Fertilizer Source in Biomass Production and Quality of Essential Oils of Thyme (Thymus vulgaris L.)

Aims: The goal of this study was performed in order to test the effect of the source of crop fertilization and harvest days in the production of biomass and measure the qualitative and quantitative properties of the principal components of the essential oil of thyme.

Study Design: A randomized complete block experimental design with five replications and a factorial arrangement was used.

Place and Duration of Study: The experiment was at the Colegio de Postgraduados, Campus Montecillo (Texcoco, Mexico), during the 2007 spring-summer season.

Methodology: We included three harvests at 60, 90 and 120 days after transplantation. The organic fertilization was with applications of humic acid in the irrigation and by adding a liquid fertilizer combined with biosynthetic amino acids. Steiner solution at 75% concentration was used for the inorganic fertilization as mineral treatment. We evaluated plant height, fresh and dry biomass of the plant, and main stem diameter. Essential oils were extracted using steam distillation of water. The concentration (μg/mL) of thymol and carvacrol was determined. Quantitative and qualitative comparisons were carried out by thin layer chromatography (TLC) and gas chromatography-mass spectrometry (GC-MS).

Results: The results show that inorganic fertilization increased plant height (PH) by 36.8%, fresh shoot biomass (FSB) by 72.19%, fresh root biomass (FRB) by 59.27%, stem diameter (SD) by 12.15%, and dry shoot biomass (DSB) and dry root biomass (DRB) by 69.85% and 68.15%, respectively. Days to harvest (DH) influenced positively (p=.05) the evaluated morphological characters but they did not show differences in the total yield of essential oil.

Conclusion: Our data show that fertilizer source modifies fresh and dry biomass production in thyme plants. The total yield of essential oils in thyme was not affected by days to harvest and fertilizer source. However, essential oil quality was higher in the mineral treatment at 90 DH due to the content of thymol and carvacrol in the extract.