Field experiment was carry out at experimental farm Oponice (West Slovakia, 48° 28´N, 18° 9´E) ) in 2004-2007. The aim of the work was to evaluate the influence of nitrogen fertilization treatments on yield and yield component and selected quality parameters (proteins, oil, fibre, isoflavones) of soybeen seeds variety Korada, in agri-environmental condition of western part of Slovakia. The fertilization treatments were as follows: (I) unfertilized treatment; (II) application of nitrogen fertilizers LAV 27 % (ammonium nitrate with lime - 40 kg ha-1 nitrogen) in the vegetative stage V2; (III) Humix complet in split application of total dose 4 +4 L ha-1 applied in growth stage of V2 and in reproductive growth stage of R1 (beginning bloom). Humix complet contain bioactive ingredient and nutrients for plant nutrition with 2.5% of humic acids, 4.0% total N, 0.5 P2O5, 3% K2O, and micronutrients. Result showed the highest variation of pods per plant in dependence of year condition (range 17.8-24.7). No significant differences between numbers of seeds were noted (2.13-2.29). The split application of Humic complet significantly influence the higher number of pods per plant (24.8) while keeping the number of seeds per pod (2.13). The yield of seeds was significantly influenced by weather conditions (2.84 t ha-1 - 4.68 t ha-1) and by fertilization treatments. Supplemental ammonium nitrate with lime (treatments II) in the vegetative stage of V2 or Humix complet (treatment III) applied in V2 and R1 stages significantly increased yield of soybean seeds up to 3.91 t ha-1 and 4.27 t ha-1 with comparison to control treatment (3.49 t ha-1). Content of protein, oil and fibre was not significantly differing between fertilization treatments. In spite of significantly higher soybean yield in Humic complet treatment, content of protein (37.67%), oil (15.83%) and fibre (9.47%) was at the same level as lower yielded treatments. Soybean seeds from higher yielded fertilization treatments have significantly less content of isoflavones. Split application of Humic complet is effective method for improving yield of soybean seeds while maintaining the composition of protein oil and fibre.
