feeding potatoes

when do  i feed my potatoes? first earlies are through now but had manure the autumn before, so I think they are ok.  The second earlies are coming through and I have read that they need feeding but when, is it round the base when the foliage is up? and is this the same for the main crop?  If so what do I feed them ??
Sorry for the long winded question but my earlies some have long stalks already and is this good or not??
Denny

Yes to the piont that the earthing is a big mound, but they still look longer than anybody elses??

I hope so, they are red duke of york and I am so looking forward to eating them what about feeding the others, when and what with. regards Denny

Thanks all for all your help regards Denny