A field experiment was conducted during the main cropping season of 2014 at Koba, North Eastern Ethiopia, to investigate the effects of seedling age and transplanting date on the yield and yield components ofte.ff A factorial combination of four seedling ages (15, 20, 25 and 30 days old teff seedlings) and three transplanting date, (first transplanting date, second week of July), transplanting delayed by ten days after the first transplanting date and transplanting delayed by 20 days after the first transplanting date) was laid out in a randomized complete block design (RCBD) with three replications using improved teff variety called Zobel (DZ -01- 1821) as a test crop. Phonological traits and yield and yield components were taken as experimental variables . Seedling age resulted in highly significant differences (p < 0. 01) for all Phenological traits and yield and yield components except straw yield which was significant at(P < 0. 05). Transplanting date was also highly significant (P < 0. OJ) affected days to physiological maturity, number of effective tillers plant", number of total tillers plant 1, EFFECTS OF SEEDLING AGE AND TRANSPLANTING DATE ON YIELD AND YIELD COMPONENTS OF TEF [Eragrostis tef (ZUCC.) TROTTER] AT KOBO , NORTH EASTERN ETHIOPIA BY Tizazu Mulugeta Major Advisor: Dr.Getachew Alemayehu ABSTRACT panicle length, grain yield, biomass yield and harvest index. But transplanting date didn't show any significant effect onl 000 grain weight, plant height and straw yield. The interaction effect of transplanting date and seedling age was also highly significant (P < 0. 01) on all Phonological traits and yield and yield components except straw yield. Grain yield of teff had positively and significantly correlation with all yield contributing parameters except days to heading and straw yield. Higher grain yields of 7.29 and 6.91 t ha·' were obtained by transplanting of 25 and 20 days old seedlings on second week of July, respectively. Hence, considering the growth and yield results of the present study, transplanting of 2 5 and 20 days old seedlings on second we~k of July can be suggested v~i~~e~'$..uction