By: Thom Weir

The weather has finally made a turn for the better. That means there will be hundreds of combines heading to the fields over the next couple of weeks. Farmers are anxious to get the remaining crops in the bins – regardless of field conditions. This opens us up to a couple of soil conditions that may cause issues in following crops. They are Rutting and Compaction.

Rutting occurs when tires sink into wet soils, causing trenches or furrows. Rutting displaces soil and damages soil structure by causing compaction. These ruts can fill with water and cause issues in following crops.

Compaction occurs when soils near saturation. The water in the soil acts as a lubricant, allowing soil aggregates to be destroyed and soil particles to be compressed together forcing out the water. The results are both surface and subsoil compaction.

Compacted soil can be “the gift that keeps on giving”.  You have all seen the results of compacted soils at the field approach area – where very little grows. These are extreme areas, but compaction will impact root development and water infiltration. You may have dug up canola plants and seen the roots going down an inch and then sideways. This is caused by compaction.  In a wet year, plants can get enough moisture and nutrients but in dry years, this type of root development can significantly impact yields. Research indicates that you can expect yield reduction in the area of 10 – 25%, depending on the soil type and extent of the compaction.

Since 2000, we have seen the rapid increase in the size of farms in Western Canada. As a result, we have larger and heavier equipment. A fully loaded combine may have an axle load of 25 tonnes per axle and a fully loaded single -axle grain cart is approximately 20 tonnes.

Harvesting in field conditions that are likely to cause soil compaction will likely be something you won’t be able to avoid this fall. Farmers are pushing to get grain harvested without further field worsening grain quality and avoiding leaving the crops out over winter. Soil compaction will be worse the wetter the soil conditions are!

Here are a few thoughts to ponder as you return to the fields.

  • Clay soils are more prone to compaction as compared to sandy soils. If you have some fields of each, it may be appropriate to harvest the sandier fields first and hope the clay fields will dry out a little.
  • Studies have shown that 60 – 80% of soil compaction occurs by the first pass of an implement of vehicle across the field. In wetter areas, dedicated traffic lanes could be considered for grain cart traffic.
  • Where possible, avoid or limit truck traffic in the field or limit it to a confined area near the field approach.
  • Where it is feasible, avoid loading combines and grain carts to full capacity.
  • Consider having grain carts remain at one end of a field and unloading combines when they reach that area. This will limit the trips across the field with a full cart.
  • Ensure tire pressures are properly adjusted to match the axle load that will be carried. Larger tires can bear heavier loads at lower pressures, reducing soil compaction. Where feasible, dual tires offer better flotation and reduce the pressure on soil surface.
  • Try to avoid or limit tillage or fertilizer on fields until they have dried to under field capacity. Soils above field capacity can be detected by digging up some soil and squeezing it in your hand. If water appears, the soil is at or above field capacity. This should be done at the depth of tillage or fertilizer banding.

I am sure this fall will continue to deal challenges. I hope that this information will allow you to react to your situations to best complete your fall operations.