Technical Yearbook 2024

FIGURE 1. Effect of in-field fractional use (augmentation) of winery wastewater with raw water on pruning mass measured for the (A) deep sand at LOR1, (B) shallow sand at LOR2, (C) sandy loam at BR1, (D) sandy clay loam at BR2, (E) loamy sand at C1, and (F) sandy clay loam at C2 in 2017, 2018, 2019, 2020 and 2021.

was also substantially lower than the control. There was a decline in cane mass in July 2019 for the BR1 experimental plot and a substantial decline in the cane mass for the BR2 experimental plot. Furthermore, the cane mass of the BR2 experimental plot was substantially lower than the control. The general decline of cane mass after two seasons of the in-field fractional use (augmentation) of winery wastewater with raw water at the experimental plots was a matter of concern. Since grapevine growth is quite sensitive to adverse environmental conditions, this trend raised questions about the sustainability of using wastewater for irrigation, irrespective of wastewater quality. Although cane mass at the LOR1 deep sand experimental plot had shown a progressive decline since the start of the project, the application of more water in the 2019/20 season improved cane mass in July 2020 (Figure 1). Cane mass at the LOR2 experimental plot showed a substantial decline from the baseline value, but had started to recover given that there was no in-field fractional use (augmentation) of winery wastewater with raw water at this experimental plot during the 2019/20 season. However, the growth at this particular site was still substantially lower compared to the control. There was a substantial decline in cane mass for the BR1 experimental plot, whereas the cane mass of the

BR2 experimental plot was similar to the previous season. The cane mass of the experimental plot at BR2 was still substantially lower than the control. At the end of the trial in 2021, the cane mass of the LOR1 deep sand and BR1 experimental plots was comparable to baseline values. However, the cane mass at the BR2 experimental plot was lower than the baseline values. This suggested that the in-field fractional use (augmentation) of winery wastewater with raw water adversely affected these particular grapevines. Despite the high amounts of K applied via the in-field fractional use (augmentation), the experimental grapevines did not contain excessive K levels in their leaves (data not shown). However, Na was accumulated in the grapevine leaves of the BR2 experimental plot. Furthermore, this particular experimental plot also had a higher leaf blade Na than the control. This suggested that under the prevailing conditions at this particular climate/soil combination, the amounts of elements applied via the in-field fractional use (augmentation) of winery wastewater with raw water and less effective leaching caused the Na to accumulate in the grapevine. The BR2 experimental plot had substantially higher permanent wood Na levels compared to the control. Given the accumulation of Na in the leaves and permanent wood part of this particular experiment plot, this is a likely explanation for

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TECHNICAL YEARBOOK 2024