9 Tips on Managing Soil Compaction by Greg Stewart, OMAF Corn Specialist
When talking about
field operations and the risk of soil compaction, it can be difficult to get
specific. Part of the reason is that the vehicle-tire-soil-plant relationship
is complex and many factors can impact a specific recommendation.
And whenever you try to get specific or put numbers to a recommendation, the
odds of it being wrong for any one particular farm go up. Nevertheless, here
are some points to consider on minimizing soil compaction.
1. Know your axle load. Know your tires. Run the correct
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 in order
to get this correct, but this should no longer be the case. 2. Increase tire size and lower inflation pressure.
In many instances, and in particular 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 to reduce inflation pressure and hence
the contact pressure applied to the ground. Selecting the tallest tire that
can possibly fit on the machine is the best starting point. 3. Duals versus singles means lower inflation pressure.
The question about which causes more compaction damage, duals or singles, is
still out there. The answer really 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 are still running them
at 24 PSI, then something is wrong! You need to look at changing something (e.g.,
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 be cheaper and more convenient to forget the
duals. 4. Plant corn into tire tracks!?
Jack Wiley, former John Deere engineer, spoke at 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 keep
the inflation pressure below this 16 PSI benchmark. Of course what this means
is that if your planter tractor gets equipped with big tires that run on low
inflation pressure, you dont worry if a corn row ends up in the track.
The higher the clay content of your soils and the wetter you tend to push your
planting, the more you should come down below the 16 PSI mark. 5. 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 subsoils 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 (i.e., wet). If you feel your dense subsoils are
costing you yield, and you move to a deep tillage operation, make adjustments
in equipment, operations and attitude to prevent soil re-consolidation. 6. No-till soys at the mercy of your corn combine.
Growers in a corn-soy-wheat rotation where soys 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 a 1050 50R 32 tire can mean dropping inflation
pressures down into the 15 PSI range and 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 years no-till beans. 7. 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 tonnes,
then low inflation pressure options will be more difficult to find. In addition,
international research 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. 8. Soil conditions matter more than any equipment or
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. 9. Still short on subsoil understanding.
Final comment is that we still have a lack of understanding in regards to our
subsoil conditions. How much are our subsoils limiting yields? Is it compaction
in these subsoils that is limiting? Which subsoils are already over-consolidated
and which are still at risk of further compaction? Researchers, the ag industry
and producers will need to continue working together to provide the specifics
on these questions.