INVESTIGATIONS INTO THE RELATIONSHIPS OF STRESS AND LEAF HEALTH OF THE GRAPEVINE (VITIS VINIFERA L.) ON GRAPE AND WINE QUALITIES by Reuben Wells BAgrSc (Hons) Submitted in fulfilment of the requirements for the Degree of Doctor of Philosophy University of Tasmania June, 2011
Declaration of Originality This thesis contains no material which has been accepted for a degree or diploma by the University or any other institution, except by way of background information and duly acknowledged in the thesis, and to the best of the my knowledge and belief no material previously published or written by another person except where due acknowledgement is made in the text of the thesis, nor does the thesis contain any material that infringes copyright. Reuben Wells ii
STATEMENT OF AUTHORITY OF ACCESS This thesis may be reproduced, archived, and communicated in any material form in whole or in part by the University of Tasmania or its agents, and may be made available for loan and copying in accordance with the Copyright Act 1968. iii
Acknowledgements Principle funding for this project came from Gunns Limited, through Tamar Ridge Estates, and from the Tasmanian Institute of Agricultural Research. Operational funds were also received from the Grape and Wine Research and Development Corporation. Project supervisors were Dr Stephen Wilson, Dr Richard Smart, Dr Jo Jones, Dr Dugald Close and Dr Robert Dambergs. Steve, thanks for helping talk me into the project. Jo, thanks for reliably being able to pull out a smile and keep me feeling buoyant. Dugald, you stepped in at just the right time and I can t imagine getting this done without your advice. Bob, your practical advice and attitude were a real benefit. And Richard, it has been a pleasure to work with you on this project, and to be able to call you both a colleague and a friend. I offer you all respect and gratitude for your time. There was also much assistance from the staff at Tamar Ridge Estates, and particular thanks go to Mick and Dorothy Humphries, Tom Ravech, Dr Andrew Pirie, and all the crew who helped in the vineyards and the microwinery. There is a long list of friends who have stepped up to the plate when I have been lost in PhD world, but Chris and Sharyn Jones, James and Nicki Gardington and Matt and Sally Lowe have gone above and beyond many times over. Thanks. Most important is to thank my family. Mum, you can have your h now, and Dad, you can have the D. From counting berries to bouncing babies, your help during the project has been great. Even greater has been the work shepherding me through the years leading up to the PhD, thanks for being great parents. Finally, to my very own little family. Kate, you have been amazingly tolerant, and I can t even imagine doing something like this without your support. You really have made it possible. Sam, Poppy and Matilda thank you for putting up with an absentee Dad. I am really looking forward to spending time with you all. I love you all. iv
Abstract 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. v
Table of Contents 1 Introduction... 1 2 General Materials and Methods... 15 2.1 Site Summary... 15 2.2 Season summaries... 15 2.3 Trial layouts... 17 2.4 Canopy and Leaf Health Measurements... 24 2.5 Fruit attribute measurements... 31 2.6 Winemaking methods... 35 2.7 Wine assessment... 37 2.8 Statistical analysis... 38 3 Impact of vine vigour on leaf health, canopy growth, fruit attributes and wine quality in Vitis vinifera L. cvs. Pinot Noir and Sauvignon Blanc... 39 3.1 Introduction... 39 3.2 Investigations into vine vigour and links to leaf health in grapevine (Vitis vinifera L.) cvs Pinot Noir and Sauvignon Blanc... 40 3.2a Introduction...40 3.2b Materials and Methods...42 3.2c Results...43 3.2d Discussion...53 3.2e Conclusions...56 3.3 The impact of variable vine vigour on fruit composition and yield in grapevine (Vitis vinifera L.) cvs Pinot Noir and Sauvignon blanc... 58 3.3a Introduction...58 3.3b Materials and Methods...59 3.3c Results...61 3.3d Discussion...70 3.3e Conclusion...73 3.4 The impact of variable vine vigour on wine composition and fermentation dynamics in grapevine (Vitis vinifera L.) cv Pinot Noir... 75 3.4a Introduction...75 3.4b Materials and Methods...76 3.4c Results...78 3.4d Discussion...85 4 Investigations in to altering vine leaf health with nitrogen fertiliser, and impacts on canopy growth, yield, fruit attributes and wine quality in grapevines (Vitis vinifera L.) cv Pinot Noir... 90 4.1 Introduction... 90 4.2 The impact of addition of nitrogen fertiliser to grapevine (Vitis vinifera L.) cv Pinot Noir at different application timing and rates: Effects on vine canopy and leaf health.. 91 4.2a Introduction...91 4.2b Materials and Methods...91 4.2c Results...95 4.2d Discussion...114 vi
4.2e Conclusion...119 4.3 Nitrogen addition to deficient grapevines (Vitis vinifera L.) cv Pinot Noir at different application timing and rates: Effects on yield, fruit development and fruit attributes. 121 4.3a Introduction...121 4.3b Materials and Methods...122 4.3c Results...124 4.3d Discussion...137 4.3e Conclusion...142 4.4 Nitrogen addition to deficient grapevines (Vitis vinifera L.) cv Pinot Noir at different application timing and rates: Effects on fermentation dynamics and wine attributes. 144 4.4a Introduction...144 4.4b Materials and Methods...145 4.4c Results...146 4.4d Discussion...155 4.5 Comparisons between the impact of supplementing must nitrogen by vine nitrogen applications or by winery applications on wine attributes... 159 4.5a Introduction...159 4.5b Materials and Methods...160 4.5c Results...162 4.5d Discussion...168 5 General Conclusions and Synthesis... 171 5.1a Research conclusions...171 5.1b Conclusions...174 5.1c Implications for management...176 6 Appendix... 178 6.1 Fermentation management: an investigation of small research scale punch down and submerged cap systems... 178 6.1a Introduction...178 6.1b Materials and Methods...179 6.1c Results...180 6.1d Discussion...184 6.1e Conclusion...185 6.2 Soil analyses... 186 vii