Verification of Optimal Dioscorea alata Thunb Harvesting Stage for Improvement of Tuber Yield and Storability
Background : Unlike Dioscorea japonica or Dioscore opposita, Dioscore alata is a high-temperature crop mainly cultivated in Africa and subtropical regions. Due to recent climate change, its cultivation area is expanding in Korea. In 2016, the Institute for Bioresource Research clarified optimal harvesting stage to increase its tuber yield and ensure safe storability. Methods and Results : As the seed-tubers for this study, Dioscorea alata tubers were cut into a size of 50 g, disinfected with lime powder, dentated on the seed bed with electrothermal wire installed on March 20th, and then planted on the main field on April 15th. The planting distance was 120 ㎝ in width, where the furrows of 90 ㎝ were cladded with black vinyl, in two rows with a column spacing of 25 ㎝. The amounts of applied fertilizers were 2,000 ㎏ compost, 34 ㎏ N2, 28 ㎏ P2O6, and 28 ㎏ K2O. The compost and P2O5 were used in full, where as N2 and K2O were used as original fertilizer 14 (10 ㎏) and additional fertilizer 20 (18 ㎏), respectively. The crop was harvested in six times from September 20th to November 9th, in an interval of 10 days. While harvesting, the ground fresh weight yield and underground tuber yield were investigated. The underground tuber yield was 836, 1,744 and 2,975 ㎏ low at the early harvests on September 20th, 30th, and October 10th, respectively, while it was 3,622, 3,828, 3,818 ㎏ high on October 20th, 30th, and November 9th, respectively. The ground fresh weight yield remained the same. To clarify tuber storability by harvest time, they were stored at 15℃after harvest, and then healthy and corrupt tubers were studied on March 23th. The corruption ratio by harvest time was highest at 39.1% and 29.3% on October 30th and November 9th, respectively, when frost and low temperature damaged harvest. It was 59.0% and 42.8% at the early harvests on September 20th and 30th, respectively. The corruption ratio was lowest on October 20th and October 10th at 29.3% and 39.1%, respectively. Conclusion : Ford. Dioscore alata cultivation, Korea presents a premature and disadvantageous environment with lower temperature and pre-harvest frost at the time of planting. After raising seeding on an electrically heated hot bed, the optimal harvesting stage should be from planting in the middle of April where temperature rises above 1 5℃ to harvesting in the period October 10th - 20th so as to achieve the maximum tuber yield and high storability.