Effects of soil properties on yield and composition of <i>Rosmarinus officinalis</i> essential oil

The effects of soil on the yield and characteristics of the oil of Rosmarinus officinalis grown in two different areas of Sardinia were investigated. The starting plant material was obtained from cuttings of R. officinalis growing spontaneously on granitic silt soil (Northern Gallura). Cuttings were divided into two homogeneous groups and planted in two different kinds of soil: one predominantly silt with granite and the other with a highly calcareous content (Sassari). The different character of the soil had a significant effect on the yield and composition of the oil. Plants grown in granitic silt soil appeared more luxuriant and had a more intense aroma than those grown in calcareous soil which, on the contrary, showed evident signs of chlorosis. The main difference in the composition of the oil was a higher percentage of oxygenated components in plants grown in calcareous soil. The main constituent of the oxygenated fraction was 1,8-cineole, reaching up to 31% in samples from rosemary grown on calcareous soil. This is particularly surprising since the oil obtained from R. officinalis, which grows naturally in calcareous soil, usually contains markedly lower levels of 1,8-cineole than oil from plants grown in granitic silt. The high content of 1,8-cineole found in the oil of rosemary grown on calcareous soil could be due to selective adaptation to conditions markedly different from the environment in which the plant originated