Abstract/Summary

There are many factors shown to have beneficial effects on many crop plants. Here we investigate the impact of fertilizers and genetic variation on Rosmarinus officinalis L. measured by both oil yield and quality. Plants grown in a temperature-controlled greenhouse with a natural photoperiod and a controlled irrigation system were treated with seaweed fertilizer and an inorganic fertilizer of matching mineral composition but with no organic content. Treatments were either by spraying on to the foliage or watering direct to the compost. The essential oil was extracted by hydro-distillation with a Clevenger apparatus and analysed by gaschromatography mass-spectrometry (GC–MS) and nuclear magnetic resonance spectroscopy (NMR). The crop responded positively to the application of fertilizer when compared to the control (no fertilizer). The seaweed treatments caused a significant increase in oil amount and leaf area as compared with both inorganic treatments and the control regardless of application method. The application of cytokinin in seaweed form also had a positive role with plant growth and oil production. The chemical compositions of the plants were compared, and qualitative differences were found between fertilizer treatments, application methods, ages of the plant and different genotype. The difference in oil composition were influenced partly by applying seaweed fertilizer. A full chemical analysis of the essential oil was conducted in order to identify the main components. Nine compounds were determined. Eucalyptol and camphene were shown to make up more than half. The other compounds made up the remaining 30%. In general, oil yields are reduced in the older plants whether from those with applied fertilizer or the control. The different genotypes showed a highly significant difference in oil composition and yield compared with other factors affecting essential oil production showing that rosemary plants vary greatly and the correct cultivar should be chosen with reference to its intended final use.