Kitchen Garden Forum

After harvesting the crops and sometimes even seeds of them, the containers on my balcony garden are full of old soil. Yes, I keep track of the crop rotation, which crops grow best after another. This works for a while, yet the soil doesn't get better automatically after four different crops have been grown on it, or does it? So I create and sometimes buy a little bit of compost to mix through the used soil in those containers. Usually I also add fertilizer and a small part new bought soil mix, then blend this thoroughly together. It's a lot more sustainable and affordable than having to buy new soil everytime I harvest something, but is it enough to re-use old soil, even after years of usage?

Morning Elmigo, as long as the plants haven't been diseaed the soil/compost is fine to keep using but, as you said, it does need a fertiliser of some sort, whether artificial or organic....no different to an allotment or flower border, really.

Goodmorning, thank you a lot!

I think I would be tempted to replace it with a loam based John Innes type of material once a year.

Yes, I'm actually tempted to use a new bought mix everytime after harvesting but that would be costing way too much if the old soil is still nutritious for other crops.

I mix most of my own potting compost from soil, leafmould and sand but when I empty pots I retrieve the compost and blend it with the fresh. I use fish, blood and bone as fertiliser when I make a mix and if I am refreshing a big pot without emptying it I stir some into the old compost before topping up with fresh.

I think existing compost needs topping up with something every year otherwise all the nutrients will eventually become exhausted and it will become impossible to grow quality plants of any description. Most vegetables are hungry growers and i would go for a John Innes type soil replacement. However, carrying bags of compost up to a flat balcony must be very inconvenient.

As previously mentioned I do occasionally top up or change a small portion of the compost in my patio containers but go for the composting in situ option during part of the year which keeps the nutrient levels up and reduces the need to change compost to a minimum. Also, - and-you won,t have this option available to you, when we cut our lawns, I regularly mix handfuls grass cuttings into the patio containers to rot down and help top up the nutrient levels.

At the end of the day, John Innes or any other compost, will only feed the plants for a certain length of time, depending on how much feed/fertiliser the companies mix in.....Hence, John Innes seed compost has very little feed, while John Innes no 3, has a larger amount of feed....

I can see your problem, Elmigo, because, presumably, if you had to get rid of old compost, where would you put it from your balcony pots? I endorse everything said above: now, without allotment, we grow lots of things in pots too and refresh the soil regularly, but eventually I throw the 'exhausted' compost onto the flower beds in the garden.

I'm pretty sure there is a company nearby that loves to take old soil to recycle or process it for other uses. Not sure but if the soil gets too old I may aswell bring it there and buy a new bag for the container it comes out of. In the meantime I can keep refreshing it for as long as the crop circle.

Agree with what everyone has said but a wee thought popped in my mind - probably the wrong thought, but my friend gave me her potato sacks & other pots with the soil in them which I used to top up the beds on lottie, (& use her sacks). When I tipped it out on the beds there were little granules of slow release fertiliser in them & I got super crops over winter so I think they were not spent even though she grew her crops first. I know nothing about these as I prefer flakey mixes that disappear immediately, but I'm sure one of the clever guys on here will advise just how slow release they are as they may be an option for you to extend the life of your compost.

The slow release is my favorite because I usually have to fertilize once every 4-6 months during spring and summer. It's a balanced 10-10-10 fertilizer made for fruits and veggies so I usually get pretty good crops for the short time I have been gardening.

Getting rid of old compost ... why does "The Great Escape" come to mind

I used a John Innes seed compost once. Cold, heavy stuff that put me off John Innes / loam based potting composts.

My beds are no dig filled with compost, at the end of a crowing season I put an inch or two on top for next year this as per Charles Dowding’s way.

There are loads of worms on my plot (the moles/molehill tell me) so guess that helps with improving the soil.

I wonder if doing same on pots would work.

How about a small wormery the worm juice will give you all the nutrients needed without the need for worms in you soil.

I did find a couple of worms when mixing my container soil with fresh compost. Left them there because they do make it more well-drained. It'll probably make it more nutritious too.