Low-dosage foliar application of nanosized macro- and micro- nutrients for enhanced yield of high-quality Rosemary oil

The quantum of nutrients supplied for efficient Rosemary plant growth and high-quality essential oil (EO) yield is relatively high, posing an environmental hazard. Therefore, developing nutrient management strategies that reduce environmental impact while maintaining or enhancing Rosemary plant growth, bio-fortification, secondary metabolite content, and EO yield is imperative. In this line, this work reports a simple mechanical milling strategy that enables low-dosage foliar application of nanosized macro-nutrient and micro-nutrient particles for extraordinary Rosemary plant growth, bio-fortification, enhanced secondary metabolites, and high-quality EO yield even at a considerably lower nutrient supply. Even for a much lower dosage than the recommended dosage, a considerable increase in the total plant weight and in nitrogen (N), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) content in plant shoots, in excellent correlation with their enhanced availability on the surface of the nanosized nutrient particles, is achieved. More importantly, an increase in the concentration of 1,8-cineole (a key metabolite in EO and the quality descriptor of EO) in EO extracted from the plants cultivated using nanoscaled nutrients at much lower inputs is achieved. The enhanced concentration of 1,8-cineole is attributed to the increased presence of Zn, Mn, and Cu, which elicit specific pathways for synthesizing 1,8-cineole in plants. This work offers a simple, scalable, sustainable alternative strategy to conventional high-nutrient-input agricultural practices. • Ball milling was used to reduce the size of macro- and micro-nutrient particles. • Size reduction to the nanoscale enhanced the nutrients’ surface availability. • Enhanced surface availability enabled the possibility of low dosages of nutrients. • Low-dosage foliar spraying of nutrients enhanced oil yield and quality in Rosemary. • The improved quality of Rosemary oil was due to enhanced 1,8-cineole content in it.