A lack of water is one of the main causes of reduced yield. Cycles of hot dry weather, followed by heavy rains which cause rapid growth, resulting in rough, knobby, malformed or cracked tubers. On the other hand, high humidity and excessive rainfall may provide ideal conditions for diseases such as late blight. Drought periods longer than 1 week can greatly reduce the growth of potatoes. On average, potatoes require about 2.5 cm of water per week.
Water is especially important during the period of tuber enlargement.
A moist soil keeps tubers cool during hot weather and thus helps prevent certain diseases and disorders from developing. One good hoeing before plants emerge will save time later. Continue to hoe until the foliage covers most of the soil surface or when plants come into bloom. Besides controlling weeds, hoeing aerates the soil and allows better absorption and retention of water. Hilling around the base of the plants prevents greening or sunburning of the tubers, in addition to providing some degree of frost protection.