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Response of 'Muscat of Alexandria' wine grapes to irrigation in eastern Spain

Perez, D., Castel, J., Intrigliolo, D. S., Castel, J. R.
Acta horticulturae 2017 no.1157 pp. 343-350
deficit irrigation, irrigation rates, leaf area, malic acid, microirrigation, shoots, small fruits, sugars, titratable acidity, total soluble solids, vines, vineyards, water potential, water shortages, water stress, wine grapes, Spain
An experiment was carried out during 2012 in a mature white grape 'Muscat of Alexandria'/161-46B, drip-irrigated vineyard conducted in a vertically positioned shoot system in Valencia, Spain. Four different irrigation strategies were studied: Sustained Deficit irrigated (SDI) vines irrigated at 50% of estimated crop evapotranspi­ration (ETc) during the whole season were compared with vines irrigated season long at 100% ETc (Control). Irrigation to the Control commenced when midday stem water potential (Ψstem) values reached -0.65 MPa. In addition, a spring water shortage strategy (ED) was applied by withholding irrigation until Ψstem reached -1.0 MPa. After that, 100% ETc was applied. Finally, an LD treatment was irrigated as per the Control up to veraison, and thereafter water application was reduced to approximately 25% ETc until harvest. The results show that no differences in yield among treatments occurred, except in the ED treatment where there was a significant reduction of about 30% with respect to the rest of irrigation regimes. This yield reduction was due to the lower cluster weight (-24%) as a consequence of smaller berry size (-14%) and also to a lower berry number per cluster (-11%). Irrigation at full ETc before veraison (as in the Control and LD) increased the leaf area, mainly due to the higher growth of secondary shoots. There were also differences in berry composition among irrigation strategies. The ED irrigation strategy was more effective than LD in reducing berry growth leading to more concentrated berries in terms of soluble solids content, while the SDI impaired berry sugar accumulation due to the detrimental effects of water stress. There was also a tendency to higher titratable acidity and higher malic acid concentration as the irrigation amount increased. Thus, in our conditions of scarce water resources, applying moderate water deficits during the entire season, as in the SDI treatment, was the most convenient irrigation strategy.