—Lancaster Firming, Saturday, March 4,1978
22
techniques explained
By LAUREL SCHAEFF
Staff Correspondent
ROBESONIA - “There
are three important factors
involved in grain drying,”
stated Joseph A. McCurdy,
professor of agricultural
engineering, Penn State
University, at a recently
held meeting of the Conrad
Weiser Young Farmers.
These factors, air volume,
temperature, and relative
humidity, determine the rate
and degree of drying.
“A twenty degree increase
in air temperature about
doubles the water holding
capacity,” the speaker
continued. But increased
temperature also increases
the chances of mold growth.
Grain drying tem
peratures should stay below
80 degrees Fahrenheit or
above 100 degrees, the
farmers were warned,
because mold growth out
weighs the drying pattern
when the temperature is
between 80 and 90 degrees.
McCurdy continued to
discuss grain drying and
storage, using com as the
basis of his lecture after first
remarking that he felt one of
the better ways of storing the
grain was in the silo.
The length storage time
is determi. by the
Grain drying
moisture and temperature
conditions of the corn,
related the speaker. A good
moisture content is 15 per
cent Com dryed to 12 or 13
per cent is close to being
overdryed. But the job is not
done when the com is at 15
per cent moisture, it has to
be cooled first, explained
McCurdy.
The effect of temperature
became evident as the
agricultural engineer ex
plained a chart that showed
the length of time com at 15
per cent moisture was stored
until the first sign of mold
appeared when held at
different temperatures. At
75 degrees Fahrenheit the
com was in storage for only
116 days before mold was
detected, but at 35 degrees
the com did not show any
sign of mold until 1140 days.
The problem with cooling
com in fall temperatures is
that it can never get as cool
as the air with only a fan
because the fan increases
the temperature a few
degrees, McCurdy stated.
Spoilage at the top center of
bins is not due to leaky roofs
but moisture migration, he
continued. Grain is a good
insulator, the grain in the
center of the bins doesn’t
change temperature as do
the outside layers.
This difference causes the
cool air on the outside to
slowly fall and the wanner
air in the center of the bins to
rise, causing moisture
migration to the top of the
bin where it is cold, resulting
in condensation. “Aeration
is needed,” said McCurdy. A
small volume of air should
be moved down the center of
the bins anytime the com is
10 degrees above the outside
temperature until the com
readies 40 degrees. This
takes hundreds of hours but
the com has to be thoroughly
cool, advised the speaker.
“Your nose is one of the
best instruments for
detecting if grain is going out
of condition.” It should be
checked at least every two
weeks, McCurdy advised.
Bin dryers' are economical
and efficient but are slow
and hard to manage, the
engineer told the local
fanners. Batch bins are
good for the conditions in
Pennsylvania, using high
temperatures for fast
drying. Continuous flow are
reserved for larger in
stallations, and good han
dling facilities are needed
with them, he explained.
McCurdy also discussed
combination systems that
reduce fuel and increase
capacity. Here com is heat
dryed to about 16 per cent
and moved to bins where the
final moisture points are
removed. But warned Mo-
Curdy, “The first bin
determines the future plan if
other bins are added.” If
more than one bin is built at
the first installation, have a
plan for future expansion.
“Plans are available, look at
them,” he advised.
The agridutural engineer
also briefly discussed dif
ferent types of ear com
storage facilities. The long
narrow cribs are expensive
storage and can only be used
for ear com, McCurdy said.
Round wire storage bins
should at least have and
open center and be
restricted to 12 feet in
diameter.
The wide cribs or sheds
seemed to be the best to the
engineer. The cribs he
recommended were about 28
feet wide and about 40 feet
long with a large triangular
or square “tunnel” running
through the center where air
is forced through. Com is
dried inside to outside. It
helps to have as much trash
removed as possible, Mc-
Curdy advised.
Low temperature, solar
assisted drying is bring
researched in the Midwest,
said McCurdy. There will be
more of it in the future, but
not by the next year, he
remarked.