Influence of nitrogen and phosphorus-potassium fertiliser on the yield and biochemical composition of common chicory (Cichorium intybus L.)

Common chicory (Cichorium intybus L.) is an important industrial crop, valuable due to its high content of inulin and functional bioactive compounds. Optimisation of mineral fertilisers remains key to maximising yields and improving biochemical composition in the face of climate change. The purpose of this study was to evaluate the effect of nitrogen and phosphorus-potassium fertilisers on the yield and biochemical parameters of chicory. Field studies were conducted in 2021-2023 in the Right-Bank Forest-Steppe of Ukraine on low-humus chernozem according to a two-factor scheme that included 5 variants of nitrogen fertiliser (0-200 kg/ha) and five variants of phosphorus-potassium fertiliser (0-120 kg P2O5 and 0-200 kg K2O). The yield of root crops, total sugar content, inulin content, reducing sugars, and degree of polymerisation were determined using standardised biochemical and statistical methods (analysis of variance, Tukey’s HSD post-hoc test, Principal Component Analysis (PCA), cluster analysis). The results of the research showed that nitrogen fertiliser affected all biochemical parameters and yield, but most of all on the content of inulin (up to 75% of dry matter) and the degree of polymerisation, while phosphorus-potassium fertilisers only on the yield and degree of polymerisation. The maximum average yield in the years of research (35.4 t/ha) was achieved with the introduction of N150P90K150, while excessive application of nitrogen and phosphorus-potassium fertilisers (200 kg/ha) reduced crop productivity and yield. The total sugar and inulin content increased with nitrogen application to 150 kg/ha, after which a decrease was observed. PCA confirmed the dominant role of nitrogen in the development of both yield and biochemical parameters. Optimal nitrogen standards (100-150 kg/ha) in combination with moderate levels of phosphorus-potassium fertiliser ensured stable root crop yields and high inulin content, which is important for both industrial processing and sustainable agricultural production