The Effect of Open Field and Foil Tunnel on Yield and Quality of the Common Thyme (Thymus vulgaris L.), in Organic Farming

Abstract

Common thyme (Thymus vulgaris L., Lamiaceae) is regarded as one of the most important aromatic plant used both as a spice and medicine. The aim of this work was to investigate the yield and quality of common thyme grown for a fresh herb, cultivated in the organic farming system, within the temperate climate in Poland. Two methods of cultivation were applied: open field and foil tunnel. Three successive cuts of herb were possible to obtain during vegetation season, from the middle of July until the end of September. The raw material was analyzed for the content of essential oil (by hydrodestillation), phenolic acids and flavonoids according to Polish pharmacopeia (PP 6th). The composition of essential oil was determined by gas chromatography-mass spectrometry (GC-MS). Sensory evaluation was carried out by quantitative descriptive analysis (QDA) with a trained panelist. The yield of fresh herb was visibly higher when regards cultivation under foil tunnel in comparison to open field, reaching up to 6.74 kg FW × 10 m2. The content of essential oil as well as the percentage share of thymol (a dominant constituent, achieving up to 57.08%) decreased with consecutive herbal cuts. The opposite result was observed for phenolic compounds (phenolic acids and flavonoids). It was shown that the amount of flavonoids was similar in both variants of cultivation, while phenolic acids were accumulated at higher level in the open field conditions. Sensory analysis indicated on slight differences in odor and taste attributes, between samples of fresh herb collected from open field and foil tunnel.