Influence of Nitrogen and Potassium fertilisation and cultivation methods on the yield and essential oil content in thyme (Thymus vulgaris L.)

The information in the literature concerning the influence of the nutrient supply on the yield of biomass and essential oil in plants belonging to the Lamiaceae, in particular in thyme, is very contradictory. However, it is well known, the quantity of fertilisers and their composition may influence not only the biomass and essential oils, but also the vitality and the hibernation of the thyme plants. Therefore, a field experiment with the cv. ‘Deutscher Winter’ was carried out in order to investigate the effects of fertilisation during a three- years-cultivation time. Five treatments were applied (standard fertilisation without N, twice of the quantity of N, twice of the quantity of K, covering with fleece, and double plant density) and their effects on the content of essential oil and thymol, yield of thyme (plant height, fresh matter, dry matter, leaf drug), nutrient uptake and influence on hibernation were analysed. The highest N- and K- uptake and yield was recorded in the treatments covered with fleece and at the double plant density with standard fertilisation in average of the three years. The lowest yield of leaf drugs was determined in the treatment without N- fertiliser, the highest at the double plant density. The quantity of essential oil was highest in the treatment double plant density, whereas the lowest essential oil quantity was determined when twice the quantity of N was applied. The content of thymol was highest in the treatment standard fertilisation without N-fertiliser. Concerning the vitality and effect on hibernation best results were determined in the treatments without N- fertilisation and covering with fleece. These results confirm the theory that nitrogen has a negative effect on the content of the essential oil and their components as well the vitality of the plants during the winter season.