Effect of Nutrition and Harvest Time on Growth and Essential Oil Content of Thymus vulgaris L.

Abstract

Thyme (<em>Thymus vulgaris</em> L.) is an important medicinal plant with highly valuable essential oils. In this study, effects of different fertilizer treatments and cuts on <em>Thymus vulgaris</em> L. was evaluated in 2008-2009. The research was conducted at Alborz Research Station, Research Institute of Forests and Rangelands, Karaj, Iran. The Experimental design was split plot in time in the form of a randomized complete block design with three replications. The main factor was nutritionin 16 levels consisting of different combinations of nitrogen (N), phosphorus (P), potassium (K) and manure (M): N₀P₀K₀M₀, N₄₀P₃₂K₄₀M₀, N₈₀P₆₄K₈₀M₀, N₁₂₀P₉₆K₁₂₀M₀, N₁₆₀P₁₂₈K₁₆₀M₀, N₁₄₀P₁₁₂K₁₄₀M₅, N₁₂₀P₉₆K₁₂₀M₁₀, N₁₀₀P₈₀K₁₀₀M₁₅, N₈₀P₆₄K₈₀M₂₀, N₆₀P₄₈K₆₀M₂₅, N₄₀P₃₂K₄₀M₃₀, N₂₀P₁₆K₂₀M₃₅, N₀P₀K₀M₄₀, N₀P₀K₀M₃₀, N₀P₀K₀M₂₀ and N₀P₀K₀M₁₀ (indices following the letters N, P and K are application rates in kg/ha, indices following the letter M are the application rates of manure in t/ha). The sub factor was harvest (cut) time (late May and early September). Results indicated that fertilizer, harvest date and their interactions significantly affected most of the traits. Mean comparison of the interactions indicated that treatments containing both chemical fertilizers and manure showed positive effects, although the most plant height was achieved with N₁₆₀P₁₂₈K₁₆₀M₀ × 1^st cut, in both years (32.5 cm in 2008 and 32.66 cm in 2009). Essential oil yield was the highest in 2008 in N₁₂₀P₉₆K₁₂₀M₁₀ × 2^nd cut (26.01 kg/ha), and in 2009 in N₁₀₀P₈₀K₁₀₀M₁₅ × 1^st cut (26.79 kg/ha). Generally, it can be concluded from the results that <em>T. vulgaris</em> responds well to fertilization, and selecting the best treatment depends on the objective of production.