Ade wrote:
My allotment has a severe drainage problem so I'm building raised beds,
which I hope will help. As well as manure and compost, I want to add
something else to improve drainage. It's clay soil. What should I use --
pea gravel or sand (builders sand?) or something else?

How deep do you need your beds to be?! You've added manure and compost
- is this around 30cm depth?! If so, I think that the manure will
improve your soil and if you keep adding it on top years after years
you'll end up with fantastic beds. I wouldn't start using gravel or
sand because you don't know what you'll grow say in 2 years time. It
depends on your rotation plan but also what you want to grow. I had a
corner on my lotty so compact with clay I thought nothing would ever
grow. I've added manure for 2 years - then potatoes and now perhaps 2
spit down it is clay but there's enough manured top soil to grow my
leeks this year, garlic and kale walking sticks )