Cool Soil Increases Potato (Solanum tuberosum) Tuber Number in Multiple Varieties and Alters Skin Color Intensity of ‘Red Norland’ and ‘Adirondack Blue’

Potato tuber number, size and quality determine crop value. Elevated soil temperature often reduces yield and quality. Effects of cool soil are less well understood. Potatoes were grown in a greenhouse with 22 °C days and 18 °C nights. Shortly after emergence, soil temperature in some pots was lowered to 10–14 °C using cooling coils wrapped around individual pots. Soil temperature of ambient temperature controls was 17–21 °C. Tuber number and total tuber weight were determined for two chip and four fresh market varieties grown in chilled and ambient temperature soil. Tuber number with chilled soil averaged 3.2 times that of controls. Tuber weight was comparable between the two treatments. ‘Red Norland’ skin was lighter red and ‘Adirondack Blue’ skin was darker purple with chilled soil compared with controls. Skin color was unchanged for the other varieties. Overall, the data suggest that cool soil influences commercially important characteristics of potato.