Study of the effects of different irrigation scheduling on some vegetative and productive characteristics of 'Vermentino'

The irrigation of vines in Sardinia is often based on empirical evaluations and does not take into account actual crop needs and soil water content. The new vineyards are often equipped with modern irrigation systems characterized by high efficiency, but they are often little or badly used by farmers. This leads to unbalanced irrigation timing and volumes, physiological problems in plants, percolation and run off of nutritional elements. The main aims of the trial were therefore to evaluate the changes of grape production and wine characteristics induced by irrigation treatments, to define the limits of farmer irrigation management compared to the deficit irrigation strategy and to improve the water use efficiency. The trial was carried out in Southern Sardinia on 'Vermentino' in 2009 and 2010. Three different irrigation scheduling were compared: two levels of deficit irrigation (DI-7d and DI-14d), and the farmer irrigation management (IS). The test was performed according to a randomized block scheme with three replications. During the vegetative phase phenology, xylem water potential, soil water content and the productive factors were measured. On must and wine, the main quality parameters were evaluated. Production was significantly affected by the increase in water volume only in 2010, when DI-7d recorded the highest production and the lowest irrigation efficiency. The irrigation management DI-14d induced a greater increase of irrigation efficiency, but a significant productive decrease in 2010. IS proved to be a wasteful irrigation strategy due to an increased use of water resources and energy in comparison to DI-14d. Qualitative results on the must showed the highest sugar content in IS, whereas acidity was higher in DI-7d. The quality of wine in DI-14d resulted higher than the other two treatments, in particular aromatic intensity, finesse and harmony fragrance. In 2010, no differences were observed in musts and wines. Irrigation management DI-14d permitted an easier management of irrigation scheduling compared to IS and, if widely adopted, may result in more frequent irrigation timing which gives a reduced impact of irrigation in the soil system.