By: Victoria Nameth, Agriculture Extension Intern, Tisdale Regional Office
The previous wet fall and current wet spring weather in the Northeast region has left soils saturated making it difficult for machinery to get into the field. One concern to be mindful of this growing season is the adverse effects soil compaction has on soil structure and function. Good soil structure is important as it defines soil water, air and nutrient holding capacity.
Soil compaction occurs when soil particles are compressed into a smaller volume and can restrict air and water movement through the soil. It is of particular concern when soils are wet as the excess moisture allows the soil particles to slide and compact easier than when they are dry, negatively impacting soil structure.
Types of Soil Compaction
Soil compaction can be grouped into three categories: deep compaction, subsurface compaction and surface compaction. While all three forms are important, deep compaction can be the most damaging and long lasting type of compaction occurring under wet soil conditions.
Deep compaction can extend 60 cm or more into the subsoil layer. The main cause of deep compaction is a combination of the increased weight of larger farm equipment that exerts greater force onto the soil surface and the anxiety felt by producers to complete seeding early in the spring when fields may not be dry enough. More compaction occurs with heavier equipment and wetter soils. Deep compaction is the hardest type of compaction to alleviate as it is so deep in the profile that tilling and freeze-thaw cycles have little effect. The result of deep compaction is water and air storage within the soil profile is reduced making crops more susceptible to moisture stress in drought years, as well as a potential increase in nitrogen losses to the atmosphere.
Subsurface compaction is compaction that is induced by tillage and is referred to as a plow pan or hardpan. This type of compaction occurs just below tillage depth and is usually 2 to 3 cm thick. Subsurface compaction results from tilling or cultivating at the same depth repeatedly. In extreme cases of subsurface compaction, root penetration and water infiltration into the subsoil can be inhibited.
Shallow or surface compaction occurs through a combination of soil tillage and raindrops impacting the soil surface. This type of compaction is seen in the upper 2.5 cm (1 inch) of the soil layer and inhibits crop emergence and water infiltration. However, both subsurface and surface compaction tend to be relatively short lived due to regular freeze-thaw and wet-dry cycles that loosen the upper portion of the soil.
Preventing Soil Compaction
Taking the appropriate steps to prevent soil compaction before it becomes an issue can save time and money. Deep compaction from high axle load can be prevented by:
- Minimizing traffic on fields when soil and subsoil conditions are wet;
- Limiting the number of overall passes made on the field;
- Reducing axle load per unit area (force exerted on soil) by attaching more tires per axle or switching to tracks;
- Using the lowest acceptable tire pressure;
- Loading, unloading and operating heavy machinery on headlands to reduce traffic throughout the field; and
- Utilizing a good crop rotation that includes plants with deeper rooting depths.
For more information on soil compaction, contact your Regional Office or the Agriculture Knowledge Centre at 1-866-457-2377.