Pruning Systems and Canopy Management Practice Interact on 'Syrah' Yield and Fruit Composition

A production trial in California's San Joaquin Valley (SJV) was conducted where the canopy microclimate of 'Syrah05/SO4' grapevines was altered through three pruning systems, and two leaf removal treatments arranged factorially to rejuvenate vineyards with declining productivity. Vines were either pruned by hand to 44 nodes each, mechanically box-pruned to a 10 cm hedge, or cane-pruned by hand to six, 8-node canes arranged in opposing directions of the row with horizontal canopy separation. Outer surface layer of leaves were removed mechanically 20 days postbloom on the east side of the canopy in a 45 cm zone above the cordon in the fruit zone, or not. Yields from spur and mechanically box-pruned vines were considered too low for the study area, and leaf removal had no effect on yield components. Spur pruned vines reached 24 °Brix earlier than mechanically box pruned and cane pruned vines, in each year. Leaf removal had no effect on fruit composition of 'Syrah' at harvest. Berry skin phenolics were not consistently affected by treatments applied. Cane pruning resulted in 3.8 leaf layers, with 32 shoots per 30 cm of row, 7.77 kg/kg Ravaz Index, and consistently ripened 22 tons/ha to 24 °Brix and should therefore be used in the SJV to improve yields in vineyards with declining productivity. The study identified a pruning system for vineyards in warm climates that can sustain yields and provides management information for growers on how to rejuvenate vines that have declined in productivity.