Producing more grapes with the same amount of water is a way to increase water use efficiency. It also ensures economic sustainability in areas where rainfall is limited, and irrigation is needed to achieve acceptable crop levels. The question posed by the researchers was, can it be done, and what is the impact on growth and juice analysis?
Project layout
Pinotage grafted onto 99R was used at the ARC site in Robertson. The experimental layout was a split-plot, randomised block design. Irrigation treatments included combinations of 50% of readily available water (RAW) depletion, 75% RAW depletion and no irrigation (NI) during budburst, flowering, pea size, veraison, 17ºB and harvest. Trellis system treatments were split between a six-strand vertical hedge and a two-tier vertical trellis. Measurements included cane mass, soil water content, yield components and juice analysis.
Results
- Vine cane mass was lower in the two-tier trellis system compared to the six-strand hedge.
- Irrigation at 75% RAW from budbreak until harvest yielded lower cane mass than more frequent irrigation treatments (50% RAW).
- Drier soils reduced berry mass in both trellis system treatments.
- Sustained water deficit treatments reduced yield but had a limited effect on juice pH and acidity.
- The two-tier vertical trellis produced a higher crop than the six-strand hedge with the same amount of irrigation.
Significance of the study
This study proves that water use efficiency can be improved by using alternative trellis systems that use the same amount of water but have the potential to bear higher crops without affecting juice pH or acidity. However, irrigating at a set depletion level (in this case, 75% of RAW) is important to achieve these benefits. The combination of effective irrigation, together with canopy choice/management, is what delivers quality at a high water use efficiency.
Reference
Howell, C.L. and Myburgh, P.A. (2024). Response of Vitis vinifera L. cv. Pinotage to irrigation strategy and trellis system in the Breede River Valley Region: Vegetative growth, yield and juice characteristics. A. Afr. J. Enol. Vitic., Vol. 45. DOI: https://doi.org/10.21548/45-2-6531
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