I've seen a number of posts here about growing potatoes within some sort of form (old tires, wooden bins, etc) and then covering the vines as they grow so that you get a longer section of the plant producing potatoes. I've also read how important it is to keep the pH down to prevent scab. So my question is: does the material used to cover the vines also need to have a low pH? I'm planning on trying this next spring with an old 4' x 4' wooden compost bin. I have hay to use to cover up the vines, but I'm wondering if I need to mix it with something to get the pH right. Maybe peat moss or pine needles? And how about watering? Can I lay drip irrigation down on the soil and just leave the built-up mulch material dry? If the covering material stays dry, maybe it's pH doesn't matter?