Application to grapevine leaves of different doses of urea at two phenology stage: effect on the aromatic composition of red wine

Abstract

AIM: This research aimed to study the effect and efficiency of foliar application of urea on the aromatic composition of red wines elaborated from Tempranillo grapes.

METHODS: This study was carried out in 2018 and 2019. The plot was located in the North of Spain. The grapes were Vitis vinifera L. Tempranillo and grafted on 110 Richter rootstocks. The vine-training system was gobelet and leave twelve buds per vine. The plot was not fertilized and not irrigated, during the two study seasons. The treatments were: control (C), whose plants were sprayed with water; and three different doses of urea: plants were sprayed with 3 kg N/ha (U3), 6 kg N/ha (U6) and 9 kg N/ha (U9). The treatments were performed at two different phenological states, pre-veraison (Pre) and veraison (Ver). Also, each treatment was repeated one week later. The applications were carried out early in the morning to maximize the absorption of urea. Treatments were organized in a complete randomised block design and were performed in triplicate. The grapes were picked at optimum maturity and then, were destemmed and crushed. Each treatment was fermented on stainless steel tanks. The alcoholic fermentation was started by inoculating with commercial Saccharomyces cerevisiae strain Uvaferm VRB and the malolactic fermentation was inoculated with commercial Oenococcus oeni strain Lalvin SILKA. After malolactic fermentation, the aliquots of each wine were frozen to determine their volatile composition. Analysis of volatile compounds from the wine was carried out by gas chromatography–mass spectrometry (GC-MS) [1]. Quantification of compounds was performed with an internal standard method. Finally, the results were studied statistically by analysis of variance (ANOVA).

RESULTS: In the two seasons, the higher alcohols were the most abundant fermentative compounds found in wines, highlighting isoamyl alcohols and 2-phenylethanol. In 2018, the content of all volatile compounds was increased by the treatment U3-Pre. Nevertheless, the treatments carried out in veraison had different effects. The acetate esters and the sum of ethyl hexanoate, octanoate and decanoate were increased by U9 treatment. Also, U6 increased the concentration of total ethyl esters, total esters, and other volatile compounds. However, the higher alcohols were lower in the all treated wines. In 2019, the wines elaborated from grapes treated with U3-Pre presented a higher concentration of aromatic compounds. Moreover, U3-Ver improved the content of alcohols, acetate esters, the sum of ethyl hexanoate, octanoate and decanoate, and total esters; while, the other volatile compounds were risen by U9-Ver.

CONCLUSIONS

In the two seasons, the lowest dose of urea (U3) applied in pre-veraison improved the aromatic composition of Tempranillo wine.