THE LONG TERM EFFECT OF FERTILIZATION ON THE CONTENT OF SOIL MICRONUTRIENTS

This work paper shows the research results of the statesupplyingsoil with micro nutrients (iron, boron andzinc) after 38 years fertilization with nitrogen and phosphorus. The analyses were performed on soil sample staken from one long term experiment with fertilizer from Research Station of Agricultural Development of Valu Traian, Constanta. The applying the increasing dosesof nitrogenand phosphorus have negatively influenced the soil content in micronutrients iron andboron.These are between inthe normal limits of supply to themost variants experienced. It found alow level of zinc supply over 0.5 ppm but less than 1 ppm in all variants of fertilization with nitrogen and phosphorus. The application of high doses of phosphorus (in particular) and nitrogen causedadecrease in zinc content of the soil