Can soil breathe?

Yes, it does! Just like most living organisms, life in soil needs air to survive.

But how does that work, since the soil do not have lungs like us?

We could think about it as the whole soil profile being a "lung" that depends on a gas exchange to thrive. A healthy soil should contain 25% air. In farming, this is often a limiting factor as heavy machinery will compact the air out of the soil and we are left with less than 25%. And we get the same effect as if we had our respiation blocked, it will be difficult to perform at our best if we do not get the air we need.

On important factor is one that we may not think about, high and low pressure in the air. When the air pressure is higher, air will be pushed into the soil and low pressure will pull air out of the soil. So we have a "breathing" taking place between changes in the air pressure.

Another factor that even less people think about is the moons impact. We all know how ebb and flow works along the coast line. It is very apparent that there is a difference depending on how close the moon are. But the very same thing takes place in ground water below the soil; when the moon is closer the water level rises and push air out of the soil when it is gone the water level will reside and pull air back.

Just because it is below ground and we can not see it does not mean it does not happen. So, there we have one more mechanism for soil "breathing".

But how do we know how much air we have in the soil? We need a quick way to check this in the field so we can compare over time. The simplest solution is the get a soil penetrometer. It is a very simple tool that will measure the force it takes to push an iron rod into the soil. There is a meter on the top that will indicate the resistance. Higher value means more compacted soil, lower value equals less compaction. It is measured in PSI and the target value will be somewhere between 150-200 PSI for a soil with 25% air.

When we aim for a more living soil, this is a good tool to check if we are on the right track.