Water stress, yield, and grape quality in a hilly rainfed “Aglianico” vineyard grown in two different soils along a slope

Vineyards from hilly areas of the Mediterranean region are mostly grown in shallow soils that present low soil water holding capacity. These vineyards are prone to water stress conditions, which if well managed can raise the grape quality potential. This study aimed to investigate the water stress development in an “Aglianico” vineyard grown along a 90 m slope. The two-year (2011–2012) trial was conducted in two soils having different hydraulic properties, the Up-slope with lower soil water holding capacity than the Down-slope site. The results showed that grapevines were more stressed in the Up-slope soil than in the Down-slope soil, as reflected by the higher crop water stress index, lower leaf water potential and leaf gas exchanges values. Consequently, the yield was significantly lower by 40% in the Up-slope, which was determined by the lower weight and volume of berries. The smaller berries improved must quality parameters of total soluble solids, total polyphenols, total anthocyanins, and color intensity within a range of 4–25% higher in the Up-slope compared to the Down-slope site. Moreover, the pre-veraison stress experienced in 2012 reduced yield by 30% and depressed berry weight and volume, compared to 2011. The post-veraison stress induced the improvement of must quality, mainly in the Up-slope 2011. Interestingly, there was no significant difference in the pH and titratable acidity between both sites, which indicates the ability of Up-slope vines to make up for more stressful conditions, and, thus, their resilient behavior to maintain their high-quality wine. This study highlights that vineyards in hilly areas may benefit from a differentiated management between different viticulture zones to bring up their high-quality wine.