Effect of Nitrogen Rate and Cultivar on
Burley Tobacco (Nicotiana tabacum L.) Yield and Leaf Quality
A Thesis
Presented for the
Master of Science
Degree
The University of Tennessee at Martin
David Kaleb Rathbone
December 2008
Acknowledgements
I would like to thank Mr. Bill Teague, Superintendent of the Mountain
Research Station, for allowing me the freedom to work on this project. I would also
like to thank Dr. Greg Hoyt, for without his generous support of time and resources,
this thesis would not have been possible.
I would like to acknowledge Dr. Barb Darroch and Dr. Wes Totten for editing
the document and Dr. Tim Burcham for guidance throughout the MSANR program.
My sincerest appreciation is extended to my wife Monica who always provides
never-ending support and encouragement for everything I do.
ii
Abstract
Proper management of nitrogen application is imperative for producing quality
burley tobacco. Current nitrogen recommendations for North Carolina are based on
older burley tobacco cultivars. Improved cultivars with high yield and disease
resistance have been developed. The objective of this study was to provide burley
tobacco growers with recommendations for application of nitrogen fertilizer to newer
cultivars. The effect of nitrogen rate and cultivar on tobacco growth, yield, and leaf
quality was investigated.
Five burley cultivars were used in this study: TN 90, KT 204, NC 2000, NC 7,
and Clay’s 403. All cultivar treatments received 112 kg N ha-1 as a pre-plant broadcast
application. Additional nitrogen fertilizer was side-dressed 30 days after planting.
The four nitrogen treatments (broadcast plus side-dressed) were 112, 168, 224, and
280 kg N ha-1. A factorial randomized complete block design with four blocks was
used at each location.
Trials were conducted in 2005, 2006 and 2007 at two locations, the Upper
Mountain Research Station, Laurel Spring, NC, and the Mountain Research Station
(MRS), Waynesville, NC. At the MRS, trials were established on a bottomland soil
and an upland terrace location. Height and flowering data were collected in late
summer. Yield data were collected after barn curing as the tobacco was graded. A
tobacco grader from North Carolina State University determined leaf grades and a
quality index was calculated for each treatment.
iii
Nitrogen rate affected tobacco height, time of flowering, yield, and leaf quality
at each location. Plant growth and yield data for the heavier clay soil (upland location
at MRS) showed that the 224 kg N ha-1 nitrogen rate (currently recommended to
growers) provided maximum yield of burley tobacco. At the two sandy soil locations,
the highest yields were produced by the 224 and 280 kg N ha-1 rates. The 280 kg N
ha-1 rate produced the highest yield in only one out of six location/years on the sandy
soils. Results indicated the newer burley tobacco cultivars (TN 90, KT 204, NC 2000,
and NC 7) produced maximum yield at the recommended 224 kg ha-1 rate of nitrogen.
iv
Table of Contents
Page
Chapter I ..................................................................................................................1
Introduction .............................................................................................................1
Research Objectives ............................................................................................2
Chapter II.................................................................................................................3
Literature Review ....................................................................................................3
Overview of Tobacco Production........................................................................3
Soil Nitrogen and Nitrogen Fertilizer..................................................................5
Cultivars Used in the Study.................................................................................7
Chapter III .............................................................................................................11
Research Methods .................................................................................................11
Chapter IV .............................................................................................................15
Results ...................................................................................................................15
Tobacco Height .................................................................................................15
Flowering...........................................................................................................19
Yield ..................................................................................................................23
Quality ...............................................................................................................31
Chapter V...............................................................................................................35
Conclusions ...........................................................................................................35
Literature Cited......................................................................................................37
Appendix A ...........................................................................................................41
Plot Plans ...............................................................................................................41
Appendix B............................................................................................................44
ANOVA Tables .....................................................................................................44
Appendix C............................................................................................................54
Weather Data .........................................................................................................54
Vita ........................................................................................................................85
v
List of Tables
Page
Table 1. Burley tobacco varieties used in this study and relative levels of disease
resistance (from Ivors and Shoemaker, 2007).................................................................9
Table 2. Yield and grade index of burley tobacco cultivars..........................................10
Table 3. Quality index values for government grades of burley tobacco (Bowman, et.
al., 1989)........................................................................................................................14
Table 4. Effect of cultivar and nitrogen rate on mean burley tobacco height (cm) at the
upland and river bottom locations of the Mountain Research Station and at the Upper
Mountain Research Station in 2005 ..............................................................................16
Table 5. Effect of cultivar and nitrogen rate on mean burley tobacco height (cm) at the
upland and river bottom locations of the Mountain Research Station and at the Upper
Mountain Research Station in 2006 ..............................................................................17
Table 6. Effect of cultivar and nitrogen rate on mean burley tobacco height (cm) at the
upland and river bottom locations of the Mountain Research Station and at the Upper
Mountain Research Station in 2007 ..............................................................................18
Table 7. Effect of cultivar and nitrogen rate on mean burley tobacco flowering (%) at
the upland and river bottom locations of the Mountain Research Station and at the
Upper Mountain Research Station in 2005 ...................................................................20
Table 8. Effect of cultivar and nitrogen rate on mean burley tobacco flowering (%) at
the upland and river bottom locations of the Mountain Research Station and at the
Upper Mountain Research Station in 2006 ...................................................................21
Table 9. Effect of cultivar and nitrogen rate on mean burley tobacco flowering (%) at
the upland and river bottom locations of the Mountain Research Station and at the
Upper Mountain Research Station in 2007 ...................................................................22
Table 10. Effect of year and location on mean burley tobacco yield and quality
analyses by location and year. .......................................................................................24
Table 11. Rainfall totals by month, location and yearz.................................................. 25
Table 12. Results of combined statistical analyses for all locations and years in the
burley tobacco experiment. ...........................................................................................26
vi
Table 13. Effect of cultivar and nitrogen rate on mean burley tobacco yield (kg ha-1) at
each site at the upland and river bottom locations of the Mountain Research Station
and at the Upper Mountain Research Station in 2005................................................... 27
Table 14. Effect of cultivar and nitrogen rate on mean burley tobacco yield (kg ha-1) at
each site at the upland and river bottom locations of the Mountain Research Station
and at the Upper Mountain Research Station in 2006................................................... 28
Table 15. Effect of cultivar and nitrogen rate on mean burley tobacco yield (kg ha-1) at
each site at the upland and river bottom locations of the Mountain Research Station
and at the Upper Mountain Research Station in 2007................................................... 29
Table 16. Effect of cultivar and nitrogen rate on mean burley tobacco quality index at
each site at the upland and river bottom locations of the Mountain Research Station
and at the Upper Mountain Research Station in 2005................................................... 32
Table 17. Effect of cultivar and nitrogen rate on mean burley tobacco quality index at
each site at the upland and river bottom locations of the Mountain Research Station
and at the Upper Mountain Research Station in 2006................................................... 33
Table 18. Effect of cultivar and nitrogen rate on mean burley tobacco quality index at
each site at the upland and river bottom locations of the Mountain Research Station
and at the Upper Mountain Research Station in 2007................................................... 34
Table B.1. Significance (P values) of cultivar, nitrogen rate and cultivar by nitrogen
rate interaction on percent flowering, height, yield, and quality of burley tobacco at the
River Bottom Location, Mountain Research Station, 2005. ......................................... 45
Table B.2. Significance (P values) of cultivar, nitrogen rate and cultivar by nitrogen
rate interaction on percent flowering, height, yield, and quality of burley tobacco at the
Upland Location, Mountain Research Station, 2005..................................................... 46
Table B.3. Significance (P values) of cultivar, nitrogen rate and cultivar by nitrogen
rate interaction on percent flowering, height, yield, and quality of burley tobacco at the
Upper Mountain Research Station, 2005....................................................................... 47
Table B.4. Significance (P values) of cultivar, nitrogen rate and cultivar by nitrogen
rate interaction on percent flowering, height, yield, and quality of burley tobacco at the
Bottom Location, Mountain Research Station, 2006 .................................................... 48
Table B.5. Significance (P values) of cultivar, nitrogen rate and cultivar by nitrogen
rate interaction on percent flowering, height, yield, and quality of burley tobacco at the
Upland Location, Mountain Research Station, 2006..................................................... 49
vii
Table B.6. Significance (P values) of cultivar, nitrogen rate and cultivar by nitrogen
rate interaction on percent flowering, height, yield, and quality of burley tobacco at the
Upper Mountain Research Station, 2006.......................................................................50
Table B.7. Significance (P values) of cultivar, nitrogen rate and cultivar by nitrogen
rate interaction on percent flowering, height, yield, and quality of burley tobacco at the
River Bottom Location, Mountain Research Station, 2007 ..........................................51
Table B.8. Significance (P values) of cultivar, nitrogen rate and cultivar by nitrogen
rate interaction on percent flowering, height, yield, and quality of burley tobacco at the
Upland Location, Mountain Research Station, 2007.....................................................52
Table B.9. Significance (P values) of cultivar, nitrogen rate and cultivar by nitrogen
rate interaction on percent flowering, height, yield, and quality of burley tobacco at the
Upper Mountain Research Station, 2007.......................................................................53
Table C.1. Weather Data Laurel Springs, NC May 2005..............................................55
Table C.2. Weather Data Laurel Springs, NC June 2005..............................................56
Table C.3. Weather Data Laurel Springs, NC July 2005 ..............................................57
Table C.4. Weather Data Laurel Springs, NC August 2005 .........................................58
Table C.5. Weather Data Laurel Springs, NC September 2005 ....................................59
Table C.6. Weather Data Laurel Springs, NC May 2006..............................................60
Table C.7. Weather Data Laurel Springs, NC June 2006..............................................61
Table C.8. Weather Data Laurel Springs, NC July 2006 ..............................................62
Table C.9. Weather Data Laurel Springs, NC August 2006 .........................................63
Table C.10. Weather Data Laurel Springs, NC September 2006 ..................................64
Table C.11. Weather Data Laurel Springs, NC May 2007............................................65
Table C.12. Weather Data Laurel Springs, NC June 2007............................................66
Table C.13. Weather Data Laurel Springs, NC July 2007 ............................................67
Table C.14. Weather Data Laurel Springs, NC August 2007 .......................................68
viii
Table C.15. Weather Data Laurel Springs, NC September 2007 .................................. 69
Table C.16. Weather Data Waynesville, NC May 2005 ............................................... 70
Table C.17. Weather Data Waynesville, NC June 2005 ............................................... 71
Table C.18. Weather Data Waynesville, NC July 2005 ................................................72
Table C.19. Weather Data Waynesville, NC August 2005 ........................................... 73
Table C.20. Weather Data Waynesville, NC September 2005...................................... 74
Table C.21. Weather Data Waynesville, NC May 2006 ............................................... 75
Table C.22. Weather Data Waynesville, NC June 2006 ............................................... 76
Table C.23. Weather Data Waynesville, NC July 2006 ................................................77
Table C.24. Weather Data Waynesville, NC August 2006 ........................................... 78
Table C.25. Weather Data Waynesville, NC September 2006...................................... 79
Table C.26. Weather Data Waynesville, NC May 2007 ............................................... 80
Table C.27. Weather Data Waynesville, NC June 2007 ............................................... 81
Table C.28. Weather Data Waynesville, NC July 2007 ................................................82
Table C.29. Weather Data Waynesville, NC August 2007 ........................................... 83
Table C.30. Weather Data Waynesville, NC September 2007...................................... 84
ix
x
Chapter I
Introduction
Tobacco, Nicotiana spp., is a member of the nightshade (Solanaceae) family.
Currently there are 70 naturally occurring species of tobacco (Lewis and Nicholson,
2007). Burley tobacco (N. tabacum L.) is the most common type of tobacco grown in
western North Carolina.
Due to increased prices of fuel, labor and other inputs, the cost of producing
quality burley tobacco has risen to historically high levels. Currently, producers are
faced with a smaller profit margin than in the past, so it is imperative that farmers
manage production costs by being as efficient in their production practices as possible.
While many production costs such as labor can vary from farm to farm, agronomic
inputs remain relatively fixed. However, these costs depend on recommended rates of
crop protectants and fertilizers. One of the highest costs of production is nitrogen
fertilizer. This also is one of the most important inputs for growers to manage because
nitrogen fertilizer affects burley tobacco yield and quality (Davis and Nielsen, 1999).
Researchers have recommended that 180 kg N ha-1 to 224 kg N ha-1 be applied
to burley tobacco in North Carolina (Shelton, 1987; Hoyt, 2008). These nitrogen
fertilizer recommendations serve as a useful guide for burley tobacco production
(Evanylo et al., 1988). While these recommended rates have served North Carolina
producers well for many years, these recommendations were based on older varieties
that were grown several years ago. Many improved burley tobacco cultivars with
increased disease resistance and potentially greater yields are now available (Miller,
1
2005). Agronomic recommendations for these new cultivars are currently being
developed in the burley tobacco growing region.
Timing of nitrogen fertilizer application is an important consideration
(Waynick et al., 2006). Burley tobacco cultivars vary in time to maturity, with early
maturing cultivars needing more nitrogen earlier in the growing season than those that
are late maturing. If nitrogen fertilizer is applied too early in the plant’s life cycle,
excessive rainfall can cause nitrate leaching before the plant is able to utilize this
available nitrogen. If this occurs, the producer may not achieve full benefit from the
nitrogen application. To minimize nitrogen loss, application of nitrogen fertilizer
should be split with an initial pre-plant application followed by an application four
weeks after planting (Collins and Hawks, 1993). Producers must be careful with
timing and rate of nitrogen fertilizer applications, as excessive nitrogen can have
adverse effects on cured leaf quality. This creates an inferior product and can result in
lower market premiums for the leaf (Collins and Hawks, 1993).
Research Objectives
This experiment was designed to meet the following research objectives:
1.
Determine the effect of nitrogen rate on growth, yield, and leaf quality of five
burley tobacco cultivars;
2.
Determine nitrogen utilization in early maturing versus late maturing varieties;
and
3.
Provide burley tobacco growers with detailed recommendations for application of
nitrogen fertilizer.
2
Chapter II
Literature Review
Overview of Tobacco Production
Tobacco (Nicotiana tabacum L.) production and marketing have undergone
many changes since tobacco was first produced commercially (Greene, 1996).
Today’s tobacco producers face the challenge of producing the highest quality tobacco
for the same premium that was paid for burley tobacco over 20 years ago. While the
price per pound of tobacco is the same as it was 20 years ago, the cost of production
has increased considerably (USDA, 1990).
Burley tobacco is an air cured type of tobacco and has been historically
produced primarily in Western North Carolina, East Tennessee, and Kentucky. The soils
and climate of these areas are well suited for production and curing of burley tobacco.
Government regulation also restricted expansion of production into other areas (Greene,
1996). In recent years, after the tobacco quota buyout of 2005, geographic restrictions
on burley tobacco production have been lifted. While there has been some expansion of
burley tobacco production into non-traditional areas, the main burley tobacco growing
areas are still Western North Carolina, East Tennessee, and Kentucky.
For optimum yields in Western North Carolina, tobacco should be transplanted
between May 20 and May 30 and harvested in mid September. (Shaw et al., 1965).
Burley tobacco is generally planted on 122 cm row spacing and 46 cm plant spacing.
This spacing gives the producer a population of 17,819 plants per hectare. Pesticides
3
labeled for weed, plant disease, and insect controls are applied at appropriate times,
with weeds also controlled by cultivation and or/by hand.
Nitrogen is one of the most important plant nutrients in tobacco production
(Collins and Hawks, 1993). Incorrect nitrogen application rates will reduce net
income. Over-application of nitrogen can lower leaf quality, cost growers additional
expense, and potentially lead to nitrogen loss by soil erosion or leaching below the
root zone. Under application of nitrogen can result in lower burley tobacco yields,
reducing net income to the grower (Flower, 1999).
One of the largest production costs for burley tobacco is nitrogen fertilizer. On
average, burley tobacco producers spend over $700.00 per ha on nitrogen fertilizer. Other
major inputs include labor, crop protectants, facilities and equipment (Brown, 2008).
Soil type plays an important role in nutrient management in tobacco
production. Clay soils tend to retain nitrogen better than sandy soils, which are prone
to nutrient leaching if rainfall is excessive. Nitrogen leaches more readily from sandy
soils because they have larger pores between soil particles and less surface area than
soils with high clay content. Sandy soils also have a lower cation exchange capacity
than clay soils. Cation exchange capacity is the quantity of negative charges in soil.
Soils with high cation exchange capacity can bind positive charged plant nutrients
(NH4+, K+, Ca++, Mg++), reducing leaching of these nutrients (Camberato, 2001). More
water can move through large pore spaces than smaller pore spaces found in clay soils.
As water moves downward (due to gravity) nitrates in solution also move through the
soil which reduces nitrogen availability to plants (Killpack and Buchholz, 1993).
4
Soil Nitrogen and Nitrogen Fertilizer
Nitrogen concentration in soil fluctuates from near zero to more than 2.5%,
and the amount of plant available nitrogen depends, to a large extent, on the amount of
organic matter in the soil (Carrow et al., 2001). The amount of nitrogen taken up and
utilized by a plant also depends on the amount of moisture in the soil. Irrigation can be
used to increase soil moisture levels and increase yields (Sifola and Postiglione, 2003).
Irrigation can help plants take up nitrogen, but could potentially increase leaching of
nitrate nitrogen.
Movement of nitrogen throughout soil, plants and the atmosphere can best be
explained by the nitrogen cycle (Figure 1). One of the most abundant sources of
nitrogen is atmospheric nitrogen. Approximately 78% of air is nitrogen (Microsoft
Encarta Online Dictionary, 2007). Conversion of this nitrogen to plant available
nitrogen in natural systems is mainly through biological nitrogen fixation (Carrow et
al., 2001). Biological nitrogen fixation is primarily carried out in legume crops which
form a symbiotic relationship with Rhizobium bacteria. This biologically fixed
nitrogen can be available to succeeding crops after the legume crops decompose.
Another way that atmospheric nitrogen can be converted to plant available
nitrogen is through lightning (Allison, 1957). Since lightning cannot be easily
harnessed to provide a consistent source of nitrogen to plants, a third method of
nitrogen conversion has been developed. Industrial nitrogen fixation through the
Haber-Bosch process is used to create synthetic nitrogen fertilizer (Carrow et al.,
2001).
5
Figure 1. The nitrogen cycle in soil (Brown and Johnson, 1991)
6
There are different sources of nitrogen in the soil and each pool has different
plant availability. Nitrogen is taken into plants in only two forms. These forms are
NO3-(nitrate) and NH4+ (ammonia). Microbes in the soil convert nitrogen found in soil
organic matter or fresh plant material into one of these two forms (Dorn, 2001).
To take advantage of biologically fixed nitrogen, tobacco can be planted after
winter legume cover crops, or perennial crops such as alfalfa, are plowed into the soil
(Hoyt and Hargrove, 1986). Animal manures can also be utilized as plant nutrients on
the farm, but availability is dependent on other farm strategies for income (animal
production) or distance to an available source (Vaughn et al., 2007/ 2008). However,
the majority of nitrogen used in tobacco production is made available through the
application of synthetic nitrogen fertilizers.
Various synthetic fertilizers are used in tobacco production. Ammonium nitrate
(NH4 NO3), which contains 34% nitrogen, has been widely used in the past
(Pendergrass, 1952). Another form of nitrogen fertilizer that is becoming increasingly
popular with tobacco growers is liquid urea ((NH2)2CO) ammonium nitrate. This
product is available as either 30% nitrogen or 32% nitrogen (Terra Industries Inc.,
2006). While liquid fertilizer is often less expensive than granular fertilizers, many
farmers do not use it for tobacco production. This is likely due to the cost of
equipment modifications or other purchases required to apply liquid fertilizers.
Cultivars Used in the Study
Cultivars can differ in their response to nutrients available in the soil (Hiatt,
1963). A producer should keep this in mind when selecting a cultivar. Some cultivars
7
contain genes that confer disease resistance. However, in some cases genes that create
disease resistance may not have the potential for excellent yields (Lewis et al., 2007).
This can reduce the return on a producer’s investment, even with higher levels of
disease resistance.
The five cultivars used in this study varied in relative levels of disease
resistance (Table 1) and yield potential and quality (Table 2). For example, Clay’s 403
has excellent yield potential but is highly susceptible to blue mold (Peronospora
tabacina) (Table 1). NC 2000, a recent cultivar with blue mold resistance, has no
tolerance to black shank. TN 90, KT 204, and NC 7 are fairly new releases that have
good yield potential due to their resistance to some tobacco diseases but all are
susceptible to blue mold. According to North Carolina Official Variety Tests, Clay’s
403 traditionally has high yields, but only in locations where root diseases were not
present and in years when blue mold had not been established (Table 2). Clay’s 403
has a very low level of resistance to all diseases listed (Table 1). This is apparent by
looking at the tobacco leaf grade index for Clay’s 403, which was the lowest of the
five cultivars shown (Table 2). Clay’s 403, TN 90, and KT 204 are earlier maturing
while NC 7 and NC 2000 mature later. In certain locations, such as Laurel Springs,
NC, where growing seasons are short, late maturing varieties may not have enough
time to reach full yield potential.
8
Table 1. Burley tobacco varieties used in this study and relative levels of disease
resistance (from Ivors and Shoemaker, 2007)
Variety
Disease
Black Root Rot
Mosaic
Fusarium Wilt
Wildfire
Black Shank
Brown Spot
Vein Mottling
Etch
Blue Mold
Clay’s 403
KT 204
NC 2000
NC 7
TN 90
S*
S
VS
H
H
S
H
H
H
M
S
L
H
VS
H
S
S
S
S
M
H
H
H
H
-
H
H
VS
H
M
H
M-H
T
*S = susceptible; VS = very susceptible; H = high level of resistance; M = moderate
level of resistance; L = low level of resistance; T= tolerant - = no data
9
Table 2. Yield and grade index of burley tobacco cultivars
Variety
Clay’s 403**
TN 90*
NC 2000*
NC 7*
KT 204*
Yield (kg ha-1)
3868
3324
3056
3716
3811
Yield (lbs acre-1)
Grade Indexz
3,450
2,965
2,726
3,315
3,400
68
77
78
80
76
*
North Carolina Official Variety Test, Mountain Research Station (Fisher et al.,
2008)
** North Carolina Official Variety Test, Mountain Research Station (Smith and
Whitley, 2005)
z
Grade index is calculated based on the government quality grade assigned to the
tobacco leaf
10
Chapter III
Research Methods
This study was conducted during the growing seasons of 2005, 2006, and 2007
at the Upper Mountain Research Station (UMRS) located near Laurel Springs, NC and
the Mountain Research Station (MRS) in Waynesville, NC. At the MRS two sites
were established for the experiment, an upland heavy clay location and a river bottom
site with a sandy loam soil. The soil series at the UMRS was a Toxaway loam (a fineloamy, mixed, nonacid, mesic Cumulic Humaquept). Trials at the river bottom
location of the MRS were established on a French loam (a fine-loamy, over sandy or
sandy skeletal, mixed, mesic Fluaquentic Dystrochrepts). A Dyke clay soil (clayey,
mixed, mesic Typic Rhodudults) was found at the upland site.
Tobacco seedlings for the trials were grown in the greenhouse at the MRS.
Seedlings were started the first week of April each year, and transplanted to the field
during the first week of June.
All production practices (except for nitrogen application) were based on
recommendations set forth in the North Carolina Cooperative Extension Service’s
Burley Tobacco Production Guide (North Carolina Cooperative Extension Service,
2008).
Five burley tobacco cultivars were used throughout the study: TN 90, KT 204,
NC 2000, NC 7, and Clay’s 403. These cultivars were selected because of present or
past use by growers throughout the burley growing region of the United States. The
cultivars differ in maturity characteristics and level of resistance or tolerance to
11
common burley diseases (Tables 1 and 2). In addition to these five cultivars, an
additional experimental cultivar was grown each year. This variety was not included in
final analysis and discussion because the cultivar was not released for production.
Research plots at each site were set up as a factorial randomized complete
block design with four blocks. Treatment factors were cultivar and nitrogen rate.
Ammonium nitrate (34 % nitrogen) was applied pre-plant and as a side-dress
application. Phosphorus and potassium were applied pre-plant based on soil test
recommendations. All treatments received 112 kg N ha-1 as a pre-plant broadcast
application. Additional nitrogen fertilizer was side-dressed at varying rates 30 days
after planting. The four nitrogen treatments were 112, 168, 224, and 280 kg N ha-1
(pre-plant plus side-dress). This wide range in rates was chosen because the study also
included disease ratings based on nitrogen rates for a separate publication. Pesticides
to control weeds and insects were applied as needed. Plants were topped, harvested,
and air cured by standard burley practices (North Carolina Cooperative Extension
Service, 2008).
Flower counts were taken beginning at the elongated bud stage through
topping. Height was measured 8 to 10 weeks after transplanting and was determined
by taking the average of 12 plants per plot.
Yield data were collected for all locations throughout the three year period of
the experiment. The plots were harvested and air cured with five stalks per stick. The
tobacco leaves were stripped from the stalk in a controlled environment. The
temperature in the facility was maintained at 20° C and the relative humidity was kept
12
between 75% and 80%. With this controlled environment, moisture content did not
affect tobacco leaf weight.
Leaf quality was measured at all locations across all three years, with one
exception. Due to an error in the experiment, quality data from the 2005 MRS River
Bottom location was not collected. The leaf quality rating was developed at North
Carolina State University based on the traditional government grading system
(Bowman et al., 1989). Glen Tart, a tobacco grader from North Carolina State
University, evaluated each plot and assigned a grade to each of the four stalk
positions. This grade was then translated into a corresponding grade index based upon
the grade index table (Table 3). The grade index is based on a formula with 100
representing the highest quality leaf and 1 representing the lowest quality (Bowman et
al., 1989).
All data were analyzed using the GLM procedure of SAS (SAS Institute,
2006). Main effects and interactions were tested using ANOVA. The effect of N
fertility level was determined using single degree of freedom polynomial (linear,
quadratic and cubic) orthogonal contrasts. Contrasts were also used to compare late
versus early maturing cultivars for all variables. In addition, Duncan’s multiple range
test (α = 0.05) was used to compare cultivar means.
13
Table 3. Quality index values for government grades of burley
tobacco (Bowman, et. al., 1989)
Flyings
Leaf
Tips
X1L
86
B1F
100
T3F
70
X2L
76
B2F
90
T4F
60
X3L
66
B3F
80
T5F
50
X4L
56
B4F
70
T3FR
70
X5L
46
B5F
60
T4FR
60
X1F
90
B2FL
75
T5FR
50
X2F
80
B3FL
65
T3R
70
X3F
70
B4FL
55
T4R
60
X4F
60
B1FR
100
T5R
50
X5F
50
B2FR
90
T4D
36
X4M
44
B3FR
80
T5D
26
X5M
34
B4FR
70
T4K
32
X4G
24
B5FR
60
T5K
22
X5G
14
B1R
100
T4VF
36
B2R
90
T5VF
26
B3R
80
T4VR
36
26
Cutters
C1L
95
B4R
70
T5VR
C2L
85
B5R
60
T4GF
24
C3L
75
B4D
40
T5GF
14
C4L
65
B5D
30
T4GR
24
C5L
55
B3K
45
T5GR
14
C1F
100
B4K
35
C2F
90
B5K
25
C3F
80
B2M
70
M3F
50
C4F
70
B3M
60
M4F
40
C5F
60
B4M
50
M5F
30
Mixed
C3K
45
B5M
40
M3FR
50
C4K
35
B3VF
50
M4R
40
C5K
25
B4VF
40
M5FR
30
C3M
60
B5VF
30
M4K
26
C4M
50
B3VR
50
M5K
16
C5M
40
B4VR
40
C3V
50
B5VR
30
Nondescript
C4V
40
B3GF
35
N1L
30
C5V
30
B4GF
25
N2L
10
C4G
25
B5GF
15
N1F
30
C5G
15
B3GR
35
N1R
30
B4GR
25
N2R
10
B5GR
15
N1G
10
N2G
5
14
Chapter IV
Results
Tobacco Height
Cultivars used in this experiment were representative of the range in maturity
types of burley tobacco cultivars. This was reflected in height data collected. While
greater heights do not necessarily translate into higher yields, effects of nitrogen rate
on the different cultivars were evident.
Height measurements were taken throughout the growing season at all three
locations and for each of the three years of production. Tobacco height data are
summarized in Tables 4 through 6. Height of the earlier maturing varieties Clay’s 403
and TN 90 was significantly greater than the later maturing varieties NC 7, KT 204,
and NC 2000, as shown by the significant contrast for all locations and years (P <
0.005) except for the upland location at the MRS in 2006 (Table 5).
Significant (P < 0.05) differences for height were observed among cultivars at
all locations and years except the UMRS location in 2007 (Appendix B). The only
significant interaction between N rate and cultivar for plant height (P = 0.024) was
observed at the upland location, MRS in 2006 (Table B.5). Nitrogen rate had a
significant effect on height (P < 0.02) at the UMRS in 2005 and 2006 (Tables B.3 and
B.6). In addition, polynomial contrasts showed that there was a linear response of
height to N rate (P < 0.005) at the UMRS in 2005 and 2006 (Tables 4 and 5). Most of
the fertilizer applied during side dressing was available for the most vigorous period of
plant growth, leading to the observed linear response to nitrogen rate.
15
Table 4. Effect of cultivar and nitrogen rate on mean burley tobacco height (cm)
at the upland and river bottom locations of the Mountain Research Station and
at the Upper Mountain Research Station in 2005
Tobacco Height (cm)
Mountain Research Station
Upland
River Bottom
Location
Cultivar
Clay 403
NC 7
KT 204
TN 90
NC 2000
Early vs. late maturingx
Nitrogen Rate
112 kg N ha-1
168 kg N ha-1
224 kg N ha-1
280 kg N ha-1
Linear Contrast
Quadratic Contrast
Cubic Contrast
Upper
Mountain
Station
149az
132b
140ab
137ab
114c
145az
126b
136ab
142a
112c
160az
138c
151b
148b
122d
0.0011y
0.0001y
<0.0001y
130az
135a
133a
141a
128az
132a
133a
137a
139bz
139b
149a
150a
0.0802y
0.6194
0.3724
0.1348y
0.9747
0.6690
<0.0001y
0.6732
0.0436
z
Letters within a column and within a treatment factor followed by the same letter are
not significantly different by Duncan’s multiple range test (P ≤ 0.05).
y
Values for contrasts represent P values from the F test (Pr > F).
x
Contrasts for Early vs. late maturing tobacco: Early includes Clay 403, KT 204 and
TN 90, Late Maturing NC 7 and NC 2000.
16
Table 5. Effect of cultivar and nitrogen rate on mean burley tobacco height (cm)
at the upland and river bottom locations of the Mountain Research Station and
at the Upper Mountain Research Station in 2006
Tobacco Height (cm)
Mountain Research Station
Cultivar
Clay 403
NC 7
KT 204
TN 90
NC 2000
Early vs. late maturingx
Nitrogen Rate
112 kg N ha-1
168 kg N ha-1
224 kg N ha-1
280 kg N ha-1
Linear Contrast
Quadratic Contrast
Cubic Contrast
Upper
Mountain
Station
Upland Location
River Bottom
111az
100ab
107ab
105ab
91b
129az
119b
124ab
132a
104c
125az
116b
118b
115b
99c
0.0987y
<0.0001y
<0.0001y
101az
105a
100a
106a
126az
121a
121a
119a
109bz
117a
115a
118a
0.6383y
0.8536
0.3896
0.1348y
0.9747
0.6690
0.0046y
0.1679
0.1051
z
Letters within a column and within a treatment factor followed by the same letter are
not significantly different by Duncan’s multiple range test (P ≤ 0.05).
y
Values for contrasts represent P values from the F test (Pr > F).
x
Contrasts for Early vs. late maturing tobacco: Early includes Clay 403, KT 204 and
TN 90, Late Maturing NC 7 and NC 2000.
17
Table 6. Effect of cultivar and nitrogen rate on mean burley tobacco height (cm)
at the upland and river bottom locations of the Mountain Research Station and
at the Upper Mountain Research Station in 2007
Tobacco Height (cm)
Mountain Research Station
Cultivar
Clay 403
NC 7
KT 204
TN 90
NC 2000
Early vs. late maturingx
Nitrogen Rate
112 kg N ha-1
168 kg N ha-1
224 kg N ha-1
280 kg N ha-1
Linear Contrast
Quadratic Contrast
Cubic Contrast
Upper
Mountain
Station
Upland Location
River Bottom
71az
64ba
54bc
62abc
53c
101abz
95b
97b
105a
84c
70az
58ab
68a
69a
52b
0.0033y
<0.0001y
0.0037y
61az
60a
59a
64a
96az
95a
98a
97a
63az
65a
66a
59a
0.5990y
0.3495
0.6763
0.2975y
0.9125
0.2267
0.4717y
0.2131
0.6310
z
Letters within a column and within a treatment factor followed by the same letter are
not significantly different by Duncan’s multiple range test (P ≤ 0.05).
y
Values for contrasts represent P values from the F test (Pr > F).
x
Contrasts for Early vs. late maturing tobacco: Early includes Clay 403, KT 204 and
TN 90, Late Maturing NC 7 and NC 2000.
18
Flowering
Tobacco flowering is a physiological characteristic that differs among tobacco
cultivars. In this study, flowering data were collected multiple times between the
elongated bud stage to full flower and topping at all locations (Tables 7 through 9).
A tobacco plant will grow and mature according to its general genetic makeup,
with some cultivars flowering and maturing earlier than others. Low nitrogen
availability late in the growing season can trigger a physiological response that results in
earlier tobacco flowering. This could have occurred in the locations where there was a
significant interaction between cultivar and N rate (Appendix B). Significant cultivar by
N rate interactions were observed at the River Bottom Location at the MRS in 2006 (P =
0.0189) and at the upland location at the MRS in 2007 (P < 0.05; Tables B.4 and B.8).
As nitrogen becomes depleted to a maturing tobacco plant, the plant can enter
the reproductive phase of its life cycle. This was observed with flowering data at five
of the nine location/years (Tables 7 through 9). There was less influence on percent
flowering early when tobacco was first flowering, but more influence of N rate later in
the growing season. This is evident by the significant linear contrasts for N rate in
2005 and 2006 (P < 0.04).
When tobacco blooms earlier in the plant’s life cycle, it reduces the period of
time the plant has to produce leaf mass and subsequently reduces crop yield. Time of
tobacco flowering also affects when the plant should be topped. Topping is the process
of cutting the blooms off the plants. By removing the flowers, plants are forced to stop
growing taller and allocate more carbohydrates to roots and leaves. Traditionally,
19
Table 7. Effect of cultivar and nitrogen rate on mean burley tobacco flowering
(%) at the upland and river bottom locations of the Mountain Research Station
and at the Upper Mountain Research Station in 2005
Tobacco flowering (%)
Mountain Research Station
Cultivar
Clay 403
NC 7
KT 204
TN 90
NC 2000
Early vs. late maturingx
Nitrogen Rate
112 kg N ha-1
168 kg N ha-1
224 kg N ha-1
280 kg N ha-1
Linear Contrast
Quadratic Contrast
Cubic Contrast
Upper
Mountain
Station
Upland Location
River Bottom
90az
48b
79a
82a
44b
85az
33b
86a
94a
17c
87az
8b
80a
77a
7b
<0.0001y
<0.0001y
<0.0001y
58bz
73a
71a
72a
59az
65a
64a
65a
48bz
46b
59a
55ab
0.0136y
0.0467
0.1845
0.2382y
0.4314
0.6537
0.0285y
0.8142
0.0434
z
Letters within a column and within a treatment factor followed by the same letter are
not significantly different by Duncan’s multiple range test (P ≤ 0.05).
y
Values for contrasts represent P values from the F test (Pr > F).
x
Contrasts for Early vs. late maturing tobacco: Early includes Clay 403, KT 204 and
TN 90, Late Maturing NC 7 and NC 2000.
20
Table 8. Effect of cultivar and nitrogen rate on mean burley tobacco flowering
(%) at the upland and river bottom locations of the Mountain Research Station
and at the Upper Mountain Research Station in 2006
Tobacco flowering (%)
Mountain Research Station
Cultivar
Clay 403
NC 7
KT 204
TN 90
NC 2000
Early vs. late maturingx
Nitrogen Rate
112 kg N ha-1
168 kg N ha-1
224 kg N ha-1
280 kg N ha-1
Linear Contrast
Quadratic Contrast
Cubic Contrast
Upper
Mountain
Station
Upland Location
River Bottom
53az
14b
43a
61a
13b
51az
2d
17c
64a
2d
80az
5d
50c
67b
4d
<0.0001y
<0.0001y
<0.0001y
40az
39a
39a
40a
32az
27ab
30ab
20b
29bz
47a
39ab
50a
0.1982y
0.4517
0.7094
0.0372y
0.5732
0.2059
0.0036y
0.4133
0.0199
z
Letters within a column and within a treatment factor followed by the same letter are
not significantly different by Duncan’s multiple range test (P ≤ 0.05).
y
Values for contrasts represent P values from the F test (Pr > F).
x
Contrasts for Early vs. late maturing tobacco: Early includes Clay 403, KT 204 and
TN 90, Late Maturing NC 7 and NC 2000.
21
Table 9. Effect of cultivar and nitrogen rate on mean burley tobacco flowering
(%) at the upland and river bottom locations of the Mountain Research Station
and at the Upper Mountain Research Station in 2007
Tobacco flowering (%)
Mountain Research Station
Cultivar
Clay 403
NC 7
KT 204
TN 90
NC 2000
Early vs. late maturingx
Nitrogen Rate
112 kg N ha-1
168 kg N ha-1
224 kg N ha-1
280 kg N ha-1
Linear Contrast
Quadratic Contrast
Cubic Contrast
Upper
Mountain
Station
Upland Location
River Bottom
49abz
21b
34ab
54a
36ab
51az
1c
17b
60a
2c
83az
69ab
70ab
87a
58b
0.0177y
<0.0001y
0.0037y
41az
46a
37a
32a
25abz
18b
30a
30a
76az
78a
69a
71a
0.3459y
0.5764
0.6559
0.0995y
0.3499
0.0407
0.4717y
0.2131
0.6310
z
Letters within a column and within a treatment factor followed by the same letter are
not significantly different by Duncan’s multiple range test (P ≤ 0.05).
y
Values for contrasts represent P values from the F test (Pr > F).
x
Contrasts for Early vs. late maturing tobacco: Early includes Clay 403, KT 204 and
TN 90, Late Maturing NC 7 and NC 2000.
22
plants are topped when 50% of the plants in the field are in bloom, allowing greater
efficiency for the grower to top the entire field (assuming same variety throughout the
field), rather than individually topping each plant when flowering begins. In these
experiments, NC 2000 and NC 7 flowered later than the other cultivars tested (Tables
7 through 9). These differences can be clearly seen in the significant early vs. late
maturing contrasts (P < 0.02) as well as in the results from Duncan’s multiple range
tests. Both of these cultivars are late maturing, which can create a problem in areas
with a shorter growing season (similar to the weather conditions at the UMRS). If late
maturing varieties are planted later than recommended dates, they may not have
enough time to reach full yield potential during the growing season.
Yield
Mean burley tobacco yield and quality are presented in Table 10. The best
burley tobacco yield (3405 kg N ha-1) was obtained in the 2007 growing season.
Because 2007 was an exceptionally dry year (Table 11 and Appendix C), irrigation
was applied as needed and disease pressure was minimal.
Table 12 shows results for combined analysis from all locations and years.
There were significant year by location interactions (P < 0.0001); therefore the data
were analyzed separately for each location within each year.
Burley tobacco yield results for 2005, 2006, and 2007 at all locations are
shown in Tables 13 through 15. The effect of cultivar on yield was significant at all
locations within all years (P < 0.02; Appendix B) except for the upland location at
MRS in 2005 and 2007 (Tables B.5 and B.7). No significant cultivar by N rate
23
Table 10. Effect of year and location on mean burley
tobacco yield and quality analyses by location and year.
Treatment
Yield(kg ha-1)
Quality Index
2803cx
3195b
3405a
96
59.9
68.8
75.3
3154b
2983c
64.3
76.4
3266a
95
68.7
y
Year
2005
2006
2007
LSD (0.05)
Locationw
UMRSu
MRS river
bottom
MRS upland
LSD (0.05)
z
The data for 2005 MRS-Lake was missing, no analyses
could be performed
y
Pooled for all locations
x
Letters within a treatment factor followed by the same
letter are not significantly different by the least significant
difference (LSD) test (P ≤ 0.05)
w
Pooled for all years
u
UMRS = Upper Mountain Research Station;
MRS = Mountain Research Station
24
Table 11. Rainfall totals by month, location and yearz.
MRSy (Both Locations)
2005
May
June
July
August
September
Season Total
UMRSx
---------------------------cm-------------------------11.1
17.8
16
14.3
2.3
61.5
7.5
17.8
20.5
14.6
1.9
62.3
2006
May
June
July
August
September
Season Total
9.9
12.4
3.5
13.8
14.8
54.4
8.7
18.8
10.2
9.7
22.1
69.5
2007
May
June
July
August
September
Season Total
3
9.8
7.7
9.9
6.9
37.3
3.9
7.1
6.8
1.75
8.8
28.35
z
Irrigation was applied to plots as needed to produce the crop. The amount of water
applied is not available.
y
MRS = Mountain Research Station
x
UMRS = Upper Mountain Research Station
25
Table 12. Results of combined statistical analyses for all
locations and years in the burley tobacco experiment.
Treatment
Yield
Quality
Year
Location
Year by Location
----------P values--------0.0001
0.0001
0.0001
0.0001
0.0001
0.0001
26
Table 13. Effect of cultivar and nitrogen rate on mean burley tobacco yield
(kg ha-1) at each site at the upland and river bottom locations of the Mountain
Research Station and at the Upper Mountain Research Station in 2005
Tobacco yield (kg ha-1)
Mountain Research Station
Upper
Mountain
Station
Upland Location
River Bottom
Cultivar
Clay 403
NC 7
KT 204
TN 90
NC 2000
3604abz
3819a
3791a
3492b
3682ab
2355cz
2523bc
2604b
2835a
2686ab
2872cz
3183b
3218b
2872c
3542a
Early vs. late maturingx
0.0053y
0.0001y
<0.0001y
Nitrogen Rate
112 kg N ha-1
168 kg N ha-1
224 kg N ha-1
280 kg N ha-1
3506bz
3721a
3636ab
3834a
2169cz
2479b
2828a
2928a
3052a
3124a
3170a
3208a
Linear Contrast
Quadratic Contrast
Cubic Contrast
0.0029y
0.9147
0.0714
<0.0001y
0.1087
0.3202
0.0915y
0.7994
0.9442
z
Letters within a column and within a treatment factor followed by the same letter are
not significantly different by Duncan’s multiple range test (P ≤ 0.05).
y
Values for contrasts represent P values from the F test (Pr > F).
x
Contrasts for Early vs. late maturing tobacco: Early includes Clay 403, KT 204 and
TN 90, Late Maturing NC 7 and NC 2000.
27
Table 14. Effect of cultivar and nitrogen rate on mean burley tobacco yield
(kg ha-1) at each site at the upland and river bottom locations of the Mountain
Research Station and at the Upper Mountain Research Station in 2006
Tobacco yield (kg ha-1)
Mountain Research Station
Upper
Mountain
Station
Upland Location
River Bottom
Cultivar
Clay 403
NC 7
KT 204
TN 90
NC 2000
3763az
3293a
3399b
3288b
3727a
3609az
3092b
3541a
3115b
3722a
4000az
3584b
3837ab
3698b
4000a
Early vs. late maturingx
0.5658y
0.2867y
0.5292 y
3542a
3478a
3541a
3541a
3413baz
3343ab
3288b
3622a
3067bz
3465a
3569a
3558a
0.3071y
0.7393
0.8773
0.2040 y
0.0445
0.4049
<0.0001y
0.0066
0.5852
Nitrogen Rate
112 kg N ha-1
168 kg N ha-1
224 kg N ha-1
280 kg N ha-1
Linear Contrast
Quadratic Contrast
Cubic Contrast
z
Letters within a column and within a treatment factor followed by the same letter are
not significantly different by Duncan’s multiple range test (P ≤ 0.05).
y
Values for contrasts represent P values from the F test (Pr > F).
x
Contrasts for Early vs. late maturing tobacco: Early includes Clay 403, KT 204 and
TN 90, Late Maturing NC 7 and NC 2000.
28
Table 15. Effect of cultivar and nitrogen rate on mean burley tobacco yield
(kg ha-1) at each site at the upland and river bottom locations of the Mountain
Research Station and at the Upper Mountain Research Station in 2007
Tobacco yield (kg ha-1)
Mountain Research Station
Upland Location
Cultivar
Clay 403
NC 7
KT 204
TN 90
NC 2000
River Bottom
Upper
Mountain
Station
3864
3645
3702
3901
3898
3863bcz
3742c
4142a
4048ab
4178a
3666az
3351b
3809a
3595a
3745a
Early vs. late maturingx
0.4213y
0.0002y
0.0086 y
Nitrogen Rate
112 kg N ha-1
168 kg N ha-1
224 kg N ha-1
280 kg N ha-1
3834abz
3653b
3707b
4016a
3763bz
4031a
4116a
4100a
3383c
3601b
3722ab
3826a
Linear Contrast
Quadratic Contrast
Cubic Contrast
0.1651y
0.0129
0.9611
0.0035 y
0.0819
0.8199
<0.0001y
0.4411
0.8079
z
Letters within a column and within a treatment factor followed by the same letter are
not significantly different by Duncan’s multiple range test (P ≤ 0.05).
y
Values for contrasts represent P values from the F test (Pr > F).
x
Contrasts for Early vs. late maturing tobacco: Early includes Clay 403, KT 204 and
TN 90, Late Maturing NC 7 and NC 2000.
29
interaction was observed at any location. A significant early vs. late maturing contrast
(P < 0.01) was observed at five of the nine location/years (Tables 13 through 15).
A significant linear response to N rate (P < 0.004), was observed in five of the
nine location/years (Tables 13 through 15). Burley tobacco yield increased as nitrogen
rate increased. The river bottom location at MRS had a significant linear or quadratic
response (P < 0.05) each year. This location has a sandy loam soil with the greatest
potential for leaching of the three locations. At the river bottom location, burley
tobacco yields were greater in the higher nitrogen rate treatments, indicating that more
nitrogen is needed to obtain optimum yield than the upland location at MRS.
The UMRS has soil with characteristics similar to the soil at the river bottom
location at MRS. Linear contrasts for response to nitrogen rate were significant (P <
0.0001) at UMRS in 2006 and 2007 (Tables 14 and 15) as well as the quadratic
contrast (P = 0.0066) in 2006 (Table 14). The upland location at the MRS has a clay
loam soil with good drainage. Soil at this location would typically not have as much
leaching potential as the soils at the other two locations. A linear response to N rate at
the upland location in 2005 (P = 0.0029) indicated that the lower N rates did not
supply enough N for the yield potential of these burley tobacco cultivars (Table 13). A
quadratic response (P = 0.0129) was observed in 2007 at the same site (Table 15).
This quadratic response indicates that the highest N rate was not needed by the
tobacco plant to make optimum yield that year.
30
Quality
Commercial value of tobacco leaf is based on quality. Efforts have been made
to improve leaf quality in tobacco through disease and pest control (Naidu, 2001).
When tobacco companies purchase tobacco from producers, the price paid per pound
of tobacco is based on tobacco leaf quality.
Nitrogen rate had a significant quadratic effect (P < 0.04) on leaf quality at the
UMRS in 2005 and 2006 (Tables 16 and 17). No significant contrasts were observed
at the other trials (Tables 16 through 18) except for a significant cubic contrast (P =
0.0218) at the upland location of the MRS in 2005 (Tables 16). The effect of cultivar
on leaf quality was significant (P = 0.0338) only at the UMRS in 2007 (Table B.9). In
addition, the contrast between early and late maturing types was significant only at the
upland location of the MRS in 2006 (P = 0.015; Table 17). The interaction between
cultivar and N rate was not significant, except at the river bottom location at the MRS
in 2007 (P = 0.0222; Table B.7). When looking at leaf quality by cultivar, it is
important to remember that quality can be reduced by diseases such as blue mold.
Clay’s 403 is a good example of this. At all locations in 2006 and two of the three
locations in 2007, Clay’s 403 had the highest leaf quality. At other year/locations,
Clay’s 403 had much lower quality leaf. The locations that had lower leaf quality
indices had blue mold infections great enough to reduce leaf quality at those
location/years. Blue mold infection rate data to complement this reduced leaf quality
data was taken by plant pathologists, and will be used in a companion paper to show
blue mold infection rate by cultivar and nitrogen rate.
31
Table 16. Effect of cultivar and nitrogen rate on mean burley tobacco quality
index at each site at the upland and river bottom locations of the Mountain
Research Station and at the Upper Mountain Research Station in 2005
Tobacco quality index
Mountain Research Station
Upland Location
Cultivar
Clay 403
NC 7
KT 204
TN 90
NC 2000
Early vs. late maturingx
Nitrogen Rate
112 kg N ha-1
168 kg N ha-1
224 kg N ha-1
280 kg N ha-1
Linear Contrast
Quadratic Contrast
Cubic Contrast
River Bottom
Upper
Mountain
Station
No data
69az
69a
72a
71a
69a
49a z
48a
46a
56a
51a
0.4327y
0.2231y
68bz
74a
68b
71ab
56a z
49ab
45b
49ab
0.5986y
0.4467
0.0218
0.0421y
0.0376
0.7867
z
Letters within a column and within a treatment factor followed by the same letter are
not significantly different by Duncan’s multiple range test (P ≤ 0.05).
y
Values for contrasts represent P values from the F test (Pr > F).
x
Contrasts for Early vs. late maturing tobacco: Early includes Clay 403, KT 204 and
TN 90, Late Maturing NC 7 and NC 2000.
32
Table 17. Effect of cultivar and nitrogen rate on mean burley tobacco quality
index at each site at the upland and river bottom locations of the Mountain
Research Station and at the Upper Mountain Research Station in 2006
Tobacco quality index
Mountain Research Station
Cultivar
Clay 403
NC 7
KT 204
TN 90
NC 2000
Early vs. late maturingx
Nitrogen Rate
112 kg N ha-1
168 kg N ha-1
224 kg N ha-1
280 kg N ha-1
Linear Contrast
Quadratic Contrast
Cubic Contrast
Upper
Mountain
Station
Upland Location
River Bottom
66az
54b
57ab
63ab
57ab
77az
76a
77a
77a
76a
76az
70b
72ba
70bc
64c
0.0150y
0.9701y
0.5292 y
63bz
73a
73a
73a
77a
76a
76a
78a
72a
74a
74a
74a
0.2583y
0.5998
0.6228
0.3524 y
0.0619
0.9932
<0.0001y
0.0066
0.5852
z
Letters within a column and within a treatment factor followed by the same letter are
not significantly different by Duncan’s multiple range test (P ≤ 0.05).
y
Values for contrasts represent P values from the F test (Pr > F).
x
Contrasts for Early vs. late maturing tobacco: Early includes Clay 403, KT 204 and
TN 90, Late Maturing NC 7 and NC 2000.
33
Table 18. Effect of cultivar and nitrogen rate on mean burley tobacco quality
index at each site at the upland and river bottom locations of the Mountain
Research Station and at the Upper Mountain Research Station in 2007
Tobacco quality index
Mountain Research Station
Cultivar
Clay 403
NC 7
KT 204
TN 90
NC 2000
Early vs. late maturingx
Nitrogen Rate
112 kg N ha-1
168 kg N ha-1
224 kg N ha-1
280 kg N ha-1
Linear Contrast
Quadratic Contrast
Cubic Contrast
Upper
Mountain
Station
Upland Location
River Bottom
77a
76a
76a
77a
77a
76abz
75b
75b
78a
77ab
76az
71ba
69b
75a
75a
0.8158y
0.2427y
0.7348 y
77a
76a
77a
77a
76a
76a
76a
77a
72a
73a
73a
74a
0.4788y
0.3388
0.7127
0.3163 y
0.5122
0.8174
0.4468y
0.8152
0.9008
z
Letters within a column and within a treatment factor followed by the same letter are
not significantly different by Duncan’s multiple range test (P ≤ 0.05).
y
Values for contrasts represent P values from the F test (Pr > F).
x
Contrasts for Early vs. late maturing tobacco: Early includes Clay 403, KT 204 and
TN 90, Late Maturing NC 7 and NC 2000.
34
Chapter V
Conclusions
Burley yield increased as nitrogen rate increased at the MRS river bottom
location as well as at the upland MRS Location. However, at these two locations
yields at 224 and 280 kg N ha-1 were not significantly different. The current burley
tobacco nitrogen fertilizer rate recommendation is 224 kg N ha-1 (Hoyt, 2008). These
results support this recommendation. In 2006, no significant difference in burley yield
among N rate treatments was observed at the MRS upland location. The MRS river
bottom location did have significant differences in yield, with 280 kg N ha-1 producing
the highest tobacco yield of 3622 kg ha-1. The results were similar at all three locations
in 2007, with the highest yields occurring at the two highest nitrogen rates. As tobacco
yield potential goes up to the 3000 kg ha-1 range, more nitrogen is needed for the
additional biomass (leaf). Yields will be reduced when soil nitrogen is depleted, as
shown by the lower yields at lower nitrogen rates. This could also be attributed to the
greater than normal irrigation needed for these crops due to the dry growing season in
2007 by increasing the amount of soil leaching of nitrogen (Sifola and Postiglione,
2003).
The results of this experiment have demonstrated the importance of nitrogen
fertilization in the production of burley tobacco as shown by yield increases at the two
higher N rates. It is apparent that in tobacco production, nitrogen has an effect on plant
height, time of flowering, crop yield and crop quality. Improved cultivars tested
35
showed similar nitrogen requirements as older cultivars, with soil type playing an
important role in burley tobacco nitrogen recommendations (Waynick et. al, 2006).
Statistical analysis showed that there were few significant (P <0.05) cultivar by
nitrogen rate interactions. The data also indicated that tobacco cultivar and nitrogen
rate play an important role in timing of maturity and tobacco yield. Leaf quality was
affected more by nitrogen rate than cultivar, but only on sandy soils in four
location/years.
Tables 13 through 15 show that the rate of 224 kg N ha-1 produced optimum
tobacco yield. These results support current recommendations for nitrogen fertilizer
application in burley tobacco (Hoyt, 2008). In clay soils, the producer could achieve
acceptable yields at even a lower rate. There was no significant difference between the
224 and the 280 kg N ha-1 rate except in 2007. Therefore producers should avoid over
application of nitrogen fertilizer.
These experiments showed that cultivar selection does play a role in tobacco
yields. Older tobacco cultivars produced yields similar to improved cultivars, but only
in years or locations where foliar or soil diseases did not affect the tobacco plant. The
improved cultivars have been selected for their reduced disease susceptibility (Pearce
et al., 2008). Overall, this experiment showed that the newer burley tobacco cultivars
(TN 90, KT 204, NC 2000, and NC 7) could be fertilized at the recommended 224 kg
ha-1 rate of nitrogen for maximum yield.
36
Literature Cited
37
Literature Cited
Allison, F.E. 1957. Nitrogen and Soil Fertility. Pp.85 – 94. in Soil, The 1957
Yearbook of Agriculture. USDA. Washington, D.C.
Bowman, D.T., R.D. Miller, A.G. Tart, C.M. Sasscer, Jr., and R.C. Rufty. 1989. A
grade index for burley tobacco. Tob Sci. 33:18-19.
Brown, B. A. 2008. Situation and Outlook. Pp. 4-9. in 2008 Burley Tobacco
Information. N. C. Cooperative Extension Publication. AG 376.
Brown, L.C. and J.W. Johnson. 1991. Ohio State University Extension Fact Sheet
AEX – 463 - 96
Camberato, J.J. 2001. CEC – Everything You Want to Know and Much More.
Clemson University, Clemson, SC.
Carrow, R.N., D.V. Waddington and P.E. Rieke. 2001. Turfgrass Soil Fertility and
Chemical Problems. John Wiley & sons, Inc., Hoboken, NJ.
Collins, W.K. and S.N. Hawks, Jr.. 1993. Principles of Flue-Cured Tobacco
Production. 1st ed. N.C. State University, Raleigh, NC.
Davis, D.L. and Nielsen. 1999. Tobacco: Production, Chemistry, and Technology. Pp.
79. CORESTA, Oxford.
Dorn, T. 2001. Nitrogen Sources. University of Nebraska Cooperative Extension.
Evanylo, G. K., J. L. Sims and J. H. Grove. 1988. Nutrient Norms for Cured Burley
Tobacco. Agronomy Journal. 80: 610-614.
Fisher, L., W.D. Smith and D.S.Whitley. 2008. Variety Information. Pp. 18–22 in:
2008 Burley Tobacco Information. N. C. Cooperative Extension Publication.
AG 376.
Flower, K.C.. 1999. Field Practices pp. 76 – 97. In: Layton Davis and Mark
Nielsen. Tobacco Production, Chemistry and Technology. Blackwell, London.
Greene, R. E. 1996. The Leaf Sellers, A History of U.S. Tobacco Warehouses: 1619 to
the Present. BAWA, Lexington, KY.
Hiatt, A. J. 1963. Varietal differences in potassium uptake by excised roots of
Nicotiana tabacum. Plant and Soil (April 1963). 18:2
38
Hoyt, G. D. and W. L. Hargrove. 1986. Legume cover crops for improving crop and
soil management in the southern U. S. HortScience. 21:397-402.
Hoyt, G. D. 2008. Fertilization. pp. 39-46. in: 2008 Burley Tobacco Information.
N. C. Cooperative Extension Publication. AG 376.
Ivors, K.L. and P.B. Shoemaker. 2007. Disease Management. Pp. 93 - 116. in 2007
Burley Tobacco Information. N. C. Cooperative Extension Publication. AG
376
Killpack, S.C. and D. Buchholz. 1993. Nitrogen in the Environment: Leaching.
University of Missouri Extension Publication. WQ262.
Lewis, R. S., L. R. Linger, M. F. Wolff, and E. A. Wernsman. 2007. The negative
influence of N-mediated TMV resistance on yield in tobacco: linkage drag
versus pleiotropy.(Author abstract). TAG Theoretical and Applied
Genetics 115.2
Lewis, R. S. and J. S. Nicholson. 2007 Aspects of the evolution of Nicotiana tabacum
L. and the status of the United States Nicotiana Germplasm Collection.(Author
abstract). Genetic Resources and Crop Evolution 54.4 (June
2007): 727(14). Academic OneFile. Gale. University of Tennessee Martin. 5
Mar. 2008
Microsoft® Encarta® Online Encyclopedia. 2007 Air. http://encarta.msn.com ©
1997-2007 Microsoft Corporation. All Rights Reserved
Miller, R. D. 2005. New Burley Tobacco Varieties Available for 2005 Production.
University of Tennessee, University of Kentucky.
Naidu, S.K. 2001. Tobacco: Production, Chemistry and Technology. Crop
Science 41.1 (Jan 2001): 255. Academic OneFile. Gale. University of
Tennessee Martin. 5 Mar. 2008
North Carolina Cooperative Extension Service 2008. Burley Tobacco Guide. AG-376.
Published by North Carolina Cooperative Extension Service, College of
Agriculture and Life Sciences.
Pearce, B., A. Bailey, G. Palmer, K. Seebold, and B. Miller. 2008. 2008 Guide to
Burley Tobacco Varieties.
Pendergrass, W. 1952. Lime, Fertilizer and Manure. University of Tennessee
Extension Service. Publication 336.
39
SAS Institute Inc. 2006. Cary, NC. Internet Website: http://www.sas.com.
Shaw, L., D.M. Gossett, and D.F. Tugman. 1965. Dates of Transplanting and the
Probabilities of Spring and Fall Freezes in Relation to the Production of Burley
Tobacco Production in Western North Carolina. Pp. 13. N. C. Cooperative
Extension Publication. Bulletin 426.
Shelton, J. E. 1987. Fertilization. Pp. 6-10 in: 1987 Burley Tobacco Information.
N. C. Cooperative Extension Publication. AG 376.
Sifola, M.I. and L. Postiglione. 2003. The effect of nitrogen fertilization on nitrogen
use efficiency of irrigated and non-irrigated tobacco (Nicotiana tabacum
L.). Plant and Soil 252.2 (May 2003): 313. Academic
OneFile. Gale. University of Tennessee Martin. 5 Mar. 2008
Smith, W.D. and D.S. Whitley. 2005. Variety Information. Pp. 14–19 in: 2005 Burley
Tobacco Information. N. C. Cooperative Extension Publication. AG 376.
Terra Industries Inc.. 2006. UAN Urea Ammonium Nitrate Solution MSDS Number
2040.
USDA. 1990. Agricultural Prices, 1989 Summary. Pp. 66-68. National Agricultural
Statistics Service.
Vaughan, J.D., G.D. Hoyt, and A.G. Wollum. 2007/2008. Assessment of Burley
Tobacco Nitrogen Needs Following Cover Cropping and Manure Application.
Tobacco Science 47:1-10.
Waynick, M.R., H.P. Denton, D.R. Peek, and R.C. Pearce. 2006. Rate and timing of
nitrogen fertilization in burley tobacco. Paper presented at the 42nd Tobacco
Workers Conference, 2006.
40
Appendix A
Plot Plans
41
42
Table A.1 Plot plan for upland location at Mountain Research Station, 2007
43
Table A.2. Plot plan for river bottom location at Mountain Research Station, 2007
Appendix B
ANOVA Tables
44
Table B.1. Significance (P values) of cultivar, nitrogen rate and cultivar by nitrogen rate interaction on
percent flowering, height, yield, and quality of burley tobacco at the River Bottom Location, Mountain
Research Station, 2005.
Treatment
Degrees of
Freedom
Percent Flowering
July 28
August 2
Tobacco Height Tobacco Yield
Tobacco Leaf
Quality
45
Cultivar
4
< 0.0001
< 0.0001
< 0.0001
< 0.0001
--z
Nitrogen rate
3
0.6843
0.5580
0.5441
< 0.0001
--
Cultivar by N rate
12
0.1033
0.9246
0.9937
0.7649
--
z
The leaf quality data is unavailable for this location.
Table B.2. Significance (P values) of cultivar, nitrogen rate and cultivar by nitrogen rate interaction on
percent flowering, height, yield, and quality of burley tobacco at the Upland Location, Mountain
Research Station, 2005
Treatment
Degrees of
Freedom
Percent Flowering
Tobacco Height
August 2
August 11
August 2
August 11
Tobacco
Yield
Tobacco
Leaf
Quality
46
Cultivar
4
0.4225
< 0.0001
0.0013
0.0062
0.1345
0.8610
Nitrogen rate
3
0.2032
0.0082
0.2585
0.1624
0.0108
0.0600
Cultivar by N
rate
12
0.8666
0.0933
0.1721
0.0557
0.1541
0.4744
Table B.3. Significance (P values) of cultivar, nitrogen rate and cultivar by nitrogen rate interaction on
percent flowering, height, yield, and quality of burley tobacco at the Upper Mountain Research Station,
2005
Degrees of
Freedom
Percent
Flowering
August 1
Tobacco Height
August 1
Tobacco Yield
Tobacco Leaf
Quality
Cultivar
4
<0.0001
<0.0001
<0.0001
0.2092
Nitrogen rate
3
0.0225
0.0004
0.4878
0.0520
Cultivar by N rate
12
0.2970
0.4804
0.6209
0.8873
Treatment
47
Table B.4. Significance (P values) of cultivar, nitrogen rate and cultivar by nitrogen rate interaction on
percent flowering, height, yield, and quality of burley tobacco at the Bottom Location, Mountain
Research Station, 2006
Treatment
Degrees of
Freedom
Percent Flowering
Tobacco Height
August 2
August 11
July 21
August 11
Tobacco
Yield
Tobacco Leaf
Quality
48
Cultivar
4
<0.0001
< 0.0001
0.0002
0.0045
0.0068
0.7125
Nitrogen rate
3
0.1244
0.2159
0.2863
0.2262
0.1127
0.5372
Cultivar by N rate
12
0.0189
0.5913
0.1088
0.2282
0.5151
0.5330
Table B.5. Significance (P values) of cultivar, nitrogen rate and cultivar by nitrogen rate interaction on
percent flowering, height, yield, and quality of burley tobacco at the Upland Location, Mountain
Research Station, 2006
Treatment
Degrees of
Freedom
Percent Flowering
Tobacco Height
August 11
August 19
August 2
August 11
Tobacco
Yield
Tobacco Leaf
Quality
49
Cultivar
4
0.1036
0.0182
0.0482
0.0802
0.0084
0.1111
Nitrogen rate
3
0.9015
0.9355
0.8162
0.8856
0.9524
0.6444
Cultivar by N rate
12
0.2226
0.2321
0.0240
0.0351
0.6047
0.3991
Table B.6. Significance (P values) of cultivar, nitrogen rate and cultivar by nitrogen rate interaction on
percent flowering, height, yield, and quality of burley tobacco at the Upper Mountain Research Station,
2006
Degrees of
Freedom
Percent
Flowering
August 2
July 20
August 3
Cultivar
4
<0.0001
<0.0001
Nitrogen rate
3
<0.0001
Cultivar by N rate
12
0.1935
Treatment
Tobacco Height
50
Tobacco Yield
Tobacco Leaf
Quality
<0.0001
0.0018
0.0870
0.0090
0.0003
<0.0001
0.0142
0.2250
0.3083
0.7356
0.2481
Table B.7. Significance (P values) of cultivar, nitrogen rate and cultivar by nitrogen rate interaction on
percent flowering, height, yield, and quality of burley tobacco at the River Bottom Location, Mountain
Research Station, 2007
Treatment
Degrees of
Freedom
Percent Flowering
Tobacco Height
August 7
August 13
July 20
July 25
Tobacco
Yield
Tobacco Leaf
Quality
51
Cultivar
4
<0.0001
<0.0001
0.0004
0.0009
0.0198
0.0562
Nitrogen rate
3
0.0736
0.3148
0.1656
0.3822
0.0110
0.6922
Cultivar by N rate
12
0.2113
0.7764
0.3764
0.5073
0.4960
0.0222
Table B.8. Significance (P values) of cultivar, nitrogen rate and cultivar by nitrogen rate interaction on
percent flowering, height, yield, and quality of burley tobacco at the Upland Location, Mountain
Research Station, 2007
Treatment
Degrees of
Freedom
Percent Flowering
Tobacco Height
August 10
August 20
July 25
July 30
Tobacco
Yield
Tobacco Leaf
Quality
52
Cultivar
4
0.0044
<0.0001
0.0003
0.0042
0.1810
0.6849
Nitrogen rate
3
0.2337
0.7398
0.6357
0.2707
0.0616
0.6834
Cultivar by N rate
12
0.1131
0.0127
0.3827
0.4479
0.6683
0.6925
Table B.9. Significance (P values) of cultivar, nitrogen rate and cultivar by nitrogen rate interaction on
percent flowering, height, yield, and quality of burley tobacco at the Upper Mountain Research Station,
2007
Treatment
Degrees of
Freedom
Percent Flowering
Tobacco Height
August 22
August 28
August 3
August 10
Tobacco
Yield
Tobacco Leaf
Quality
53
Cultivar
4
<0.0001
0.0007
0.1217
0.0841
0.0037
0.0338
Nitrogen rate
3
0.9937
0.3545
0.8442
0.5870
0.0016
0.8938
Cultivar by N rate
12
0.6222
0.3047
0.2516
0.1755
0.4000
0.3732
Appendix C
Weather Data
54
Table C.1. Weather Data Laurel Springs, NC May 2005
55
Table C.2. Weather Data Laurel Springs, NC June 2005
56
Table C.3. Weather Data Laurel Springs, NC July 2005
57
Table C.4. Weather Data Laurel Springs, NC August 2005
58
Table C.5. Weather Data Laurel Springs, NC September 2005
59
Table C.6. Weather Data Laurel Springs, NC May 2006
60
Table C.7. Weather Data Laurel Springs, NC June 2006
61
Table C.8. Weather Data Laurel Springs, NC July 2006
62
Table C.9. Weather Data Laurel Springs, NC August 2006
63
Table C.10. Weather Data Laurel Springs, NC September 2006
64
Table C.11. Weather Data Laurel Springs, NC May 2007
65
Table C.12. Weather Data Laurel Springs, NC June 2007
66
Table C.13. Weather Data Laurel Springs, NC July 2007
67
Table C.14. Weather Data Laurel Springs, NC August 2007
68
Table C.15. Weather Data Laurel Springs, NC September 2007
69
Table C.16. Weather Data Waynesville, NC May 2005
70
Table C.17. Weather Data Waynesville, NC June 2005
71
Table C.18. Weather Data Waynesville, NC July 2005
72
Table C.19. Weather Data Waynesville, NC August 2005
73
Table C.20. Weather Data Waynesville, NC September 2005
74
Table C.21. Weather Data Waynesville, NC May 2006
75
Table C.22. Weather Data Waynesville, NC June 2006
76
Table C.23. Weather Data Waynesville, NC July 2006
77
Table C.24. Weather Data Waynesville, NC August 2006
78
Table C.25. Weather Data Waynesville, NC September 2006
79
Table C.26. Weather Data Waynesville, NC May 2007
80
Table C.27. Weather Data Waynesville, NC June 2007
81
Table C.28. Weather Data Waynesville, NC July 2007
82
Table C.29. Weather Data Waynesville, NC August 2007
83
Table C.30. Weather Data Waynesville, NC September 2007
84
Vita
David Kaleb Rathbone was born in Waynesville, NC on March 16, 1983. He
graduated from Tuscola High School in 2001. In 2006 he graduated from The
University of Tennessee with a B.S. in Environmental and Soil Sciences with a
concentration in Agricultural Systems Technology and a Minor in Biosystems
Engineering Technology. Kaleb is currently employed by the North Carolina
Department of Agriculture at the Mountain Research Station as a Tobacco Research
Specialist.
85