By David_clarke
United Kingdom 
I have just acquired an allotment & plan to have some raised beds as the soil is clay based.
I will be using scaffolding boards which are 9 inches wide, therefore if I sink them just one inch this leaves 8 inches in which to fill.
Q1 - Is it best to use a combination of top soil & pro grow or will it be ok to use just pro grow.
Q2 - As I will have 8 inches of hopefully good quality soil will I need to work the allotment soil at all & if so what will need to be done.
20 Mar, 2011
Previous question
I would cultivate the soil, because clay soil with grit and humus (rotted manure or compost) added is usually very fertile and would be fine for brassicas for instance without bothering with raised beds. Raised beds would probably be better for root crops though as they do better with a finer grained soil. I think you would need to bury your boards more than one inch deep unless you secure the corners very securely or they would probably not be very stable.
21 Mar, 2011