Rain, axles and soil compaction


Tony Nye - OSU Extension



I have heard several remark they can’t believe November is already here. The ghouls and goblins have hardly been put away from Halloween, and now the Christmas frenzy is upon us — at least the materialistic world wants us to start believing that.

My family watches a specific TV channel and they have already started playing Christmas shows. Ugh! What happened to looking forward to Thanksgiving with all the trimmings?

I am sure many of you still trying to get harvest complete would like to go back a few weeks when weather was more cooperating than it has become lately. In fact, the weather experts suggest November will be marked with above normal rainfall and temperatures trending from near normal to above or much above normal for the second half of the month.

If you still have crops to be harvested, and I know many do, be mindful of the compaction you may be creating.

Keep in mind, if you are leaving ruts, you are causing compaction. As machinery carries heavy loads across these fields, deep rutting with heavy subsurface compaction can develop.

Axle load is a determining factor in the overall depth of soil compaction. The risk and severity of compaction increases when field activities occur on wet soils.

The best way to avoid causing severe soil compaction is to avoid field activities when field conditions are marginal.

However, recent, heavy rain events across Ohio may create a situation where it may not be possible to wait for fields to dry completely out.

Heavy farm machinery compacts the soil, both on tilled ground and no-tilled ground. Compaction induced by agricultural machinery often affects soil properties and crop production.

Axle load is the first factor that has to be considered in soil compaction, according to Randall Reeder, Ohio State University Emeriti, and Dr. Sjoerd Duiker, Penn State Soil Specialist.

Axle load is the total load supported by one axle, usually expressed in tons or pounds.

Farm equipment with high axle loads on wet soil will cause compaction in the topsoil and subsoil, whereas low axle loads will cause compaction in the topsoil and the upper part of the subsoil only. Deep subsoil compaction can only partially be alleviated with subsoilers, and at considerable cost.

Freezing/thawing and drying/wetting cycles have been shown not to remediate soil compaction at this depth.

Finally, biological activity (such as cover crops) is concentrated in the topsoil except deep root crops (e.g. radish or annual ryegrass) and therefore also contributes little to alleviation of deep subsoil compaction. Therefore, avoiding deep subsoil compaction is critical. The key to eliminating deep subsoil compaction is to keep axle load low.

A warning to producers — anytime wet soil compaction is a possibility, deep subsoil compaction is permanent and should be avoided at all costs.

This can be done by keeping axle loads below 10 tons, and preferably below 6 tons. Driving on soil that is wetter than the plastic limit (soil crumbles, ideal for tillage) should be avoided at all times.

If you are planning to head back out before conditions are perfect, here are some tips Ohio State University specialists recommend to minimize damage during this wet harvest season:

• Use a controlled traffic strategy to minimize the amount of field traversed by combines and grain carts. Most damage occurs with the first pass of the machine.

• Make sure tire pressure is properly adjusted for the axle load. Larger tires with lower air pressure allow for better flotation and reduce pressure on the soil surface. Larger tires that are properly inflated increases the “footprint” on the soil. (Note: pressures for road travel should not be the same as field travel).

• Minimize filling grain carts to max capacity, thereby reducing overall axle load.

• High inflation pressures lead to more serious compaction events.

• Hold off on soil tillage operations until soil conditions are drier than field capacity. Tilling too wet can cause issues as well and not accomplish the intended results of tillage.

• Collect machine data to evaluate trafficked areas after harvest. These data can identify where multiple pass of equipment occurred and where areas need to be deep ripped.

• Where funds allow, consider making the switch to tracks from wheeled tractors and carts. Tracked machinery and equipment more evenly distribute weight and cause less damage than their wheeled counterparts.

Tony Nye is the state coordinator for the Ohio State University Extension Small Farm Program and has been an OSU Extension Educator for agriculture and natural resources for over 30 years, currently serving Clinton County and the Miami Valley EERA.

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Tony Nye

OSU Extension