I've only started gardening this year. I have some raised beds, 3m x 1m
each, in which I'm trying 'square foot gardening' (hampered mainly by the
slugs and local cats) and a lot of tubs and pots.

What do I do with spent compost from the pots and tubs? I've been doing a
form of crop rotation in some tubs - peas followed by carrots, for
instance - but I've got a good 100l of compost that I grew potatoes in that
I know I can't grow the next set of potatoes in, in case of disease. So what
can I do with this compost? I'll use some of it to fill up the raised beds
but I can't do that every year. Does it go in the compost bin to help out
there?

I've just realised I can shove a fair bit of it on the borders but even so,
I'll take answers!