Handbook for Irrigation of Wine Grapes in South Africa

Chapter 6

" Wet"

" Dry"

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į 13 C

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FIGURE 6.10. Comparison between δ 13 C of Merlot/110 R in “wet” and “dry” plots within the same vineyard near Stellenbosch (adapted from Strever & Myburgh, 2018). Vertical bars indicate ± one standard deviation. -27 Since δ 13 C measurements can only be carried out by specialized laboratories, it may take some time to obtain the results. Therefore, it is not suitable for determining grapevine water status for irrigation management. However, δ 13 C measurements can be useful in research studies to compare the degree of cumulative water constraints between different irrigation strategies, and the effect thereof on grapevine growth, yield and wine quality characteristics. The relationships between selected grapevine responses and δ 13 C, as well as midday Ψ S , are illustrated in Figure 6.11. In this particular study, the effects of low and high frequency irrigation on grapevine rows or in work rows, as well as partial root zone drying on Merlot/99 R, were compared to no irrigation. Measuring δ 13 C in terroir studies can also be of great value to compare cumulative grapevine water constraints between different localities.

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