Weed Interference Duration Effect on Yield and Yield Components of Cumin (Cuminum cyminum L.) in Conventional and Organic Conditions

To investigate the effect of duration of weed interference on yield and yield components of cumin grown under conventional and organic condition, a field experiment was conducted in a private farm in Sabzevar in 2017-2018. A split plot experiment based on a randomized complete block design with three replications was conducted. Factors were conventional and organic growing was considered as the main factor and duration of weed interference (0, 2, 4, 6 weeks after emergence and weedy) as subplots. The results showed that conventional farming in terms of weed density, weed dry matter, plant height, lateral branch number, number of seed per umbrella, biologic and seed yield were better than organic farming, while, number of umbrella per plant under organic farming was higher than that of conventional farming. Increasing duration of interference decreased plant height (20.21%), lateral branches (42.85%), the number of umbrella per plant (47.91%), the number of seeds per umbrella (37.5%), biological yield (33.96%) and seed yield (43.90%). Fitted logistic regression function coefficients showed that the onset of yield loss was earlier (11 days after emergence) in conventional condition while in organic condition it was postponed to 17.5 days after emergence. Overall, the results showed that weed interference, under both conventional and organic conditions, reduced seed yield. Weed interference under organic farming delayed 4 weeks and under conventional condition to 2 weeks after cumin emergence and yield reduction was not significant. Thus, control of weeds in conventional conditions should commence from 12 days after emergence and under organic conditions from 18 days after emergence.