Amino Acid Composition of Grape (Vitis viniferaL.) Juice in Response to Applications of Urea to the Soil or Foliage

Effect of two doses of urea foliar application on leaves and grape nitrogen composition during two vintages

“…‘Tempranillo’ vines treated with several nitrogen sources. Hannam et al did not observe differences in pH and total acidity between cv. ‘Merlot’ grapevines untreated and treated with foliar urea and soil urea; however, in the case of the cv.…”

“…hydrogen sulphide) and higher alcohols, as well as a decrease in the production of esters and long chain volatile fatty acids . Hannam et al observed that the foliar nitrogen treatment applied to ‘Merlot’ and ‘Pinot noir’ grapevines increased the YAN concentration with respect to both the soil nitrogen treatment and the control (untreated vines). That suggests that foliar nitrogen applications could represent a more reliable method for enhancing must nitrogen concentrations than soil nitrogen supplies.…”

“…When N‐labelled urea was applied as foliar spray at ‘Pinot noir’ variety grapevines, Hannam et al suggested that the quantity of the applied nitrogen from a foliar nitrogen application accounted for a greater fraction of the must total amino acid content (23%) than that from a soil nitrogen treatment (12%). Schreiber et al found that 30% of the nitrogen absorbed by grapevine leaves ends up in the grapes, whereas only 2% of root‐absorbed nitrogen ends up in the grapes.…”

“…Besides, foliar fertilisation allows nutrients to pass directly to the grape, and so a small quantity of fertiliser may be applied. This is an advantage over the use of soil fertilisation, together with the reduction of leachating as a result of nitrate salts from soil fertilisation. In recent years, several commercial nitrogen foliar fertilisers that include different amino acids in their composition have appeared on the market.…”

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

“…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 . In contrast, when applied to Cabernet Sauvignon grapevines, this treatment barely affected the grape amino acid contents, and negatively influenced the wine flavonoid concentrations .…”