Partial root-zone drying irrigation, shading, or mulching effects on water savings, productivity and quality of 'Syrah' grapevines

The effects of irrigation water savings by partial root zone drying (PRD) irrigation, shading or mulching on physiology, growth, yield, and wine quality of 'Syrah' grapevine (Vitis vinifera L.) was investigated. The study was conducted in a vineyard at two different sites, each with a different soil type and vegetation index. Plants were subjected to the following four treatments: T0) control, with conventional irrigation regimes used by local growers; T1) shade cloth covering the vine canopy resulting in a 50% reduction in irrigation volume compared to the control; T2) double color plastic mulch (white color facing up and black on the inside facing the soil) resulting in a 50% reduction in irrigation volume compared to the control; and T3) PRD irrigation resulting in a 50% reduction in irrigation volume compared to the control. In general, the use of PRD irrigation, shade cloth or plastic mulch did not significantly affect the physiological, growth or yield variables measured, except for fruit cluster weight, which was lower in T3 than in the other treatments, and wine alcohol and polyphenol content, which were higher in T3 than in the other treatments. Shade cloth and plastic mulch treatments resulted in a 50% reduction in water use with no detrimental effects on plant physiology, yield, or wine quality. In addition to a 50% reduction in the amount of irrigation water applied, PRD irrigation also improved wine quality by increasing alcohol and polyphenol contents.