Effect of Compost and Bio-fertilizers on Growth, Yield and Essential Oil of Sweet Marjoram (Majorana hortensis) Plant

A pot experiment was conducted to determine the effect of compost and bio-fertilizers on the growth, yield and oil constituents of marjoram (Majorana hortensis L.). Forty five days old seedling were transplanted in soil treated with 15 and 30% aqueous extracts of compost and/or biofertilizers (mixture of Azospirillum brasilienses, Azotobacter chroococcum, Bacillus polymyxa & B. circulans) in addition to the recommended nitrogen, phosphorus and potassium (NPK) doses as control. Use of combined treatment of bio-fertilizers gave better results for all studied traits than those obtained from either nitrogen fixers (Azos. brasiliense, Azot. chroococcum & B. polymyxa) or (B. circulans) alone. The oil percentage and yield per plant for three cuttings was almost twofold higher on fresh weight basis as a result of aqueous extracts of compost at low level + bio-fertilizers compared with control, indicating that combinations of low input system of integrated nutrient management could be beneficial to obtain relatively good yields of essential oil. Oil composition using GC/MS revealed that marjoram belongs to the cis-sabinene hydrate/terpinene-4-ol chemotype. The chemical composition of marjoram essential oil did not change due to the fertilization type or level; rather the relative percentages of certain constituents were affected. The highest level of cis-sabinene hydrate (18.47%) and terpinene-4-ol (24.24%) was obtained with aqueous extracts of compost at 30% + B. circulans and aqueous extracts of compost at 30% + (A. brasiliense + A. chroococcum + B. polymyxa), respectively. Other components showed different concentrations depending on treatment and level of compost.