Station


TABLE 19.-AVERAGE NUMBERS OF MICROORGANISMS PER GRAM OF DRY
SOIL IN NORFOLK FINE SAND UNDER PINEAPPLE ORANGE GROVE, PALM HAR-
BOR, MARCH SAMPLING.
Plot Percent I Bacteria and
No. Moisture I pH Molds P* Actinomyces P*
1 2.7 6.10 4,000 0.58 1,450,000 0.07
2 3.0 6.40 9,000 0.52 650,000 0.62
3 3.2 6.15 6,000 0.84 1,800,000 0.99
4 4.4 5.90 20,000 0.10 1,350,000 0.94
5 3.9 5.85 13,000 0.56 450,000 0.63

*Probability of the mean numbers of organisms.

TABLE 20.-AVERAGE NUMBERS OF MICROORGANISMS PER GRAM OF DRY
SOIL IN NORFOLK FINE SAND UNDER PINEAPPLE ORANGE GROVE, PALM HAR-
BOR, APRIL SAMPLING.
Plot Percent Bacteria and
No. Moisture pH I Molds IP* Actinomyces P*

1 2.1 6.37 17,000 0.06 1,700,000 0.92
2 2.0 6.32 29,000 0.83 1,950,000 0.01
3 2.0 6.32 18,000 0.07 2,300,000 0.78
4 3.4 6.28 25,000 0.87 3,050,000 0.69
5 1.7 6.32 33,000 0.47 700,000 0.64

Probability of the mean numbers of organisms.

the mineral supplement of copper, zinc and manganese was
effective in increasing the numbers of molds in the soil consider-
ably and a decrease was brought about in the numbers of bacteria
and actinomyces. The number of molds was higher in the virgin
soil than in the fertilized soils under orange grove, except in the
case of those fertilized with uramon and the mineral supplement
of copper, zinc and manganese. The virgin soil contained fewer
bacteria and actinomyces than any of the fertilized soils under
orange grove. The total numbers of organisms were low in all
soils at this sampling.
The data in Table 20 show a stimulation of all organisms in the
soil by the mineral supplement of copper, zinc and manganese.
The virgin soil contained a higher average number of molds and
a considerably lower average number of bacteria and actino-
myces than those fertilized. There was a marked increase in
total numbers of organisms in all soils over the numbers found
at the previous sampling.
The soils were quite dry in the Palm Harbor grove at the May
sampling. The average numbers of molds were increased con-
siderably by the mineral supplement treatment in the case of the
soils receiving organic nitrogen fertilizers and only slightly in






Types and Distribution of Microorganisms


TABLE 21.-AVERAGE NUMBERS OF MICROORGANISMS PER GRAM OF DRY
SOIL IN NORFOLK FINE SAND UNDER PINEAPPLE ORANGE GROVE, PALM HAR-
BOR, MAY SAMPLING.
Plot Percent I Bacteria and |
No. Moisture pH Molds P* Actinomyces P*

1 0.6 6.21 10,000 0.75 1,000,000 0.93
2 0.8 6.43 26,000 0.87 650,000 0.69
3 0.7 6.60 11,000 0.47 850,000 0.64
4 0.6 6.60 12,000 0.75 500,000 0.99
5 0.6 5.92 25,000 0.45 300,000 0.99

Probability of the mean numbers of organisms.
TABLE 22.-AVERAGE NUMBERS OF MICROORGANISMS PER GRAM OF DRY
SOIL IN NORFOLK FINE SAND UNDER PINEAPPLE ORANGE GROVE, WINDER-
MERE, APRIL SAMPLING.
Plot Percent I I Bacteria and I
No. Moisture pH IMolds P* Actinomyces P*

1 4.0 6.39 6,000 0.89 2,450,000 0.50
2 3.6 6.23 6,000 0.34 1,700,000 0.81
3 3.9 6.25 9,000 0.04 3,350,000 0.01
4 3.5 5.90 5,000 0.49 2,200,000 0.02
5 7.9 5.75 15,000 0.11 1,150,000 I 0.01

Probability of the mean numbers of organisms.
TABLE 23.-AVERAGE NUMBERS OF MICROORGANISMS PER GRAM OF DRY
SOIL IN NORFOLK FINE SAND UNDER PINEAPPLE ORANGE GROVE, WINDER-
MERE, MAY SAMPLING.
Plot Percent I I Bacteria and
No. Moisture pH Molds P* Actinomyces P*

1 1.9 6.78 7,000 0.92 1,150,000 0.93
2 1.7 6.98 6,000 0.97 800,000 0.96
3 2.6 6.65 10,000 0.76 1,550,000 0.74
4 1.7 7.02 8,000 0.87 850,000 0.87
5 4.5 6.43 16,000 0.83 1,250,000 0.40

Probability of the mean numbers of organisms.
the case of uramon. At this sampling the average numbers of
bacteria and actinomyces were significantly lower in the soils
receiving the mineral supplement than in the soils without the
supplemental treatment. The number of molds in the soil treated
with organic nitrogen plus the mineral supplement and in the
virgin soil were considerably higher than in the other fertilized
soils under grove conditions. The numbers of bacteria and
actinomyces were considerably lower in the virgin soils than in
the fertilized soils.
The data in Table 22 indicate no significant differences in the
numbers of molds in any of the fertilized soils at the April sam-
pling. The numbers of molds were low in all soils but signifi-






Florida Agricultural Experiment Station


cantly higher in the virgin soil than in the fertilized soil under
orange grove. There was a significant decrease in the numbers
of bacteria and actinomyces in the soils receiving the mineral
supplement below that of the soil not treated with the mineral
supplement.
At the May sampling of the soils at the Windermere grove the
numbers of all organisms were decreased in the soils receiving
the mineral supplement of copper, zinc and manganese below
those without the supplemental treatment. The numbers of
organisms were slightly higher in the soils treated with uramon
than in the soils treated with organic. The numbers of molds
were higher in the virgin soils than in the fertilized soils under
grove. The numbers of bacteria and actinomyces in the virgin
soil were exceeded only by the numbers found in the soil treated
with uramon. The total numbers of organisms were low in all
soils of this grove at this sampling.
These soils were characterized by small total numbers of micro-
organisms, indicating low organic matter content, and low micro-
biological activity. In general, the numbers of bacteria and
actinomyces were considerably larger under grove conditions
than in the virgin condition but the numbers of molds were
greatly reduced under grove conditions compared with the virgin
soils. There was considerable variation in the total numbers of
organisms in the soils receiving the different fertilizers but no
significant differences were observed.

THE NUMBERS OF MICROORGANISMS IN THE PROFILE OF A
LEON FINE SAND
The profile of a virgin Leon fine sand near Paradise, Florida,
was sampled at monthly intervals from January to March and
June to August, 1941, for a determination of the molds, bacteria
and actinomyces and the kinds of algae in the various horizons.
The area sampled was typical of this soil type, being poorly
drained and very wet in wet weather and exceedingly dry in
dry weather. The vegetation was cut-over longleaf pine, slash
pine, saw palmetto, wiregrass and gallberry. The profile charac-
teristics of the soil sampled were:
Horizon : Depth Inches : Description
A1 0 to 5 Gray fine sand
As 5 to 12 Light gray to white fine sand
B1 12 to 14 Dark gray to black fine sand
B1 14 to 18 Dark brown fine sand, cemented
B, 18 to 30 Light brown fine sand






Types and Distribution of Microorganisms


A pit was dug about 2 feet wide and 3 feet long, exposing the
profile. Samples were taken aseptically from the:
As horizon at 2 to 4-inch depth.
A2 horizon at 5 to 7-inch depth.
B1 horizon at 12 to 14-inch depth.
Be horizon at 15 to 17-inch depth.
A new pit was dug for each sample of the profile. The samples
were brought into the laboratory and the numbers of molds,
bacteria and actinomyces determined by the dilution plate
method. The algae were studied by a procedure to be described
in another section of this report. The results obtained on the
numbers of microorganisms are presented in Table 24.
At the January sampling the water-table was 30 inches from
the surface and the moisture content of the soil was high through-
out the profile, being 23.15 percent in the B,2 horizon. The total
numbers of organisms were low in all horizons of this profile, the
A1 horizon containing an average of only 449,400 per gram of
dry soil. The numbers of molds decreased from 37,400 per gram
in the A1 horizon to 100 per gram in the B2 horizon. The num-
bers of molds and bacteria were higher in the B1 horizon than in
the A2 horizon.
There was a slight decrease in the numbers of molds in the A1
horizon at the February sampling below that found at the Janu-
ary sampling but an increase occurred in all lower horizons.
There was a considerable decrease in the numbers of bacteria in
the A. horizon, a slight increase in the A2, a large increase in the
B1 horizon at this sampling. There was a marked decrease in
the numbers of actinomyces in the A1 horizon below the numbers
contained in this horizon at the January sampling. The numbers
of actinomyces in the lower horizons increased over those at the
January sampling.
At the March sampling the numbers of molds in the A, horizon
increased, the numbers of bacteria decreased markedly and the
numbers of actinomyces remained the same as at the February
sampling. The A2 horizon contained more bacteria per gram
of soil than the A1 horizon at this sampling.
There was a marked decrease in the total numbers of organ-
isms in the A, horizon from January to March, but an increase
in the total numbers in the A2 horizon. There was a marked
drying of the soil throughout the profile during this time.
Very little rain fell after the March sampling until June. The
surface soil contained 0.9 percent moisture at the June sampling.
The July and August samplings were made during the rainy







Florida Agricultural Experiment Station


TABLE 24.-THE NUMBERS OF MOLDS, BACTERIA AND ACTINOMYCES PER
GRAM OF DRY SOIL IN LEON FINE SAND.
January Sampling

Numbers of Microorganisms per Gram of Dry Soil


Horizon


Molds


37,400
1,600
1,700
100


Bacteria Actinomyces

334,000 78,000
45,000 6,000
59,000 5,000
45,000 600


February Sampling

A, 36,000 230,000 60,000
A2 7,100 46,000 18,000
B1 4,300 85,000 10,000
B, 600 16,000 2,000

March Sampling

A, 47,000 80,000 60,000
A, 5,500 87,000 5,000
B1 4,000 11,000 5,000
B2 1,300 15,000 2,000

June Sampling

A, 58,000 174,000 150,000
As 2,500 35,000 14,000
B1 760 4,000 1,400
B, 240 2,200 800

July Sampling

A1 85,000 420,000 130,000
A2 6,400 37,000 15,000
B 3,500 13,000 9,000
B2 900 3,000 3,000

August Sampling


- A,
As
B,
B,


46,000
3,070
8,320
370


470,000
58,800
21,000
19,200


90,000
7,800
6,300
3,500


season. The B1 horizon contained 21.30 percent moisture at the
July sampling and 21.0 percent at the August sampling.
There were 58,000 molds per gram of dry soil in the A1 horizon
at the June sampling. The numbers of molds decreased in the






Types and Distribution of Microorganisms


lower horizons to 240 per gram in the B2 horizon. There were
174,000 bacteria per gram in the A1 horizon and a marked de-
crease in numbers of bacteria with an increase in depth. The
A1 horizon contained 150,000 actinomyces per gram at this sam-
pling and the numbers in the lower horizons decreased sharply
to 800 per gram in the B2 horizon. The total numbers of organ-
isms increased considerably in the A1 horizon above the numbers
present at the March sampling but the lower horizons contained
fewer total numbers of organisms.
There was a marked increase in number of molds in the A1
horizon and a slight increase in the lower horizons at the July
sampling over the numbers present at the June sampling. The
numbers of bacteria increased in all horizons at this sampling,
the most pronounced increase being in the A1 horizon. At this
sampling there was a slight decrease in the numbers of actino-
myces in the A1 horizon, but an increase in the lower horizons.
The total numbers of organisms increased in all horizons at the
July sampling over the numbers present at the June sampling,
the numbers for the A, horizon being 382,000 per gram in June
and 635,000 in July.
At the August sampling there was a decrease in the numbers
of molds in all horizons below the numbers present at the July
sampling, except in the B1 horizon where there was a consider-
able increase. The numbers of bacteria increased in all horizons
over the numbers present in July. The numbers of actinomyces
decreased in all horizons, below the numbers present at the pre-
vious sampling, except in the B2 horizon where there was a silght
increase. The total numbers of organisms in the A1 horizon were
slightly lower at this sampling than at the July sampling but the
numbers in the lower horizons were considerably higher.

THE ALGAL FLORA OF A LEON FINE SAND
A preliminary paper on the algal flora of some Florida soils
(6) reported only species of the Myxophyceae in the surface
(A) horizons of the Norfolk fine sand and the Portsmouth fine
sand sampled in September, 1940. The report referred to above
also dealt with species of algae isolated from the A1 and A2 hori-
zons of the Leon fine sand. The investigation has been continued
to include further samplings of the Leon fine sand profile at
different seasons of the year.
Samples of soil from the Leon fine sand profile were taken for
a determination of the kinds of algae present at the same time






Florida Agricultural Experiment Station


this soil profile was sampled for a determination of the numbers
of molds, bacteria and actinomyces, namely, January, February,
March, June, July, August and again in November, 1941. Long
periods of dry weather followed the March and August
samplings.
A quantity of moist soil equivalent to 10 grams of dry soil was
weighed into 500 cc. sterilized Erlenmeyer flasks containing 100
grams of washed sand and 100 cc. of Beijerinck's medium. The
flasks were shaken vigorously to disperse the soil and micro-
organisms. The flasks were then placed in a window where the
sun could strike them for a part of the day. After growth ap-
peared, dilution plates were poured and the colonies were trans-
ferred to agar slants or preparations made directly from the soil
were used for identification.
Growth usually occurred in 12 to 15 days but in many cases a
much longer incubation period was required. The same algae
were found in the A2 horizon as in the A, horizon of the Leon fine
sand but no growth occurred in the cultures inoculated with soil
from the lower horizons. After the March sampling, only the
surface (A,) horizon was sampled for algae. The same species
were present at the January, February, and March samplings
and consisted of: 'Palmella sp., Chroococcus subtilis (Naeg.),
Stichoococcus subtilis (Kuetz.) Klecker, Protococcus viridis Ag.,
Westella sp., Geminella sp. and Lyngbya martensiana Menegh.
At the June sampling the dominant species was Chlorococcum
humicola (Naeg.) Rab. There were also an occasional Rivru-
laria sp. and Protococcus sp. The dominant species at the July
and August samplings was Chlorococcum humicola (Naeg.) Rab.
At the November sampling there were numerous Chlorococcum
humicola (Naeg.) Rab., Chlorella sp. and Protococcus sp., several
Gloeocystis sp. and an occasional Stichococcus sp.

DISCUSSION AND SUMMARY
The numbers of molds, bacteria and actinomyces in the surface
of Norfolk, Blanton, Hernando, Gainesville, Orlando, Leon and
Portsmouth fine sands were determined at monthly intervals
from June, 1938, to June, 1939, inclusive. The most outstanding
result of these studies was the demonstration of a characteristic
flora for the different soil types in spite of the large interactions
between soil type and temperature, rainfall and moisture content
of soils. Because of soil texture and drainage conditions, rainfall
did not have as pronounced effect on numbers of organisms in






Types and Distribution of Microorganisms


these soils, as is commonly the case with soils of heavier texture.
The effect of temperature on numbers of organisms was most
apparent in the case of the bacteria. There were larger average
numbers of bacteria in the soil after the mean monthly tempera-
tures dropped below 700F. than when the mean temperature was
above 700F. Undoubtedly the correlations would have been
closer with soil temperature than with air temperature. The
effect of temperature on numbers of actinomyces and molds was
complicated by the time of application and types of organic
matter used.
The average numbers of bacteria for June, July, August, Sep-
tember and October were 407,750 per gram of soil and for No-
vember, December, January, February and March 1,312,800 per
gram of soil. All 7 of the soils studied were moderately to
strongly acid and the influence of acidity on total numbers of
organisms was evident. The Leon fine sand was the most strongly
acid soil of the 7 and it contained the smallest average total
numbers of organisms, whereas the Gainesville fine sand was the
least acid of the 7 soils and it contained the largest average total
number of organisms. The high acidity and low organic matter
content of these soils were reflected in relatively low total num-
bers of organisms and a highly carbonaceous type of organic
matter that is being completely decomposed is reflected in the
relatives -high proportion of actinomyces to other microorgan-
is
The numbers of molds were Tected significantly in the Arre-
Sdondo fine sand by the croppirig system practiced. The average
numbers of molds were lower in the .-'i; cropped continuously
to corn and peanuts than in the soils pl-n i& to corn and peanuts
in alternate years with crotalaria or continuous corn and peanuts
with a summer cover crop of crotalaria.
The average numbers of molds and actinomyces were larger in
the Norfolk loamy fine sand cropped to corn and peanuts than in
the "resting" soil, but the average numbers of bacteria were
larger in the uncropped land than in the soil under cultivation.
This result is undoubtedly explained by the small amount of
residues available for plowing under, the type of residue and the
short duration of the experiment.
The detrimental effects of strong soil acidity on numbers of
microorganisms and consequently on all biological action in soils
were clearly indicated in the results obtained in the Norfolk
loamy fine sand that had been brought to different pH levels by







Florida Agricultural Experiment Station


treatment with sulfur and lime. The tolerance of molds for acid-
ity, the sensitivity of bacteria and actinomyces to acid soil con-
ditions, and the acute need for organic matter in this soil were
emphasized by the results obtained.
The numbers of molds and bacteria in the surface horizon of
the Leon fine sand sampled in 1941 were not noticeably different
from those obtained in the same soil type at another location in
1938-39. However, the numbers of actinomyces varied consid-
erably in the 2 experiments. This was no doubt a moisture and
temperature effect. The bulk of the organisms in this soil is
confined to the surface 4 or 5 inches, especially during periods
of wet weather.
The results obtained in the study on the algal flora of the soil
were purely qualitative in nature but a scientific approach has
been made and the basis laid for a systematic study of the role
of these organisms in soil fertility. Their possible economic
importance in Florida soils will be investigated further.


LITERATURE CITED

1. ALLEN, M. C., and C. M. HAENSELER. Antagonistic action of Tricho-
derma lignorum and Rhizoctonia and other soil fungi. Plytopath.
25: 244-252, 1935.

2. ALLISON, F. E., and H. J. MORRIs. Nitrogen fixation by soil algae.
Proc. Second International Cong. Soil Science III Com. 3: 24-28,
1932.

3. JAMES, NORMAN, and MARJORIE L. SUTHERLAND. The accuracy of the
plating method foir estimating the numbers of soil bacteria, actino-
myces and fungi' in the dilution plate. Canadian Journal of Re-
search C. 17: 72-86, 1939.

4. ----. The accuracy of the plat-
ing method for estimating the numbers of bacteria and fungi from
one aliquot of a laboratory sample of soil. Canadian Journal of Re-
search C. 17: 97-108, 1939.
5. MOORE, G. T., and J. L. KARRER. A subterranean algal flora. Ann.
Mo. Bot. Garden 6: 281-307, 1919.

6. SMITH, F. B., and H. R. ELLIS. Preliminary report on the algal flora
of some Florida soils. Proc. Fla. Acad. of Science. 6: 59-65, 1943.

7. STOKES, J. L. The influence of environmental factors upon the devel-
opment of algae and other microorganisms in soil. Soil Sci. 49:
265-275, 1939.







Types and Distribution of Microorganisms 41

8. STOKES, W. E., J. P. CAMP and GEO. E. RITCHEY. Crop rotation stud-
ies with corn, cotton, crotalaria and Austrian peas. II. Corn and
runner peanuts with crotalaria and with native cover crops. Fla.
Agr. Exp. Sta. Ann. Rpt. 1939. pp. 40-41.

9. VOLK, G. M., EUGENE BORDA and R. V. ALLISON. The comparative
value of various nitrogen fertlizires for citrus. Proc. Soil Sci. Soc.
of Florida. IV-B., 1942. (In Press).









APPENDIX I.- THE PERCENT MOISTURE AND pH OF ARREDONDO FINE SAND UNDER DIFFERENT CROPPING SYSTEMS.


June '38 July Aug. Sept.

Cropping System Z


-- -- -- W jj'.

1 11.3 5.95 9.1 5.28 5.5 5.68 6.3 5.68
Continuous corn 2 10.4 5.78 8.6 5.83 4.6 5.66 6.1 5.76
and peanuts 3 12.1 5.85 9.3 6.10 5.2 5.82 6.6 6.01
4 11.5 5.81 8.5 5.86 5.3 5.86 5.6 5.85

Corn and peanuts 1 11.9 5.9510.8 5.81 6.2 5.62 6.9 5.85
with summer 2 11.7 5.91 9.4 5.93 5.1 5.781 5.3 5.98
cover crop of 3 11.2 5.78 8.9 6.06 5.1 6.02 6.0 5.90
Crotalaria 4 12.2 5.95 8.2 5.83 5.1 6.01 6.4 5.90

Crotalaria 1 112.3 6.05 8.6 5.81 6.1 5.72 5.6 5.95
1 year, 2 112.2 5.75J 9.5 5.96 5.3 5.82 5.3 5.85
corn and peanuts 3 12.7 5.91 8.9 6.001 6.3 5.98 5.0 6.01
1 year 4 12.4 5.91 8.6 5.95 5.2 5.92 5.6 6.01

Native cover 1 11.9 5.91 8.9 6.08 5.4 5.82 5.5 5.90
1 year, 2 12.1 5.98 9.5 6.00 6.0 5.88 5.8 5.98
corn and peanuts 3 11.5 6.01 9.4 6.00 5.6 5.85 6.0 6.01
1 year 4 11.8 6.05 8.1 5.95 5.2 5.66 5.0 6.08

Native cover 1 10.4 5.91 9.3 6.11 5.2 5.82 5.5 5.88
2 years, 2 12.1 5.88 9.8 5.88 6.1 5.68 5.8 5.95
corn and peanuts 3 112.1 6.08 9.4 5.85 5.1 5.66 6.1 6.05
1 year 4 111.7 6.08 8.6 6.001 5.3 6.111 5.6 6.05


Date of Sampling


Oct.


Q) .4
QV W



6.4 5.74
6.2 5.76
- 5.89
- 5.88

7.4 5.59
5.7 5.72
- 5.74
- 5.80

6.2 5.75
6.7 5.92
- 5.89
- 5.90

6.8 5.98
7.4 5.821
- 5.89
- 5.80

7.4 5.80
6.9 5.851
- 5.901
- 6.151


Nov. Dec. Jan.
a) i4 (


6.3 5.00
5.7 5.73
6.8 5.91
5.8 6.18

7.0 5.76
6.2 5.911
5.9 5.981
5.7 6.101

6.6 5.70
6.8 5.60
6.7 6.08
5.9 6.011

6.1 5.981
6.8 6.10
6.8 6.16
5.7 6.01

6.5 6.051
6.8 6.111
6.7 6.11
6.5 6.16


8.8 5.78
8.1 5.92
8.5 6.22
7.5 6.04

9.2 5.95
8.6 5.98
8.9 6.02
7.8 6.04

9.5 5.84
8.9 5.94
8.8 6.06
8.2 5.83

8.9 5.98
9.1 6.14
8.9 6.09
7.9 6.02

8.3 6.09
8.7 6.06
8.2 6.09
8.5 6.02


Feb. March April

I

PLO


8.4 5.80 7.2
7.8 5.50 6.3
8.4 5.50 8.3
7.8 5.60 7.1

9.6 5.50 8.0
7.6 5.40 6.6
8.5 5.40 7.1
9.3 5.20 7.9

8.8 5.70 7.1
8.5 5.70 7.5
8.5 5.69 7.4
8.4 5.65 7.9

7.9 5.80 7.3
8.7 5.90 8.2
8.5 5.65 7.6
7.7 5.55 7.3

8.1 5.90 7.5
8.5 6.00 8.0
8.2 5.60 7.7
8.1 5.60 12.6


May '39



0 QQ
(Sl a


5.80 6.7 5.80
5.65 5.7 5.85
5.70 6.3 5.90
5.70 6.5 6.15

5.70 6.7 5.80
5.80 5.6 5.80
5.80 6.1 6.00
5.75 6.5 6.20

5.90 7.5 5.80
5.90 7.9 5.90
6.90 7.2 5.80
5.60 7.4 6.30

5.90 6.9 5.80
6.10 7.7 5.90
5.90 6.6 5.80
5.95 7.1 6.00

5.90 6.7 5.80
5.70 7.9 5.85
6.00 7.3 5.85
5.801 7.6 6.25












APPENDIX II.-THE PERCENT MOISTURE AND pH OF NORFOLK LOAMY FINE SAND CULTIVATED AND RESTING.

Date of Sampling
August September| October November December January 1 February March

Treatment 0 P




Cropped to corn and 5.3 6.01 4.9 6.09 4.5 6.05 4.9 5.92 4.5 5.79 5.6 6.02 7.4 6.00 5.6 5.89
peanuts 5.5 6.15 5.3 6.27 4.0 6.00 5.8 5.95 4.9 5.84 6.1 5.97 7.9 5.86 6.1 6.11

Land resting 5.1 5.96 6.2 6.45 4.2 5.86 5.5 6.08 4.3 6.09 6.2 5.99 7.9 6.05 5.8 6.34
5.6 6.10 6.2 6.35 4.7 6.10 5.9 6.13 4.6 6.06 6.5 6.05 8.6 6.19 6.5 6.45




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