Saturday, February 27, 2010

Why you wait to walk on wet soil

Our gardens love the rain! But be careful, wet soil is more vulnerable to compaction, especially clayey soils. The physical damage from compaction can
  • increase bulk density, where soil pores are now too small to accommodate the root cap's growth
  • increase soil's ability to resist deformation (soil strength), and prevent root penetration.
  • crushes natural soil aggregates and associated macropores, thereby preventing adequate water and air flow.
All this means reduced root growth and therefore less overall vigor of a plant, from your garden plants to large trees! Clay soils are more vulnerable to having their structure damaged due to their increased plasticity and cohesion. Try not to walk too much on your wet soils; perhaps make a permanent path in your garden to help you remember.

Here are some definitions:

Bulk density: weight per volume of soil
Soil Strength: ability of a soil to resist deformation (change in shape)
Plasticity: ability of a soil to be molded or deformed by pressure
Cohesion: stick/stay together
Soil aggregates: soil particles that are held together in one mass
Macropores: soil pores large enough to allow for air and water flow, and even some small animals (some animals make macropores!)


  1. How about stepping on more worms? They tend to come up to the surface when it rains. Get rid of them, and you might have an aeration problem.

  2. Good question. Worms are important! Please be nice to them. I'm not sure how much weight per square inch they can tolerate (they might be OK with your footprint), but it is better to be safe than sorry!