Nitrogen fertilizer affects the chemical composition of the substrate, the foliar nutrient content, the vegetative growth, the production and fruit quality of blueberry
The objective of this study was to investigate the influence of different nitrogen fertilizer rates on chemical composition of substrate, vegetative growth, yield, fruit quality and leaf nutrient concentration of Misty and O'Neal blueberry cultivars. It was applied five nitrogen rates. In the years 2008 and 2009 were: 0, 5, 10, 15, and 20 g plant-1, whereas, in 2010, due to the growth and development of plants, the rates were: 0; 7.5; 15; 22.5; and 30 g plant-1. The variables analized were: plant height, dry mass of pruning, shoot length, chlorophyll content, yield, fruit mass, pH, titratable acidity, soluble solids, anthocyanin content, antioxidant activity, total phenolics of fruits, leaf nutrient concentration (N, P, K, Ca, Mg, B, Fe, Mn and Zn), and chemical properties of the substrate. Levels of N reduced the pH, exchangeable Ca and Mg and increased the Al content in the substrate. In leaves, there was an increase in N, P and Fe and a decrease in Ca, Zn, Mn and B. The highest yield was obtained with the estimated rate of 7.37 g plant-1 of N. Regarding functional compounds, there was a linear increase in antioxidant activity and phenolic compounds. It can be concluded that N fertilization with ammonium sulfate, significantly influenced the chemical composition of the substrate, nutrient content of leaves, vegetative growth, yield, and fruit quality of blueberries.
Additional keywords: ammonium sulfate; mineral fertilization; pH; Vaccinium.
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