Application of the regulated deficit of irrigation to grapevines (Vitis vinifera) in a sub-humid area

The use of the Regulated Deficit of Irrigation (RDT) techniques in a sub-humid area, like the Emilia Romagna region (Northern Italy Po Valley), could be difficult. The good rainfall distribution during the summer and the high water storage capacity of the soils often limit the possibility to apply the RDI techniques. The aim of the trial, carried out in the years 1993-98, was to check the possibility to apply RDI on grapevine in the Po Valley and, at the same time, to identify the most suitable irrigation scheduling. The tests in comparison were: NLI (not limited irrigation) water supply from the flowering end to the veraison, according to the daily calculation of a water balance and RDI water supply only during the fruit enlargement stage (from the cluster closure to the veraison) according to the daily calculation of a water balance. In the sub-plots were compared several irrigation regimes: rainfed; 50%, 100% and 150% of ETc. The RDI technique allows a reduction in the water use which ranges from 16.5%, in rainy years, to a maximum of 52.9% in dry years. The yield was not influenced significantly by the application of the RDI technique, neither was the quality of the must. The vegetative growth was not modified in a significant way too. Sugar, acidity and pH evolution trends were recorded according to each treatments. No interaction was observed among the irrigation regimes and the NLI and RDI techniques.