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

Abstract

Canopy architecture, yield components, fruit composition and vigor of Syrah were measured in response to the following treatments. Four crop load levels were imposed by dormant pruning to 22, two node spurs (HP) with no further manipulation, and mechanically box-pruning others to 10 cm hedges and mechanically thinning the canopy to a density of five (CLL); and seven count shoots/30 cm of row (CLM); or mechanically box-pruning to a 10 cm hedge with no shoot thinning (CLH). Control vines were irrigated to 70% of ET_o from fruit set until harvest (RDIC). Other vines received 70% of full vine ET_o until veraison, and 50% of ET_o (RDIL) thereafter or vines received 50% of ET_o 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. This translated to four leaf layers and 12.6 m² of 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. To achieve vine balance with a crop load of 9.9 kg of yield/kg of pruning weight and a leaf area to fruit ratio of 0.75 m²·kg⁻¹, a combination of CLM and RDIE was needed. The study identified a canopy management method that can be used in combination with RDI that reduces input costs through mechanization, enhances berry composition with a vine balance that provides sustainable production.