onions/leeks

Hi have 4 plots to rotate on my allotment am confused as to where to put onions and leeks any help please

Onions, garlic and shallots are usually grown with the other roots such as carrots, beetroot and parsnips in the rotation as their management through the season is similar.

I include leeks in with them because they share onion diseases and like carrots, parsnips, and usually carrots, stay in the ground until now. I grow a catch crop of salads before the leeks are planted out in July.