The Effects of Nitrogen Fertilisation on the Anatomical Properties of the Populus alba L. Clone ‘Villafranca’ Juvenile Wood

SIMPLE SUMMARY: In 2020 and 2021, the world underwent the COVID-19 crisis, and in 2022, it is going through another war crisis. These crises have greatly affected the global economy and raw material supply chains, and trade is either disabled or very slow. The wood industry and other industries that depend on primary raw materials feel this effect strongly. These are important reasons why the wood industry should not depend on only one market and why it is necessary to study less valuable types of wood species as potential substitutes for the current ones, at least in products where this is possible due to their characteristics. Fertilising forested plantations with nitrogen fertilisers is not new, but its influence on different types of wood species has not been sufficiently investigated. Fast-growing clones are particularly interesting for such a procedure. This paper studies the effect of fertilisation with nitrogen fertilisers on the anatomical properties of the Poplar clone ‘Villafranca’. ABSTRACT: This study investigates the effect of nitrogen fertilisation on the anatomical properties of the juvenile wood of the Populus alba L. clone ‘Villafranca’ from an experimental trial near the Drava River in Croatia. Nitrogen was applied for two consecutive years, and the immediate and potential post-treatment effects were investigated. The correlation between annual ring width (ARW) and individual wood anatomical properties was also examined. The fertilisation effect was confirmed after the first year of nitrogen application for all wood anatomical properties except the vessel lumen area (VLA). Fibre length (FL) was reduced, and double cell wall thickness (DCWT), ray area (RA), and cell wall area (CWA) increased. In contrast, the vessel lumen diameter (VLD) and vessel lumen area changed inconsistently between treatments. The second year of nitrogen application was determined to be effective for FL only. Due to the insignificant results in the second year of the application of nitrogen, the post-fertilisation effect of nitrogen fertilisation was not confirmed.