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Investigations into the relationships of stress and leaf health of the grapevine (Vitis vinifera L.)on grape and wine qualities


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Wells, R 2011 , 'Investigations into the relationships of stress and leaf health of the grapevine (Vitis vinifera L.)on grape and wine qualities', PhD thesis, University of Tasmania.

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Trials were established to investigate links between late season leaf health and wine
quality in Pinot Noir and Sauvignon Blanc, on a vineyard in Northern Tasmania.
One series of trials located areas within Pinot Noir and Sauvignon Blanc vineyards with
regions of pre-existing shoot vigour variation. Ground-based measurements of vine
canopy along with aerial imaging of near infrared and red light reflectance were used to
characterise the canopies, and compare vigour assessment systems compared. Leaf
health was assessed by chlorophyll concentration and late season retention. Yield and
fruit chemistry attributes were assessed, and small-scale winemaking was used to
investigate fermentation rate and wine quality.
Four nitrogen application trials were established: a nitrogen by irrigation trial (2005-06); a
nitrogen rate (0, 20, 35 and 50 g N/vine in 2006-07 and 0, 20 and 50 g N/vine in 2007-
08) by timing (pre-bloom, post bloom, pre-veraison and post veraison) trial; a nitrogen
by exposure trial (nil or 100 g N/vine, shaded or exposed clusters) and a comparison of
wine from must nitrogen increase by field fertiliser application or winery
supplementation. Changes to shoot growth, leaf chlorophyll and retention, fruit yield
and chemical attributes, and wine fermentation and composition were assessed.
Shoot vigour was correlated with leaf chlorophyll concentration and late season leaf
retention in vigour trials, however leaf health measures could be influenced by nitrogen
application timing independent of shoot vigour. Shoot growth responded to nitrogen
availability prior to fruit set, while leaf chlorophyll was altered by nitrogen availability at
any stage. Pre-bloom additions increase shoot growth in year 1 but in year 2 there was no
impact from nitrogen timing. Leaf retention was improved by nitrogen applications after
fruit set, but not before, and was independent of preceding season applications.
Pinot Noir fruit did not vary in total soluble solids (TSS) as a result of vine vigour.
Sauvignon Blanc juice TSS from high vigour vines decreased, while titratable acidity
increased in high vigour vines in all trials. Nitrogen application increased TSS in one
season, while TA was higher after high rates of nitrogen, particularly when applied post
bloom. Yeast assimilable nitrogen (YAN) influenced fermentation rates, and increased
with vigour, and could also be increased by nitrogen addition. Wine tannins decreased
with vigour and high rates of nitrogen, with changing sunlight exposure being the major
influence. DAP additions produced wines that were distinct from field applied nitrogen,
and when applied prior to inoculation led to an increase in wine colour density.

Item Type: Thesis - PhD
Authors/Creators:Wells, R
Keywords: vine, wine, pinot noir, nitrogen
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