The Relationship Between Soil Temperature and Sugar Ends in Potato

Sugar ends is a serious defect in processed potatoes. Among the more important factors associated with the development of sugar ends are soil temperature and soil moisture, particularly during early tuber bulking. This 2-year study was designed to examine the effects of soil temperature on the development of sugar ends. Soil temperature was recorded in different zones (0-10 cm and 10-20 cm depths) of potato rows oriented in north-south and east-west directions. At harvest, tubers from four sections in each field were hand excavated from each quadrant of the hill. The rows were divided vertically through the center and horizontally at the 10-cm depth. Tubers from each quadrant were weighed and then evaluated for fry color after 3 months of storage. Temperature profiles within the different regions of the row showed considerable variation throughout the season. Row orientation had a slight effect on soil temperature, but soil depth appeared to be more important. The deeper portion of the row (below 10 cm) was generally cooler throughout the day. East and north facing portions of rows also tended to be cooler than the opposite side that was exposed to more solar radiation. The highest yields and highest incidence of tubers with sugar ends tended to be found in areas below 10 cm in depth. These results contradict the notion that soil temperature is the primary factor leading to development of sugar ends. Therefore, individual tuber growth rate and temperature exposure of the entire plant may be more important in causing the development of sugar ends than was previously thought.