N DYNAMIC IN MOUNTAIN GRASSLAND WITH DIFF ERENT INTENSITY OF CULTIVATION

The aim of this research was to investigate the N dynamics in mountain grassland with different intensity of cultivation. We compared three meadows (extensive, medium intensive and intensive) on Entic Hapludoll (American Soil System) and one medium intensive meadow on Dystrochrep t. Microbial biomass, N-min content and net nitrogen mineralization (N NM) were measured at a depth of 0-20 cm from April to September at 6-w eek intervals. The plots on Entic Hapludoll showed an increase of micr obia biomass N, N-min, and N content from extensive to medium intensiv e cultivation. Compared with the medium intensive plot the intensive s howed generally similar N-min contents, but lower biomass N and N-org contents. The medium intensive plot on Entic Hapludoll differed from t he Dystrochrept plot greatly in biomass N, N-org and N-min contents. T he ratio biomass N to total N (N-milk/N-org) was the lowest in the ext ensive plot. The NNM was greatest in the intensive plot. Due to high v ariability the differences were significant only for the medium intens ive plot on Dystrochrept. The NNM (medium intensive on Dystrochrept, m edium intensive and intensive on Entic Hapludoll 126, 153 and 251 kg N ha(-1) 24 weeks(-1), respectively) showed, with exception of the exte nsive plot, good responses to the N output through cutting (medium int ensive on Dystrochrept, medium intensive and intensive on Entic Haplud oll 139, 208 and 283 kg N ha(-1), respectively). The N supply from NNM and the N output were not always synchronous over the season.