I was watching a discussion on a popular garden forum between two well known seasoned gardeners. They were discussing the difference between “soil” and “compost”. One gentleman said that “soil” was anything consisting of decomposed matter. The other gentleman argued that “soil” was rocks and minerals.
Well, for arguments sake, I’ll have to disagree with both of them.
The second gentleman was only partially right.
What is the difference?
Soil is basically the top 6 inch or so layer of the earth. It’s made up of sand, silt, rock, minerals, gases and even decomposed matter like plant material and dead carcasses from animals and insects (compost). It also includes microbes and fungi know as the food web. All of this matter is considered “topsoil” and sits on the TOP of the earth (hence the name)
Unfortunately, the earth is being rapidly depleted of this resource as commercial farmers scrape the top layer off to remove weeds and level the land. This results in a dead, dry and parched earth. This is where farmers like to plant. But the sad reality is, they are depriving themselves of the best growing medium on the planet. They are then forced to till in fertilizers to replenish what was lost. And then this vicious cycle starts over again year after year.
Compost is basically decomposed plant matter like kitchen waste and rotting plants. It also includes dead shrubs, tree branches, and basically anything living thing that falls to the earth and dies. It is broken down slowly over time and turned back into what many would call dirt. It turns into one of the richest organic fertilizers that money can buy.
So when you hear someone say “I added soil from my compost pile to my raised beds”, what they are really saying is, I added compost to my raised bed from my compost pile 🙂
So to simplify things, You can amend your topsoil with compost to increase its mineral content or to make the soil more loamy for planting, but you never amend your compost with soil. Topsoil will contain compost, but compost does not contain topsoil.