Management of soil cover plants impacted the composition of Cabernet-Sauvignon grapes and red wines in a temperate climate

Abstract

Several practices can be applied to vineyards to ensure good healthy for soil and grapevines, adequate yield and fruit quality, among them the use of cover crops. It increases the organic matter, improves water infiltration, reduces risks of soil erosion, in addition improving microbiological biodiversity in the vineyard. This study aimed to evaluate the influence of different cover plants in the vineyard on yield, physical chemical and phenolic composition of Cabernet Sauvignon grapes and wines, in a temperate climate of Brazil. Cabernet Sauvignon vines grafted onto Paulsen 1103 was planted in 2010, and two consecutive vintages were evaluated, 2020 and 2021. The field design was established in randomized blocks with 4 treatments and 3 replications, each plot consisted by 18 plants, in a sandy-clayey soil. The treatments were: T1: without cover plants, eliminated by manual weeding; T2: 100% vetch implanted by seeding; T3: 100% grasses; T4: 50% vetch and 50% grasses. At the harvest date, the yield per vine was determined, as well as the analytical parameters of grapes. The wines were elaborated in duplicate using traditional protocol of red vinification, with 40 kg of grapes for each treatment. The wines were characterized by determining the physical chemical parameters, minerals and phenolic composition. Even both seasons were dry, strong differences were observed on grapes and wine composition, except for the yield. In 2020, grapes had higher amounts of sugars and pH, and low acidity as compared to grapes from 2021. Wines from 2020 had higher amounts of alcohol content and pH, and lower concentration of minerals and phenolic compounds as compared to wines from 2021. The cover plants had different behavior in the seasons. In 2020, grapes from T1 (without plants) had the highest values of sugar and the lowest pH, while in 2021 no significant differences were observed. In 2020, wines from T1 (without plants) had the highest values of alcohol content, calcium, magnesium and manganese, delphinidin-3-O-glucoside, flavanols and caftaric acid, and the lowest concentration of potassium, malvidin-3-O-glucoside, flavanols and stilbene. In 2021 vintage, no differences were observed for grapes and wines for physical chemical analyses, but higher amounts of caftaric acid and total flavonols were observed in wines from T1, and lower amounts of total anthocyanins. Vintage was the prominent factor affecting grape and wine quality, and significant differences were observed on mineral and phenolic compounds of wines, according to different cover plants in Cabernet Sauvignon vines.