Winter and summer performance of potato (Solanum tuberosum) in isohyperthermic regimes

Potato production in isohyperthermic temperature regimes (mean annual soil temperature higher than 22°C) has been considered impractical physiologically and economically. However, recent experiments with potatoes (var. Kennebec) on a clayey, kaolinitic, isohyperthermic Tropeptic Eutrustox of Hawaii during the winters of 1980 and 1981 and the summer of 1980, indicate that although seasonal variation in the tropics is minimal when compared to temperate regions, there is enough of a distinction in temperature that potato production is possible and favored during the cooler winter months. Soil temperatures, measured at 20-cm depth, in irrigated plots range from 18 to 20°C in winter and 24 to 26°C in summer. Tuber initiation in winter and summer began at 40 and 55 days after planting, respectively. Maturity was delayed by 20 days in summer. Yields in irrigated plots were 36,000 in winter and 25,000 kg/ha in summer; in nonirrigated plots, yields were 14,600 in winter and 7,900 kg/ha in summer. Nutrient uptake and water and energy use were less efficient in summer. The results indicated that winter is the most suitable season for potato production in the warm tropics.