xt7cfx73wc38 https://exploreuk.uky.edu/dips/xt7cfx73wc38/data/mets.xml   Kentucky Agricultural Experiment Station.  journals kaes_circulars_004_600 English Lexington : The Service, 1913-1958. Contact the Special Collections Research Center for information regarding rights and use of this collection. Kentucky Agricultural Experiment Station Circular (Kentucky Agricultural Experiment Station) n. 600 text Circular (Kentucky Agricultural Experiment Station) n. 600  2014 true xt7cfx73wc38 section xt7cfx73wc38 Circular 600 Unie;cra·ity of Kentucky
Cnupcralicc lfxterusimx Scruicz:
By IRA E_ MASSIE AND GEORGE H_ JENKINS, JR_ A;;ricuHurc and Ilrmw E(j()Il()I7li("S

 C O N T E N T S , 4
PAGE i
Cutting ........................................................................................................ 1
Housing ...................................................................................................... 1 . ,
Barn Management ............,...........................,........................................... 3 T ~
Curing ....................................,................................................................... 5
Air Curing .......................................................................................... 8 4
\Vlicn to Open or Close the Ventilators ................................ 8
Use of Fans ...............,................................................................ 9 " `
Controlling Humidity with Heat ......................................,............. 9 _ i
Fuels and Stoves ,................... . ................................................... 10 ‘
Cas Equipment ....,..................................................................... 12
Distribution of Heat .................................................................. 12 I
Bulk Tobacco as Soon as Fully Cured ........ . ........................................... 14
Progress in Curing ...................................................,,............................... 14
Tobacco Barn Plans Available ................................................................ 17
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I Harvesting and Curmg Burley Tobacco
By IRA E. MASSIE, GEORGE I·I. JENKINS, JR., and JONES I··I. SMILEY
. A good cured burley crop depends on whether you cut your
tobacco at the right time, house it correctly, practice good barn
{ management, and bulk it properly. Curing burley is more than just
drying the leaves. You must control temperature, humidity, and air
circulation if you hope to market good tobacco.
. ~ Many fine crops are injured by improper handling, inadequate
_ housing, and lack of control over curing conditions. Furthermore,
proper harvesting and curing can often improve some of the poorer
crops. Remember, the care and good management you used from
plant bed to cutting time must be continued in the barn if burley is
to return profits.
CUTTING
I llipening does much to improve the quality of your burley tobacco.
Priming the lower leaves once or twice, if necessary, helps you obtain
, the highest acre-returns from burley. Cut when nearly all the upper
leaves show a distinct yellow tinge (Fig. 1). lt usually pays to delay
cutting until nearly all the upper leaves are ripe even though you
don’t prime. Added growth and improved quality of the plant during
- ripening more than make up for the loss of lower leaves. In very
humid harvest seasons if no priming is done, nothing is gained by
delaying cutting beyond the time that the middle leaves show a
distinct yellow tinge.
If late tobacco is cut, provide heat to speed up curing and prevent
freezing in the barn. Put the plants directly on the sticks as they are
cut, five or six plants to the stick. lleave the tobacco in the field on
the standing stick (or on scaffold) long enough for it to wilt (your
housing facilities will partly govern the length of time) but never
longer than 3 days. Fully matured tobacco is not likely to sunburn.
However, green tobacco, usually cut when temperatures are high,
often sunburus, Sunburned tobacco should be left sticking in lield for
about 3 days so that the dew and sun can remove the damage.
HOUSING
Good housing practices are essential to control the curing of burley
tobacco. Many crops that come from the field in fine condition are ·
1

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Fig. `|.—- Cut burley when nearly all the upper leaves show a distinct yellow tinge.
seriously damaged by poor housing facilities. ()ne of the greatest
building needs on Kentucky farms is the remodeling of tobacco barns. `
Correct housing means filling each bent completely from top to
bottom as the crop is put in the barn. Leave enough space under the
lowest rails so you can use heat if necessary. Starting the Hll on the
southwest side of the barn takes advantage of air movements ill the
early stages of curing. AI1v<1g;.s· spread the stalks on sticks (Fig. 2).
Make sure that the leaves are hanging down. not doubled up. Also,
tip leaves should fall in between lower sticks. not rest on the butts of
stalks below. Never hang fresh-cut tobacco under tobacco harvested
earlier and partially cured. \\`ater evaporating from the fresh tobacco
will cause partly cured tobacco to darken.
lf you don`t have enough tobacco to lill your barn. don`t jam all
of it into a small area. Space it throughout the barn so air can cir-
culate evenly through the tobacco. Air seeks the level of least resist-
ance. lt will accumulate in empty parts of the barn, while Hlled
portions will not receive full benefit of air curing.
2

 BARN MANAGEMENT
_ Locate the barn on an open, well-drained area for best ventilation.
The best location is on a ridge, hill, or a high point in the field
(Fig.   Valleys tend to be foggy. You will get better ventilation if
the barn is placed so that a side faces the direction of the prevailing
- winds.
. Provided that one side, with its proper number of ventilator doors,
faces the prevailing winds, the structure’s length and height will not
i noticeably affect air circulation within the barn. \Vidth is the most
important dimension affecting ventilation. \\’idth determines   the
distance the air must move as it passes through the barn and   the
- · quantity of tobacco through which the air must pass. The wider the
_ barn, the slower the air moves through it when actually greater air
movement is needed because of the increased capacity for tobacco.
T/iris lllll.S’h`(IlL€.S' why a. shed added to a barn always lowers efficiency
in aiwcuring tobacco (Fig.  
For economic reasons, barn dimensions must conform with sound
construction practices and the the extra profit you can expect from
better tobacco. A standard barn is 40 feet wide and 60 feet or more
A long with a sidewall 20 feet high and a gable roof of % pitch. The
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Fig. 2.— When sticks are spaced on a rail, air can move freely in and around ·
the tobacco.
3

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Fig. 3.- An open, well-drained area such as a ridge or hill is the best location ,
for a curing barn.
only ventilators are full-length, sidewall vertical doors equivalent in ‘
area to at least one-third of the sides. Since larger tobacco now is .
being grown, some farmers are building barns with rails 6 feet apart .
vertically.
The more cracks and ventilators in the side of the barn, the more
air that will pass through the housed tobacco and the closer tobacco
can be spaced. Your curing barn, therefore should have enough side -
ventilators for rapid exchange of air. Few old barns have enough
side ventilators for best curing.
\Vhen repairing old barns or building new ones, provide ample
ventilators on the sides (Figs. 5 and 6). In barns 36-4() feet wide, A
hinge at least one-third of the boxing or siding to permit opening
and closing. \Vider barns need even more ventilation. To make a
third of the side in ventilators, start at one end and nail four boards,
hinge two, nail four, hinge two across the side of the barn. To have
half of the side open, nail two boards, hinge two, nail two, hinge two
aeross the side.
Ventilators are not needed at the ends of burley barns unless
prevailing winds strike the end of the barn and tier rails run parallel
with the width,
If prevailing winds strike the side of the barn and tier rails are
parallel to width, the barn should be remodeled and tier rails changed
4

 to run parallel to the length of the barn (Fig. 7). Ventilators should
then be >rovided on the sides. Research at the Kentuck f A fricultural
l t
Ex >eriment Station has shown that ventilators in the roof are almost
l
useless.
Because of reduced acreages, the smaller, 32-foot wide pole-type
barns are becoming popular and practical. Plans for these lower-
‘ cost barns are available (see page 16).
I CURING
Curing occurs when tem nerature, humiditv and air brin about
e 4 7
desirable changes in the chemical composition ot the leaf. Curing is
more than 'ust drving. It is a livin r vrocess durin Y which res Jiration
_ _ l . e l—» 1 B
takes place, using up the plant’s food reserves. Color and quality
‘ develop in the leaf during curing.
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Fig. 4.— You have little control over curing conditions in a barn such as this.
Sheds placed on the sides of a burley barn cut off ventilation completely. Also,
ridge ventilators are useless. ·
5

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Fi . S.- A well-built barn with these dimensions, adequately ventilated, and prop- -
9 d d
erly locate can improve curing con itions.
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  _ ’'’      ‘`` 7  
Fig. 6.— This old barn was remodeled to give maximum control over curing con-
ditions.
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ln.
nn-
7
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l*l*l\ l‘llll ll*l l Ih-
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with i i i * i  
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i III IIII IIII
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7 7
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Fig. 7.— This drawing shows how to remodel a barn when tiers run parallel to
width and prevailing winds hit the end of a barn.
'1`lic final quality ol curcd burlcy tobacco is dctcrinincd vcry
largcly by inoisturc conditions wliicli prcyail insidc tlic tobacco barn
during tlic curing pcriod. lligli inoisturc causcs tobacco lo curc too
. slowly, producing rcd or liouscburncd lcat and licayy losscs in wciglit.
\Vlicn tobacco stays in "brittlc casc." it curcs too last. causing.; a
. grccnisli tingc. inottlcd. or picbald lcal witb licayicr yiclds ol lcss
usctul tobacco. In tact. thi- cliaractcristics on wbicli buycrs judgc
air-curcd burlcy arc scycrly altcrcd by fast curing;.
For good barn inanagcnicnt you inust know tlic approximate
rclatiyc lnunidity insidc tlic barn. (Zurcd tobacco lcavcs arc vcry
scnsitiyc to cliangcs in tlic inoisturc contcnt of surrounding; air. Tlicy
coinc in and go out ot casc as a rcsult ol sucli clianqcs. Sincc `°casc"
or "ordcr" ot curcd tobacco is intcrprctcd by tlic way thi- lcal l`<·cls_
tlic rclativc lunnidity at various locations in a barn can bc dctcrinincd
fairly closcly by cliccking tlic condition or "lccl" of curcd lcal sainplcs.
rl`ablc 1 giycs a satisfactory scalc ol inoisturc in tlic lcal`. You can
clicck rclatiyc lunnidity tliis way at any tiinc during tlic curing scason.
  F

 Table `I.-— Feel cf Cured Tobacco Flyings in Relation to Relative Humidity"
7 7 TT 7 7177 iiii   'w7T'7" 4—F_m4ii ]$aHKj
l·`r·¤-I ot (lured Leaf (Percent)
lligh case ...................................................,............,............. 90 to 100 _
Medium to high case .....................................,...................... 85 to 90
Xledium ease .......................................................................... 80 to 85
Low to medium case .............................................................. 75 to 80 _
Low case ................................................................................ 70 to 75
Dry to low case .......................................,.............................. 65 t0 70 ·
Dry .......................................................................................... 60 to 65
l)ry to brittle .......................................................................... 55 to 60 *
llrittle ........................................................................,............. 50 to 55 b
Fragile .................................................................................... 0 to 50
=* l·`ro1n Kentucky Agricultural lixperiment Station Bulletin 501, "Prineiples ol` Burley To-
bacco llnrn ()peration."
\Vhen the samples {eel “dry to low case,” the humidity is about right 4
lor best curing.
Moisture can be controlled in barley barns fairly well through
proper use ot vcntilators, plus careful use ot heat in humid Weather.
Burley cures favorably when the temperature inside the barn ranges
between 6()" and 90"F provided relative humidity averages 65-70
percent in the barn over a 24-hour period. ln normal weather during -
the tobacco-curing season in Kentucky, the outdoor temperature
seldom goes above $)0' or below 60’F tor any great length ot time.
rl`herel`ore, lavorable curing conditions depend largely on whether
relative humidity can be kept around ($5-70 percent.
Air Curing
Curing conditions in tl1e barn may be varied by management
practices. tlow well you cure your crop depends largely on how well ~
you regulate humidity. how close you space sticks, width of your
barn. size ot tobacco. and amount ot ventilation. »
Small plants permit closer spacing than large ones. \Vith the 531116
amount ol side ventilation. a narrow barn will sately hold IT]Ol'€
tobacco per rail than a wider barn. Barns 36-40 feet wide are best
tor housing tobacco.
During some periods every year. relative humidity cannot be con-
trolled by ventilators. and heat should be used. \Vhenever tobacco
remains in case tor more than 24 hours. houseburning will start.
WHEN TO OPEN OR CLOSE THE VENTILATORS
During .»\ugust and September the air is usually dry during the
day and moist at night. (lenerally. therefore. open the ventilators as
soon as the dew dries in the morning and close them in late aiternoon.
It you are not sure whether to open or close the curing barn. put
S

 a few cured leaves in a sheltered place such as an open shed near
. the tobacco barn. \Vhen these leaves are damp and hang limp, the
- air is high in moisture, and the barn should be closed. In general,
whenever these leaves feel drier than the tobacco inside the barn the
_ ventilators should be opened. But when the tobacco inside the barn
feels drier than those leaves outside, then keep the barn tightly
K closed (see Table_1).
u During cool periods open the barn to get the benefit of the warmer
outside air. ln cool weather the temperature may be 1()° lower in a
closed barn than outside because of cooling from evaporation. If no
i fire is used in curing, provide as much ventilation as possible until
curing is nearly complete.
` If the weather is very dry and your tobacco is curing too fast,
close the barn in the daytime, and open it at night. This method traps
the cool, moist night air and keeps the drier, daytime air out of the
barn.
If you primed, usually the primed leaves will need some heat in
curing.
l USE OF FANS
The use of fans in the present procedure of curing tobacco seems
to be limited. Do not attempt to use fans for general air or heat
distribution in the barn. \Vhen improper stick spacing or undesirable
construction or location of the barn causes poor curing in limited
sections within the barn, you might use fans to supplement the natural
` ventilation in these sections. Locate the fans to blow the air directly
through the section of tobacco that is curing poorly. The locations
and size of the fans are important, for too strong an air movement
. will bruise or shatter the tobacco. Operate the fans only long enough
to overcome the curing stresses.
Controlling Humidity with Heat
Heat is used primarily to control humidity or moisture content of
the air surrounding the tobacco in the barn. If too much heat is
added. the moisture level of the air becomes too low, resulting in too
fast a cure. If the weather dries the cured leaves each day without
Hre. then firing is a waste of fuel and time.
Always practice care and good management when using supple-
mentary heat. Control the rate of heat to keep the temperature S5-
9(YF directly above the burner at the lowest level of tobacco. You
should use enough burners so that the temperature does not vary
more than 15 degrees throughout the barn. \Iake all temperature Y
measurements at the lowest level of the tobacco.
9

 Normally, the side ventilators of the barn are closed when heat is · · ·
being used. .~\s the warm, dry air rises through the tobacco, it absorbs _
moisture released by the tobacco. The moist air must not be allowed
to remain in the barn; therefore. some veiitilzilors will liaue to be A
partially opened to allow the moist air to escape. It may be best to
open the ventilators on the leeward side of the barn rather than the l i
windward side. This will help prevent moist outside air from entering .
the barn, yet allow the moist inside air to escape. t
FUELS AND STOVES
Coke long has given good results when used properly. The first
precaution with coke is to be sure it has a low sulfur eontent—not
more than 1 percent by laboratory analysis. The dealer selling coke
for tobacco curing should provide a statement concerning the sulfur A
content of the fuel.
The next precaution is to use enough stoves with low or moderate
fires rather than a few stoves burning with high Hres     This
will distribute the heat better and minimize hot spots. Do not use
large coke stoves made from 55—gallon oil drums. They release too
much heat near the stove. cause hot spots, and result in green or "0lf” ‘
colors being set in the tobacco.
.·\lthough coke is an inexpensive fuel. considerable labor is required
to tend a coke-fired barn properly. Coke stoves must be started out-
side the barn and then moved in after the fires are started. They T
require attention at least twice a day. Shaking out ashes and refilling
the stoves are rather hard work. lleat output is difficult to control and
not uniform. (Zoke stoves usually burn the hottest shortly after being
tended. then taper oll to a rather small heat output before being
tended again.
\\`hen properly used. 1 ton of coke on thc average, will cure I
acre of tobacco. Follow these suggestions:
1. flxtremely hot fires will destroy the stoves and cause poor heat
distribution.
2. .\fter the curing season. remove the ashes and coke from the
stoves. (Ioat them thoroughly with crankcase oil inside and
out and store in a dry place. (Ioke stoves when properly cared
for will last lll years or longer.
\`alural gas is an excellent fuel for use in tobacco barns. .»\ll
natural gas supplied through commercial pipelines is safe for use in
tobacco barns. llarmful impurities have been removed from the gas
at scrubbing plants. (las from most private Wells is also pure enough
for use in tobacco barns. The harmful impurity in natural gas is
10 _

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Fig. 8.—- Use enough coke stoves to distribute heat better and reduce hot spots.
sulfur, usually in the form of hydrogen sulfide which is easily detected
by its foul odor. Cas with as little as one part per million of hydrogen
sulfide will have a foul odor. Therefore, any gas that smells "swcet”
is safe for tobacco, and even some gas that has a slight odor is safe.
Natural gas, where it is available. will supply heat to the tobacco
barn for less cost than any other non-solid fuel that has proved
satisfactory for tobacco.
Propane gas or LP gas contains practically no sulfur and is being
used successfully as a fuel for heating tobacco barns. It costs slightly
inorc than natural gas or coke. but the heat content is higher than
that of natural gas. Propane. like natural gas. lights instantly. is easily
controlled. and is a constant and uniform source of heat (Table 2 l.
Venting of propane gas stoves is not necessary under ordinary
firing. Labor rcrpiireinents for firing with propane are comparable to
those for natural gas and both of them are much lower than colye.
ll.

 Table 2.- Combustion Data of Fuels Used for Heating Burley Tobacco l
Curing Barns
lteleased _ _
eumiliaaim
Heating (Pounds B.t.u.s _
Value Per Pound ter
l·`ueI 41s.r.a./uml) or Fuel) Fue1C¤a 1 Cem V
LP eas 92,(fE.iEQQ.1 1.621T 15r /;;.11 ti 6,156
Natural Cas 1,000 B.t.u./eu ft 2.25 80C/1,000 cu ft 12,500
Coke 12,000 B.t.u./lb 0.22 $25/ton an H   ·
\Vhen properly used, gas stoves will last 10 years or longer. How-
ever, after the curing season, store the stoves in a cool, dry place and
the hoses in a dark, cool, and dry place.
GAS EQUIPMENT
Two types of gas burners, shown in Figs. 9 and 10, will operate .
on either natural or LP gas. They require different orifices when using
natural gas—chccl< with your gas dealer.
The small gas unit (Fig. 9) has a maximum heat output of 30,000 V
B.t.u. per hour. Each stove will cure an area in the barn of about
12 X 12 feet. The larger unit (Fig. 10) has a maximum output of ,
75.000 l%.t.u. per hour and will cure an area in the barn about 12 X 40 ,
feet.
Automatic controls, available for all gas heaters, are very helpful ·
in adjusting relative lnunidity in the barn. Hygrometers or humidistats
will also help you determine relative lnunidity in the barn. These ‘
tools. used as guidelines, ought to be used since they will help in
curing your tobacco.
DISTRIBUTION OF HEAT
lleat distribution is a factor to be considered. llot spots will
frequently occur in localized areas directly above the stoves. These
hot spots indicate poor heat distribution which, in turn, cause green
or "oil" colors in the tobacco. llot spots are usually caused by burning
too few stoves too hard. The result is too much heat immediately
around and above the stove and not enough heat in the rest of the
barn. Xloving the stoves from place to place in the barn does not
solve the problem. The hot spots are not eliminated. and the tobacco
that was near a stove and has dried out may absorb moisture from
wet tobacco in another part of the barn when the stove is moved.
You get uniform heat distribution only by using an adequate
number of stoves. each burning at a moderate rate. If you use coke,
12

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