Application of Lavandula angustifolia Essential Oil Enhances Sustainable Baby Lettuce Cultivation

Chemical fertilizers improve crop yields but poses serious environmental concerns. Biostimulants offer a sustainable alternative by promoting plant growth and reducing the need for synthetic inputs. Essential oils, rich in bioactive compounds have been explored as natural biostimulants, and the effects on plant growth are not fully understood. This study aimed to evaluate the dose-dependent effects of Lavandula angustifolia essential oil on growth, pigments, and mineral–nitrate balance in baby leaf lettuce (Lactuca sativa L.), to assess its potential as a natural and sustainable biostimulant. Baby leaf lettuce plants were foliar sprayed with L. angustifolia essential oil at 0.5%, 1.0%, and 2.0% concentrations and compared to water and an emulsifier (polysorbate 80) used as controls. The effects of the treatments were evaluated by measuring biometric parameters, biomass, pigment content, leaf mineral composition, and nitrate levels. Treatment with 0.5% and 1.0% essential oil significantly increased leaf area, specific leaf area (p < 0.01), biomass (leaf and root fresh and dry weight) (p < 0.05), chlorophyll and carotenoid content (p < 0.001). At 2.0%, a significant decrease in all these parameters was observed. The foliar mineral composition was significantly affected by the essential oil treatment, with notable changes in N, P, Ca2⁺, and Mg2⁺ concentrations, as well as an approximately 30% reduction in nitrate content when lavender essential oil was applied. Foliar application of L. angustifolia essential oil at low concentrations (0.5–1.0%) enhances growth, pigment accumulation, and mineral uptake while decreasing nitrate content in baby leaf lettuce, indicating its potential as a sustainable biostimulant for leafy crops.