CHANGES IN PRODUCTION PARAMETERS OF FAST-GROWING ENERGY GREY POPLAR VARIETES (POPULUS x CANESCENS) IN SLOVAKIA

The paper presents results of the research aimed at the production potential of Italian varieties of Grey poplar (Populus x Canescens) in soil and climatic conditions of southwestern Slovakia. The research was conducted in the first year (2013) of the second four-year growing cycle (one year after the cut back) on four Italian varieties (Monviso, Pegaso, AF-2, Sirio). The following selected growth indicators were monitored: number of shoots, shoot length and shoot diameter. The average weight per plant of the individual varieties ranged from 3.6 kg (variety Monviso) to 3.43 kg (variety AF-2). The greatest amount of the biomass per plant on average was obtained by Monviso. The average number of shoots of the studied varieties ranged from 8 shoots (Monviso) to 10 shoots (Pegaso). The average shoot length of the varieties ranged from 3.19 m (Monviso) to 2.59 m (AF-2). The average diameter of shoots of the individual varieties measured in the height of 1 m ranged from 17.47 mm (Monviso) to 13.54 mm (AF-2). The growth indicators analysis of the studied varieties proved statistically significant differences. The biomass production in the fourth year (2012) of the first growing cycle differed among the varieties. The cut back affected a reduction in the biomass production on average by 76.83% in all four studied varieties. The most significant biomass decrease was observed in the variety Pegaso (-80.08%). The presented results show a significant impact of the cut back on the studied varieties of Populus x Canescens and support the findings about the regeneration ability of the varieties as a potential for the biomass production that can be utilized for energy purposes.