Effects of timing and intensity of basal leaf removal in cv. Sauvignon

Abstract

Leaf removal has been the subject of several studies, many of them in order to know the best time and intensity in order to promote yield and quality of the grapes. During 2011 in Quinta do Gradil, at Lisbon wine region, a trial field with a 6 year old Sauvignon, grafted onto SO4 and trained to a vertical shoot positioning (VSP) was installed to study the effect of leaf removal on three dates (FB – full bloom, PC – pepper corn size and V – veraison) and three intensities (NR – no leaves removed, 1S – leaves removed from north side of the canopy and 2S – leaves removed from both sides of the canopy), resulting in seven single treatments (NR, FB1S, FB2S, PC1S, PC2S, V1S and V2S).

The leaf removal was handmade and consisted on a removing strip of 35 to 40 cm height at the fruit zone, in order to simulate a mechanical defoliation. A hazard blocks experiment with 3 replications was designed.

The most intense defoliation (2S) in any date induced a significant reduction of exposed leaf area, leaf layer number and consequently an increase in porosity, clusters exposure and light interception at fruit zone compared to the non-defoliated vines (NR). This improvement on canopy microclimate induces a reduction on bunch rot incidence, except when the leaf removal was done at veraison (V).

In comparison with NR, the most intense defoliation (2S) significantly reduced the yield, at all dates (except veraison), with no changes on must or wine composition.

The wines from the leaf removal treatments (except FB2S and V1S) were preferred in the sensorial analysis, especially the PC2S and V2S wines.