LEAF NUTRIENT ANALYSIS IN SALIX-VIMINALIS (L) ENERGY FOREST STANDS GROWING ON AGRICULTURAL LAND

The seasonal pattern of morphological leaf characteristics, leaf nutri ent and carbohydrate contents in two energy forest stands growing on f ertile clay soil and consisting of Salix viminalis (L.) was investigat ed. One of the stands was irrigated and liquid fertilized (IL) daily f rom May to August while the other stand was untreated (C). The study w as carried out on shoots growing for their second year on five-year-ol d roots. A pronounced seasonal variation in length, weight, and area o f leaves of the same developmental stage was observed, while differenc es between the stands were small. The leaf content of carbohydrates an d starch was low. Nitrogen was the only nutrient that was significantl y higher in the IL stand compared with the C stand throughout the grow ing season. The small differences between stands were most probably an effect of the initially high soil fertility. Different bases for expr essing plant nutrient status during the growing season, i.e. nutrient amount per leaf dry weight with and without carbohydrates, nutrient am ounts per leaf or leaf area, nutrient proportions in leaves, and nutri ent amounts in the total canopy, were compared and discussed. It was c oncluded that the common expression, nutrient weight per dry weight of leaves, without correction for non-structural carbohydrates, was adeq uate to describe the nutrient situation in well-growing basket willow plantations. The most appropriate time for leaf sampling was proposed to be the phase of most intensive growth.