Abstract Of all the essential nutrients, nitrogen is required by plants in the largest quantity and is most frequently the limiting factor in crop productivity. Proper management of nitrogen is important because it is often the most limiting nutrient in crop production and easily lost from the soil system. In this paper are presented some results regarding the nitrogen dynamics in soil after mineral fertilization. The researches have been made on soil intensively fertilized with mineral fertilizers without micronutrients. Intensive mineral fertilization was made on winter wheat. The experiments were of bifactorial type, with 5 variants and 4 repetitions. Experimental variants were: nitrogen fertilization N0 (0 kg/ha), 2 – N50 (50 kg/ha), 3 – N100 ( 100 kg/ha), 4 – N150 ( 150 kg/ha), 5 – N200 (200 kg/ha) and Phosphorus and potassium fertilization: 1.– P0K0 (0 kg/ha), 2-.P50K50 (50 kg/ha), 3.-P100K100 (100 kg/ha),4.- P150K150 (150 kg/ha). Fertilizars used were: ammonium nitrate and complex mineral fertilizer 15:15:15. Parameters analyzed were: pH, total nitogen, amonium nitrogen and nitrates. The usefulness of the resarch is very important, because world-wide every year are applied great amounts of mineral fertilizers and nitrogen is a key element for plants.For the cultivars this type of information is very important because they can apply in a durable and cheap way the fertilizers. The largest quantities of nitrogen were determined in the cold season (December), because the leading low temperatures had reduced the leaching.

Key words: nitrogen , mineral fertilization, ammonium, nitrates, soil pH.

Presentation: oral