>When using arborist's wood chips (not retail bark chips) in the garden, the >chips do not bind up nitrogen in the soil if you just lay them on top of the >soil. Here the arborist's chips are free but you do have to take a truck >load, about 10-13 cu.ft. if you are spreading them yourself. In a semiarid climate like mine, wood mulches, like mulches of other organic matter, prevent rainfall from reaching the soil. I use gravel, or no mulch at all. Bob Nold Denver, Colorado, USA