EFFECTS OF NITROGEN FERTILIZATION ON THE BIOCHEMICAL AND PHYSIOLOGICAL PARAMETERS IN LEAVES AND ROOT OF SUGAR BEET ASSOCIATED WITH AZOTOBACTER CHROOCOCCUM

A field experiment was conducted to investigate the effect of nitrogen (N) application on the growth and metabolism of sugar beet (Beta vulgaris L.). Changes in nitrate, ammonium, soluble protein and pigment levels, nitrogen metabolism enzyme activity, biomass of leaves and beet, and sucrose and -amino-N were studied in relation to five different NPK application rates (0, 50, 100, 150, and 200 kg N ha-1) and association with Azotobacter chrooccocum. The availability of nitrate and ammonium ions in the leaves proved to be influenced by the different nitrogen treatments. The most important enzymatic activities within nitrogen metabolism were affected negatively by the highest NPK rate. With increasing nitrogen supply, the concentration of -amino-N increased considerably and that of sucrose decreased. Application of NPK had a significant positive effect on the growth and biomass production. The measured parameters of plants associated with A. chrooccocum were of similar magnitude comparing to the controls.