Compost....

I need to fill four half barrels (so around 180 litres each) with ericaceous compost for my blueberries, but that is going to be a tad costly - I have some barely used 'spent' compost (ordinary general purpose) which I was thinking of using for the bottom half of the barrels - however it's PH will be all wrong. Is there anything I can do to change it/improve it for the blueberries or am I as well sticking with the ericaceous stuff

 

I wouldn't use the mushroom compost, as you know it has added chalk to make it alkaline, the opposite to what blueberries want. So the aim is to save money? Rather than buying ericaceous maybe you could use Wickes Multi-purpose, from memory it has some 80% or more peat so should have a low pH. Peat in itself is acidic and used to be the major component of ericaceous composts. I have a bag of Wickes MPC at home and if I remember I'll stick my pH meter in it later so see what it says. It's currently on offer at 4p/litre (you'll need eleven 70l bags will be £27.39 in total).

If the pH is still too high you can add acidifiers like Sulphur chips (slow acting) or Ferrous Sulphate (quick and easy to find in a GC).

 

Ah, sorry for the confusion - when I say 'spent' compost, I didn't mean the mushroom stuff. It is simply the old stuff from this years growing (brassicas and carrots mainly) - all I was thinking of doing was using it for the lower half of each barrel topping off with the new ericaceous which would be more than deep enough for the current rootballs. The MPC I have is Homebase stuff, but I don't have a PH meter to check it.

Could I just add sulphur chips to the lower part before whacking the ericaceous on top?

 

Thanks

I will need to see if I can find sulphur chips at the garden centre. Is there a recommended dosage rate?

 

My turn to apologise FC, I miss-read your post, it's quite clear what you said, I somehow thought you had mentioned mushroom compost.

Anyway I just had a look at my bag of Wickes MPC and it is labelled as being in the range pH 5 to 6 which would be ideal.

Now I realise you have old MPC I would think that is just as good for a base. Yes add some suplur to that then top up with ericaceous or maybe a soil/loam based compost such as John Innes, as MPC especially peat based can dry out especially in containers.

 

Thanks @JWK - I got 300 litres of Westland GroSure Ericaceous last night (still in the car boot), so just need some sulphur and I am sorted.