Mineral composition, biomass and essential oil yield of french lavender grown under two sources of increasing potassium fertilization

French lavender (Lavandula dentata L.) is an ornamental, aromatic and medicinal plant. Potassium (K) is an essential macronutrient for plants and its complementation is a routine practice in crops in weathered soils. The most used source of potassium in Brazil is potassium chloride (KCl), which is often questioned by the presence of the Cl- ion. This study tested the performance of L. dentata plants grown under five levels (0, 50, 100, 200 and 300 mg.dm−3) of K supplied from: KCl and potassium sulfate (K2SO4). Rooted stem cuttings were transplanted in pots, in a greenhouse, with a random arrangement of blocks in a double factorial scheme. At the full blooming, plants were collected and evaluated for morphological characteristics. After, analyzes of the shoot mineral nutrients contents were carried out. The material was also used for the essential oils extractions. The only plant morphological characteristic that showed influence of the treatments was the number of inflorescences, where the plants fertilized with KCl showed superior results, being possible to calculate the maximum flower spikes production when applied an estimated level of 230 mg.dm−3 of K, as KCl. Among the contents of 14 nutrients evaluated, plants grown under KCl fertilizer showed changes in 12 nutrients contents, while plants from K2SO4 treatments showed only six altered nutritional contents. The essential oil yield was higher when K2SO4 was applied, with the maximum calculated yield (1.44%) achieved when the estimated level of 206 mg.dm−3 of K is applied (as K2SO4).