Effects of fertiliser application and shading on pomological properties and chemical composition of Aronia melanocarpa fruit in organic production

Agronomic and chemical parameters of chokeberry (Aronia melanocarpa) with respect to the effects of different rates of fertiliser and of net shading were evaluated in a plantation that was in the fifth and sixth year of cultivation. Two commercial organic fertilisers, Fertor and Siforga, were applied at four rates (0.5, 1.0, 1.5, and 2.0 t ha(-1)), and shading was applied with two types of green polyethylene shading nets, retaining 30% and 50% of sunlight, respectively. Among the pomological characteristics, the clearest difference was observed for the number of clusters, which, in the second year, was significantly increased by both factors. The number of clusters was shown to have the highest correlation with the yield of berries. In the first year, only the higher rates of fertilisation affected the yields, but in the second year, the yields were significantly increased by all of the fertiliser treatments, compared with the control. For metabolic parameters such as dry matter, soluble solids, titratable acidity, sugars and ascorbic acid, the effects of the treatments were inconsistent. Only the highest rates of the fertilisers and the dark net had significant positive effects on the total phenolics. The concentrations of hyperoside in fruit from the shaded shrubs were significantly higher than in the control, with a similar pattern also for isoquercetin, but only for the dark net. Concentrations of the other individual phenolic compounds differed only slightly.