محسن جان محمدی

Moldavian balm is an annual herbaceous plant and its lemon-scented leaves contains essential oil. However, weeds adversely affect its growth through allelochemicals release, and/or direct competition for nutrient, moisture, light and space. Current experiment was conducted to evaluate the different weed control methods including preventive approache (soil pasteurization), mechanical methods (one hand weeding, two hand weeding, and successive hand weeding for weed free condition), and chemical control through synthetic herbicides (haloxyfop-R-methyl and trifluralin). Result revealed that stem diameter, number of secondary branches, number of flower-bearing branches and leaf numbers significantly affected by weed control traetments, sothe highest lateral growth was obtioned by successive mechanical weed control and two hand weeding, respectively. This trend also was observed for canopy spread and chlorophyl content. Pre-emergence control through trifluralin considerably accelerate the initiation of flowering in Moldavian balm. However, investigation of qualitative traits showed that the highest essential oil content and oil yield was related to plant grown under weed free and soil pasteurized condition. Between the recognized essential oils the most responsive composition was were Geranial, Geranyl acetate, Neral and Geraniol. The lowest amount of Neral was recorded for post-emergence control through haloxyfop-R-methyl herbicide.