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Dry Weather
Makes Field Fires a Safety Concern for Farmers and Neighbors
By Sam Custer
OSU Extension, Darke County
This season, farmers are at a high risk of having a field fire.
In less than a week we have had at least two field fires in the county
and a few in our neighboring counties.
What is fueling these fires you may ask? We had a tremendous
amount of rain this past growing season which in turn produced a corn
crop with a lot of fodder. We also have had less than a half inch
of rain for most of the county since corn harvest began. Add in
high winds, a discarded cigarette or a blowing ember from a trash fire
and you have the opportunity for a major field fire.
These field fires can grow out of control in a matter of minutes.
Adjacent homes, buildings and standing crops all are at risk
Additionally the conditions present during harvest season include dry
plant material and grain dust that are highly combustible. Hot
equipment or engine sparks are great ignition sources. It is not
uncommon for exhaust pipes or catalytic converters to exceed 1,000°F.
Add a little wind and there is a perfect opportunity for a field
fire.
Fighting a field fire can be quite the challenge and should be directed
by the fire department in charge. You may be of assistance if you
have a tillage tool ready to go to “plow” a barrier. When plowing
the barrier you do not want to attempt to till the ground at the
fire. You would want to keep a safe distance between the fire and
your tractor. Directly tilling the ground at the fire may result
in severe damage to the tractor and a risk to the operator.
Being prepared to handle field fires is important for all workers and
transport drivers. Combines, tractors, grain trucks, and pick-ups
should all be equipped with a trustworthy fire extinguisher as the
first lines of defense. Combines should carry an ABC 10-pound
fire extinguisher in the cab and a larger 20-pound unit at the ground
level. Tractors and trucks are recommended to have a 5-pound minimum
extinguisher available. These extinguishers should be in EACH
vehicle in the field. Nothing is worse than watching the combine
go up in flames while you're running to the end of the field to
retrieve the fire extinguisher on the grain cart. Having an
extinguisher on each piece of equipment ensures you will be ready to
react on the first signs of smoke.
Don't get caught with a false sense of security.
If you follow the recommendations and own enough fire extinguishers,
then you must also follow the maintenance recommendations. Check
the pressure gages periodically, making sure the needle remains in the
"charged" zone. If a unit has been partially discharged, it must
be fully recharged before using it again. Even a slight discharge
can create a gap in the internal seal of the extinguisher valve,
causing the pressure to leak out. The pressure needle may linger
in the charged zone; however there may not be adequate pressure to
expel the contents.
Extinguishers could use a little shake a few times a year. By inverting
the extinguisher and shaking it several times each season makes sure
the powder doesn’t get lodged at the bottom of the unit. Equipment
vibrations are notorious for compacting the reactive ingredients of
fire extinguishers; making them worthless when they are needed.
Extinguishers should also be inspected periodically by a fire
professional. Fire service companies can be found in community
directories. Your local fire department or insurance company can
also point you in the right direction for service companies. Some
extinguishers are not designed to be refilled, or are too old to be
refilled. These units should be replaced when they expire.
Having these old extinguishers around does no good when the time comes
to pull the pin.
Follow other fire prevention practices.
It is also important to keep machinery in good repair. Apply
grease to bearings and oil chains regularly to reduce friction.
It is recommended to perform maintenance checks at the end of the day,
rather than at the beginning, to detect any hot smoldering areas that
may break out into flames overnight.
Keep machinery clean and free from plant materials, especially around
the wrap points. Wipe up any fuel or oil leaks to eliminate
additional fuel sources; and do not leave oily rags on equipment or in
the cab.
Use an air compressor or leaf blower to remove crop residue, and a
pressure washer to remove built up oil or caked-on grease.
Take time to cool down the equipment each night, and check for any hot
spots. These steps can make a difference to save equipment,
facilities, commodities, and lives.
Being prepared to handle field fires is important for all
workers. Having machinery equipped with a trustworthy fire
extinguisher is one of the first lines of defense.
Nutrient Losses from Burning of Corn Residues
With dry weather and corn stubble sitting in the field, residue can be
quickly turned to ashes due to accidental fires. A question
frequently asked afterward is how much nitrogen (N) just went up in
smoke? N is volatilized and lost when plant material burns.
Phosphorus and K remain and return to the ground with ash.
However, P and K could be lost if ash is blown away from the field
during or after the fire. Fire damage in a field is usually
variable in scale. Not all material is completely turned to ash,
and rarely is the entire field burned (from one end to another).
Understanding what was burned and how much area was affected has an
impact on the total amount of N lost. The amount of N contained
in corn residue has been well documented from the late 60’s and clearly
delineated by John Sawyer at Iowa State
(http://www.ipm.iastate.edu/ipm/icm/2000/10-23-2000/dryfallfires.html).
To estimate how much N was lost, the grain yield level for the previous
year must be considered. The harvest index (in corn, the ratio of
grain weight to total plant dry weight) is another piece of information
that must be known (if unknown – assume 0.5). Providing a
relatively accurate measure of the area affected is obviously
important. Additionally, recognizing the residue remaining and
adjusting the material burned can provide a more quantitative measure
of the actual damage (if this is unknown - assume 100%). N lost based
on the previous year’s corn yield ranges from N lost 40 at 120 yield to
N lost 67 at 200 yield.
Along with the loss of N, carbon contained in the plant material is
lost as well. It would have been incorporated into the soil
organic fraction. This too has value. While there is no
specific dollar amount tied directly to a loss of organic matter, an
Iowa State University article recommends that one dollar per acre
should be claimed. Unfortunately, the economic impact associated
with the loss of residue cannot be fully realized until later,
especially in fields with high erosion potential.
Be fire smart, and safe harvesting.
For more detailed information, visit the Darke County OSU Extension web
site at www.darke.osu.edu, the OSU Extension Darke County Facebook page
or contact Sam Custer, at 937.548.5215.
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