we also mulch up the potatoes, as per bob flowerdew, once the soil gets too high, then cover with grass clippings, seems to work for us :)
I recycle the cards by making new ones out of them,
all cardboard goes for mulching up somewhere, under fruit, covering spaces until they're needed, apart from the really silly coloured ones, and small ones like pill packets go in the composter in the garden, as much as I can :)