Advice by this gardening guru says to make the soil slightly acidic by adding oak leaves, sawdust, or pine needles to the soil, dust seed potatoes with sulfur just before planting, avoid adding manure or lime, but add bone meal (high in phosphorus) and mound periodically with new soil before the plants start to flower.  But don’t hoe after that because you’ll disturb the shoots the potatoes are forming on.

Never add a fertilizer high in nitrogen to your potato patch as it will produce plants as large as you but no potatoes will develop. Go here for more details:  http://rainyriverrecord.com/node/4553

You can also add sulfur to lower the ph.  To calculate ph to know how much sulfur to add to the soil before planting, go here:  http://homeguides.sfgate.com/add-sulfur-potato-beds-93337.html