The Rural Voice, 2003-05, Page 55Advice
Reduce soil compaction by being specific
By Greg Stewart
OMAF Corn Specialist
In talking about field operations
and the risk of soil compaction, it can
be difficult to be specific. The
vehicle -tire -soil -plant relationship is
complex and many factors can
impact a "specific" recommendation.
Whenever you try to get specific or
put numbers to a recommendation,
the odds of it being wrong for your
particular farm go up. Nevertheless
here are some points to consider on
minimizing soil compaction.
Know your axle load. Know your
tires. Run the correct inflation
pressure!
Some very interesting work out of
Ohio State in the mid-1990s shows
large increases in the amount of air
that is squeezed out of the soil when
tires are over -inflated. At one time it
was difficult to obtain weights and
tire specifications to get this correct,
but this should no longer be the case.
Increase tire size and lower inflation
pressure.
In many instances, particularly
with tractors and combines, you buy
the size of equipment that you feel
you must have for the work to be
done. This generally locks you into a
certain total axle load. The only
compaction -reducing option you
have is to increase tire size in order
to reduce inflation pressure, and
hence the contact pressure applied to
the ground. Selecting the tallest tire
that can fit on the machine is the best
starting point.
Duals versus singles means lower
inflation pressure.
The question about which causes
more compaction damage, duals
versus singles, is still out there. The
answer lies in making sure that your
dual tire selection actually involves a
larger total air volume carrying the
weight of the vehicle, and at
significantly lower inflation
pressures, than the single tire option.
For example, if you put duals on your
tractor and you're still running them
at 24 PSI, then something is wrong!
You need to look at changing
something — tire type, tire size,
weights on the tractor, or check
inflation pressure recommendations.
If on the other hand you can put a
single large volume radial on your
tractor and operate at 10 PSI, it might
cheaper and more convenient to
forget the duals.
Plant corn into tire tracks!
Jack Wiley, former John Deere
engineer, spoke at the South-West
Ag Conference in 2003 and made the
point that planting corn into tire
tracks is not a problem providing
your inflation pressure is 16 PSI or
less. The growers he has worked with
in the Corn Belt all seem to be
getting along fine as long as they
kept the inflation pressure below this
16 -PSI benchmark. What this means
is that if your planter tractor gets
equipped with big tires that run on
low inflation pressure, you don't
worry if a corn row ends up in track.
The higher the clay content of your
soils and the wetter you tend to push
your planting, the more I would like
to come down below the 16 PSI
mark.
Deep tillage; solve a problem —
create a problem.
If you are doing deep tillage in the
range of 6 -14 inches (i.e. disk -
ripper) you should be aware of the
possibility that those disturbed sub-
soils may re -compact worse than they
were in the first place. This is
particularly a risk if you traffic them
with high axle loads and/or high
inflation pressures while soils are
susceptible to compaction. If you feel
your dense sub -soils are costing you
yield and you move to a deep tillage
operation, make the adjustments at
the same time in equipment,
operations, and attitude to prevent
soil re -consolidation.
No -till soybeans at the mercy of
your corn combine.
Growers in a corn -soy -wheat
rotation where soybeans are no -tilled
after corn may want to make their
first move to low inflation running
gear on the combine. Moving from a
30.5 - 32 tire to an 1050 50R 32 tire
can mean dropping inflation
pressures down into the 15 PSI range.
They will still fit behind most 6 -row
heads. Soil that gets compacted
during a wet corn harvest with high
inflation pressure tires and high axle
loads cannot be expected to recover
in time for next year's no -till beans.
High axle loads hold the hammer.
Inflation pressure management is
a great tool, but what limits your tire
options and what puts the sub -soil at
risk is total axle load. If you are
determined to select grain carts and
manure tankers that have axle loads
over 15 tonne, then low inflation
pressure options will be more
difficult to find. In addition, there is a
nice bit of international research that
indicates that under some conditions
high axle loads and large tires will
force compaction deep into the soil
profile even in the face of relatively
low inflation pressures.
Soil conditions matter more than
any equipment or tire option.
If you farm soils with relatively
low clay contents (less than 15%),
you absolutely will not operate
equipment on soils that are wet
enough to show any rut, and you are
in conventional tillage, then save the
money you would spend on low
compaction tires and go to Florida.
We still have a lack of
understanding in regards to our sub-
soil conditions. How much are our
sub -soils limiting yields? Is it
compaction in these sub -soils that is
limiting? Which sub -soils are already
over -consolidated and which are still
at risk to further compaction?
Researchers, ag industry and
producers will need to continue to
work together to provide the specifics
on these questions.0
Final application
date for Crop
Insurance May 1
The last day to apply for Crop
Insurance is May 1, 2003 for spring -
seeded crops and forages, and May
10, 2003 for seed corn and
processing sweet corn. For more
information about the Crop Insurance
program, call our Customer Action
Centre toll-free at 1-888-247-4999
between 7:00 a.m. to 5:00 p.m.
Monday to Friday.0
MAY 2003 51