PREFACE

The participants came from 12 different countries and from tropical, subtropical and 'cool climate' regions and from irrigation and non irrigation areas. The importance of water for photosynthesis and production was obvious in virtually all papers. Different approaches were presented to use this knowledge for the production of quality grapes and wine.

During an excursion to the 'Mundelsheimer Käsberg', a step hill site in the heart of the wine growing region of Württemberg, the participants learned about traditional grape growing in Germany and the particular drought problems on shallow, gravely soils with low water holding capacity.

On behalf of the organisation committee, I hope that it was a successful meeting for all participants, that they heard interesting presentations, saw new data, had interesting discussions and enjoyed - like us - the company of colleagues working on the same subject and aiming to increase the knowledge in the field of 'Water Relation of Grapevines'.

I would like to thank everybody involved in the preparation and actual running of the workshop, in particular Dr. Dietmar Rupp, from the Weinsberg Research Station for organising the excursion to Mundelsheim and Wildeck, the staff of the Deutsche Weinbauverband (German Wine Grower Association) for their patience with us during the meeting, Dr. John Possingham and Dr. Reinhard Muth for the idea of the workshop.

Finally, a special thank you to all participants(German Wine Grower Association), for coming, presenting their results and ideas and turning the workshop in a success for all of us.


Ernst H. Rühl
Geisenheim, June 1999


FOREWORD - WATER RELATIONS OF GRAPEVINES

It gives me great pleasure to provide some opening remarks to this I.S.H.S. Viticultural Section, Workshop concerned with the "Water relations of grapevines".

It is abundantly clear that our convener professor Rühl has chosen a topic that is of very real interest to vitculturists and vine-physiologists from many parts of the world. We have with us today scientists who have come from a wide cross-section of the world's grape-growing countries including participants from the USA, Venezuela, Israel, South Africa, Australia, as well as many from the grape growing countries of Europe.

There a number of papers concerned with measuring of the water usage of grapevines using some of the newer direct methods such as heat pulse sensors. There are others in which vine water usage has been calculated from changes in soil water content. Another group of papers are concerned with evapo-transpiration aspects and with the diurnal variations which occur in the water potential of grape vine leaves and stems. These provide highly reliable information about plant water status but are difficult methods for growers to to use.

There are a group of papers concerned with the effects of vine water status on aspects of grape and wine quality. Wine grape quality has been a recurring theme in the workshops of the viticultural section for the obvious reason that currently we are faced with the paradox of a very strong world demand for quality wine and a sharply falling demand for ordinary wine.

There are a number of papers in which the responses of grapevines and grapes to supplemental water have been measured which will inevitably draw our discussions towards the viticulturally vexed question of irrigation. Dependant on where one comes from viticulturists have either a love or a hate relationship with irrigation. In climates where there is little or no summer rain grape vines are increasingly irrigated. However in a number of European countries irrigation is not permitted and accordingly this topic is not extensively studied. Perhaps these divergent attitudes are at a point of change as field experimentation is demonstrating that the judicious addition of supplemental water to grapevines can increase both the quantity and quality of production.

In a number of new world countries grapevine vines have been planted in viticultural areas where they would not survive through the hot summer months if they were not irrigated. It is now becoming clear that wines of moderate to high quality can be produced in these areas by choosing appropriate varieties and using some of the newer irrigation technologies such as drip, fertigation, regulated deficit irrigation and more recently partial root zone wetting (or is it partial drying?).

Perhaps in these opening remarks I have stressed the importance of supplemental water too much, but this is because I am of the view that as we learn more about the "Water relations of grapevines" we will have a powerful tool in water that is capable of modifying and improving both the production level of grapevines and the quality of the grapes. I congratulate the convener and his organising committee on the choice of topic and on the quality of the speakers they have been able to attract to Stuttgart, Germany. I also believe it has been an excellent idea to hold this meeting at the same time as the "Intervitis" meeting of the German Grape Growers Association. The combination of a trade gathering with a scientific meeting is a powerful synergy.

I am sure this workshop will cause us to challenge our existing ideas about the water relations of grapevines and it will enable us to advance our knowledge in this important practical area.