Influence of nitrogen fertilizers on the concentrations of inulin and micronutrients in Jerusalem artichoke tubers and root chicory

The aim of the study was to evaluate the effect of nitrogen fertilization on the content of inulin and microelements in tubers of Jerusalem artichoke (JA) and roots of chicory grown in the climatic and soil conditions of north-eastern Poland. Three cultivars of JA and root chicory were grown in a field experiment. The content of inulin and micronutrients was determined in JA tubers and chicory roots harvested in autumn, JA tubers left in the ground over winter, and stored chicory roots. Jerusalem artichoke tubers fertilized with N (80 and 120 kg ha-1) contained more inulin (803.3 and 737.0 g kg-1 DM) than unfertilized plants (635.0 g kg-1 DM); the opposite was noted in chicory roots (without N fertilizer – 392.8 and 352.0 and 337.0 g kg-1 DM fertilized with 80 and 120 kg N ha-1 respectively). Inulin content was lowest in JA tubers and chicory roots harvested in the wet and cold 2017. The highest decrease in inulin content was observed in tubers left in soil over winter and stored roots. The concentrations of Zn, Mn and Fe were higher in JA tubers and chicory roots harvested in the wet seasons of 2016 and 2017, and the content of B and Cu was highest in the warm and dry 2018. The micronutrient content of JA tubers and chicory roots was less affected by cultivar and N rate then years of study. Cultivar exerted a significant influence on the content of Cu and Fe in JA tubers left in soil over winter, and on B content in stored chicory roots. The micronutrient concentrations in JA tubers overwintering in the soil and stored chicory roots were not affected by N fertilization.