Group Title: ARC-A research report - Agricultral Research Center-Apopka ; RH-78-6
Title: Heating for leatherleaf fern cold protection
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 Material Information
Title: Heating for leatherleaf fern cold protection
Series Title: ARC-A research report
Physical Description: 4 leaves : ; 28 cm.
Language: English
Creator: Conover, Charles Albert, 1934-
Poole, R. T ( Richard Turk )
Sanders, G. A
Agricultural Research Center (Apopka, Fla.)
Publisher: University of Florida, Agricultural Research Center
Place of Publication: Apopka FL
Publication Date: 1978
Subject: Leatherleaf fern -- Florida   ( lcsh )
Leatherleaf fern -- Effect of cold on -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
Statement of Responsibility: C.A. Conover, R.T. Poole, and G.A. Sanders.
General Note: Caption title.
 Record Information
Bibliographic ID: UF00065896
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 70631235

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not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
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site maintained by the Florida
Cooperative Extension Service.

Copyright 2005, Board of Trustees, University
of Florida


liU- E LU .BPA.
C. A. Conover, R. T. Poole and G. A. Sanders
Agricultural Research Center Apopka
University of Florida ib3
ARC-A Research Report RH-78-6
I.F.AS.- Univ. of Fiori

Sprinkler irrigation of leatherleaf fern for frost and freeze control

has proven to be an effective method of freeze prevention. However, in recent

years hydrological considerations have had an influence on this method, and

some producers are considering other ways to heat.

One method of heating used in the past was use of jumbo cone or return

stack citrus grove heaters. These units have performed well in protected

ferneries, but are inefficient, expensive to operate (fuel and labor) and

present considerable fire danger in some ferneries.

Other systems of heating fern have been used at the Agricultural Research

Center, Apopka during the last 6 years, and include enclosing the fernery with

2 or 4 mil polyethylene and heating beneath the plastic. Several factors that

must be considered prior to utilizing this system include type of heater, type

of fuel, method of installing plastic and type of plastic to use. Enclosing

the fernery not only allows heating during cold periods, but also the increase

in air and soil temperatures increase yield.

Although some ferneries built in recent years do not provide attachment

points for the plastic, there are many constructed in the proper way. These

are generally wood frame units where the plastic can be stapled along the edges

of purlins between 10 to 14 foot sections. Between the sections, plastic is

supported by 14 guage galvanized wire running 900 to the purlins and spaced

every 2 to 4 feet, depending on the amount of sag that is acceptable. The

S2 to 4 mil plastic used on the top should be perforated with 3/8" drill bits

while in the roll, so that 1 to 2, 3/8" holes exist per square foot*. The

plastic used on the side walls should not be perforated. The holes drilled

in the top allow rainfall to enter, which prevents destruction of the flat

top structure and allows for air exchange.

Several types of heaters have been used inside the enclosed structures,

but pollution from unburned hydrocarbons or other compounds can be a problem.

Based on experience at this research center, and on observation in ferneries

and foliage operations, the following information is presented for consideration:

1. Standard "Modine" type unit heaters can be used with or without venting,

provided they are in good operating condition. Units not properly cali-

brated for the proper air-fuel ratio can emit excessive pollutants. Heaters

of this type in our experience can be used to maintain temperatures as high

as 55F without danger from pollutants if vented or if a perforated top is

used. However, we suggest maintaining a temperature of about 34 to 360F,

which reduces heating costs, provides adequate fern protection and reduces

possibility of pollution damage.

Natural gas may also be used in this type of heater, but sulphur content

of natural gas is sometimes high. Thus, prior to purchasing heaters designed

to burn natural gas, determine the amount of sulphur present in the gas

source since it produces sulphur dioxide during the combustion process.

The natural gas supplier can provide the information needed, and levels of

less than 1/10 of 1% sulphur are most acceptable.

Keep the bit cooled by dipping in water because a hot drill bit will melt

the layers together around the holes.

2. Several barrel-type heaters of local and regional manufacture are also

available that burn propane or natural gas. Unlike "Modine" types these

units are not designed for venting, but this is not a factor for this

type of perforated top installation. These units when properly adjusted

will operate satisfactorily in a fernery operation, and data listed in

(1) will be applicable.

3, In recent years a number of cone-type heaters that burn kerosene or diesel

fuel have become available. Generally, these were designed as industrial

spot heaters, and not for agricultural heating. However, if caution is

exercised, they can be used in ferneries. Generally, if low sulphur (less

than 1/10 of 1%) kerosene is used there is not much danger of pollutants

damaging fern if the fernery has a perforated top and a maximum temperature

of 36F is maintained.

A number of these heaters also burn diesel fuel. Generally, a notice-

able increase in pollutants has occurred where we burn diesel fuel, but when

we only attempted to maintain 35F, fern damage was avoided. However, it

is possible that damage can occur under the same conditions if burners are

not efficient or adjusted correctly. Any of the portable heating units

have the advantage of being easily moved during production operations and

to a dry storage area during summer months.

4. Of the several types of grove heaters available, return stack heaters are

the most efficient and produce the least pollutants. If kerosene is used

as fuel, very little pollution occurs provided temperatures of 300 to 35F

are maintained. Where diesel fuel is used in these heaters, excessive

levels of pollutants may occur if they are operated for 8 hours or more.

This build-up of pollutants relates to the rate of air exchange through

the perforated top, and presents the most serious problem on a still cold

night. Soot from these heaters may also make the fern unsalable if heaters

are operated for a lengthy period. These heaters also present fire hazards,

require watching and do not distribute heat well because they do not provide

forced circulation. When these heaters are used, a 3 foot square piece of

transit or asbestos should be placed above these units to deflect the hot

air and prevent melting a hole in the cover.

WARNING Any producer planning to entirely enclose a fernery with non-

perforated top and sides should remember that only vented heaters can be used

in such an installation. Generally, "Modine" type heaters are best for this

purpose and can be used to maintain any temperature desired. If non-vented

heaters are used in a non-perforated top installation, pollution damage is sure

to result.

CAUTION Where non-vented heaters are used in structures with perforated

tops, remember that pollution is more likely to occur where an attempt is made

to increase temperatures to 400F or more, heaters are out of adjustment or

pollutant containing fuels are used.

Our experience with heating of fern indicates a winter yield increase of

up to 25% is possible without any increase in disease, insect or nematode prob-

lems. One problem we have observed is cold water damage, which occurs beneath

holes in the perforated top when water of near 32F runs through a hole onto

fern that is 10F or higher in temperature than the water. This damage appears

as a grayish water soaked area in the tissue, and occurs most frequently on

young, immature fronds.

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