We don't use anything on our lawn either. I don't mind dandelions (our bunnies and chickens love them) but the really bad weeds, we just pull. Like those dang stick-tight things that get on everything-I try to pull those when they're small and don't have stickers yet. We don't use any fertilizer either. It just fends for itself. lol.
But as far as the food supply, we're at the mercy of what the farmers use.