how can nitrogen be "tied up"
I was considering putting down mini bark nuggets on my raised veggie beds as a mulch but I've been reading here and there that bark nuggets and wood chips tie up nitrogen.
What does tying up nitrogen really mean? If I don't mix the mulch into the soil (by using it only as a top layer) I won't have to worry about it breaking down. If I ever want to ammend my beds, I would simply rake the nuggets off, place them into a wheelbarrow, make my ammendments and reapply the nuggets.
Just (still) trying to figure out the best option for mulching my beds before the heat kicks in a few weeks from now.