Effects of seed rhizophore weight and planting density on the yield of a high yielding variety of Chinese yam (Dioscorea opposita Thunb.)

To establish a cultural technique for commercial production of a new high yielding variety of Chinese yam (D, opposita Thunb.) "Shintanmaru", we examined the effects of seed rhizophore weight and planting density on the yield at a commercial field in 1997 and 1998. The heavier the seed rhizophore, the higher the yield, but the increase in the yield was cancelled by the increase in the cost of heavier seed rhizophores. On the other hand, the yield was not reduced by reducing the weight of seed rhizophore to a half. Therefore, the use of small seed rhizophore may be suitable for a high yielding variety. By increasing the planting density, the weight of each harvested rhizophore was reduced, but the yield per area was increased due to the increase in the number of harvested rhizophores. However, the number of most marketable rhizophores over 250 g in weight per plant was reduced by the increase in planting density. Therefore, the planting density of the high yielding variety like "Shintanmaru", for the fresh market should be the same as other standard varieties; 120 cm between rows and 30 cm spacing between hills.