Foliar application of proline, phenylalanine, and urea to Tempranillo vines: Effect on grape volatile composition and comparison with the use of commercial nitrogen fertilizers

In this work the influence of the foliar application of proline, phenylalanine, urea and two commercial nitrogen fertilizers, with and without amino acids, on grape aroma composition was studied. The treatments were applied in a Tempranillo vineyard, at a dose of total N of 900 g/ha, at veraison and a week later. Enological parameters and volatile compound content were determined in grapes. The results showed that terpenoids synthesis decreased with all treatments carried out in the vineyard, and there were not significant differences either in the amount of C13 norisoprenoids or in esters between treated and control samples. The treatment with phenylalanine increased the presence of benzenoid compounds and decreased C6 compounds. Therefore, this treatment could be considered the best from the point of view of grape aroma composition. The treatments with the commercial nitrogen fertilizers did not affect the total compound content present in the samples.