A question I see a lot from people who container garden is what to do with the soil from last year that is in their containers. Do they get rid of it? Reuse it? What? It seems like every year once we get close to growing season that this question comes up.
There are a lot of options. If you have a compost pile, you can dump all of the old soil that doesn't have plants currently growing in it, bulbs that will come back each year, etc. This gives it a chance to be reinvigorated by the nutrients it picks up from your compost heap. But what if you don't have a compost heap?
What I've done is reuse my soil every year. But I don't just reuse it as it is - I amend it. I bought some cheap tarps at the store - one for my tomato plants, one for everything else. I don't want to to reuse my tomato soil two years in a tow for tomatoes, so all of the pots that had tomato plants in them get handled separately.
We dump out all of the containers onto the tarp. We use a rake to help break up the soil so that it's not in huge clumps. We then pour in some fresh organic soil as well as compost that we purchase at the store. I have some all-purpose granular fertilizer that I purchased at a local farm store. I also pour in some of that.
Using our hands and the rake, we mix everything up as good as we can. Then we refill the containers.
This allows us to get the most use out of the soil we purchased while also giving the plants the nutrients they need.