Front Cover
 Table of Contents
 Review of literature
 Materials and methods
 Results and discussion
 Summary and conclusions
 Literature cited
 Back Cover

Group Title: Bulletin - University of Florida Agricultural Experiment Station ; 715
Title: Fertilizing flue-cured tobacco in the Suwanee Valley
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00027636/00001
 Material Information
Title: Fertilizing flue-cured tobacco in the Suwanee Valley
Series Title: Bulletin - University of Florida Agricultural Experiment Station ; 715
Physical Description: Book
Language: English
Creator: Pritchett, W. L.
Breland, H. L.
Lundy, H. W.
Publisher: Agricultural Experiment Stations, Institute of Food and Agricultural Sciences, University of Florida,
Publication Date: 1967
 Record Information
Bibliographic ID: UF00027636
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.

Table of Contents
    Front Cover
        Page 1
    Table of Contents
        Page 2
    Review of literature
        Page 3
    Materials and methods
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
    Results and discussion
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
    Summary and conclusions
        Page 27
        Page 28
    Literature cited
        Page 29
    Back Cover
        Back Cover
Full Text
ulletin 715 (technical)

Fertilizing Flue-Cured

Tobacco in the

Suwannee Valley

W. L. Pritchett, H. L. Brelnnd

S APR 27 1967

U.F A.S. Univ. of Florida
agricultural Experiment Stations Institute of Food and Agricultural Sciences
R. Beckenbach, Director University of Florida, Gainesville

February 1967

e._:i7~L ` "'i
-;. 5-
tP ~
5- ~
I$ r~-ai
'r' I-~HI



Review of Literature 3

Materials and Methods 4

Field Experiments 4

A. Nitrogen-Potassium Rates 5

B. Source of Potassium 7

C. Micronutrients 7

D. Fertilizer Rates, Plant Population,
and Varieties 8

Laboratory Procedures 9

Results and Discussion 9

A. Nitrogen-Potassium Rates 9

B. Source of Potassium 17

C. Micronutrients 19

D. Fertilizer Rates, Plant Population,
and Varieties 23

Summary and Conclusions 27

Literature Cited 29

Fertilizing Flue-Cured Tobacco
in the Suwannee Valley
W. L. Pritchett, H. L. Breland, and H. W. Lundy1

Flue-cured tobacco is the principal cash crop in the Suwan-
nee Valley. Total Florida acreage, which is centered in that area,
consists of about 12,600 acres with an estimated value in excess
of $13,000,000 (7)2. The sandy soils of the area are particularly
suited for the production of tobacco, although they contain only
small reserves of essential plant nutrients.
Since tobacco requires relatively large amounts of plant nu-
trients for good growth and yields, fertilizer applications are
needed to meet the nutrient requirements of the crop. The
amounts and ratios of nutrients applied to tobacco have changed
drastically during the past decade. These changes were due to
the development of higher yielding varieties, improved cultural
practices including widespread use of irrigation, and changes in
market demands for certain grades of tobacco. While six special
tobacco fertilizer grades account for over 95% of the estimated
14,000 tons of mixed fertilizers used for flue-cured tobacco an-
nually, fertilizer programs vary widely from farm to farm.
This publication reports results of a series of experiments
conducted over an eight year period to determine the influence
of plant nutrients on yield, value, and chemical composition of
flue-cured tobacco in the Suwannee Valley.

Numerous fertilizer experiments have been conducted with
flue-cured tobacco in the southeastern United States, including
Florida. Clark et al. (3) reviewed results of many of these ex-
periments and stressed the importance of a balanced fertilizer
program for production of high yields and good quality tobacco.
They reported that the Southern Agronomy Research Commit-
tee for flue-cured tobacco recommended 800 to 1,200 pounds of
fertilizer containing 3% nitrogen (N), 10% phosphoric acid
(P2Os), 6 to 10% potash (K20), 2% magnesium oxide (MgO),
2% chlorine (Cl), and not less than 6% calcium oxide (CaO).
However, these recommendations were for tobacco grown under
natural rainfall conditions. For irrigated tobacco, Clark et al.
1 Soil Technologist and Associate Soil Chemist, Agricultural Experiment Sta-
tion, Gainesville, and Associate Agronomist and head, Suwannee Valley
Experiment Station, Live Oak.
Numbers in parentheses refer to Literature Cited.

(3) reported that 1,600 pounds of 3-8-8 fertilizer gave greater
yields than 800 pounds. Clark and Meyers (4) found that high-
er tobacco yields were obtained by applying fertilizer in two ap-
plications, one-half prior to transplanting and the remaining
one-half approximately three weeks after transplanting, than by
applying the same quantity of fertilizer in a smaller or larger
number of applications. Clark and Meyers (4) also reported
that a 12,500 plant population resulted in a high percentage of
nondescript tobacco. On the other hand, 5,000 plants per acre
produced excellent quality tobacco, but the yield was depressed
considerably below yields obtained with 7,500 and 10,000 plants
per acre.
Nitrogen (N), perhaps the most difficult of the plant nutri-
ents to control at a desired level of availability in the soil, is
closely related to both yield and composition of tobacco. Broth-
ers and Clark (2) suggested in 1960 the need of 36 to 48 pounds
of N for the production of tobacco on sandy soils. Later, Pritch-
ett et al. (9) reported increased yields with increasing N rates
up to 135 pounds per acre, without a reduction in value per
pound of tobacco, under some conditions. They also reported
that although total N, total alkaloid, and nicotine contents of
tobacco were generally lower in tobacco in experiments at the
Suwannee Valley Experiment Station than in tobacco from other
areas of the United States, these constituents increased with in-
creased rates of N fertilizers. Tobacco flavor and taste depend
primarily on N compounds. A strong, pungent, irritating smoke
is related to a high content of nitrogenous constituents, while a
flat smoke is related to low values (6). Elliot and Vickery (6)
stated, "While all essential elements play an important role in
flue-cured tobacco production, applications of N exert the great-
est effect on leaf quality."
Flue-cured tobacco produced on Florida's sandy soils is gen-
erally recognized for its good quality (2), with relatively high
sugar and low nicotine contents. However, quality is influenced
by fertilization and other soil management practices. Fluctua-
tions in market demands for certain grades emphasized the need
for studying the relationship of fertilization to yield, quality,
and chemical composition of tobacco.


Field Experiments
Experiments reported herein were conducted at the Suwan-
nee Valley Experiment Station from 1956 through 1964. They

were located in old cultivated fields in which Blanton and Klej
fine sands were the principal soil types. These deep, highly
leached sands, like most soils of the Suwannee Valley, have a
cation exchange capacity of 3 to 5 meq per 100 grams. The un-
treated surface (0 to 6 inches) soil averaged 60, 27, and 67
pounds per acre exchangeable calcium (Ca), magnesium (Mg),
and potassium (K), respectively, and had a pH of 5.2.
The experiments were conducted in new areas each year,
except when residual effects of previous treatments were stud-
ied. Individual plots consisted of 4 rows, 3 feet apart and 50
feet long. Data were collected from the two center rows. The
rows were fumigated with 36 pounds of ethylene dibromide per
acre, applied as 83 solution about two weeks before transplant-
ing. Hick's Broadleaf variety was planted in all the experiments,
except where treatment effects on varieties were studied. Ex-
perimental areas were irrigated as needed and other cultural
practices (field preparation, planting, cultivation, and disease
and insect control) were the same as those generally used for
tobacco production in the area.
Harvesting normally began during the first two weeks of
June, but varied from year to year. The tobacco was primed
(harvested) from 5 to 7 times during the harvest period, as
leaves matured. The tobacco leaves from each plot were labelled
and kept separate throughout curing, sorting, and grading. After
the leaves were sorted into lots, a federal tobacco inspector grad-
ed the tobacco from each plot into appropriate government
grades. Value per acre was calculated by multiplying the num-
ber of pounds of each grade by the season market price paid for
those grades on the local market.
Experiments were conducted in four different studies to in-
vestigate the effects of rates of N and K, sources of K, micro-
nutrients, and fertilizer rates, plant populations, and varieties
respectively. The individual experiments conducted under these
studies are described as follows.

A. Nitrogen-Potassium Rates
These experiments were conducted in 1958, 1959, and from
1961 through 1964 to study the effect of varying rates of N and
K fertilizers on yield, value, and composition of flue-cured to-
bacco. Experiments conducted in 1958 and 1959 were factorially
designed with four rates of N and three rates of K. In addition,
the plots were split so that one-half received dolomite and the
other half received no limestone. All treatments were replicated
four times. Same N and K treatments were applied to the plots

in 1958 and 1959. However, dolomite was applied at the rate
of 2,000 pounds per acre the first year, but only 1,000 pounds the
second year. A base application of 1,500 pounds of 3-9-93 to-
bacco fertilizer per acre was applied uniformly in the row to all
plots in two equal applications-the first two weeks before and
the second three weeks after transplanting. This base applica-
tion was calculated to supply sufficient phosphorus (P) but a
low level of N and K for tobacco on Klej fine sand. Additional N
and K were sidedressed on appropriate plots as NH4N03 and
K2S04 about five weeks after transplanting. The N rates were
45, 60, 75, and 90 pounds per acre the first year and 45, 90, 135,
and 180 the second year. The K rates were 112, 149, and 186
pounds (equivalent to 135, 180, and 225 pounds of K20) per acre
the first year and 112, 174, and 237 pounds (equivalent to 135,
210, and 285 pounds of K20) the second year (Tables 1 and 2).
The experiments conducted in 1961 through 1964 were rep-
licated 3 x 3 factorial experiments, with three rates of N (60,
90, and 120 pounds of N per acre) and three rates of K (125,
166, and 207 pounds-equivalent to 150, 200, and 250 pounds of
K20 per acre), as shown in Table 3. However, the source of K
in 1961 and 1964 was K2S04, a soluble material, while that used
in 1962 and 1963 was FN 519', a slowly-soluble potassium sili-
cate frit. In an attempt to control and prolong the period of
availability of potassium in the soil, slowly-available, glass-like
frits were developed. Frits should results in greater efficiency
by reducing leaching losses and luxury consumption, and by ob-
taining more satisfactory plant growth from steady supply of
the nutrient.
In 1961, and 1964 uniform applications of a mixed fertilizer
were used to meet the P requirements and to supply part of the
N and K. Additional N and K were sidedressed, as in the 1958
and 1959 experiments. As no mixed fertilizer was available in
which the K was derived solely from a frit, all nutrients in fer-
tilizers for base application in the 1962 and 1963 experiments
were applied as single materials. In those two experiments, uni-
form applications of P (44 pounds of P per acre as superphos-
phate) and N (30 pounds per acre as NH4N03) were made two

3 Throughout this publication commercial fertilizer grades are expressed as
percent of N-P205 K20. In other instances plant nutrients are expressed
as elements. The following factors may be helpful in converting from the
elemental to the oxide form of expression:
1 lb. P05 = 0.44 lb. P; or 1 lb. P = 2.3 lb. Ps05
1 lb KO = 0.83 lb. K; or 1 lb K 1.2 lb. K2O
' FN 519 is a potassium silicate product of the Ferro Corporation, Cleve-
land, Ohio, containing about 25% K.

weeks before planting. The remaining N comprising the various
treatments was sidedressed in either one or two applications.
B. Source of Potassium
Potassium sulfate is generally the K source used in tobacco
fertilizers. Like most K fertilizer, it is water soluble and mod-
erately subject to leaching losses in sandy soils. In order to de-
termine the relative advantage of frits over soluble sources,
three experiments were conducted from 1961 through 1963 with
these two types of K materials on Klej fine sand.
An experiment was conducted in 1961 comparing four sources
of K for the production of Hick's Broadleaf tobacco (Table 4).
The sources included KOSO4, KNOs and slowly-soluble fritted
compounds [FN 519 and potassium-calcium pyrophosphate
(K2CaP207)5]. The fertilizer materials were applied at rates
equivalent to 2,000 pounds of 3-9-9 per acre so adjusted that all
plots received equal amounts of N, P, Mg, Ca, and sulfur (S).
In 1962 and 1963 tests were conducted comparing the rela-
tive efficiency of a potassium frit (FN 519) with that of K2S04
(Tables 5 and 6). The K sources were applied at rates of 125,
166, and 207 pounds of K per acre in four replications of ran-
domized blocks (except that in 1962 the K2S04 was applied only
at the 166 pounds per acre rate). Ammonium nitrate and super-
phosphate were applied to all plots at rates of 90 and 44 pounds
N and P per acre, respectively.
C. Micronutrients
Five experiments were conducted involving micronutrient ap-
plications to tobacco. Treatments varied somewhat from year to
year and are described below:
1. Three micronutrient treatments were applied in conjunc-
tion with lime in experiment conducted in 1957. Molybdenum
(Mo), boron (B), and zinc (Zn) were applied as sodium molyb-
date, Colemanite (a form of calcium borate), and zinc frit, as
shown in Table 7. These materials were drill applied two weeks
before planting. Sixteen hundred pounds of 3-9-12 tobacco ferti-
lizer were applied, one-half at two weeks before and the remain-
der three weeks after transplanting.
2. Liming experiments with and without added B were con-
ducted from 1959 through 1963. Colemanite was drill applied at
the rate of 0.5 pound of B per acre. All plots were fertilized uni-
formly with 2,000 pounds of 4-8-12 fertilizer per acre split into

SPotassium calcium pyrophosphate produced by T.V.A., Wilson, Dam, Ala-
bama, and containing 15% P and 21% K.

applications as previously described. The treatments are shown
in Table 8.
3. A split-plot factorial experiment containing 13 micronu-
trient treatments in sub-plots and 2 lime treatments, in whole-
plots was conducted in 1962. The 13 micronutrient treatments
shown in Table 9, and one-half of the base application of 2,000
pounds of 4-8-12 fertilizer per acre were row applied immediately
prior to transplanting the tobacco. The remainder of the base
fertilizer was applied about three weeks after transplanting. A
uniform sidedress application of 400 pounds of 6-3-24 fertilizer
per acre was made on May 28, 1962, about 10 weeks after trans-
planting. Three micronutrient mixes and a slag were used in
this experiment. The compositions are given in Table 9.
The main-plot treatments in this experiment were 1) 2,000
pounds of calcic limestone per acre and 2) 2,000 pounds of
calcic limestone plus 2,000 pounds of dolomite per acre. These
treatments were applied to appropriate plots about two months
prior to transplanting.
4. An experiment conducted in 1963 consisted of four treat-
ments, including a check, a B source, and two micronutrient
mixes (Table 10). The materials were row applied at rates to
supply 1.0 pounds of B per acre, prior to transplanting F-22 vari-
ety tobacco. The composition of the mixes (FTE 503 frit and
IMC Minor Element Mix) are given in Table 9. A uniform ap-
plication of 2,000 pounds of dolomite per acre was made 6 weeks
before planting. Two thousand pounds of 4-8-12 fertilizer, split
into two applications, and a sidedress application of 200 pounds
of 6-3-24 per acre were made uniformly to all plots.
5. An experiment was conducted in 1962 to determine wheth-
er a yield response associated with N derived from natural or-
ganic sources was caused by micronutrients in the organic. Fer-
tilizers containing all inorganic N were compared with fertilizers
containing 33% of the N from natural organic. Additional
treatments included all mineral fertilizers plus micronutrients,
and all mineral fertilizers plus poultry manure (Table 11). All
plots received the equivalent of 1,500 pounds of 3-9-12 fertilizer
per acre.
D. Fertilizer Rates, Plant Population, and Varieties
Three rates of fertilizer, three varieties of flue-cured tobac-
co, and three spacings within the row were used in a factorial
experiment of 27 treatments in 1963 (Table 12). The 4-8-12
fertilizer was applied at rates of 1,500, 2,000, and 2,500 pounds
per acre, split in two equal applications. The first application

was made two weeks before and the second three weeks after
transplanting. A second sidedressing consisting of 150, 200, or
300 pounds per acre of 6-3-24 fertilizer, was applied to plots that
received low, medium, or high rates of fertilizer, respectively.
The three varieties-Hick's Broadleaf, F-22, and NC-95-
were those used or recommended in the area. They were trans-
planted in 3-foot rows at spacings to give a final population of
7,500, 10,000, and 12,500 plants per acre.

Laboratory Procedures
Soil and plant samples were collected from plots of each ex-
periment for chemical analyses. Surface soil (0 to 6 inches)
samples were collected from each area prior to treatment and
from each plot during the period of rapid tobacco growth and
development (about the last two weeks of May). Each sample
was a composite of 15 cores taken with a 1-inch soil tube. For
pre-treatment samples, the cores were taken at random over the
entire area. However, for the post-treatment samples, five cores
were taken across the tobacco bed at each of three locations with-
in a plot. The samples were air-dried, sieved, and analyzed for
pH, and NH.OAc (pH 4.8) extractable nutrients (1).
Fifteen to 20 cured tobacco leaves were randomly selected
from the second and fourth primings from each plot for chem-
ical analyses. The leaves were oven-dried at 650C, and the lam-
ina portion was ground in a Wiley mill. Total N was determined
by a Kjeldahl procedure (8). Samples were dry ashed at 500C
and dissolved in 0.1 N HC1, and the Deniges-Truog method (8)
was used for the colorimetric determination of P. Potassium, Ca,
and Mg were determined with flame spectrophotometers (1).
Calcium and Mg were determined after the solutions were passed
through a column of Dowex 1-X8 anion exchange resin. Total
alkaloids, nicotine, and nornicotine-type alkaloids were deter-
mined according to the method of Cundiff and Markunas (5).

A. Nitrogen-Potassium Rates
Nitrogen and K are the two most critical nutrients in tobacco
production in the Suwannee Valley. They are not only required
in large amounts by the plants, but are generally deficient in
sandy soils. This series of experiments was conducted to study
the effects of varying rates of N and K fertilizers on the yield,
value, and chemical composition of flue-cured tobacco.

Yield and values of tobacco, as influenced by N and K treat-
ments, are summarized in Table 1 for 1958, in Table 2 for 1959,
and in Table 3 for the 1961-64 period.
In 1958 and 1959, 0 and 2,000 pounds of dolomite per acre
were main-plot treatments. Although the yield of tobacco in
plots that received dolomite averaged 125 pounds more in 1958
and 113 pounds more in 1959 than yields in plots that received
no dolomite applications, these differences were not statistically
Yields and values differences associated with the N K treat-
ments in 1958 were not sufficiently large to give statistical sig-
nificance. However, the average yields associated with 45, 60,
75, and 90 pounds of N per acre were 1420, 1482, 1515, and 1555
pounds, respectively, (Table 1). Potassium applications of 149
pounds per acre resulted in greater yields than applications of
either greater or smaller amounts. Yields from plots that re-
ceived 149 and 186 pounds of K per acre averaged 9 and 6%
greater, respectively, than yields from plots that received 112
pounds of K.
Yields were significantly increased at all levels of N up to
180 pounds per acre in 1959-a year of relatively favorable rain-
fall during the growing period. Values per acre also increased
with increasing rates of N fertilizer. Linear regressions of yield
and value on N rates were highly significant (the price received
per pound of tobacco was not materially influenced by N ap-
plications). The increase for each 15 pounds of N applied was
50.6 pounds of tobacco with a value of $20.02 per acre.

Table 1.-Yield, value, and chemical composition of flue-cured tobacco in
N-K rates experiment in 1958.
Application Chemical Composition
N K Yields Value N K P Ca Mg
lb/acre lb/acre $/acre % % % % %
45 112 1315 766.13 1.46 2.77 0.29 1.62 1.20
45 149 1471 875.20 1.36 2.87 0.28 1.57 1.11
45 186 1474 847.30 1.41 3.39 0.29 1.37 1.17
60 112 1464 851.47 1.60 2.67 0.32 1.81 1.26
60 149 1575 869.58 1.58 2.92 0.26 1.70 1.20
60 186 1406 828.12 1.64 3.18 0.25 1.80 1.17
75 112 1439 832.88 1.51 2.88 0.28 1.99 1.35
75 149 1561 846.99 1.58 3.29 0.29 1.78 1.37
75 186 1543 896.18 1.79 3.62 0.24 2.10 1.23
90 112 1498 848.52 1.75 2.87 0.30 2.30 1.30
90 149 1555 859.04 1.66 3.54 0.26 1.82 1.23
90 186 1612 864.96 1.69 4.08 0.28 2.04 1.34

Potassium sulfate applied at rates in excess of 112 pounds
of K per acre did not increase yields in the 1959 experiment.
Yields increased with increasing rates of N up to 120 pounds
per acre in the 1961-1964 experiments. Plots that received 90
and 120 pounds of N per acre averaged 108 and 146 pounds
more tobacco, respectively, than plots that received 60 pounds
of N. Potassium applications also increased total yields, as seen
in Table 4.
Value in dollars per acre-a product of yield multiplied by
the price per pound received at the local market-is closely re-
lated to yield. However, it should be pointed out that the higher
rates of N used in these experiments decreased leaf quality. For
example, N increased yields up to the highest rate of application
(90 pounds per acre) in 1958, but it increased the value of the
crop only up to an application of 75 pounds per acre of N. In
1959, the highest yields were obtained at the 180 pounds-per-acre
rate, but the greatest returns were obtained from 90 pounds per
acre of N. Furthermore, considering data from the 1961-64 ex-
periments, yields increased with each rate of N, but values per
acre increased with increments only up to the 90-pound rate
(Figure 1), due to a reduction in the price per pound paid for
tobacco which received the 120 pound of N per acre.
The increase in potassium applications from 166 to 207
pounds of K generally increased both yields and values of the
tobacco crop on these sandy soils.
Chemical composition of tobacco leaves is influenced by a
number of factors, among which are climatic conditions during
the growing season, position on the plant, stage of maturity, and
fertility of the soil. Dolomitic limestone applications significant-
ly increased the percent of Mg and P in the leaves. However,
liming had no effect on N and Ca percentages, but suppressed
the potassium content of leaves in these N-K rate experiments.
The effects of N and K fertilizer on the composition of leaves
are shown in Tables 1 and 2.
Potassium fertilizers had little consistent influence on the
chemical composition of tobacco in these experiments, except
to increase the K content. On the. other hand, the influence of
N fertilizers on the mineral contents and nitrogenous constitu-
ents was quite striking. There was a significant increase in per-
cent Ca and K in leaves from plots that received the higher
rates of N. These two elements have been positively related to
leaf burn and quality (6). The K percentage of leaves was found
to be considerably higher and Ca lower than values reported for
"good quality" flue-cured tobacco. (6).

Table 2.-Yield, value and chemical composition of flue-cured tobacco in N-K rates experiment in 1959.

Chemical Composition

Total Nor-
Mg nicotine nicotine Alkaloids
/% %/ % %











LSD (5%) 227 146.53 0.09 0.25 0.03 0.32 0.12 0.08 .0.09







- 90































1.22 3.37 0.23 1.34 0.56 0.86

1.25 3.89 0.24 2.51 0.87 0.75

1.28 4.02 0.24 2.15 0.76 0.74

1.78 3.41 0.27 1.84 0.67 1.27

1.80 3.56 0.27 1.97 0.79 1.36

1.64 3.22 0.25 1.92 0.68 1.24

1.92 3.79 0.25 2.22 0.73 1.42

2.06 3.42 0.23 1.75 0.68 1.46

1.86 3.01 0.26 1.53 0.74 1.31

2.16 3.41 0.25 1.99 0.67 1.41

2.15 3.81 0.27 2.37 0.78 1.42

1.99 3.42 0.24 2.09 0.79 1.41

Table 3.-Yield and value of flue-cured tobacco in N-K rates experiments in 1961 through 1964.

Application 1961 1962 1963 1964 1961-64 Avg.
N K Yield Value Yield Value Yield Value Yield Value Yield Value
lb/acre lb/acre $/acre lb/acre $/acre lb/acre $/acre lb/acre $/acre lb/acre $/acre







60 125

60 166

60 207

90 125

90 166

90 207

120 125

120 166

120 207

2093 1169.04

2048 1188.50

2254 1305.99

2046 1228.16

2268 1342.05

2444 1482.69

2477 1396.36

2345 1395.21

2564 1505.03

1941 1149.51 1235 744.76 1767 1048.93

2040 1270.09 1274 787.36 1791 1104.12

2516 1563.97 1338 835.38 1974 1203.96

1922 1135.57 1478 920.22 1853 1121.75

2167 1187.16 1500 938.39 1934 1154.10

2238 1296.54 1574 998.62 2068 1257.73

2221 1290.11 1503 933.61 2019 1195.08

1913 989.36 1642 990.74 1898 1103.28

2110 1178.83 1637 1025.91 2053 1210.45

1876 1160.26

1691 1037.80

1900 1132.03


1950 1175
Value U)

1900 1150
,-i f

1850 1125

60 90 120

Nitrogen applied, Ib/acre

Figure 1.-Yield and value of flue-cured tobacco as influenced by N ferti-
lizer (N-K experiments, 1961-64).

The greatest influence of N on tobacco composition was in
the nitrogenous constituents. Total N percentage of leaves from
plots that received the various treatments is shown in Tables
1 and 2. An increase of 0.09% N in the leaves was obtained for
each 15 pounds of N fertilizer. Elliot and Vickery (6) reported
that "flue-cured tobaccos containing 1.6 to 2.3% total N give the
most desirable smoking quality." However, in our experiments
only tobacco that received a total of 90 pounds or more of fer-
tilizer N produced leaves which contained this much N.
The percentages of total alkaloids, nornicotine (primary and
secondary amine alkaloids), and nicotine (tertiary amine alka-
loids) in tobacco from the 1959 experiment are given in Table 2.
Both nicotine and total alkaloids significantly increased with in-
creasing rates of N. Linear regression of nicotine on fertilizer
N rates was highly significant, increasing by 0.07% for each 15
pounds of N applied (Figure 2). The quadratic regression was
also significant, indicating that nicotine content did not increase

2.0 1.5

0 I 1.0 0
1.5 .0

=mm -= Nitrogen
S--- Nicotine

0 45 90 135
Nitrogen applied, Ib/acre

Figure 2.-Effect of N fertilizer on the N and nicotine contents of flue-cured
tobacco (N-K experiment, 1959).

as rapidly at higher N rates as at lower N rates. The relation-
ship of total N to nicotine in the leaves is shown in Figure 3.
Each 1.0% increase of N content increased nicotine content of
the leaf about 0.7%. The nicotine content of leaves near the top
of the plant was greater than in bottom leaves. For example,
nicotine contents of leaves from the second and fourth primings
were 1.01 and 1.45%, respectively.
The percent nitrogen content of the 1959 tobacco was lower
than that of the previous year from plots fertilized with 45
pounds of N per acre. This was probably a reflection of the
relatively heavy rainfall during the 1959 season. Nevertheless,
N content of leaves from plots fertilized with the heaviest rate
of N in 1959 (180 pounds of N per acre) averaged 26% greater
than from plots that received the heaviest rate in 1958 (90
pounds of N). Potassium percentages were generally higher in
tobacco from the 1959 experiment, but composition was gener-
ally less influenced by the fertilizer treatments than in the 1958

Nematode root rot, or "coarse root," incidence was not great-
ly affected by K fertilizers, but it was significantly decreased by
increasing rates of N fertilizer. For example, tobacco roots aver-
aged 86, 78, 71, and 65% infestation from fumigated soils that
received 45, 60, 75, and 90 pounds N fertilizer per acre, respec-
tively. Although the severity of infestation varied from year
to year, the average effect of N fertilizer on tobacco root rot
from experiments in 1958 through 1961 was beneficial (Figure



1.5 2.0 2.5

Nitrogen in leaves, %

Figure 3.-Relationship on N to nicotine in flue-cured tobacco (N-K experi-
ment, 1959).

No evidence of blackshank was noted in these experiments.
The incidence of root knot nematode was very low as a result of
fumigating the soil each year. The incidence of root knot did
not appear to be related to fertilizer treatments.

0 0


70 0__


0 45 90 135 180

Nitrogen applied, Ib/acre

Figure 4.-Effect of N fertilizers on the incidence of root rot in flue-cured
tobacco (N-K experiment, 1958 through 1961).

B. Source of Potassium
Yields and values per acre of three experiments using vari-
ous sources of K are given in Tables 4 and 5. In 1961, the two
fritted materials (FN 519 and K2CaPa07) resulted in greater
yields and returns per acre than the two soluble K sources
(K2SO4 and KNO3). Yields of plots that received the K frits
averaged 385 pounds per acre more than plots that received the
soluble sources of K. As a result of these encouraging data, fur-
ther tests were conducted with frits. Although K2CaP207 re-
sulted in the greatest yield in 1961, FN 519 was used in 1962 and
1963, because K2CaP207 an experimental product was not gen-
erally available.
In 1962, tobacco yields in plots fertilized with 166 pounds of
K per acre from K2SO4 were greater than those fertilized with
125, 166, or 207 pounds from FN 519. However, the highest cash
return was from tobacco fertilized with 207 pounds K per acre

Table 4.-Effects of K sources on yield, value and some chemical constituents
of flue-cured tobacco in K-source experiment, 1961.
Potassium* Chemical Composition
Source Yields Values N Ca Mg P K
lb/acre $/acre % % % % %
K2SO, 2067 1259.46 1.66 1.60 1.09 0.28 2.16
FN 519t 2281 1309.90 2.08 2.27 1.67 0.28 1.77
K.CaP207s 2578 1405.11 1.88 2.26 1.70 0.30 1.81
KNO, 2021 1176.72 1.98 2.41 1.73 0.30 2.04

LSD (5%) 261 N.S. -

* All sources applied at the rate of 149 pounds of K per acre. Adjustments were made in
base fertilizer so that all plots received comparable rates of all essential nutrients.
t FN 519 is a potash frit containing 25% K produced by Ferro Corporation, Cleveland, Ohio.
t Potassium calcium pyrophosphate is a slow-release potassium fertilizer containing 21%
and produced by TVA, Wilson Dam, Alabama.

from FN 519. The price per pound obtained for tobacco ferti-
lized with K2S04 averaged $0.564 while that obtained for tobac-
co fertilized with the frit $0.600.
Yields decreased with increasing rates of K2S04, but in-
creased with increasing rates of FN 519 frit in 1963. However,
since the yield obtained from the lowest rate of K2S04 was al-
most as large as that obtained from the highest rate of frit,
there seemed to be little or no advantage in using frit in prefer-
ence to K2SO4.
Chemical composition of leaves was not greatly influenced by
the K source (Tables 4 and 6). However, the K content of to-
bacco fertilized with the soluble source was higher than the K
content of tobacco fertilized with K frits. The higher K content
of tobacco that receive K2S04 was apparently due to a higher
level of soil available K in those plots throughout the growing

Table 5.-Effect of two K sources on yield and value
in K-source experiment, 1962 and 1963.

of flue-cured tobacco

K Application 1962 1963
Source K Yield Value Yield Value
lb/acre lb/acre $/acre lb/acre $/acre
K2SO4 125 2208 1281.31
KSO4 166 2515 1417.58 1931 1149.40
KzSO, 207 ... 1788 1055.88
FN 519* 125 2046 1228.16 1922 1135.57
FN 519 166 2268 1342.05 2167 1187.16
FN 519 207 2444 1482.69 2238 1296.54
LSD (5%) 309.60 215.42 402.89 271.46

* FN 519 is a K frit containing 25% K produced by Ferro Corporation, Cleveland, Ohio.

season. At harvest time, plots fertilized with 166 pounds per
acre of K from frit averaged 92 pounds of soil extractable K,
while those fertilized with equivalent amounts of K from K2S04
averaged 113 pounds of extractable K. However, both of these
levels of K were apparently adequate for good yields of tobacco.
The level of residual K in plots that received the frit was not
determined for subsequent years.

Table 6.-Effect of two sources of K on the chemical composition of flue-
cured tobacco in K-source experiment, 1963.
Potas- Appli- Chemical Composition
sium cation Ca Mg P K N Nico- Nor- Total
Source K tine nicotine alka-
lb/acre % % % % % % % %
K2SO4 125 1.66 1.08 0.26 3.71 2.25 1.52 0.061 1.59
K2SOM 166 1.60 1.06 0.25 4.22 2.14 1.57 0.067 1.64
K2SO. 207 1.51 1.09 0.25 4.47 2.13 1.51 0.073 1.59
FN 519 125 1.61 1.07 0.26 3.55 2.07 1.53 0.061 1.61
FN 519 166 1.55 1.03 0.25 3.61 2.13 1.60 0.049 1.67
FN 519 207 1.50 0.95 0.25 3.74 1.98 1.58 0.061 1.64

C. Micronutrients
1. In the 1957 experiment, applications of 1 ton calcic lime-
stone per acre increased tobacco yields 55 pounds per acre over
yields from check plots (Table 7). Furthermore, plots that re-
ceived a row application of 1 pound sodium molybdate per acre
yielded 120 pounds more tobacco than plots that received only
base fertilizer. However, it cannot be inferred from these re-
sults that lime is needed on these soils nor that Mo can be used
in the place of lime, because yields from neither treatment were
significantly greater than yields from the check (Table 7). In
fact, none of the treatments significantly increased yields over
those obtained with the base fertilizer alone. On the other hand,
plots that received Colemanite (Ca2BeOn 5H20) outyielded
check plots by an average of 195 pounds per acre. These encour-
aging results prompted further research with B in 1959 through

2. The results of the 1959-63 tests in which B was applied
with dolomitic limestone, as compared to limestone alone, are
shown in Table 8. Yields were increased in limed plots as com-
pared to unlimed plots in four of the five years. However, when
0.5 pound of B per acre was applied in addition to the limestone,

Table 7.-Yield and acre-value of flue-cured tobacco as influenced by micro-
nutrients treatments in Klej fine sand in 1957.
Materials Rates Yield Value
lb/acre lb/acre $/acre
Check 1425 823.08
Calcic Limestone 2000.0 1480 850.90
Colemanite 5.2 1545 890.88
Sodium Molybdate 1.0 1398 807.91
Colemanite + 5.2
Calcic Limestone 2000.0 1620 934.70
Zinc frit 10.0 1559 917.87
Zinc frit + 10.0
Calcic Limestone 2000.0 1508 887.92
LSD (5%) 291 181.71

Table 8.-The yield of flue-cured tobacco as influenced by B on Klej fine
Treatments Yields
Materials Rates 1959 1960 1961 1962 1963 Avg.

Check 1593 1823 1742 1576 2328 1812
Dolomitic Limestone 2000.0 1795 1631 1754 1612 2334 1825
Colemanite + 5.2
Dolomitic Limestone 2000.0 2032 1939 1763 1792 2412 1988
LSD (5%) 278 201 245 181 255

yields increased in every instance, with statistically significant
increases in 1959 and 1962. The 5-year average yield increase
for the B treatment was 163 pounds per acre over the yields ob-
tained from limed plots without added B. The average increase
in returns per acre for the same treatment was $105.53. The
yield response to applications of B on these sandy soils was prob-
ably increased due to a reduction in availability of the already
low supply of native boron following liming of the soil. The soil
pH was raised to 5.8 6.0 with application of 2,000 pounds of
dolomite per acre. It was apparent that in soils at pH 5.8 or
above the inclusion of B in the tobacco fertilizer was advisable.

3. There were no statistically significant responses due to
micronutrient treatments in the 1962 experiment-either in plots
that received 1 ton of dolomite per acre or in plots that received
1 ton of dolomite plus 1 ton of calcic lime per acre. In fact, there
were no significant differences in yield between 1- and 2-ton lime

treatments, although the soil pH in the 1-ton plots averaged 5.3
as compared to 5.6 in the 2-ton plots. Consequently, only yields
and values of the tobacco from plots that received a uniform
application of 1 ton of dolomite are given in Table 9. Plots that
received the higher rates of the IMC mix consistently produced
higher yields than other treatments, however, when the IMC mix
was applied at rates comparable to the FTE 503 frit (20 pounds
per acre), the two materials produced about the same yields.

4. In the 1963 experiment, the micronutrient mixes which
had shown promise in 1962, did not increase yields significantly
above yields obtained from check plots (Table 10). The highest
yields were obtained from the use of Colemanite, as in previous
years. Chemical constituents of the leaves for which determi-

nation were made (Table 10) were not
by the micronutrient treatments.

Table 9.-Effect of micronutrient applications
cured tobacco in micronutrient experiment, 1962.

significantly influenced

on yield and value of flue-

Materials Rate Yield Value
lb/acre lb/acre $/acre
Check (Base fertilizer only)* 3049 1733.85
Boron-"Saftebor", (4% B) 15 3037 1750.48
Copper-"Tribasic" CuSO4, (53% Cu) 1 3090 1781.61
Iron-"Nu-iron" (30% Fe) 12 3049 1695.85
Manganese-"T.C. Green Element"
(23.6% Mn) 4 3031 1722.17
Zinc-"T.C. ZnSO," (40% Zn) 3 3168 1840.34
Mix-FTE 503 fritt 33 3144 1815.29
Mix-FTE 503 fritt 20 3105 1776.94
Mix-IMC micronutrient mixt 20 3106 1760.79
Mix-IMC micronutrient mixt 60 3249 1883.71
Mix-IMC micronutrient mixt 100 3319 1926.97
Mix-Tennessee Corp. SMM 1000t 225 3050 1754.40
Basic slag-Fairfield slagt 500 3061 1750.77
LSD (5%) 356

* All plots received uniform fertilizer applications equivalent to 104 pounds of N, 84 pounds
of P, and 288 pounds of K per acre.
t Composition of micronutrient mixes:

Composition of Materials
Materials Fe Zn Mn Cu B Mo Mg
% % % % % % %
FTE 503 18.0 7.0 7.5 3.0 3.0 0.2
IMC ME Mix 14.0 6.0 9.0 3.0 1.3 0.2
Tennessee Corp. SMM 1000 0.1 0.4 0.3 0.2 0.2 1.2
Fairfield Slag 12.4 Trace 3.0 Trace Trace Trace 6.0

Table 10.-Effect of Colemanite and two micronutrient mixes on yield, value, and chemical composition of flue-cured tobacco in
micronutrient experiment, 1963.

Chemical Composition
Materials Rate Yield Value N Ca Mg P K Nicotine Total alkaloids
lb/acre lb/acre $/acre % % % % % % %

Check 2682 1516.55 2.13 2.91 0.62 0.310 4.76 1.35 1.40

Colemanite 5.2 2855 1613.21 2.13 2.81 0.61 0.298 4.61 1.48 1.53

FTE 503 33.5 2696 1513.02 2.32 2.84 0.60 0.303 4.69 1.46 1.52

IMC Mix 100.0 2762 1582.83 2.10 2.75 0.57 0.305 4.71 1.40 1.44

LSD (5%) 304 ..

Table 11.-Effect of source of fertilizer N and micronutrients on yield and
value of flue-cured tobacco in micronutrient experiment, 1962.
Material Yield Value
lb/acre $/acre
All mineral fertilizer* 2735 1559.67
1/3 natural organic fertilizer 2607 1466.33
All mineral fertilizer +
micronutrientst 2809 1599.53
All mineral fertilizer +
500 lbs. chicken manure 2667 1513.86
All mineral fertilizer +
1000 lbs. chicken manure 2658 1521.85
All mineral fertilizer +
1500 lbs. chicken manure 2684 1520.26

* All treatments received a base application of 1500 pounds of 3-9-12 all-mineral fertilizer
per acre, except the second in which 1/3 of nitrogen was derived from natural organic
(seed meals).
t FTE 503 micronutrient frit applied at rate of 33.5 pounds per acre.

5. The results of an experiment conducted in 1962 to test the
possibility that a response to natural organic was due, in part,
to their content of micronutrients, are given in Table 11. Fer-
tilizers in which all N was derived from mineral sources result-
ed in higher tobacco yields than when equivalent amount of the
major nutrients were applied as a fertilizer in which one-third
of the N was derived from natural organic (seed meals). Fur-
thermore, use of 500, 1,000, or 1,500 pounds of chicken manure
per acre, in addition to an all mineral fertilizer, did not increase
yields above that of the mineral fertilizer alone. Only when a
micronutrient mix was applied in conjunction with the base fer-
tilizer were yields increased.

D. Fertilizer Rates, Plant Population, and Varieties

Effects of fertilizer rates and plant populations on the yield
and value of three varieties of flue-cured tobacco are shown in
Table 12. The average yield of Hick's Broadleaf tobacco was
2,424 pounds per acre. Yields of F-22 and NC-95 varieties were
2,785 and 2,731 pounds per acre.
The average yield of plots planted at populations of 7,500,
10,000, and 12,500 plants per acre were 2,538, 2,686, and 2,716
pounds respectively. While there was an average increase in
yields with increases in plant population up to 12,500 plants per
acre, there were considerable differences in the effect of popu-
lation on varietal yields. For example, with Hick's variety, yields
increased 12% when the population was increased from 7,500

Table 12.-Effects of fertilizers on yield, value, and composition of three varieties of flue-cured tobacco grown at different plant
populations in fertilization-population-variety experiment, 1963.

Fertilizer Applied Hick's Variety NC-95 Variety F-22 Variety
lb. per acre plants per acre plants per acre plants per acre
Base Sidedress 7,500 10,000 12,500 7,500 10,000 12,500 7,500 10,000 12,500

Yields-pounds per acre

2242 2578 2573 2573 2495 2942 2836 2819 2458
2325 2290 2604 2629 2761 2936 2682 2978 2547
2264 2511 2430 2591 2732 2918 2696 3007 3041

Value-dollars per acre
1268.81 1526.31 1485.36 1417.18 1229.62 1560.09 1506.50 1557.34 1282.12
1202.96 1225.75 1383.62 1264.76 1384.47 1456.81 1308.18 1534.10 1348.06
1191.94 1301.27 1203.39 1237.18 1305.00 1404.73 1346.64 1534.64 1548.95

Total N-percent
1.99 2.28 1.99 2.18 2.08 2.19 2.16 2.42 2.16
2.21 2.33 2.11 2.25 2.31 2.19 2.29 2.37 2.30
2.63 2.38 2.40 2.41 2.29 2.50 2.68 2.47 2.22






Fertilizer Applied Hick's Variety NC-95 Variety F-22 Variety
bi. per acre plants per acre plants per acre plants per acre
Base Sidedress 7,500 10,000 12,500 7,500 10,000 12,000 7,500 10,000 12,000

Total Alkaloids-percent

1500 150 1.72 1.20 1.39 0.97 1.11 1.04 1.60 1.21 1.29
2000 300 1.47 1.20 1.28 1.06 0.98 0.98 1.64 1.59 1.44
2500 450 1.54 1.32 1.08 0.83 0.96 0.91 1.46 1.54 1.28

X 100
Total Alkaloids

1500 150 94.2 93.3 95.7 88.6 92.8 91.3 95.6 92.6 94.6
2000 300 94.5 95.0 95.3 96.2 93.9 93.8 94.5 96.8 93.0
2500 450 90.9 96.9 98.1 90.4 93.7 93.4 94.5 94.1 98.4

Total N

1500 150 1.23 2.03 1.50 2.53 2.02 2.30 1.41 1.83 1.77
2000 300 1.59 2.04 1.73 2.20 2.51 2.38 1.48 1.54 1.72
2500 450 1.88 1.86 2.26 3.21 2.54 2.94 1.94 1.70 1.76

to 12,500 plants per acre. The highest yields of NC-95 tobacco
were also obtained with the highest plant population, but highest
yields of F-22 were obtained at the intermediate (10,000 plants
per acre) plant spacing.
When the fertilizer application was increased from 1,500 to
2,000 and 2,500 pounds per acre, yields were only increased 26
and 75 pounds per acre, respectively, over yields of plots that re-
ceived 1,500 pounds of fertilizer. However, there were some sig-
nificant interactions among fertilizer rates, plant population and
varieties. The average yields decreased with increasing fertilizer
rates with a population of 7,500 plants per acre, but there was
an increase of 139 pounds per acre when the fertilizer applica-
tion was increased from 1,500 to 2,500 pounds with a population
of 12,500 plants.
Even more interesting results were obtained when varieties
were considered individually. There were increased yields with
increased population of Hick's variety, but little yield increase
due to increased fertilizer rates regardless of the population.
The highest yield was obtained from a combination of 12,500
plants and 2,000 pounds of base fertilizer per acre. With the
F-22 variety, yields decreased as fertilizer rates increased at a
population of 7,500 plants, but increased greatly as fertilizer
rates increased at population of 12,500 plants per acre. On the
other hand, highest yields of NC-95 variety were obtained from
the closest plant spacing (12,500 plants per acre) and lowest fer-
tilizer rate (1,500 pounds per acre).
The composition of leaves was affected to a greater extent by
variety than by plant population or fertilizer treatment. Al-
though not shown in Table 12, the average Ca content of the
leaves ranked in the order: NC-95 > Hick's Broadleaf > F-22.
The content of Mg in leaves did not vary greatly. However, va-
rieties ranked in the same order for Mg content as for Ca. The
average K content was 5.69% in NC-95, 5.51% in F-22, and
5.07% in Hick's Broadleaf variety.
The contents of nitrogenous constituents found in the tobacco
are shown in Table 12. Total nitrogen content generally in-
creased as fertilizer rates increased. Plant population had little
consistent effect on total N content, although there was a slight
tendency for it to decrease as population increased. Further-
more, there was little difference in N content among varieties.
Average values were 2.26, 2.27, and 2.34% for Hick's Broadleaf,
NC-95, and F-22, respectively. On the other hand, nicotine con-
tent varied considerably among varieties (NC-95 contained

0.91%0, Hick's Broadleaf 1.29%, and F-22 contained 1.40%).
Since total alkaloid content varies with nicotine content the ratio
of the two constituents was similar for all varieties. However,
the ratio of total N to nicotine varied considerably among fer-
tilizer treatments and varieties. As fertilizer rates increased,
the ratio of total N:nicotine increased, with NC-95 having a
higher ratio than the other two varieties.

Experiments to study the effects of fertilizers on the yield,
market value, and chemical composition of flue-cured tobacco
were conducted on Blanton and Klej fine sands at the Suwannee
Valley Experiment Station from 1957 through 1963. The tests
involved the use of varying rates and ratios of N and K in to-
bacco fertilizers; sources of K fertilizers; micronutrients; and
fertilizer rates in combinations with plant population of three
tobacco varieties. All experiments were irrigated as needed and
managed according to prevailing practices in the area. Uniform
applications of P fertilizers were applied to all experiments at
the rate of about 54 pounds of P per acre-which preliminary
tests had shown to be adequate for tobacco on these soils. The
following conclusions were drawn from the results:
A. Yields of tobacco were closely related to the amounts of N
fertilizer applied. Increases of about 50 pounds of tobacco per
15 pounds of nitrogen applied above the base application of 45
pounds were obtained in 1958 and 1959. Maximum yields were
generally obtained with about 90 pounds of nitrogen per acre.
Higher rates of N were required to reach maximum yields in
years of excessive rainfall during the growing period. However,
excessive N delayed maturity of the tobacco and in some in-
stances reduced the market value. Maximum returns were gen-
erally obtained from use of 75 to 90 pounds of N per acre.
Total N content increased with N fertilizer applications,
as did nicotine content of the tobacco. However, nicotine content
did not increase as rapidly as N. Contents of nitrogenous con-
stituents were lower in tobacco from these experiments than re-
ported for tobacco from other areas (2). The content of these
constituents apparently can be increased-if desired-and con-
trolled to some extent by regulating the rate of N fertilization.
B. Yields and crop values were generally increased with ap-
plications of K fertilizers up to 166-207 pounds of K per acre on
these sandy soils. Potassium sulfate, the source of K used in
most tobacco fertilizers, is water-soluble and subject to some loss

by leaching. However, slowly available K sources, such as frit-
ted materials, were not consistently better than soluble sources.
Potassium nitrate was no better as a K source than K2S04.
C. In experiments comparing the effect of single micronutri-
ent applications on tobacco, only B proved beneficial. Calcium
borate (Colemanite), row applied at the rate of 0.5 pound of B
per acre, resulted in significant yield increases on soils limed
to pH 5.8. Micronutrient mixes, containing fritted sources of
elements and applied at rates of about 100 pounds per acre, also
increased tobacco yields in most instances.
No benefit was derived from use of natural organic as N
sources in tobacco fertilizers over that obtained from equiva-
lent rates of N in all mineral fertilizers.
D. In a one-year study of effects of fertilizers on three vari-
eties planted at three population densities, highest average yields
were obtained at the greatest population density (12,500 plants
per acre) for Hick's Broadleaf and NC-95 varieties. Highest
yields of F-22 tobacco were obtained from the intermediate den-
sities (10,000 plants per acre).
Responses to fertilizers were dependent on both variety and
population. For example, with Hick's Broadleaf there was little
increase in yield due to increased fertilizer rates at any popula-
tion-the highest yield was obtained with 12,500 plants per acre
and 2,000 pounds of base fertilizer. Yields of F-22 decreased as
fertilizer rates increased at 7,500 plants per acre, but greatly in-
creased with increased fertilizer rates when 12,500 plants were
used. On the other hand, the highest yields of NC-95 were ob-
tained from the closest spacing (12,500 plants) and the lowest
fertilizer rate (1,500 pounds per acre).


1. Breland, H. L. 1957. Methods of analysis used in soil testing. Fla. Agr.
Exp. Sta., Dept. of Soils Mimeo Rept. 58-3.
2. Brothers, S. L., and F. Clark. 1958. Flue-cured tobacco in Florida. Fla.
Dept. of Agr. Bull. 40.
3. Clark, F., J. M. Meyers, H. C. Harris, and R. W. Bledsoe. 1956. Yield
and quality of flue-cured tobacco as affected by fertilization and irriga-
tion. Fla. Agr. Exp. Sta. Bull. 572.
4. Clark, F., and J. M. Meyers. 1956. The effect of rates of irrigation,
fertilizers, and plant spacing on the yield and quality of flue-cured
tobacco in Florida. Fla. Soil and Crop Sci. Soc. Proc. 16: 249-57.
5. Cundiff, R. H., and P. C. Markunas. 1955. Determination of nicotine,
nor-nicotine, and total alkaloids in tobacco. Anal. Chem. 27: 1950-53.
6. Elliot, J. M., and L. S. Vickery. 1956. Ontario flue-cured tobacco soils
and their fertilizer requirements. Canada Dept. of Agr. Publ. 987.
7. Florida State Department of Agriculture. 1964. Fla. Agr. Stat.
8. Jackson. M. L. 1956. Soil Chemical Analysis. Prentice Hall, Inc., Engle-
wood Cliffs, N. J. 498 pp.
9. Pritchett, W. L., H. L. Breland, and H. W. Lundy. 1959. Effects of
nitrogen fertilizer on the yield and composition of flue-cured tobacco.
Fla. Soil and Crop Sci. Soc. Proc. 19: 418-27.


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