Soil for garden
What is the difference between top soil, potting soil, and compost? Which should I fill my raised bed gardens and pots with for growing vegetables?
Deschutes County Oregon
All three of these materials vary quite a bit. In general, top soil is a mixture of sand soil dug from the ground and mixed with something that gives it "body" like bark dust or in some cases, composted manure. It this last case it is more expensive and referred to a "rich mix". It is suitable for raised beds but not pots. One can purchase it be the truck load and have it delivered.
Potting soil is mostly "soil less". It is mostly inert materials like peat moss, perlite, mica, bark dust, very well composted materials, and maybe some sandy soil. It is very well drained, and thus suitable for pots. Compost is highly variable. Municipal compost has a lot of composted wood chips in it, ground up trees and shrubs that are caramelized in a hot composting system. Chicken and cow manure is piled up for six to twelve months where it composts and stabilizes. Then of course, there is home compost piles.
Top soil is the cheapest. If you make beds out of it, you have to add fertility to in the form of compost or salt based fertilizer or both.
Potting soil is the most expensive and usually has no fertility in it. It is designed to be used with fertilizers like "Miracle Grow".
Compost is all over the board. You have to ask 1) what was composted? and 2) how was it composted and for how long?
Watch out for weeds coming in with top soil and compost.