Ideal nitrogen concentration in leaves for the production of high-quality grapes cv 'Alicante Bouschet' (Vitis vinifera L.) subjected to modes of application and nitrogen doses

The low N use efficiency of vines calls for more efficient fertilization processes, which must mitigate losses caused by volatilization. Thus, N dose applications through different methods, such as fertigation, can potentiate N harnessing by vines. The study aimed to determine ideal N concentration in leaves for the production of highquality grapes cv 'Alicante Bouschet' (Vitis vinifera L.) subjected to modes of application and N doses. The experiment was carried out in a bifactorial arrangement (N dose x modes of application) in a vineyard implanted in 2011, in Southern Brazil. The N doses were 0, 20, 40, 60, 80, and 100 kg N ha(-1) year The modes of application were N application without irrigation (NAWI), N application followed by irrigation (NAFI), and N application via fertigation (Fert). The study lasted three crop seasons. Complete leaves were collected at flowering and veraison to determine total N concentration. Grape yield and yield components were determined. Total soluble solids, total anthocyanins, and total polyphenols in grape must be assessed. The maximal recovery rate in grapes was at 36 kg N ha(-1), when N concentration was higher than 2.75 % in leaves at flowering, and higher than 2.25 % at veraison, regardless of the N application mode. The concentrations of total anthocyanins, total polyphenols, and total soluble solids in grape must have diminished at doses higher than 60 kg N ha(-1). Thus, N concentration in leaves can be used as a reference for grape yield, the concentration of anthocyanins, and soluble solids as indicators of high-quality grape.

Automated summary

The study found that the concentration of nitrogen in leaves can be used as an indicator for grape yield, anthocyanins, and soluble solids, while concentrations of total anthocyanins, total polyphenols, and total soluble solids in grape must decrease at doses higher than 60 kg N ha(-1).