Effect of Plant Density on <i>Artemisia annua</i> L. Biomass and Essential Oil Yield and Its Weed Seed Germination Suppression
2025
Flavio Polito | Michele Denora | Donato Casiello | Pierluigi Casiero | Loriana Cardone | Vincenzo Candido | Michele Perniola | Vincenzo De Feo | Valentino Palombo | Sebastiano Delfine
During spring–summer 2023 and 2024, an <i>Artemisia annua</i> crop was carried out, using two planting densities (20D = 5.0 plants m<sup>−2</sup>; 40D = 2.5 plants m<sup>−2</sup>). Morphological traits were measured, including height, stem number, diameter, weight, and dry above-ground biomass. The aerial parts were hydro-distilled, and the essential oil (EO) yield increased from the 1st to 2nd year, from 0.117 to 0.439% for 20D and from 0.157 to 0.550% for 40D. There were significant variations in chemical composition between the years, with an increase in the presence of oxygenated monoterpenes in the 2nd year and the disappearance of oxygenated sesquiterpenes. In the 1st year, sesquiterpene hydrocarbons were the main class, while in the 2nd, oxygenated monoterpenes predominated. The main components were artemisia ketone (8.05–65.77%), eucalyptol (4.70–13.14%), and β-selinene (5.38–37.53%), present in all the EOs, and <i>trans</i>-caryophyllene (11.65%), present only in the 1st year EOs. The possible phytotoxicity of the EOs on seeds of plants found in the <i>A. annua</i> crops was evaluated. The most susceptible seeds were <i>Sinapis alba</i>, <i>Papaver rhoeas,</i> and <i>Portulaca oleracea</i>. The phytotoxicity was greater in the 2nd year, with more marked effects on the germination of <i>P. rhoeas</i> and <i>P. oleracea</i> (up to 100%). The inhibition of root elongation reached 100% for those at the higher concentrations tested.
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