This experiment was carried out to clear optimum planting time for yield enlargement by comparing yield with dry matter at Miryang from 2005 to 2006. Variety used were Daewon, Daepung, Daol and Cheongja 3. Seeding was performed on April 30 to June 30 with 20day intervals and planting density was 142,857 palnts/ha (70×20㎝, 2plants per hill) with black vinyl mulching. In R2~R4 stages, crop growth rate(CGR) was largest on June 10 seeding. Although net assimilation rate(NAR) increased as seeding date was delayed, NAR on June 10 seeding was the highest throughout the growth period. Positive relationships were observed between NAR from R2 to R4 the ratio of pod to total dry matter weight. The LAI and total dry matter weight at the R4 stage was higher at earlier seeding date. In the case when seeding date was delayed, the ratio of leaf(source) and pod(sink) increased. From the comparison of all factors such as dry weight, optimum LAI, and of source to sink, the optimum planting date for high seed production was June 10. The highest yield was recorded with on June 10 seeding. Also, this seeding date showed high ratio of seed yield to dry matter in R2 stage. Difference between surveyed pod no. and theological pod no. which was calculated by dry matter ratio compared with standard seeding date(June 10) at R2 stage was the smallest in June 10 seeding.