Effects of different deficit irrigation strategies on vine water status, canopy and cluster temperatures, fruit total phenolics, and the color of white table grapes (Vitis vinifera L., cv. Muscat of Alexandria) were compared to a well-irrigated control in 2004 from veraison to harvest at the Okayama University Experimental Vineyard, Japan. The treatments included: (1) well-irrigated control: re-irrigation when the soil moisture tension reached 15 kPa; (2) regulated deficit irrigation (RDI): re-irrigation 4 to 7 days after reaching a soil moisture tension of 15 kPa; (3) fixed partial root-zone wetting (FPRW): one part of the root system was re-irrigated when the soil moisture tension reached 15 kPa; and (4) alternate partial root-zone wetting (APRW): one part of the root system was re-irrigated when the soil moisture tension reached 15 kPa, and every week the irrigated part was switched. As the stress developed in RDI vines, leaf water potential and transpiration rate decreased and canopy and cluster temperatures increased as compared
with the control. In contrast, both FPRW and APRW vines had similar leaf water potential and canopy and cluster temperatures, but less leaf transpiration rate as compared with the control. At harvest, fruits from all treatments had higher skin total phenolics and CIELAB a* values than
the control. RDI fruit had higher total soluble solids (TSS), a similar acidity, and smaller size compared with the control. FPRW and APRW fruits had slightly higher TSS, lower acidity, and a similar size compared with the control.
grape
deficit irrigation
partial root-zone wetting
phenolics
color