I have a small container garden (veggiepod) 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?

The soil may be safe, but probably needs to be revitalized with beneficial microbes and nutrients. This can be accomplished by breaking up the present soil and adding (you may have to remove some of the present soil if you don't have enough room) nutrients and beneficial microbes. Ingredients such as compost, worm castings and a fertilizer formulated for whatever you plan to grow will help.

Overtime different plants will use up different nutrients from the soil. So you likely should add more to the soil but I don't think you need to completely toss and start over. I'm not sure where you are from but I live around farms in Ohio and that's actually why you see different things in fields each year. They rotate crops to ensure there is enough nutrients for what they're planting.

I would imagine adding some extra compost should help

I sometimes recycle potting soil, but only after screening out the dust and fines through a 1/16" mesh. This gets rid of fine sand and the broken-down organics which pack and exclude air.

I'm always interested in hearing about a premium potting soil, because most bagged mixes are now made from shredded scrap wood and tree trimmings from landfill operations. As such, they're good for one season, and tend to be marginal at that. Check the labels; "Composted Forest Products" and "Aged Forest Products" are code for ground-up scrap wood.

Wood fibers (cellulose) break down quickly and support invasive fungal overgrowth (mushrooms, dry-rot). It's one of the worst things to grow in.

Ground bark is one of the best and most stable potting ingredients available. The function of bark in nature is to resist breakdown, and protect the relatively fragile wood fiber of the tree.

Peat of one sort or another is a classic, time-honored and common potting mix ingredient, and while superior to wood, it's fine-textured, and can pack down. When it's wet, it holds too much water with little air space, and when it's dry, it's difficult to re-wet.

My favorite potting mix is home blended, with ground bark as the primary component. I use fine orchid bark or landscape bark as the primary component. (Landscape bark is cheaper, but involves a little more work to screen out the dust, oversized chunks and other junk. Always use bark chunks, not shredded, fibrous, or 'hairy' bark)

Search the web for 5-1-1 container mix, there are a few YouTube videos on this subject as well. Briefly, it's:

5 parts 3/16"—1/2" bark
1 part 'medium' perlite (no dust)
1 part peat (or peat-based soil mix)

The bark will need lime. About a week before using the bark, moisten it well and add 1/2 to 1 tablespoon dolomitic lime per gallon of bark. Shake or stir, bag it up, and let it rest for a week or so.

Blend and moisten the ingredients just before use, and when potting up, add a time-release fertilizer. Thereafter, give regular feedings with Dyna-Gro Foliage Pro. It has an ideal nutrient balance (including micros) as well as calcium, important in soilless mixes. A dilution of 1/4 tsp/gallon is suitable for use at every watering.

This mix is stable, holds water well, and has plenty of air space to keep roots healthy. It will last for years. It's made a huge difference in the health of my container plants.

I always start new! Why take a chance and waste precious time growing in used soil. That's like wearing dirty socks over and over. It will work but why do it if you don't have to.

oneeyeluke said:That's like wearing dirty socks over and over.

We tried using a soil that was old to grow squash and the plant stayed tiny. Can putting fertilizer in the dirt improve its composition, or does it have to be natural stuff?

I reuse my potting soil all the time. But I revitalize it with compost and fertilizer (usually, but not always, organic). If I have a pot of soil I am not using, I dump the soil into a plastic bag, add coffee grounds, egg shells and banana peels, then tie up the bag and put it down in the basement. When I get it back out to use again, I add some fertilizer to it. Seems to work very well for me. Also, if I am concerned about disease, or planting something very susceptible to disease, I sometimes put the soil into the oven and heat it.