Influence of trellis system and shoot density in yield and grape composition of a vineyard of Cabernet Sauvignon, in warm climate

Abstract

Context and purpose of the study – In vineyards grown in warm areas, it is usual that the stage of maturity of the grapes is fast and easily reach a high concentration of sugar and low acidity, but not a adequate phenolic maturation. The geometry of the trellis system and the shoot density can modify the microclimate of the cluster and, therefore, the maturation process.

Material and methods – In order to know whether, in warm areas, free or semi-free foliage systems are most appropriate to achieve a maturity more balanced than systems with guided foliage, such as the vertical shoot positioned, during 2013 and 2014 developed a test in a vineyard of Cabernet Sauvignon in Albacete (Spain). Comparing two trellis systems – vertical shoot positioned and sprawl -, each of them with three shoot densities – 35000, 55000 and 70000 shoots per hectare-. During maturation were determined the weight of the grape and the basic composition of the must (° Brix, pH and total acidity). Yield components and the grape phenolic components were determined at harvest.

Results – In both trellis systems the increased of crop load generated a proporcional increase in yield respect number of shoot, in addition to a delay in maturation, with lower concentrations of sugar and total phenols, and higher acidity. The vineyard in sprawl reached, usually, higher concentrations of sugar, but with equal or lower levels of acidity on vertical shoot positioned, which means a better sugar/acidity balance. The effect of the trellis system on the grape phenolic components was not consistent for the two years of study.