Assessment of post-emergence herbicides application effects on weed control and grain yield of Dragon's head (Lallemantia iberica) under cold dryland condition

Dragon's head medicinal plant, despite adapted to Iran's dryland conditions, due to low competitive ability with weeds at the beginning of growth and reduced yield, the cultivation and development of this plant is limited. In order to survey the effect of diuron, oxyfluorfen, oxadiazon, and metribuzin as post emergence in different doses (0, 50%, 75%, and 100% of recommended dose) on weeds control in Dragon's head, an experiment based on a randomized complete block design with three replications was done in Dryland Agricultural Research Institute in Maragheh 2020-2021. Treatments including Diuron, Oxyfluorfen, Oxadiazon, and Metribuzin at 50%, 75%, and 100% of the recommended dose, split application of oxyfluorfen (50% at crop emergence, and 50% after 30 days), weed-free (control (hand weeding)), and weed infests (control). Minimum weeds density and biomass was recorded in 100% and 75% recommended doses of Metribuzin and 100% of recommended dose of Oxyfluorfen with 1.9, 2 and 2.2 plants m-2 and 0.33, 0.45 and 0.52 g m-2 respectively at 30 days after herbicides application. At the maturity stage, the minimum weed biomass was observed in 100% dose of recommended of Metribuzin (23 gr.m-2). Maximum Dragon's head biomass and densitywas observed in weed-free (control) and 50% recommended dose of Metribuzin at 30 days after herbicides and the highest biomass and grain yield of Dragon's head was recorded for 100% recommended dose of Metribuzin (76, and 32 gr.m-2, respectively). Based on the results Metribuzin is suitable herbicide for weeds control in Dragon's head field.