Project Number: WW 12-20B (100557)
Project Title: The effect of row orientation, soil water status and ripeness level on the physiological, viticultural and enological performance of Shiraz/101-14 Mgt
Project Leader: Dr Kobus Hunter
Objectives & Rationale:
Determine the combined effect of row orientation, plant water status and ripeness level on the physiological, viticultural and oenological (wine style) performance of Shiraz/101-14 Mgt. Advanced knowledge is required to improve the establishment, management, and outcomes of vineyards on terroirs in different environmental conditions (climate, soil, topography).
Methods:
The project is carried out at Robertson experiment farm of ARC Infruitec-Nietvoorbij, using VSP trellised Shiraz(clone SH 9C)/101-14 Mgt, planted during 2003 to four-row orientations (NS, EW, NE-SW, NW-SE) on flat terroir with uniform clayey loam soil. Vines are spaced to a fixed distance of 1.8 x 2.7 m and pruned to two buds per spur. Two water deficit levels are applied to each row orientation treatment, i.e. 75 % and 50 %, of the control (reference), the latter receiving the full soil water adjustment per week (based on ET0 values and standard seasonal crop factors).
Key Results:
• Total relative evapotranspiration (ETo) fluctuated prominently according to Tmax, RHmin and especially Radiation changes.
• Technical sensor installation, vine growth, and management practices are important in the correct determination of grapevine response.
• Photosynthetic activity of EW control and 75% irrigation treatments seemed highest, and the 50% irrigation treatment tended to be lower across row orientations. The photosynthetic activity of primary leaves decreased during the season, confirming the importance of correct management to increase the presence of younger leaves to support grape ripening. Stem water potential generally decreased with a higher water deficit.
• Clear diurnal and nocturnal profiles of photosynthesis and water potential occurred.
• Physiological response of vines to various environmental factors (light, water availability, temperature, humidity) is complicated and requires knowledge at whole plant level.
• Results on vegetative and reproductive growth characteristics, as well as grape composition, were variable, but trends are surfacing.
• A thorough understanding of vines’ physiological response mechanisms to management practices and environmental conditions is required for sound deductions in the field.
Conclusion/Discussion:
The past season was the second during which water deficit treatments in combination with row orientation were introduced. Trends, as discussed, may, therefore, change, and others may become more prominent as vines respond with time. Differences between row orientation/irrigation treatment combinations surfaced, but no factual deductions from results are possible at this stage.
Publications:
1. Hunter, J., & Volschenk, C. (2024). Vine spacing of Vitis vinifera cv. Shiraz/101-14 Mgt. I. root growth and physiological activity . OENO One, 58(1). https://doi.org/10.20870/oeno-one.2024.58.1.7827
2. Hunter, J. J., & Volschenk, C. G. (2024). Vine spacing of Vitis vinifera cv. Shiraz/101-14 Mgt II. Establishment, and vegetative and reproductive growth. OENO One, 58(3). https://doi.org/10.20870/oeno-one.2024.58.3.7828
3. Hunter, J. J., Booyse, M., & Volschenk, C. G. (2024). Vine spacing of Vitis vinifera cv. Shiraz/101-14 Mgt. III. Grape and wine quality. OENO One, 58(3). https://doi.org/10.20870/oeno-one.2024.58.3.7829
Final Progress Report WW 12-20B (100557)