Plastic Mulching or Conventional Cultivation of Lavender Flower: What Influence on the Yield, Essential Oil and Their Neuroprotective Effects?

Lavender (Lavandula angustifolia Mill.) flowers and its distilled products are of major raw materials for cosmetic, perfumery, medicine and cleaning industries. Lavender flower production, essential oils and their qualities are affected by growing conditions and used agricultural methods. Mulching is a cultural application used for horticultural production in order to combat weeds, keep the soil temperature constant, eliminate soil moisture evaporation, provide favourable growth conditions for ample flower production, and improve the quality essential oil production. In this sense, plastic mulch application is the mainly preferred method by the growers, due to its low costs and durability. In the present study, two-year field (2014-2015) studies were carried out to evaluate the lavender flower production, essential oil yield in both conventional (without mulch) and plastic mulching systems in city of Kilis-Turkey. The individual essential oil compounds were identified using Gas Chromatography-Mass Spectrometer (GC-MS). Essential oils obtained from dried flowers were assayed for their neuroprotective effects. According to the results, fresh and dry inflorescence yields, dry flower yields, flower essential oil contents and compositions were affected by different growing methods, including (1) plastic mulching system and (2) conventional (without mulch) system. Considering the fresh inflorescence changes, mulching increased the yield by 147.84% in the first year while no significant changes were noted between treatments. Interestingly, dry inflorescence yield did not show a significant increase for both growing systems at first year but mulching enhanced the yield by 9.87% in the second year, in related to the traditional treatment. The results revealed that dry flower was not affected by both growing systems corresponding to the years. As for essential oil content, no changes were noted for both growing systems in the first year, whilst mulching increased the content by 13.73% in the second year. As the case of agricultural yield, the neuroprotective activities of essential oils obtained from mulching conditions exerted higher inhibitory roles against Acetyl-cholinesterase (AChE), butyryl-cholinesterase (BChE), and tyrosinase (TYRO) enzymes, in relative to the traditional treatments by 81.62%, 84.12%, 73.34% in the first year and by 76.15%, 79.80% and 68.02% in the second year. Such a high variation in neuroprotective activities can be explained by changes in essential oil contents, as observed for the percentage of the compounds. Consequently, these findings reveal that mulching application significantly contributes to the increase of agricultural yield and the growing of medicinal and aromatic plants that are more resistant to changing environmental conditions and biotic stress factors.