In gardens and farms you'll usually amend the soil not only with fertilizers but also with as much organic material as you can sensibly get. This way a healthy soil ecosphere is created that will take care of a lot of the soil depletion and pests issues.
On a balcony usually the containers are too small and too shallow to establish this kind of natural system. Also the environmental conditions are often varying too much. The containers might dry out at some time and be over watered at other times.
It is similar to keeping a very small aquarium healthy. The smaller it gets, the more delicate and instable it becomes. Thus to keep it simple, balcony and container gardeners are advised to exchange the pot soil on a regular basis.
Whan you can do to avoid wasting the "spent" soil, is simply to rejuvenate it. Mix it together with a large amount of fresh and healthy compost and other components to give it a boost. No need to throw it away.
If you want to make sure that pests do not survive and accumulate in this process, simply collect the spent container soil into a large compartment and heat it up to 90°C in the oven for an hour or so, sterilizing it in the process.
The other alternative would be to use hydroponics and specifically Kratky Hydroponics on the balcony and window shelf. I'm growing some beet root plants this way atm. Very easy and low maintenance.
As has been said, you can't really go wrong with adding organic matter to your soil. Probably that means lots of manure if you can get it and then mulch.
A really simple way to see how good or bad your soil is starting out is to just dig up a couple of lumps of earth and see if you find earthworms. If you do, then you're off to a good start!
On a balcony usually the containers are too small and too shallow to establish this kind of natural system. Also the environmental conditions are often varying too much. The containers might dry out at some time and be over watered at other times.
It is similar to keeping a very small aquarium healthy. The smaller it gets, the more delicate and instable it becomes. Thus to keep it simple, balcony and container gardeners are advised to exchange the pot soil on a regular basis.
Whan you can do to avoid wasting the "spent" soil, is simply to rejuvenate it. Mix it together with a large amount of fresh and healthy compost and other components to give it a boost. No need to throw it away.
If you want to make sure that pests do not survive and accumulate in this process, simply collect the spent container soil into a large compartment and heat it up to 90°C in the oven for an hour or so, sterilizing it in the process.
The other alternative would be to use hydroponics and specifically Kratky Hydroponics on the balcony and window shelf. I'm growing some beet root plants this way atm. Very easy and low maintenance.