As in the heading, I have a lot of straw and wondered if putting around apple trees to kill weeds is a good idea.
I have used it round my artichokes.
Grass cuttings work, so staw would doubtless work as well. It might blow about a bit, which is the big drawback of autumn leaves, if you used it on bare ground.
My plot neighbours did it, actually from the manure pile but the choose mainly straw. They have done it several times now. Apples seem to be doing well. Keeps the weeds down under young trees.