The effect of weed control on growth, yield and physicochemical properties of valerian (Valeriana officinalis L.)

A limiting factor in valerian production is weed interference so, the crop protection from weed is essential. Field experiments were conducted for two consecutive seasons (20142015) to evaluate different weed control methods on growth, yield, and oil quality of valerian in Iran. The experimental design was a randomized block with 7 treatment and 4 replicates. Treatments included untreated control, manual weeding, barley straw, sorghum straw, wheat, black plastic and postemergence oxadiargyl. The lowest density and dry weight of weeds was related to the manual weeding treatment. Result showed that the maximum growth parameters of valerian were obtained from manual weeding treatment followed by black plastic, barely straw and sorghum straw reflecting superior weed control. Essential oil analyses indicated that bornyl acetate, valerenal, camphene and αpinene were the most abundant constituents. These components on average represent 27.7, 14.7, 4.1 and 2.2% of the oils that were extracted from plant, respectively. Bornyl acetate, valerenal and camphene contents did not vary with the various studied treatments although there was a trend toward higher in manual weeding treatment. Overall finding of current experiments suggested that barely straw and sorghum straw are potential substitutes for manual weeding and black plastic mulch for weed control in valerian.