Inverse Temperature Studies to Reduce Canopy Growth of Sweetpotato

Sweetpotato [Ipomoea batatas (L.) Lam.] cv TU-82-155 was grown in controlled environments to determine if inverse day/night temperatures could effectively control the height of the canopy without adversely affecting storage root yield. Plants were exposed to temperatures of 18/24, 24/18, 20/26, 26/20, 22/28, and 28/22°C (Experiment 1); 22/28 and the control 28/22°C (Experiment 2); and in Experiment 3, 28/22°C for the first 6-8 weeks of growth and then 22/28°C thereafter, and 22/28°C continuously. Storage root yield was either reduced by about 50% among plants grown under cool days and warm nights (Experiment 1), was similar to the control plants if plant population was increased (64 vs. 48 m^-2, Experiment 2), or if cool days/warm night regimes were initiated 6-8 weeks after planting (Experiment 3). There was a substantial reduction in canopy growth (height) for inverted temperature treatments. For every 2 °C decrease there was a 3.1 cm decrease in canopy height. Canopy height was effectively controlled regardless of whether cool days/warm night regimes were initiated at planting or 6-8 weeks after planting. The reduction in storage root yields can be arrested if plant population is increased from 48 to 64 plants m^-2 or if temperature treatments are initiated 6-8 weeks after planting.