Why no digging is better for our soil

Until two decades ago it was considered completely normal to digg the soil of our gardens and vegetable plots / beds. People learned it from their ancestors and I can still see my grandfather digging in cow manure each year in March. But science hasn't been dormant and today we have much more scientific knowledge about how the soil works.

When we look in forests or countryside we see healthy growth without digging or interference. The soil in nature doesn't need digging to bring air and organic material in. There are very good reasons why that's the case:

Remember my emphasis on the topsoil containing the black gold called humus? Well it's that upper layer of soil which hates digging. Our layer of topsoil contains billions of good bacteria and they digest the organic material which falls on that topsoil. With the help of earthworms that topsoil is one big busy energy factory making all the goodies for our roses and other plants. They also get help from Mycorhizza fungi in breaking down organic matter. It's a giant network underneath the surface. 

What happens when we dig into the soil and flip it over? Or what happens when we bring in organic material into the topsoil? All organic material which breaks down needs oxygen to do so. The bacteria need it. So when we dig in organic material like compost or manure the bacteria in that organic material gets deprived of that necessary oxygen and what happens? They extract it from the topsoil, from the humus layer. This is very bad for our plants as the roots need oxygen. If we spread out our compost, worm castings, composted cow and horse manure as a mulch it will extract the much needed oxygen from the air with no harm for the topsoil. 

A second problem that occurs when we dig and flip soil over is that the bacteria living in the topsoil get exposed to UV light and die. In the soil are lots of anaerobic bacteria working day and night to produce healthy soil but when they suddenly get exposed to the air and oxygen they also will die. We intervene in a perfect working process by digging and it has big consequences for our soils.

So the best way to create a healthy soil is to leave it alone as much as possible and to give it each year a thick layer of organic material on top of the topsoil. Nature will do the rest.