The study was carried out in the experimental filed of the Maize Research Institute, Zemun Polje, on calcareous chernozem in the period 2001-2003. The traits of two maize inbred lines (L 1 –FAO 400 and L 2 –FAO 600) were observed in dependence on the two fertiliser variants: N o –control without fertilising; N min –PK (const.) + fertilising in spring on the basis of the Nmin method, and forms of applied nitrogen: Urea (amidic form), KAN (ammonium-nitrate form) and (NH 4 ) 2 SO 4 (ammonium form). The highest amount of (NH 4 +NO 3 )–N in the soil (0–120 cm) in the silking stage of maize inbred lines was recorded in 2002 (72.6 kg ha -1 ), under the inbred line L 2 (84.0 kg ha -1 ) and in the treatment with Urea (86.4 kg ha -1 ). The amount of –N and (NH 4 +NO 3 )–N in the soil (0-120 cm) measured at the end of the growing season of observed maize inbred lines was the highest in the second year of investigation (48.9 and 55.8 kg ha -1 , respectively). The application of nitrogen in the amidic form highly significantly affected the increase of the amount of accessible nitrogen in the soil at the end of the growing period in the inbred L 1 (46.3 kg ha -1 ), while the application of different nitrogen forms did not express statistical significance in the inbred L 2

nitrogen fertilizing; nitrogen form; mineral nitrogen in soil; maize inbred lines

Presentation: oral