Effects of soil characteristics and leaf thinning on micronutrient uptake and redistribution in 'Cabernet Sauvignon'

Abstract

This study investigated the uptake and distribution in grape tissues of the micronutrients copper (Cu), zinc (Zn) and manganese (Mn), in a 16 year-old 'Cabernet  Sauvignon' vineyard and their relationship with soil characteristics and management. The analysis was carried out in two plots with differences in vigour, grown in a calcareous soil. Two different management treatments (with and without leaf thinning after bloom) were applied in each plot. Partitioning and distribution of micronutrients (Cu, Zn and Mn) in petiole, seeds skin and flesh were evaluated from veraison to harvest. The relationship between micronutrients and grape parameters such as pH, total acidity and berry weight were also evaluated. Differences in nutrient concentration were found between the areas with differences in vigour, but concentration in petiole did not present good correlation with the soil fraction extracted with CaCl2+DTPA+Trietanolamine. The results showed that micronutrient concentrations varied in a different way between organs during ripening. Cu and Zn in petioles had higher concentrations at veraison than at harvest, while for Mn the concentrations were higher at the end of the cycle. Zn and Mn were within the acceptable levels, while Cu levels were above them. Mn and Zn were mainly concentrated in seeds and skins. Cu and Mn concentrations in petiole, skins and seeds were higher in the leaf tinning treatment, but the results were opposite for Zn. Zn and Cu in flesh increased with berry weight while Mn decreased. Acidity and pH affected Zn in skins and flesh and Mn in seeds.