Response of the yield and mineral composition of garden thyme (Thymus vulgaris L.) herbage to various NPK proportions

Garden thyme is a very important essential herbal plant grown in Poland. As well as being able to regulate digestion processes, thyme herbage possesses disinfecting, expectorant, antioxidant, spasmolytic properties. Research has been launched to define the effect of NPK fertilisation on yielding, the content of essential oil as well as the mineral composition of garden thyme (Thymus vulgaris L.) herbage. The experimental factor consisted of NPK mineral fertilisation applied into soil at the following doses per hectare and proportions: A0 – without mineral fertilisation, A1 – 30 kg N + 22 kg P + 100 kg K (N:P:K was: 1:0.75:3.33), A2 – 60 kg N (30 kg N + 30 kg N) + 22 kg P + 100 kg K (1:0.37:1.67), A3 – 90 kg N (45 kg N + 45 kg N) + 22 kg P + 100 kg K (1:0.24:1.11). The experiment comprised 4 fertilisation objects with 4 replications, and the sowing area and the harvest area of 3 m2 plot-1. Nitrogen was applied in the form of ammonium nitrate twice: pre-sowing as well as after plant emergence. Phosphorus and potassium were used pre-sowing, in the form of triple superphosphate 40% and 60% of potassium salt, respectively. The doses of 152 kg NPK ha-1 (1:0.75:3.33) – A1 and 182 kg NPK ha-1 (1:0.37:1.67) - A2 showed the most favourable effect on the yield of fresh weight, air-dried weight and essential oil of herbage as well as the quality characteristics of the yields. The dose of 152 kg NPK ha-1 (A1), including 30 kg less nitrogen, was as favourable as that of 182 kg NPK ha-1 in terms of the content of air-dry weight of herbage, essential oil as well as mineral nutrients. Its application also resulted in a similar yield of essential oil. The application of 212 kg NPK ha-1 (1:0.24:1.11) was economically unjustified since, in general, it decreased the size of the yield of fresh weight of herbage and the values of its parameters studied.