Winetech Technical Yearbook 2022

FIGURE 1. Irrigation graph of Shiraz from October to the end of December 2020.

PHOTO 2. Pressure bomb.

TABLE 2. Threshold values for water stress classes for wine grapes according to pre-dawn leaf water potential ( Ψ PD ), as well as mid-day leaf water potential ( Ψ L ) and stem water potential ( Ψ S ).

Water potential (MPa)

Class

Water stress

Ψ PD

Ψ L

Ψ S

Ψ PD ≥ -0.2

Ψ L ≥ -1.0

Ψ S ≥ -0.6

I

None

-0.2 > Ψ PD ≥ -0.4 -0.4 > Ψ PD ≥ -0.6 -0.6 > Ψ PD ≥ -0.8

-1.1 > Ψ L ≥ -1.2 -1.2 > Ψ L ≥ -1.4 -1.4 > Ψ L ≥ -1.6

-0.6 > Ψ S ≥ -0.9 -0.9 > Ψ S ≥ -1.1 -1.1 > Ψ S ≥ -1.4

II

Mild

II

Moderate

IV

High

Ψ PD < -0.8

Ψ L < -1.6

Ψ S < -1.4

V

Severe

80

WINETECH TECHNICAL YEARBOOK 2022