Can i just put wood chip down without any sheet mulch?
Yes! Putting plastic under wood chips is not helpful. The chips will break down in a few years, and weeds will grow in them despite the plastic. Also if the plastic gets exposed, it’s ugly. Putting fabric under wood chips is worse. If you get weeds in the chips eventually, the roots grow into the fabric and make them hard to pull. Both plastic and fabric work better beneath rock mulch, if you can keep the rocks free of debris that will break down to humus. You can skip having an underlayer altogether. In that case, put your mulch thick to smother any remaining weeds and to prevent light from getting to weed seeds in the soil Light triggers germination for many seeds. Do not worry about nitrogen loss in the soil. It has been shown that very little nitrogen is lost, because very little mulch is actually in contact with the soil. (If you till it in, that’s another story.) Wood chips will eventually help the soil by increasing the organic matter in it. The worms will mix it up for you over
