The influence of defoliation date and harvest interval on the quality of potatoes for french fry production

Summary Trials were carried out in 1984, 1985 and 1986 in which the effect of four dates of defoliation (0, +10, +20, +30 days) and three intervals to harvest (0, +10, +20 days) on yield, tuber size, dry matter, reducing sugar, fry test colour and finish fried sensory quality were examined for two cultivars (Pentland Dell, Maris Piper) on two sites (medium silt, peaty loam). Dry matter content and yield of tubers were influenced by all factors in the trial. Later dates of defoliation gave the lowest reducing sugar levels, palest fry colour, highest yield and dry matter content. Increasing the interval from defoliation to harvest reduced dry matter and raised yield. Significant year effects were obtained for dry matter and reducing sugar content.