Holding of cut-sprouts in sweet potato (Ipomoea batatas Lam.). III. Effects of holding on the field establishment, formation and yield of tubers.

Abstract

Effects of holding of cut-sprouts in sweet potato on the field establishment of cut-sprouts, the formation and the yield of tubers were investigated in the field condition with polyethylene film mulching using cv. Koganesengan and Kokei 14 in 1985 and 1986. The holdings were carried out under the condition with 13.5±1°C, 80±3%RH and weak light. Most leaf blades in the non-holding cut-sprouts wilted down to the soil surface after planting, whereas few leaves wilted down to the soil surface in the 5-10 day holding cut-sprouts. Although the survival ratio of cut sprouts was nearly 100% in every treatment, the number of leaves and transpiration rate of the 2nd or 3rd leaves from the terminal one at 1 or 2 weeks after planting were higher in the 5-10 day holding than in the non-holding. At 5 weeks after planting the number and the dry weight of tubers in the holding were higher than in the non -holding. The total dry weight and leaf area tended to increase with the holding practice. Although there was no significant difference in the tuber yield among the holding periods in 1985, higher yields at 1% significant level were obtained in 1986, and the number of tubers and average weight of a tuber tended to increase in the holding. The increases of total dry matter and harvest index were found in the holding. These seemed to bring about the yield increase in the holding.