NORTH FLORIDA EXPERIMENT STATION
November 7, 1961
NFES Mimeo Rpt. 64 (.-
PLASTIC COVERED PLANT BEDS FOR CIGAR-WRAPPER TOBACCO
By C. E. Dean
Tobacco seed, because of their small sise and the low temperatures which
are prevalent during the early growing season, akr soah in protected beds and
subjected to a program of very intensive management. As a means of protection,
plant beds for cigar-wrapper tobacco are covered With shade cloth (10x12, 12x12,
12x14 threads/inch) suspended eight to nine feet above the surface of the bed.
The sides are made of the same material) i'ai ly doubled to reduce air movement
and to provide additional protection against cold damage. Flue-cured tobacco
plant beds are also covered with cloth) but the cove& is mtch cd19se to the bed
surface, usually 10 to 12 ihdhes with sides made of boards or poles*
Cigar-wrapper tobacco plant beds in the Quincy, Florida, area are usually
seeded during the period from December 26th through January 10th. Beds seeded
during this time usually produce transplants of suitable size beginning about
March 20th, depending on the season. This extended period of twelve weeks or
more between seeding and transplanting is brought about by low temperatures
which prevail during this time of year.
It has been found in experiments with flue-cured tobacco plant beds
(1, 2, 3) that the use of a polyethylene plastic cover instead of the conven-
tional cloth cover can materially reduce the length of time necessary to
produce transplants. This is brought about primarily by the maintenance of
higher temperatures during the critical periods of germination and early plant
growth. The polyethylene cover also prevents rapid moisture loss and eliminates
the leaching effects of heavy rainfall, in addition to promoting other conditions
beneficial to seed germination and plant growth.
In view of these findings with flue-cured tobacco, it was desired to
test and adapt this procedure to cigar-wrapper tobacco plant beds, and to
evaluate the performance in comparison to the conventional plant bed practices.
MATERIALS AND METHODS
In 1961 an experimental plastic covered plant bed was constructed at the
North Florida Experiment Station. This bed was 18' long and 6' wide and was
similar in construction to those used in growing flue-cured tobacco plants. The
sides were constructed from 1" x 10" boards and a framework of 1" x 2" material 4
was erected to support the plastic. The ridge pole was elevated 18"'tabove the
bed surface and rafters were placed every 3' to prevent the plastic .from sagging.
The plastic was permanently secured down the length of one side, stretched across'
the top and fastened on the other side and ends so that it could be easily folded
back for bed maintenance operations. To provide a comparison with plants
produced in the usual manner under cloth, a similar bed was constructed along
side. This bed differed only in that no frame work supported the cloth cover.
Both beds were fertilized with a 5-4-5 fertilizer at the rate of l4 pounds
per square yard.
To obtain information on the best date to seed, three trial dates were
selected January 6th, January 23rd, and February 1st. The most prevalent
cigar-wrapper variety Dixie Shade was used in the test, and both beds were
seeded at the rate of 0.4 oz. per 100 square yards. Since temperature was
considered the most important factor, measurements were made 3" above and 1"
below the soil surface in both the plastic and cloth covered beds.
Plants from beds seeded January 6th under plastic, January 6th under
cloth and January 23rd under plastic were transplanted in the field. A
randomized complete block design with four replications was used, with plots
consisting of rows 36? long containing 37 plants. The tobacco was harvested
and cured in the usual manner and data were computed on yield and quality of
cured and fermented leaf.
RESULTS AND DISCUSSION
Data on minimum temperatures recorded under plastic and cloth covers
in air and soil for the seven-day period beginning January 20th are presented
in Table 1.
Date Cloth Plastic Cloth Plastic
1-20-61 31 40 36 44
1-21-61 32 38 39 47
1-22-61 23 29 33 44
1-23-61 33 42 39 49
1-24-61 55 56 55 58
1-25-61 35 44 44 50
1-26-61 42 47 47 52
Average 36 42 42 49
It can be seen in comparing the averages under cloth and plastic that the
plastic cover increased the temperature an average of six and seven degrees
in both air and soil, respectively. From other data not shown it was found
that this differential increased as higher temperatures were reached, thus
with an air temperature of 85 degrees under cloth the temperature under plastic
might reach 110 degrees, giving a differential of 25 degrees. Temperatures
as high as 121 degrees were recorded with no visible effect on plant growth.
Germination was observed under plastic in an average of 12 days
following seeding, compared with three to four weeks under cloth. Stand
counts in number of seedlings per square yard for the three seeding dates
are presented in Table 2.
Seeding Date Cloth Plastic % Increase
Jan. 6 838 1083 29
Jan. 23 1167 1243 7
Feb. 1 972 1109 4
The plastic cover resulted in a higher stand count for all three dates of
seeding, with the January 6th date having the highest percent increase. These
increases in stand count under the plastic cover as compared with the cloth
cover seem to be related to an overall temperature increase over the time
covered by the three seeding dates. At lower temperatures such as were
encountered after the January 6 seeding, better germination resulted under
plastic, while after the other two dates temperatures under cloth as well as
plastic were conducive to germination. During the plant bed season in 1961
warmer temperatures prevailed than would normally be expected. This tended
to reduce the advantage of the plastic cover when compared with the cloth
cover, particularly as the season progressed. The stand counts obtained
under plastic were too great for best plant production and a reduction in
seeding rate down to I oz. per 100 square yards was indicated.
No blue mold was observed on plants produced under plastic even though
the disease was found in the adjoining cloth covered bed. This was mainly
because of higher temperatures which tended to check the development of the
As might be expected, the plastic covered bed seeded on January 6th
produced plants much earlier than the time during which transplanting is
normally done. Field plots were transplanted from these beds on March 2nd,
or 61 days after seeding, however, no data are presented on these plots.
Beds seeded January 6th under cloth and January 23rd under plastic produced
plants about the usual transplanting time and were transplanted on March 22nd,
or 78 and 60 days, respectively, after seeding. These two groups of transplants
were used in comparing the field performance of plants produced under cloth and
plastic. The January 23rd seeding under cloth, and both cloth and plastic beds
seeded February 1st did not produce transplants in time for the normal season,
and consequently were not included in the field test.
Table 3 presents the number of days from seeding to transplanting and
measurements of some important agronomic characteristics for plots transplanted
with seedlings from the January 6th cloth and January 23rd plastic treatments.
Seeding Date Days to No. Leaves Ht. Last Leaf Total Leaf
and Cover Transplanting Exceeding 16" Exceeding 16" Leaf No. Spacing
Jan. 6 78 22.8 93.7 28.3 4.2
Jan. 23 60 24.6 99.0 30.1 4.1
Plants produced under plastic had more leaves exceeding the sixteen-inch
minimum and the position of the last sixteen-inch leaf was higher than on plants
originally produced under cloth. In addition, the total leaf number was greater
and leaf spacing was closer for plastic-produced plants.
Comparisons of yield and quality data from plots
seedlings produced in plastic and cloth covered beds are
shown in Table 4.
Seeding Date Yield % in Top
and Cover (lbs./A) Three Grades
Jan. 6 1809 68
Jan. 23 1830 66
The yield of plastic produced plants was slightly higher than that of plants
grown under cloth, perhaps reflecting the greater leaf number of these plants.
Quality as expressed by percent of the total crop in the top three grades was
approximately the same.
The most convenient method of attaching the plastic to the plant bed
seems to be on a low frame such as was described earlier. A cover attached
in this manner can be easily removed for bed maintenance operations. An
alternate but less desirable method would be to elevate the plastic on wires
much in the same way that shade cloth is used. Even though the beds are more
accessible from underneath, problems are encountered in removing the cover for
watering. Difficulty may also be experienced in obtaining sufficient slope on
the plastic to prevent water from accumulating on top during periods of rainfall.
In the operation of a plastic plant bed the cover should be rolled back
for short periods of time when the weather is warm to prevent excessive heat
build-up and also to take advantage of rainfall to water the beds. The cover
can actually be used to regulate the growth of the plants by removing it to slow
the growth or by keeping it on continuously to accelerate it.
Plastic plant bed covers had several advantages over conventional cloth
covers in the production of tobacco transplants. These advantages are listed
1. Temperatures in air and soil were maintained 6 to 7 degrees higher at
lower general temperatures, with a greater differential at higher
2. A lower seeding rate was found to be desirable. One-fourth oz. per 100
square yards seems adequate under plastic, while one-half oz. has been
considered necessary under cloth.
3. Seed germinated much faster and with a higher germination percentage.
4. Plant bed diseases, principally blue mold, were not as damaging.
Daytime temperatures in excess of 850 F checked the spread of blue mold.
5. Transplants were produced in 60 days under plastic, as compared with
78 days under cloth.
6. Beds seeded on January 23rd produced seedlings for transplanting on
7. Mature plants reared to transplant size under plastic were equal if
not superior to cloth-produced plants in several important agronomic
8. Yield and quality were comparable with that of plants produced under
Perhaps the most valuable feature of the plastic covered plant bed is
that the grower can more accurately predict when the seedlings will reach
transplant size and can arrange labor and equipment accordingly.
1. Brothers, S. L. Plastic covers for flue-cured tobacco plant beds.
Fla. Agr. Ext. Cir. 1960.
2. Saunders, E. S., and Clark, Fred. Plastic films for tobacco plant
bed covers. Down to Earth, Summer, 1961.
3. Whitty, E. B., and Clark, Fred. Tobacco plant production as affected
by plant bed management practices. Soil and Crop Science Society
Florida Proc. Vol. 20. 1960 (In Press)