Evaluation of the effects of two deficit irrigation strategies on Vitis vinifera 'Cabernet Sauvignon' yield, fruit composition, cold acclimation and hardiness
Basinger, Ashley R.
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Regulated Deficit Irrigation (RDI) and Partial Rootzone Drying (PRD) were evaluated for effects on total yield, fruit composition, periderm development, bud cold hardiness, and xylem sap ABA concentration. RDI treatments in 2002 were applied at the following stages: post-fruit set to veraison, veraison to harvest, post-harvest, and no-deficit control. Treatments in 2003 were post-fruit set to veraison and no-deficit control. The PRD treatments consisted of water application to alternating halves of the rootzone (PRD), application of an equal volume of water to both halves of the rootzone (Equal), and application of 2X volume of water to both halves of the rootzone (Double). RDI treatments in 2002 produced significantly lower yield and cluster weight from the postfiriit set to veraison treatment, but there was no difference in 2003. Soluble solids content was significantly higher in 2003 in the post-fruit set to veraison treatment compared to no-deficit; 24.6 and 23.6 °Brix, respectively. Periderm development began earlier and occurred at a faster rate in the post-fruit set to veraison RDI treatment compared to other RDI treatments and no-deficit, but earlier periderm development did not result in greater bud cold hardiness. Xylem sap ABA content peaked during the post-fruit set to veraison water deficit period, which coincided with the onset of periderm development. For all parameters in both years, PRD was not significantly different from Equal. The Double treatment had significantly higher yield, and lower soluble solids in 2003 compared to PRD and Equal. In both years, Double had significantly later periderm development than PRD and Equal. Double was slightly lower in bud cold hardiness at the first two sampling dates in October 2003, and again for two dates in December. Our results suggest that RDI has potential for reducing water usage with little if any penalty in yield or fruit quality, and can advance periderm development. Earlier periderm development was related to slighter better bud cold hardiness at some sampling dates in PRD studies. The PRD irrigation strategy performed similarly to standard deficit irrigation with an equal volume of water applied to the entire root system