Combating Compaction

yield loss cmp

Resources: “Effects of Soil Compaction”, Sjoerd W. Duiker, Penn State /  IFAO Compaction Action Day, Sept 2017 Arthur Ontario

Compaction is a real problem on most farms today due to the significant increase in equipment size and weight over the last 50 years. Often in our hurry to get the job done we can’t or don’t stop to wait for ideal soil conditions or think about the consequences of tire pressure or wheel load.  Soil compaction causes significant yield loss.  As the chart below depicts yield loss due to compaction can be up to 15% in the first year following the compacting event with losses continuing for many years even without further compaction occurring.  Repeated surface compaction causes a 20% yield reduction annually even with tillage.

 

It is a common belief that tillage removes soil compaction problems.  This is true only for surface compaction of sandy soils.  Heavier soils, loam and clay, will require repeated freeze dry cycles and time without additional compaction to combat surface compaction. For most soils in our area topsoil compaction will reduce yields, even with tillage.  Subsoil compaction is considered permanent because it occurs below the depth of normal tillage operations and is not alleviated by freeze thaw or wetting—drying cyles in any soil type. Subsoil compaction should be avoided at all costs.

High tire pressure creates topsoil compaction. 

High wheel load creates subsoil compaction.

A good rule of thumb is to keep wheel load under 5 tonne to avoid subsoil compaction and reduce tire pressure for any wheel loads over 3 tonne.      

Soil compaction causes several detrimental effects to soil and crop health as well as reducing yield. These detrimental effects include:

  • Decreased porosity or fewer pores for air and water movement in the soil which impedes root growth and function.
  • Root penetration resistance. Root growth slows at 100 psi penetration resistance and completely stops at 300 psi.
  • Destroyed soil structure. Linked to the decrease in porosity, compacted soils become blockier in structure.
  • Slower water infiltration which causes reduced aeration and increased runoff and erosion, especially in the wheel tracks.
  • Limited root growth. Due to penetration resistance, roots can only grow in areas above or beside the compacted soil zone.
  • Reduced nutrient and water uptake. Compaction significantly reduces phosphorus uptake by the plants because P is immobile in the soil. Potassium uptake is similarly affected by compaction.

Don’t get caught in the compaction—tillage downward spiral of soil degradation. Stay off wet soil. Keep wheel loads under 5 tonne. Reduce tire pressure in the field. Increase soil organic matter content and soil organisms.