ORGANIC CARBON, TOTAL NITROGEN AND MACRONUTRIENTS IN SOIL UNDER SHORT-ROTATION WILLOW AND POPLAR

Plant cultivation for energy purposes in a short rotation coppice system not only provides biomass for industry and power generation, but it is also beneficial for the environment. This study examined the effect of the species (cultivar/clone), harvest cycle and fertilization on selected soil parameters. A four-factorial strip-split-split-plot experiment was conducted in the north-east section of Poland. The treatment were two willow - Ekotur and ??ubr (Salix viminalis L.) and one poplar cultivar (P. nigra x P. maximowiczii Henry) that were grown in one- and three-year harvest cycles. The species were fertilized with mineral and organic fertilizers (0, 85 and 170 kg ha-1 N). Soil samples were collected prior to the growing season (early spring) in 2016, 2017 and 2018. The experiment demonstrated that the annual cycle contained significantly more organic carbon (1.09%) than the triennial cycle. Moreover, organic carbon content was higher (p=0.0009) at sites where cultivars of S. viminalis L. were grown compared to those where the poplar clone was grown. Furthermore, total nitrogen content, phosphorus and potassium were higher at sites with the annual cycle. In contrast, these parameters were similar at most sites in the triennial cycle. These results indicate that fertilization did not affect soil organic carbon, pH, total nitrogen and macronutrients content in the triennial harvest cycle. The research needs to be continued during longer plantation use to confirm or refure these relationships.