Soil.  It’s the one thing we all depend upon.  Not just for growing pretty gardens in.  It’s vital for food production for managing climate change and for physical health.  Soil compaction is a huge problem in the UK and it’s affecting all of us in one way or another.

What Is Soil Compaction?

I trolled the internet for find the definition of compaction.  There are a lot of different versions.  Most use technical jargon that you would need an engineer to translate for you.  This definition is from the Cambridge Dictionary and it’s the one that made the most sense to me.

“the process by which the pressure on buried solid material causes the material to stick together and change to rock”

When we drive heavy machinery across a field or continually walk across the same piece of lawn the soil gets compacted – or squished.  The soil structure is changed and if the damage is severe enough, it becomes more like rock.

Why Does Soil Compaction Matter?

Soil structure is what provides the right conditions for living things to survive in the soil.  That includes plant roots, worms, nematodes, bacteria, fungi, microbes, seeds and a whole plethora or organisms that we’re still learning about. 

Soil is made up of differing proportions of sand, silt and clay particles along with air, water and organic matter (which includes dead leaves and roots, seeds and living organisms).   In healthy soil there would be 45% minerals, 25% water, 25% air and 5% organic matter.

One teaspoon of soil contains in the region of 1 billion organisms.  A ton of microscopic bacteria may be active in each acre of soil.  That’s a lot!  They all need air and water to survive.  When soil is compacted, the air is squeezed out of it (you can’t easily compact mineral matter) and the creatures cease to live. 

Plant roots cannot access water or nutrients unless there is air in the soil.  Compacted soil won’t support plant life either.

Other Problems Associated With Soil Compaction Include:

  • Poor water infiltration – the soil cannot soak up excess water
  • Flooding
  • Restricted root development – this especially problematic near trees.  Trees use their roots to keep them upright.  Restricted root development leads to falling trees!
  • Drought stress in plants – not enough water gets into the soil, plants die (and it doesn’t matter how expensive they were or how much time you spend watering them. If the water can’t soak into the soil, the plants can’t use it)
  • Low microbial activity.  Soil microbes make plant food from the air. Without microbes you need to add more and more chemical fertilisers.  Yuk.  Plus, there are not enough good bacteria to suppress the ones that cause plant diseases – so you have poorly plants and need even more chemicals to control the disease.

How To Avoid Soil Compaction

Don’t handle wet soil.  Soggy soil is more vulnerable to compaction.  Keep off it if you can and don’t even think about trying to create a seedbed in it – or worse still, lay turf.

If you must drive across the soil – for example on a construction site – use vehicles with wide wheels – or better still, caterpillar tracks.

If your soil is mostly silt or clay it will be vulnerable to compaction.  Adding fine sand and/or organic material such as compost will help to open up the structure. 

Regular de-compaction of heavily trafficked areas is advisable.  That’s why lawn experts recommend aeration and topdressing.  It works wonders for keeping soil, roots and grass in tip top condition.

Grow flowers fruit and veg in raised beds.  You never need to stand on the soil because it can be reached from all sides of the bed.  Simple but effective.  Trust me, it works.