Reuse of soil in a container garden?

Question

I have a small container garden (https://vegepod.com.au/collections/raised-garden-beds/products/raised-garden-bed-small) which I used to grow some bok-choy and silverbeet about 18 months ago.

The soil that I used is a combination of premium potting mix, and some cow manure.

Since moving about a year ago the container garden has been sitting on my balcony, and has not been used to grow anything since the move.

I'm looking at planting some new vegetables, and I am wondering if it will be safe/effective to reuse the soil, or whether I should replace the soil?

Answer 1

Spread the soil on a sheet and let it completely dry and soak some sunlight for a day or two. Mix a small quantity of compost / manure and two spoonful of wood ash. Try to grow any microgreens in it using seeds. If soil is healthy, seeds will germinate and you will get small plants in a week. It will be more beneficial if the microgreen you have selected is of nitrogen fixing kind like alfalfa, clover, pea etc.

In a week, not only you will get an idea about the quality of soil but you will also end up in improving it.

Answer 2

A "closed" environment like this is not exactly the same as an open garden, because you don't have the full natural ecosystem to recycle what accumulates in the soil - for example no earthworms or other below-ground-living critters, probably only limited mycelium from (mostly invisible) soil-living fungi, a limited population of bacteria compared with open soil, etc.

Therefore "bad stuff" will tend to accumulate in the soil over time, which is why you need to replace it.

That said, if you only grew one crop in good quality compost, it would most likely be OK for another season, provided you realize that the original supply of fertilizer in the compost needs to be replaced, by regular feeding of the plants.