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.