The season is winding down and now’s the time to keep in mind that current actions can have an impact on future crop success. One yield robber that can be reduced during harvest is soil compaction.

Reducing compaction starts with understanding what kind of compaction can occur and how it happens in the first place.

According to Penn State University Extension, there are two types of soil compaction: surface and subsoil. Surface compaction is what’s created within the first foot of soil depth, and it’s caused by high contact pressure, such as high tire PSI and iron wheels.

The good news is no-tillers don’t have to worry as much about surface compaction. While it can cause dramatic yield losses, these fields should bounce back quickly thanks to higher biological activity typical in no-tilled soils. The University of Kentucky found that continuously no-tilled soils will recuperate from most surface compaction without tillage within a year.

Subsoil compaction, on the other hand, occurs deeper than 12 inches and is caused by axle load. “If you traffic soil that is really too wet with axle loads of 10 tons or higher, you’re likely causing subsoil compaction below 20 inches,” Penn State soil scientist Sjoerd Duiker says.

And once subsoil compaction happens it’s likely to stay. One research study showed a 5% yield decrease due to subsoil compaction that lasted longer than 10 years. The only way to avoid subsoil compaction is to keep axle loads below 10 tons by reducing load, or increasing the number of axles.

So how can a grower tell if compaction is a concern for his fields? At the 2014 Farm Progress Show held last month in Boone, Iowa, AGCO North America marketing manager Conor Bergin shared some typical signs of compaction.

They include:

  • Slow crop emergence
  • Uneven crop growth
  • Abnormal rooting patterns
  • Crusting after it rains
  • Standing water in the field
  • Excessive erosion
  • Slow decomposition of residue

If you’re seeing some of these symptoms show up in your no-till fields, you may want to consider taking more precautions to mitigate compaction. Here are some additional tips: 

  1. Continue no-tilling. Duiker says the increased biological activity and organic-matter accumulation will help soil resist compaction better.
  2. Stay off the field until the soil has dried out sufficiently. Bergin says as soil moisture increases, so does the compaction zone. Soils with a high water-holding capacity, typically clays, are more susceptible to compaction than sandier soils. 
  3. Use the lowest allowable tire inflation pressure. Reducing tire pressure expands the tire footprint, which spreads the load across the whole tire. Bigger tires with IF and VF technology will allow this. Duiker recommends keeping the PSI under 35.
  4. Avoid trafficking the entire field by creating and respecting traffic lanes.
  5. Use cover crops. Duiker says their root system helps soils resist compaction better.