Originally written February 1, 2006 | Last updated October 16, 2012
Usually more prevalent in reduced tillage systems because reduced tillage means
fewer opportunities to loosen the soil
Regardless of the tillage system used, the major cause of compaction is conducting
field operations when fields are too wet
e of compaction is conducting
field operations when fields are too wet
- Fall harvesting
- Spring tillage, etc
- Other factors leading to compaction
- Heavy equipment
- Emphasis on early planting
- Reducing the number and extent of tillage operations
Major effect of compaction on crop growth is restriction of root development, which
may lower yields
Methods of alleviating compaction
- Minimize field operations on wet soils
- Rotate crops
- Periodic moldboard plowing
- Subsoiler, paraplow, etc
- Use flotation tires on large equipment
Compaction Management at Harvest Time
Make soil more resilient to compaction.
Resilience is a term used by ecologists to describe the ability of an
ecosystem to resist perturbation or disturbance by resisting damage and
recovering rapidly. Soil can be made to resist compaction by eliminating
tillage, increasing organic matter content, and maintaining a living root
system in the soil for as much time as possible.
Any long-term no-till
farmer will testify to the fact that tires do not sink as deep as in tilled
soil. Soil that was tilled this spring or even in last yearâ€™s spring, will
be more susceptible to compaction than a soil that has been in no-till
Increasing organic matter content will also increase the
resistance of the soil to compaction, because the spongy humus maintains
porosity and also increases aggregate stability.
Finally, a living root
system at time of traffic would increase the resistance of the soil to
compaction. While it is uncommon to see living root systems at harvest time,
some exciting work is being done at Penn State University with establishment
of cover crops into standing corn or soybean, combined in one pass with
herbicide application and side-dressing.
Resilience also includes the
concept of recovering after disturbance. To make soil recover from the
effects of compaction, it is important to try to establish a cover crop
after harvest. The roots of the cover crop will help alleviate compaction
that has been caused. It is also a practice that helps increase biological
activity in the soil â€“ the mycorrhyzae and bacteria growing in the
rhizosphere of cover crops produce glomalin and other organic substances
that improve aggregation of the soil. If manure is available to give the
cover crop a boost and supply additional food for soil microbes that will
also be helpful. It should also be noted that without soil disturbance and
leaving soil covered with mulch smaller and larger organisms such as
nightcrawlers will be much more prevalent and active than if soil is tilled
and left bare. Therefore, fall moldboard plowing should be avoided
especially, and even chisel plowing in the fall will reduce the activity of
these organisms that can help soil kick back from the effects of compaction
while also improving drainage of the soil.
It is advised to stay off the field until conditions are fit for traffic,
but sometimes we never reach those conditions! At least, try to avoid
creating ruts. If you have different soil types on the farm, start harvest
on the better-drained soil types first. A
little frost in the soil will also help to make the soil much less sensitive
to compaction. Increase tire foot print by using flotation tires, duals and
reducing tire pressure. Tracks can
do a very good job as long as the weight of the vehicle is equally
distributed along the whole length of the track.
The effectiveness of
flotation tires is determined by inflation pressure â€“ inflated at high
pressures they will cause much more compaction than at low pressures. Check
inflation tables to determine what the minimum allowable pressure is for
your tires. If you need to get new tires, ask your equipment representative
about tires that cause less compaction. Radial tires have a bigger footprint
than bias-ply tires and are therefore recommended to avoid compaction. As
far as harvest traffic: Keep trucks with road tires out of the field.
Axle load also plays a role, with axle loads above 10 tons being able to
cause subsoil compaction that will be virtually permanent and very difficult
to alleviate. Also, try to limit repeated traffic to certain areas of the
field. Although these will be more compacted, it will be possible to correct
compaction here without having to do remedial action on the whole field.
When compaction has been caused, remedial action may be needed. This is
especially the case if ruts have been created. If no ruts are seen it is
probably not needed to do tillage â€“ instead plant a cover crop to use the
living root system to alleviate compaction. Ruts need to be smoothened out
to be able to plant the next crop successfully, however. If ruts are
uniformly distributed across the whole field, some type of tillage may need
to be done on the whole field.
In many cases, however, ruts are localized
and only need localized repair. It will be necessary to till deeper than the depth of compaction.
Shallow â€˜vertical tillageâ€™ tools that only do tillage in the top 4 inches
will not be sufficient to manage soil compaction. Very tough shanks are
needed that will penetrate instead of bounce on top of the compacted layer.
New subsoilers can do maximum fracturing without doing much surface
disturbance with straight or bent-leg shanks. Parabolic shanks do much more
surface disturbance and will need more secondary tillage for seedbed
preparation and are therefore not preferred. Deep tillage may be what you
could use in the fall, and then come back in the spring to smoothen the
field up with a field cultivator or disk harrow. However, it may be tough to
find the right soil moisture conditions this fall for deep tillage.
tillage should fracture the soil and it therefore needs to be performed in
relatively dry soil. With the temperatures coming down now the soil is not
likely to dry out sufficiently, and it may be necessary to wait until spring
to do deep tillage. Deep tillage can be performed in a living cover crop in
the spring â€“ if you use the modern, low disturbance subsoilers. So let
subsoiling not deter you from planting a cover crop. The more tillage you
do, however, the more you set yourself up for increased compaction problems
in the future.