Urea is frequently used as a fertiliser in agriculture. In addition, foliar applications of urea in the vineyard have improved the nitrogen composition of the grapes and could improve their quality. There are many studies about the effect of foliar application of urea on red grapevines, but there are no works about the effect of timing application and three doses of urea on nitrogen composition in Tempranillo Blanco grapes. Consequently, the objective of this study was to determine the influence of three doses of urea, applied at two different phenological stages (pre-veraison and veraison), on the nitrogen composition of Tempranillo Blanco grapes during two consecutive years. The results showed that, in general, the foliar application of urea, at both phenological stages, increased the amino acids concentration in Tempranillo Blanco grapes, without modified oenology parameters and yield. A different behaviour was observed between the three doses applied at pre-veraison and veraison, because 6 kg N ha−1 treatment, applied at pre-veraison, and 9 kg N ha−1 treatment, applied at veraison, improved the concentration of amino acids during the two years. In addition, amino acids concentrations were mainly affected by year and treatment factors. Consequently, foliar application could be considered a good strategy to increase amino acids concentration in Tempranillo Blanco grapes that are poor in these compounds.

We thank the European Regional Development Fund (ERDF) and the Government of La Rioja for the financial assistance provided to the projects P.R.03-19 and P.R.03-20. R. Murillo-Peña thanks the National Institute for Agricultural and Food Research and Technology (INIA) and the Government of La Rioja for her predoctoral contract (PRE2019-088633).

Peer reviewed