Effects of nutrition strategy on the levels of nutrients and bioactive compounds in blackberries

The effects of nutrition strategy on levels of nutrients and bioactive compounds in fruit and leaves of blackberries were studied in greenhouse-grown blackberry plants fertilised with combinations of two levels (low, high) of nitrogen (60 and 100 kg ha(-1), respectively) and potassium (66.4 and 104 kg ha(-1), respectively). Plant concentrations of organic phytochemicals were quantitatively analysed by high-performance liquid chromatography. High amounts of both fertilisers produced high amounts of all nutrients and bioactive compounds analysed in fruit except total acidity and ellagic acid. There were major differences in compounds affecting taste in fruit, e. g., sugars (fructose and glucose), total soluble solids and pH, and also in anthocyanin content. The concentrations of secondary metabolites, vitamin C and ellagic acid in fruit also varied significantly between treatments, although the differences were smaller. Storage of blackberries showed variable effects in the different levels of compounds, and the changes found were small. Nutrient regime did not affect blackberry leaves to the same extent, and only minor changes were found. The findings show that by optimising plant nutrition, phytonutrient levels can be maximised and maintained in fresh and stored berry crops, especially those grown in greenhouses, where conditions can easily be regulated.