PRELIMINARY RESULTS OF A LONG-TERM EXPERIMENT ABOUT RDI AND PRD IRRIGATION STRATEGIES IN WINEGRAPES IN SÃO FRANCISCO VALLEY, BRAZIL

In the São Francisco Valley, Northeast Brazil, an evaluation of the regulated deficit irrigation (RDI) and partial rootzone drying (PRD) has been performed in winegrape cv. ‘Syrah’ grafted on rootstocks ‘IAC 572’ and ‘1103 P’. Crop coefficients (Kc) throughout the vineyard establishment and the 1^st cycle was estimated. RDI (depletion until 60% of total available soil water, initiated at the beginning of fruit maturation) and PRD (14 days watering of one side of the vine, initiated at fruit set) were tested in the 1^st cycle. Water amount applied was slightly lower in PRD, so water use efficiency was slightly higher than RDI. Phenology, physiological measurements (net photosynthesis, transpiration, stomatal resistance, leaf water potential), yield, cluster number and weight, total soluble solids, and total titratable acidity were not influenced by irrigation strategies. Only phenol concentration was higher with PRD strategy. Further evaluations throughout growing seasons are needed to remarkable conclusions.