Selection of Willows (Salix sp.) for Biomass Production

Background and Purpose: Willows compared with other species are the most suitable for biomass production in short rotations because of their very abundant growth during the first years. Nowadays, in Croatia, a large number of selected and registered willow clones are available. The main objective of the research should be to find genotypes which, with minimum nutrients, will produce the maximum quantity of biomass. Material and Methods: Clonal test of the arborescent willows include the autochthonous White Willow (Salix alba), interracial hybrids of the autochthonous White Willow and the English ‘cricket’ Willow (S. alba var. calva), interspecies hybrids (S. matsudana × S. alba), as well as multispecies hybrids of willows. Average production of dry biomass (DM∙ha-1∙a-1) per hectare was estimated in regard to the clone, survival, spacing and the number of shoots per stump. Results: The highest biomass production as well as the best adaptedness and phenotypic stability on testing site was shown by clones (‘V 374’, ‘V 461’, ‘V 578’ from 15.2 - 25.0 t∙DM∙ha-1∙a-1) originated from backcross hybrid S. matsudana × (S. matsudana × S. alba) and by one S. alba clone (‘V 95’, 23.1 - 25.7 t∙DM∙ha-1∙a-1). These clones are now at the stage of registration and these results indicate significant potential for further breeding aimed at biomass production in short rotations. Conclusions: Willow clones showed high biomass production on marginal sites and dry biomass could be considerably increased with the application of intensive silvicultural and agro technical measures. No nutrition or pest control measures were applied (a practice otherwise widely used in intensive cultivation system), while weed vegetation was regulated only at the earliest age