Don't allow sprout to get too long or you will weaken seed and sprout will break off too easy. Soil Preparation Its important to loosen the soil well for a potato crop. Work the soil to a depth of 18 inches if possible. This allows good root and tuber development. Some humus can be very beneficial for potato production.
Potatoes prefer slightly acidic soil, alkaline soil can lead to somewhat scabby potatoes.
Potatoes respond to calcium and a balanced fertilizer program of nitrogen, phosphorus and potassium. Some varieties prefer splitting the total nitrogen application. Consult the varieties profiles for details . If you want to grow organically, working in 100 lbs. In both cases work the fertilizer in well before planting.