Effet des divers niveaux d'irrigation sur les performances végétatives et sur la qualité finale des raisins du cépage Sauvignon blanc cultivé en montagne

EFFECT OF DIFFERENT WATER SUPPLY MANAGEMENT SYSTEMS ON THE
GROWTH AND QUALITY PERFORMANCES OF SAUVIGNON BLANC
GRAPEVINE CULTIVATED IN MOUNTAIN CONDITIONS

Abstract

Climate change will particularly affect temperature and precipitation regimes in Alpine areas. Mountain viticulture will therefore experience new threats for its economical and environmental sustainability. Under such modified climatic conditions, there is a need to enhance the use efficiency of the irrigation water. Against this background, the aim of this research was to investigate the grapevine performances under different levels of water deficit application. The trial was conducted on a young Sauvignon Blanc vineyard located at an altitude of approximately 500 m a.s.l. in a hilly area close to Bozen-Bolzano (South Tyrol, Italy). Treatments consisted of 3 water volume regimes: i) full irrigation (FI, water supplied according the normal farm management); ii) deficit irrigation (DI, 50% of the water volume delivered with FI); iii) no irrigation (rain fed, RF). The main drought period in 2014 occurred between the end of May and the beginning of June, during grapevine blooming. RF and, to a lesser extent, DI vines reacted to this stress by strongly reducing shoot growth and fruit set. July and August were characterized by intense rainfall (approximately 350 mm), which induced a strong vegetative growing activity especially in RF vines. This new period of intense vegetative growth, with the development of numerous lateral shoots, took place in RF vines simultaneously with berry growth and maturation, with possible negative consequences on the vegetative-reproductive equilibrium. Berry average weight was reduced by approximately 50% in RF as compared to FI vines, whereas the reduction was less pronounced for DI vines. Berry quality traits at harvest were only slightly affected by treatments. Although the research is still in progress and data are based only on one vegetative season, the study suggests that the deficit irrigation approach allowed a relevant reduction of irrigation volume, meanwhile maintaining the vegetative-reproductive equilibrium of vines and grape quality. A better understanding of grapevine’s critical periods for water supply is needed in order to achieve optimal results also with deficit irrigation techniques.

Keywords : deficit irrigation, mountain viticulture, water use efficiency, controlled drought stress

Résumé

Le changement climatique va particulièrement affecter les régimes des précipitations et des températures des régions Alpines. La gestion des ressources en eau, forcement limitées, va devenir un enjeu prioritaire. Dans une zone habituellement irriguée (Sud Tyrol, Italie), nous avons étudié les effets de trois niveaux d’irrigation sur les performances végétatives et reproductives, et sur la qualité finale des raisins. Pendant la saison de l'étude (2014), caractérisé par des précipitations élevées en été, des périodes de sécheresse de quelques jours ont été observées pendant la floraison des vignes entre fin mai et début de Juin. Le poids moyen et le rendement en raisins ont été réduits d'environ 50% sans irrigation, par rapport au résultat avec irrigation totale. La qualité des grains de raisin à la récolte présente des différences mineures. Cette étude met en évidence des impacts significatifs de la sécheresse, même sur de courtes périodes pendant la nouaison, et elle suggère la mise en place d’une irrigation visant à satisfaire les besoins en eau de la vigne.

Mots-clés : changement climatique, irrigation, équilibre végétative-reproductive, gestion de l’eau