Yield and Growth of Sweetpotato Using Plug Transplants as Affected by Cell Volume of Plug Tray and Type of Cutting

Abstract

Sweetpotato (Ipomoea batatas (L.) Lam., cv. Beniazuma) plug transplants were produced in a closed-type transplant production system using single-node cuttings and shoot-tip cuttings each with one unfolded leaf. The two types of cuttings were grown for 11 days in two different multi-celled plug trays with cell volume of 35 or 55 mL. The four types of plug transplants (two cutting types x two cell volumes of plug trays) and the conventional vine-cuttings as a Control were transplanted in an experimental field on 23 May 1999, and were cultivated for 155 days. The planting density was 50,000 plants ha-1 with intervals of 0.33 m between plants and 0.60 m between rows. After transplanting, the conventional vine-cuttings wilted and it took about 15 days to recover, while the plug transplants grew vigorously without wilting. Storage root yield in fresh mass harvested 125 days after transplanting (DAT) was about 26–31 t ha-1, and was no significant differences among the treatments. It harvested 155 DAT was about 42–48 t ha-1 in the treatments of plug transplants, and 1.5–1.7 times greater than that in the Control (29 t ha-1). The cell volume of plug tray and type of cutting did not affect the storage root yield. Their date support conclusion that the plug transplants can be used as transplant materials and transplanted directly into the field. However, some of the storage roots harvested in the treatments of plug transplants were coiled or irregular in shape.