Study on the harvest time of cultivated Dioscorea nipponica Makino in Changbai Mountain

To make certain the optimum cultivated fixed number of year and harvest time of D.nipponica,we have mensurated the output and content of diosgenin in different years of D.nipponica in Changbai Mountain.Results showed that the yield of D.nipponica was high after the fruitage ripeness term in autumn or before the scourge-end term in spring;the content of diosgenin in the 2-year-old plant rhizome reached the standard of Pharmacopoeia of People's Repubilc of China.what's more,the content of diosgenin in 3 or 4-year-old plant rootstock is far higher than that in 2-year-old plant rhizome,and the content of diosgenin rhizome in May collection reached the highest.So the best cultivated fixed number of year for D.nipponica in Changbai Mountain should be 3 years,and the best harvest time should be at the middle ten days of May.