Planting density experiments with Dioscorea trifida, Dioscorea alata and Dioscorea nummularia cultivation raised yield by a 50% when going from 14,000 plants to three times more per hectare. Significant gain in yield was not obtained when planting density was raised by 30 to 50% only. High" density planting seems to be economical only with Cush-cush Yam.