Rogue River courier. (Grants Pass, Or.) 1886-1927, 1908-11-13
INVESTIGATIONS TO
AVOID FROST DAMAGE
Suggestions Which May Soon be
of Great Pro actical Value
to Fruit Men.

me thods to protect fruit and other
orops from frost. The following ar
ticle, considerable Of which relates 10
California, may suggest some good
ideas to Josephine County fruit
growers;
The problem OF protection from frost
may be considered under four sec
tions, as follows:
1. The issuance of adequate frost
warnings.
2. A discussion of the physical
process operative in the formation
and dissipation of frost.
3. The construction of devices ana
apparatus based upoon the principles
enumerated in No. 2.
4. The intelligent use OF these
devices so that a maximum efficiency
may be obtained at the critical hour
In California frosts are found to
occur under certain pressure condl'
tions.
A period of strong north winds fol-
lowed by clear skies is a period OF
danger. Frost is essentially prob
lem in air drainage and some know
ledge Of the movement OF the air over
tue ground. or in other words, the
local air circulation is essential for
successful frost forecastlng. The
chief cause of cooling is undoubtedly
radiation, and this is controlled TO
large degree by the relative purity and
stiffness of the air. When, therefore,
the lower air strata are quiet and dust
free, also vapor free, conditions are
favorable for intense radiation, and
consequently rapid cooling Of both
vegetable fibre and the soil. All fruit
growers should carefully study the
weather conditions preceding frost in
their localities. The district fore.
caster at San Francisco and observers
at any Weather Bureau station will
gladly receive suggestions in the mat.
ter of local air drainage and frost for.
nation and will. so far as their time
permits, investigate and report upon
local features.
Under the second heading, discuss
ion of the physical processes involved
in frost formation, we would call at
tention to the following ways Of pre-.
venting the fall in temperature:
/. Adding heat
90. Adding water vapor
8. Adding both heat and water
vapor.
4. Ventilation, or mixing of the
air.
Irrigation, or use of water.
6. Use of heated water.
I. Use of scresus or covers, prevent
ing loss of heat by radiation.
8 Spraying,
All of the above processes can be
found explained in detail in publioa.
tions of the Weather Bureau. The
action of water il any of it's forms
whether solid, as ice or frost fluid,
as water or gaseous, rs water vspor,
protective. Large amounts of heat
are given off in the change from
vapor and from LIQUID to solid.
theoretically, 1t is possible by the
application of sufficient water to pre-
vent injury by frost. As the plant
cools, owing to radiation and an in-
draft of cold air, the vapor present
condens $, giving free large guam
tity of heat something like GOO
calories and il the water turns to
frost, more heat is set free, about SOC
calories. If, for example, IN An ordi-
nary rain gauge enough frost has form
ed TO weigh, when melted, about au
ounce, then the latent heat of conden-
sation is approximately 90S times $50,
or 6l1, 440 calories, enough to raise the
temperature of the air at freezing
degrees over space of 10 feet square
and to considerable height.
Note also that the water plays an
important part when the sun rises aud
the warming of the vegetable fiber
begins. Here the water retsrds the
beating, and is thus very beneficial.
Chilled plauts sprayed with cold water
about sunrise are less liable TO injury.
The latent heat OF evaporation and
fusion now comes into action in an
opposite direction, the heat being
utilized in hanging the frost into
water or the water into vspor. This,
in the writer's opinion, is the critical
period, and he believes that more in.
jury results from the too rapid
warming of plant fiber after it has
been chilled than from the chilling
itself. He has known of cases where
delicate flowers have been incased in
ice and yet no injury resulted. largely
because the thswing out was gradual
In examining many orchards il has
been sscertained that the portion most
exposed to the suns heat in the