Well, the soil ain't no friend to metal, but a good old coat of oil will keep it from rustin’. First, clean the blade clean, no dirt or grit. Then rub a thin layer of linseed oil or even a little beeswax on it – that'll create a barrier. Store it in a dry place, maybe wrapped in cloth, and avoid keeping it in damp earth. If you see any rust start, scrub it off with steel wool and reapply oil. That's the old way, simple and steady.