Re-Using Compost

I have two bags growing potatoes on my decking soon to be harvested, would it be ok to re-use this multi purpose compost in the bags by putting it into a raised planter (Vegtrug) which has a mix of MPC and John Innes No 3 that I use for other veg?

 

I always use my old container compost to plant my spring bulbs in . I loosen it completely removing any big clumps , top up with a little new MPC and add some Blood Fish and Bonemeal or Growmore . Seems to work great . I do start with new MPC every spring.
I would like to know what the growing value of used MPC with plant roots in it is though

 

Thanks Harry, I've just harvested the 2 bags of spuds which had approx. mix of 80% MPC and 20% John Innes No 3. The spuds were nothing to write home about and make got about a kilo or two if I'm lucky, the yield wasn't really worth the effort or money spent on soil/compost etc.

 

I did post at sometime how I use old compost. A couple of gardening mags pointed out how to save on compost and how to be "more green" .They suggested the following, at the start of a new season to fill bottom half of pot/container with the old compost and put the new on top.

If I got a large pot/container I mix some growmore in the old compost in the bottom of the pot and fresh on top. I see no difference at all in the quality of plants than if I used all fresh.

If I have a much smaller pot/container then all fresh goes in. For potatoes again we have a system we have used for a few years and it works. Once season is over and all flowers are out we get our 4 plastic trugs we are going to grow spuds in.

We then put all the old compost + a load of manure into a wheelbarrow and mix it all up. It then all goes into 4 strong plastic bags and put bags somewhere hidden with tops sealed from rain with a brick,all ready for next early spuds.
We have always found the spuds again grow just as well with this method than using fresh compost. We will use old compost for one season only then throw it all out. To be honest if we had loads of space & large borders and even trees we would spread the old compost over these. Since we have to transport the old compost down to the dump it saves a lot of time and even money.

 

@auldreekie ,That was my experience when I grew container spuds a few years ago , cost me aboyt £10 a KG ! The only veg I grow now are Onions from sets and Chillies , both productive , tasty and fun to grow.
Now there is one thing they do know about on GC and that's growing potatoes I am sure that the spud gurus on here can advise on the best type to grow and technique for your conditions. - I presume you are in Edinburgh ?

 

Aye your right I'm in Edinburgh, seems like the term auld reekie is quite well known these days :-) Will be doing onions, chillies next year, my first year with leeks and celery were successful, love home made celery soup. Want to try garlic too, I think I need to be putting them in about now, all will be in planter troughs.

 

I wouldn't grow spuds in multipurpose compost. Spuds like poo. The more, the better, so if I was growing them in containers, I'd probably use rotted manure.

After spuds, there'll be pretty much no nutrients left in the compost, but I guess that's not a problem if you're just using it as a base, and then mixing it with some good feed.

I reuse compost, but mostly as either a top dressing to keep our clay soil a bit loose, or in the bottom half of containers.

One extra thing to beware of is pests and diseases that might have bred in the compost, and by reusing it in containers I think you sort of concentrate the problem. I worry less about that on open ground. Not sure if there's any logical reason for that though.

 

This thread is interesting. I have the dilemma of about 10 large 14" pots. I grew dahlias in them last year and have reused the multi purpose compost for tulips, which so far seem to be fine. So that's probably worked.

The challenge now is what to do with it. We only have one bed that I could dump some of it on, but as its good soil and this has no nutrient value it doesn't seem like a good idea.

So I guess now it has to go to the dump?


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I always reuse my old compost. It gets recycled into the bottoms of pots for the following year/s and then eventually gets put on the flower boarders. It may not have many nutrients in it by this stage, Jack, but it is still valuable organic matter.

 

As my soil is quite heavy old compost gets mixed in 50:50 and then I use this in planting holes, the bottom of large pots.
Old grow bags get dug into the vegetable plot. I learnt the hard way not to use on Ericaceous plants when a Rhodendron went and died on me after being mulched with old grow bag compost.

 

I'm totally new to all this so please don't take the piss if I'm wrong but could you not grow a green manure on the old compost after use for a couple months then turn it in and let it break down ??? Would that not replace nutrients in it for the following year ??

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Has anyone used green manure to improve the soil/compost which was used in the past with any success? I tried green manure a few years ago in some large pots which had not been planted in to test.

 

I just posted my above message before reading this

 

I've used a variety of green manures on vegetable plots over the years. This was to help improve soil structure, add organic matter to the soil, suppress weeds and prevent rain damage over the winter.
On a small scale in pots I'm not sure they would have much effect as they would only add small amounts of nutrient to the compost and they require nitrogen to break down when turned in.
I think the main advantage of them is to improve soil structure and add organic matter to the soil.

 

I tend to use re use compost when planting in the garden mixed with some bonemeal are manure