Effects of nitrogen fertilization upon the content of essential amino acids in head chicory ( Cichorium intybus L. var. foliosum)

Abstract

Total nitrogen and essential amino acids in red head chicory were monitored in relation to nitrogen fertilizer rates. Head chicory ( Cichorium intybus L. var. foliosum) was grown in a 3-year field trial involving different nitrogen rates (0, 100, 200 kg N ha −1) while potassium and phosphorus fertilization was uniform in all three trial treatments (100 kg K 2O ha −1 and 100 kg P 2O 5 ha −1). Total nitrogen increased under the influence of nitrogen fertilizer and a significant increase ( P<0.05) was recorded at the higher fertilizer rate. Plant response to nitrogen fertilizer was manifested differently in the contents of particular essential amino acids both in chicory dry matter and in proteins. A significant decrease ( P<0.05) of methionine, valine and lysine contents was determined. The relative decrease, in comparison with the control, was much higher in proteins than in dry matter, especially when the higher nitrogen fertilizer rate was applied. Interaction of nitrogen fertilizer rates and climatic conditions was significant ( P<0.05). The adverse effect of nitrogen fertilization was most expressed in methionine content. Regardless of the effect of climatic conditions, the correlation between the relative decrease of this amino acid in proteins and the nitrogen rate applied was highly significant (r=0.919, P<0.01) .