Technical Yearbook 2024

wastewater had been applied. 12 In addition, the leaves of the grapevines receiving the winery wastewater contained more Na and magnesium (Mg) and less K and calcium (Ca) than the control. Unfortunately, no data pertaining to grapevine yield and its’ parameters were presented by the authors. If winery wastewater irrigation is applied, such as overhead irrigation, contact between irrigation water and bunches is inevitable. Grapevines exposed to smoke between véraison and harvest caused a ‘smoke taint’ in the resulting wines. 13 Wines made from grapevines, which are situated near Eucalyptus tree plantations, have also been found to obtain higher Eucalyptus -like or minty characters, which may be obtained from the trees. 14,15 If these odours can be transferred from the atmosphere onto or into grapes and the resulting wines, it is also possible that the foul odour of winery wastewater could be transferred onto or into grapes and wine if there is direct contact between the wastewater and the grapes. In a study where grape bunches were deliberately sprayed with diluted winery wastewater, a winery wastewater like odour was detected in the wines, and their spicy character was reduced. 16 This research highlights the importance of avoiding contact between grapes and winery wastewater. Where Shiraz grapevines were irrigated with sewage water, there were also no differences with regard to wine quality. 17 Likewise, although there were slight differences with regard to wine colour and tannin content where winery wastewater was used for vineyard irrigation, there were no differences in the sensorial evaluation of the wines. 18 Irrigation of grapevines using diluted winery wastewater did not have detrimental effects on juice characteristics regarding ripeness parameters, ion content and wine sensorial quality. 11 Where winery wastewater was used to irrigate two vineyards in California, there was no difference in wines from control and where grapevines were irrigated with winery wastewater. 12 If winery wastewater could be used to irrigate vineyards with no detrimental impacts on grapevines or wine, it could be a viable alternative to abstracting raw water from natural resources. Therefore, the objective of this study was to determine the effect of irrigation with in-field fractional use (augmentation) of winery wastewater with raw water on grapevine growth, yield and wine characteristics. Methods Details of the plot selection, augmentation, climatic conditions, irrigation application, water quality, nutrient load and soil responses were given previously. 19 Briefly, there was a loamy sand (C1) and sandy clay loam (C2) experimental plot in the Coastal region, a sandy loam (BR1) and sandy clay loam (BR2) experimental plot in the Breede River region, as well as a deep sand (LOR1) and shallow sand (LOR2) experimental plot in the Lower Olifants River. Experimental plots were irrigated using the in-field fractional use (augmentation) of winery wastewater with raw water for vineyard irrigation from the 2017/18 to 2020/21 seasons. Experimental grapevines in the Breede River and Lower Olifants River regions were pruned to two bud spurs in July 2017, and the baseline cane mass per grapevine was determined. Thereafter, to quantify growth vigour in

each season, cane mass at pruning (July) was weighed per experimental plot using a hanging balance. The cane mass per experimental plot (kg) was converted to tons per hectare. It should be noted that each of the selected vineyards had an experimental plot that was irrigated with winery wastewater, and this was compared to the rest of the surrounding vineyard block, which acted as the control. The cane mass of the control was also measured in the 2018/19, 2019/20 and 2020/21 seasons. Grapes were harvested as close as logistically possible to a total soluble solids (TSS) value of 24°B. Ten bunches were randomly picked at harvest to determine berry mass. All bunches of the experimental grapevines of each experimental plot were picked and counted. Grapes were weighed using a top loader mechanical balance to obtain the total mass per experimental plot. The number of bunches per grapevine was calculated by dividing the total number of bunches per experimental plot by the number of experimental grapevines per plot. Grape mass per grapevine (kg/grapevine) was calculated and converted to yield (t/ha). Wines were made from the grapes of each experimental plot according to the standard procedure for making red wine used by the experimental winery at ARC Infruitec-Nietvoorbij. After seven months, a panel of at least 12 industry experts evaluated the wines sensorially for wine colour, overall intensity, vegetative character, berry character, spicy character, acidity, body, astringency and overall quality. A commercial laboratory analysed the wines for their element content. Results Cane mass Following one season of irrigation with the in-field fractional use (augmentation) of winery wastewater with raw water, cane mass decreased at both experimental plots in the Lower Olifants River region (Figure 1). However, the decline was more pronounced at the LOR2 experimental plot. Cane mass at the BR1 and BR2 experimental plots differed substantially prior to the in-field fractional use (augmentation) of winery wastewater with raw water. The reason for this difference is still uncertain. However, soil compaction due to tractor traffic is more likely to occur at the BR2 experimental plot due to the heavier soil texture. Therefore, the lower vegetative growth may have resulted from restricted root development. Compared to the baseline values, cane mass at both BR1 and BR2 experimental plots remained unchanged after the 2017/18 season. This was to be expected since only two irrigations were applied at these experimental plots during the 2017/18 season. 19 Since the grapevines in the Coastal region were only planted in September 2017, baseline cane mass was not determined at these experimental plots prior to the in-field fractional use (augmentation) of winery wastewater with raw water. Cane mass at pruning was substantially lower in the 2018/19 season compared to the baseline values measured during July 2017 (Figure 1). Cane mass at the LOR1 experimental plot showed a progressive decline since winter 2017. The cane mass at the LOR2 shallow sand experimental plot showed a substantial decline from the baseline value and

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TECHNICAL YEARBOOK 2024