Weighing the cost of compaction

Anne Verhallen, Soil Management Specialist

“Stay off wet soil” is the best advice to prevent compaction but with wet forecasts and the calendar marching on what to do?

Don’t fool yourself; sand does pack. Most of our soils have poorly sorted sands so with high soil moisture, weight and a bit of vibration, the soils particles readily move and pack together.

At what cost?

Field crop research on the impact of compaction has suggested yield reductions of 0 to 75%. Of course weather, soil type, rotation and other management factors influence the long-term impact of compaction. Generally you can count on compaction and poor soil structure to make a field more prone to stress in the poor years. That is just the impact in field crops.

More disturbing is some work from Cornell in New York with a variety of vegetable crops that suggests the impact is a bit more severe, with yield reductions of 20 to 50 per cent plus.

Options to reduce the compaction

The potential for compaction is a bit different in the spring. Most of the operations do involve lighter equipment so are less likely to pack at subsoil depth, however the packing although shallow will have a significant impact on developing root systems. Research has suggested that 80% of the packing happens with the first pass in the spring.

• Stay off wet soil as long as possible – shift to better drained fields, change hybrids or varieties, select different herbicides if possible etc.
• Minimize the weight of the equipment
• Increase the footprint, eg. duals will help to increase flotation
• Improve weight distribution – lower tire pressure, keep axle weights below 5 tons, etc.
• Reduce the number of trips over a field