Factors influencing the performance of planting material in Dioscorea alata L. and Dioscorea cayenensis Lam.

The effects of sett type and sett weight, methods of planting and cultivation system on the sprouting and tuber yield of White Yam (D. alata) setts were studied. In addition, the sprouting of Yellow Yam (D. cayenensis) setts was evaluated based on maturity and storage of mother tubers, sett type, and sprouting media. A preliminary study was also done to select seasonal types of Yellow Yam on the basis of uniformity in sprouting. With White Yam, the results indicated that head setts of the lower sett weights showed higher rates of sprouting than middle and tail setts of the same weight. All sett types gave similar sprouting percentage at the 90 g sett weight. White Yam setts planted directly in the field showed delayed plant establishment when compared to transplanted setts. Mulching resulted in higher percentage plant establishment than treatments without mulching in White Yam. With Yellow Yam, seven seasonal types were selected on the basis of uniformity in sprouting. Based on the cropping system practiced, Yellow Yam showed a growth cycle ranging from 13 to 15 months. The sprouting percentage of setts derived from mother tubers harvested after 10 and 11 months of field growth, was more influenced by the age of the setts than by the duration of tuber storage time or sett nursery time. The sprouting percentage of setts taken from mother tubers harvested at 12 months after planting was influenced more by the duration of tuber storage time before sett preparation than by that of sett nursery time. There was a direct relationship between sett weight and percentage sprouting of Yellow Yam setts. Although head setts were superior in sprouting compared with middle and tail setts, the differences diminished with time after planting. Suggests that none of the media tested were better in terms of sprouting than the fresh saw dust with pine, which is normally used. In general, it was observed that D. alata setts gave earlier and more uniform sprouting from lower sett weight than D. cayenensis setts. With regards to tuber yield, there was a positive relationship between sett weight and tuber yield for head and tail setts in White Yam. Mulching resulted in significantly higher tuber yield in White Yam than treatments without mulching. Concludes that small setts (preferably 90 g) planted directly in the field, with mulching may be appropriate for the production of White Yam. As for Yellow Yam setts, the sprouting is influenced by a number of factors which include, sett weight, sett type and maturity of mother tubers.