Foliar application of urea to “Sauvignon Blanc” and “Merlot” vines: doses and time of application

Abstract

A careful control of the N nutritional status of grapevines can have a determining effect on wine characteristics; therefore a suitable management of N fertilization might allow some wine parameters to be modified, thereby improving product quality. The aim of this study was to determine the effect of foliar application of urea at different doses and different times of the growing season on the parameters of Sauvignon Blanc and Merlot grape juice. The research described herein involved Sauvignon Blanc and Merlot grapevines (V. vinifera L.) at a commercial vineyard and was conducted over 2 years. In the first year, N treatment involved a foliar application at a dose of 10 kg N ha -1 during veraison, whereas in the second year it involved a foliar urea application at two doses (10 and 50 kg N ha -1 ) and at three different times-3 weeks before veraison, during veraison and 3 weeks after veraison. In this second year, the urea applied at a dose of 10 kg N ha -1 was isotopically labelled with 1% 15 N. Chemical parameters, yeast assimilable N, amino acid content, amino acid profile and N isotopic composition were determined for all treatments. Grape and grape-juice parameters for Merlot were found to be more affected by N fertilization than for Sauvignon Blanc and were also more affected during the second year than during the first year, thus indicating that the climatic characteristics of each campaign could affect these parameters. The yeast assimilable N in grape juice was found to be higher for late applications of foliar urea, with application of the higher dose of urea during veraison increasing the amino acid and proline contents in both varieties. The isotopic analysis data showed that the urea applied to leaves was transferred to the berries, with the maximum translocation in Sauvignon Blanc occurring for the post-veraison treatment and in Merlot for the veraison treatment. We can therefore conclude that foliar application of urea could modify grape juice quality and could therefore be used as a tool for obtaining quality wines.

Effect of foliar urea fertilisation on volatile compounds in Tempranillo wine

“…(a)). These results agree with those obtained by Lasa et al . for Sauvignon Blanc and Merlot grape varieties.…”

“…Thus the lower ethanol content in the wine from grapevines fertilised with 4 kg N ha −1 of urea could have contributed to its fruitier character. Meanwhile, the wines obtained from musts with foliar urea fertilisation showed lower concentrations of isoamyl alcohol and 2‐phenylethanol, which can mask wine aroma …”

A review of the use of biostimulants in the vineyard for improved grape and wine quality: effects on prevention of grapevine diseases

“…Urea has been one of the most used sources of nitrogen for application in the vineyard, due to its high solubility and low cost. Thus, urea applied over two consecutive seasons at different doses had greater effects on the oenological parameters and amino acid concentrations of musts obtained from Merlot than from Sauvignon Blanc grapevines . Urea treatments applied to Merlot and Pinot Gris grapevines improved the must amino acid concentrations over two consecutive seasons, with the effects more appreciable for Merlot .…”

Quantitative Investigation of Leaf Photosynthetic Pigments during Annual Biological Cycle of Vitis vinifera L. Table Grape Cultivars

“…Regarding the moisture content of the leaves, the highest variability intra-cultivar, determined on the basis of the standard deviation (n = 3), was observed in the phase of shoot growth. This phase starts in the last ten days of May, when, according to Lasa et al (2012), the vine water requirements are lower.…”