Achieving Vine Balance of Syrah with Mechanical Canopy Management and Regulated Deficit Irrigation

Canopy architecture, yield components, fruit composition, and vigor of Syrah were measured in response to four canopy management and three regulated deficit irrigation (RDI) treatments. The control consisted of dormant hand pruning to 22, two-node spurs (HP) with no further manipulation. Other treatments consisted of mechanically box pruning vines to 10 cm hedges and mechanically thinning the canopy to a density of 5 (CLL) or 7 (CLM) count shoots per 30 cm of row or mechanically box pruning to a 10 cm hedge with no shoot thinning (CLH). Control vines were irrigated to 70% of evapotranspiration (ET0) from fruit set until harvest (RDIC). Other vines either received 70% of full vine ET until veraison and 50% of ET0 (RDIL) thereafter or received 50% of ET between fruit set and veraison (RDIE) and 70% thereafter. Mechanical shoot thinning (CLM) removed 25% of the total shoots, exposing 70,600 shoots.ha(-1) with a distance of 4.6 cm between count shoots on the cordon, which translated to four leaf layers and 12.6 m(2) leaf area. The combination of the CLM and RDIE decreased, berry weight at harvest by 12% without decreasing yield compared to HP, resulting in 21.5 tons.ha(-1) yield. A combination of CLM and RDIE was needed to achieve vine balance with a crop load of 9.9 kg yield/kg pruning weight and a leaf area to fruit ratio of 0.75 m(2).kg(-1). The study identified a canopy management method that can be used in combination with regulated deficit irrigation that reduces input costs through mechanization and enhances berry composition with a vine balance that provides sustainable production.