EN
Yield and chemical composition of oat grown with graded amounts of undersown spring vetch was investigated in a mountainous region (Czyrna near Krynica) over a 4-year period (1996- 1999). The highest yields of grains were obtained when the oat was grown as a pure culture whereas undersowing the oat with increasing amounts of spring vetch reduced grain yields. The environmental conditions significantly affected oat grain yields, irrespective of the type of sowing. With undersown oat (40 and 50 kg spring vetch/ha), contents of N, P, K, Mn, and Zn in oat grain were higher, than with oat grown as a pure culture or undersown with the lowest amount of spring vetch (30 kg/ha). Environmental conditions during growing seasons significantly affected N, Mn, Cu, and Cu contents.