INCREASE OF BIOMASS PRODUCTION OF FAST-GROWING WILLOWS IN THE FIRST YEAR OF THE SECOND HARVEST CYCLE

The aim of the paper is to evaluate biomass production of three different willow varieties (Salix spp.) at the end of the first year of the second harvest cycle (2012) and to compare the results with those obtained in the first harvest cycle at the end of the first growing season after cutback (2008). The observed growth parameters included number of shoots per plant, shoot height and diameter, and weight of fresh matter per plant. Three willow varieties were studied (Tora, Gudrun and Tordis). The individual growth parameters were determined by destructive method. The number of the shoots per plant varied from 17.83 (Tora) to 30.17 (Gudrun). The shoot height ranged from 2.66 m (Gudrun) to 3.62 m (Tordis) and the shoot diameter ranged from 10.85 mm (Gudrun) to 13.14 mm (Tordis). The variety with the greatest biomass production of the fresh above-ground matter was Tora (5.43 kg plant-1), followed by Gudrun (4.97 kg plant-1). Tordis provided the lowest yield (4.55 kg plant-1). All of the observed growth parameters had higher values than those determined at the end of the first year after cutback in the first harvest cycle. The most significant increase was recorded in the above-ground biomass production with the percentage increase of 114%, 122% and 226% in Tora, Tordis and Gudrun, respectively.