Abstract
To make a new growing area for Chinese yam(D.opposita Thunb.), producers need a lot of rhizophore for seed. To establish an efficient cultural technique for its seed propagation, we examined the effects of seed rhizophore weight and planting density on the yield at a commercial field in 1997 and 1998. The suitable size of rhizophore for seed is different from the size for fresh market. The weight of new rhizophore was reduced by reducing the seed rhizophore weight or increasing the planting density. The smaller the seed rhizophore, however the lower the yield. The higher the planting density, the lower the propagation rate of new rhizophore to seed one. With their combination, the problems were resolved. The optimum seed rhizophore weight and planting density of the standard variety GSIA for seed propagation were 20g and 8, 333 plants per 10a, each "Shintanmaru" was 10g and 16, 667 plants per l0a. Under these conditions, all rhizophores were under 350g(cut in four with a standard variety or in eight with "Shintanmaru"). With the smaller seed rhizophore weight and the higher planting density, it could provide smaller new rhizophore for seed in "Shintanmaru."
