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