Technical Yearbook 2024

FIGURE 1. Variation in soil water content (SWC) during the 2018/19 season where the in-field fractional use (augmentation) of winery wastewater with raw water was used to irrigate young Cabernet Sauvignon grapevines in the C1 plot [P is precipitation, I r is raw water irrigation, and I is where the in-field fractional use (augmentation) of winery wastewater with raw water for vineyard irrigation was applied].

it was decided to decrease the ratio of winery wastewater to raw water at this specific plot. In this regard, from December 2018, a ratio of 25% winery wastewater to 75% raw water was applied, i.e. a fractional ratio of 0.25. In total, nine irrigations were applied to the grapevines growing in the LOR2 experimental plot (Figure 3). In the 2019/20 season, two raw water irrigations and three irrigations using the in-field fractional use (augmentation) of winery wastewater with raw water were applied to the C1 and C2 experimental plots. Five raw water irrigations and two irrigations using the in-field fractional use (augmentation) of winery wastewater with raw water were applied to the BR1 and BR2 experimental plots. Six raw water irrigations and four irrigations using the in-field fractional use (augmentation) of winery wastewater with raw water were applied to the LOR1 experimental plot. Given the extremely poor performance of the grapevines after two seasons of being irrigated according to the in-field fractional use (augmentation) of winery wastewater with raw water at the LOR2 experimental plot, wastewater irrigation at this particular experiment plot had to be terminated from the beginning of the season to prevent any further damage. Salt deposits on the lower section of the grapevine trunks in the LOR2 experimental plot were clearly visible in September 2019 (Figure 4). Thereafter, the vineyard was irrigated according to the grower’s schedule to facilitate the recovery of the grapevines. In the 2020/21 season, winery wastewater was only available at the Coastal region plots from early February 2021. Therefore, until then, where the experimental plots required irrigation, they were irrigated with raw water. As soon as wastewater became available at these sites, the in-field fractional use (augmentation) of winery wastewater with raw water for vineyard irrigation commenced. Four and three raw water irrigations were applied to the C1 and C2 experimental

plots, respectively. Four irrigations using the in-field fractional use (augmentation) of winery wastewater with raw water were applied to the C1 and C2 experimental plots. Four raw water irrigations and two irrigations using the in-field fractional use (augmentation) of winery wastewater with raw water were applied to the BR1 and BR2 experimental plots. Eight raw water irrigations and two irrigations using the in field fractional use (augmentation) of winery wastewater with raw water were applied at the LOR1 experimental plot. The LOR2 experimental plot was still irrigated according to the grower’s schedule to facilitate the recovery of the grapevines. Water quality In the Coastal region, the average pH, EC and COD of the undiluted winery wastewater applied using the in-field fractional use (augmentation) of winery wastewater with raw water for vineyard irrigation over four seasons was 5.53, 1.28 dS/m and 2 440 mg/L, respectively. The average Na, K, Ca and Mg content of the winery wastewater was 34 mg/L, 303 mg/L, 25 mg/L and 8 mg/L, respectively. The average SAR and PAR of the winery wastewater was 1.57 and 8.03, respectively. The average pH, EC and COD of the raw water over four seasons was 7.00, 0.18 dS/m and 3. The average Na, K, Ca and Mg content of the raw water was 19 mg/L, 3 mg/L, 7 mg/L and 4 mg/L, respectively. The average SAR and PAR of the raw water was 1.45 and 0.12, respectively. In the Breede River region, the average pH, EC and COD of the winery water applied using the in-field fractional use (augmentation) of winery wastewater with raw water for vineyard irrigation over four seasons was 5.49, 1.17 dS/m and 4 445 mg/L, respectively. The average Na, K, Ca and Mg content of the winery wastewater was 29 mg/L, 171 mg/L, 38 mg/L and 14 mg/L, respectively. The average SAR and PAR of the winery wastewater was 1.02 and 3.51, respectively. The average pH, EC and COD of the raw water over four seasons was 6.84, 0.24 dS/m and 3 mg/L,

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TECHNICAL YEARBOOK 2024