Conquering soil compaction

During a recent informational session at FarmSmart – a producer-focused, innovative management conference held in Guelph, Ontario, on January 20 – Peter Johnson, an expert agronomist, reviewed the findings of an on-farm compaction demonstration event held the previous year.

Compaction causing more problems than we realise

Using 35 pieces of equipment of various sizes on 53 different weight and soil configurations, Johnson and his colleagues demonstrated just how seriously – and quickly – compaction can cause major problems.

“Compaction is a drainage issue. It’s an erosion issue. It’s causing a lot more problems than we think it is, and North America is way behind Europe in taking compaction seriously,” says Johnson.

Ever-enlarging farm equipment a significant factor

According to both Johnson and Alex Barrie – an environmental engineer with the provincial agriculture ministry and Johnson’s co-presenter – ever-enlarging farm equipment is one of the most significant factors behind compaction, and specifically deep sub-soil compaction.

Even one pass with a large piece of machinery on mildly damp ground, whether on tracks or tires, can compress the pores and waterways within soil by upwards of 35%. Consider the amount of driving the average field is subjected to each year, and that number is certainly significant.

“Surface compaction isn’t nearly as big of a deal, but it adds up year after year,” says Johnson.

Impact of decreasing levels of organic matter

The damage wrought by compaction, whatever its source, is also compounded by a decades-long trend of decreasing levels of organic matter in Ontario farmland. Farmers cause compaction, they say, when above-ground pressure exceeds the elasticity of the soil. Since organic matter is critical to soil elasticity, lower levels mean the pressure threshold is also lower.

“We only have 40% of the organic matter left that [Ontario had] 50 years ago. We really do need higher levels of organic matter,” says Johnson.

So what are the solutions?

• Both Johnson and Barrie say keeping tires inflated to different levels for the field and the road is a start. That likely means investing in on-demand inflation technology – which is not standard even on new equipment sold in Canada.
• Tracks can work, they say, though they are not inherently better since any given piece of ground is being compressed for a longer period of time. Indeed, their work shows very similar levels of compaction between tires and tracks.
• Their 2017 field tests also showed duals tires can cut deep compaction by half, and even leaving the head on a loaded combine can help keep weight off the smaller, narrower rear steering axel.
• Working cover crops into one’s rotation is a great way to build organic matter, too, and literally prevent compaction from the ground up.
• But critically, both Johnson and Barrie say any solution has to start with a change in thinking on the part of farmers themselves – that means knowing how much your equipment actually weighs, and just staying out of the field under wet or damp conditions.

“Patience is the greatest tool to avoid compaction, but it’s the hardest one to use,” says Johnson.

More information about the on-farm compaction workshop