Controlled drought can increase the yield of rosemary essential oil by up to 30%, making this plant an ideal candidate for the enhancement of marginal agricultural land and land with limited water availability. This is the result of a study carried out by the University of Pisa, the National Institute of Optics INO-CNR Pisa, the Scuola Superiore Sant’Anna and the University of Catania, which has been published in the magazine Industrial Crops and Products. The experiments were conducted in Sicily, on farms in the province of Ragusa, between autumn 2022 and spring 2023.
“Rosemary 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 Professor Celia Duce from the Department of Chemistry and Industrial Chemistry of the University of Pisa. “Under stressful conditions, particularly abiotic stresses such as drought, the production of essential oils increases as a defensive mechanism.”
Researcher of the University of Catania and first author of the paper, Valentina Formica working in the lab
The trials were planned together with the farmers, who selected the fields to be tested and the varieties of rosemary to be used. Two different varieties 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 when the synthesis and concentration of essential oils reaches its 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 Scicli area. Water stress also significantly altered the chemical composition of the essential oils, leading to changes that are crucial for the industry as they can improve the aromatic profile and bioactive properties of the oils.
“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 – funded by Sicily RDP 2014-2022, which aims to create a sustainable supply chain for the production of essential oils in Sicily, helping farmers to adopt agricultural practices that optimise the use of resources, especially water,” concludes Federico Leoni, researcher at the Scuola Superiore Sant’Anna. “The main idea is that by applying a moderate water stress close to the balsamic period, the concentration and quality of essential oils in rosemary plants can be increased, without significantly affecting the biomass yield.”