The effects of crop load on 'Sangiovese' grapevines

A study to evaluate the effects of crop load on the qualitative and quantitative fruit production as well as vegetative performance of grapevines was performed. The research was conducted from 2000 to 2002 on 12-year-old 'Sangiovese' grapevines grafted onto '420A'. The vines were spur pruned, the foliage was vertically trained and planted to a 3.0 by 1.2 m row and vine spacing, respectively. Ten crop load treatments were imposed at veraison, by removing clusters to the following levels: 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 and 20 clusters per vine. Yield was highly correlated with cluster number. Berry and cluster weights were not correlated with cluster number per vine. Sugar content in the must was inversely related to cluster number as well as to yield across all years of the study. This difference was more apparent during the initial period of berry ripening. Good correlations were also found between crop load and must titratable acidity and pH as well as anthocyanins content. Cluster thinning did not affect vegetative growth or leaf gas exchange.