the effect of irrigation intervals and harvesting time on grain yield and essential oil of anise (pimpinella anisum l.)

in order to investigate the effect of irrigation intervals and harvesting time on yield and yield components of anise (pimpinella anisum l.) a field experiment was conducted at the agricultural research station, university of zanjan in 2010. for this purpose a spilt-plot experiment based on complete randomized block design with three replications was used. three irrigation intervals (every 7, 12 and 17 days) allocated in main plots and three harvesting time, including harvest at soft dough (waxy), hard dough and full maturity stages allocated to sub plots. the results indicated that effect of  irrigation intervals on majority of measured traits including number of seed in umbellet, number of seed in umbrella, number of umbrella in plant, seed thousand weight, grain yield, grain essence content and essence yield was significant (p ≤ 0.05). with increasing irrigation interval from 7 to 17 days, majority of measured traits such as grain yield and essence yield decreased significantly but grain essence content significantly increased. so the highest grain yield (636.07 kg/ha) and essence yield (23.76 kg/ha) was obtained in 7 days irrigation interval and the lowest amount of mentioned traits was obtained from 17 days irrigation interval. also harvesting time had significant effect (p ≤ 0.05) on some of traits including seed thousand weight, number of seed in umbrella, grain yield, grain essence content and essence yield. so with delay in harvesting time from hard dough to full maturity stage, number of seed in umbrella, grain yield, grain essence content and essence yield significantly decreased. the results also showed that interaction effect of irrigation intervals and harvesting time on grain yield was significant. the highest grain yield was obtained with 7 days irrigation interval and hard dough stage.