Posted: 26/06/2014 at 13:45
So pretty much the same as a raised bed then - when I filled my raised beds I used a mixture of about half and half topsoil and well-rotted farmyard manure - both bought in bags from the GC.
I then treat them as I would the rest of the garden, adding Fish, Blood & Bone at planting time and later on using tomato or other fertiliser as appropriate.
Each year in the early spring before planting/sowing time I dig in another bag of FYM as I do with the ordinary veg patch.
In the past I've found that if you use bagged potting compost from the garden centre for long term jobs like raised beds the structure breaks down and it becomes thin and dusty after a couple of years.
Hope that helps