Rosemary: controlled drought increases yield and quality of essential oil. The results of experiments conducted in Sicily as part of a project in which the Sant'Anna School was one of the partners

Controlled drought can increase the essential oil yield of rosemary by up to 30 per cent, making this plant an ideal candidate for enhancing marginal agricultural land with limited water availability. The result comes from a study carried out bytheUniversityof Pisa, the National Institute of Optics INO-CNR Pisa, the Sant'Anna School (Institute of Plant Sciences) and the University of Catania that was published in the journal Industrial Crops and Products. The trials were conducted in Sicily, on farms in the province of Ragusa, between autumn 2022 and spring 2023.
 

‘Rosemary (Salvia rosmarinus Spenn.) is a medicinal and aromatic plant native to the Mediterranean that produces essential oils known for their antimicrobial, antioxidant, anti-tumour and anti-inflammatory properties,’ explains Celia Duce, associate professor at the Department of Chemistry and Industrial Chemistry at the University of Pisa, ‘and when subjected to stress conditions, particularly abiotic stresses such as drought, it intensifies the production of essential oils as a defensive mechanism.

The experiments were planned together with the farmers, who chose the fields to be used for the experiments and the rosemary varieties to be used. Two different varieties of rosemary were tested, ‘Tuscan blue’ and ‘Barbecue’. Water stress was applied for three weeks before harvesting, i.e. during the autumn and spring balsamic period, a crucial phase in which the synthesis and concentration of essential oils reach their peak.

The result was an increase in yield of up to 30% in plants of the ‘Tuscan blue’ variety grown on a farm in the municipality of Scicli, in Sicily. The water stress also significantly altered the chemical composition of the essential oils, changes that are crucial for the industry as they can improve the aromatic profile and bioactive properties.

‘The study is part of a larger project called InSole - Agronomic and technological innovations for the sustainable cultivation of medicinal plants and the production of quality essential oils,’ concludes Federico Leoni, a research fellow at the Scuola Superiore Sant'Anna, ’financed by the sub-measure 16.1 of the 2014-2022 Sicily RDP, whose aim is to create a sustainable supply chain for the production of essential oils in Sicily, supporting farmers in adopting agricultural practices that optimise the use of resources, particularly water. The main idea is that through the application of moderate water stress close to the balsamic period can increase the concentration and quality of essential oils in rosemary, without significantly compromising the biomass yield'. 

The link to the scientific study is available HERE.