Technical Yearbook 2024

Breede River regions, but in the Lower Olifants River region, the experimental plots were on separate farms. Both experimental plots in the Coastal region formed part of a newly planted commercial Vitis vinifera L. cv. Cabernet Sauvignon/US8-7 vineyard which was established in September 2017 (Table 2). The plots in the Breede River region were part of a commercial V. vinifera L. cv. Shiraz/SO4 vineyard which was established in 2001. In the Lower Olifants River region, a V. vinifera L. cv. Shiraz/Ramsey vineyard, established in 2012, was selected near the Lutzville Winery to represent the deep, sandy soil which is typically found in the region. At Spruitdrift, the experimental plot was a V. vinifera L. cv. Cabernet Sauvignon/99R vineyard established in 2001 in a shallow, sandy loam soil overlying Dorbank. Each of the six experimental plots compromised of two rows of 10 grapevines each, i.e. 20 experiment grapevines per plot. A buffer row of grapevines was located on the one side of each of the experiment rows and two buffer grapevines at each end that also received the in-field fractional use (augmentation) of winery wastewater with raw water for vineyard irrigation. Based on general plant spacing in South African vineyards, each experimental plot covered approximately 80 m 2 . They were managed according to the grower’s normal viticultural practices in terms of canopy management. No fertilisers were

applied with the exception of 20 kg/ha LAN in the winter of 2018 in the Coastal region. Weeds were removed routinely by means of chemical and mechanical control. Soil texture In terms of soil texture, clay content in the 0 - 30 cm soil layer ranged from 5 - 27% (Figure 2), and in the 30 - 60 cm soil layer ranged from 5 - 29%. In the 60 - 90 cm soil layer, clay content ranged from 3 - 25%. The silt content in the 0 - 30 cm soil layer ranged from 5 - 27% (data not shown). The silt content in the 30 - 60 cm soil layer ranged from 0 - 14% (data not shown). In the 60 - 90 cm soil layer, silt content ranged from 4 - 12% (data not shown). The sand content in the 0 - 30 cm soil layer ranged from 59 - 95% (Figure 3), and in the 30 - 60 cm soil layer ranged from 57 - 91%. In the 60 - 90 cm soil layer, the sand content ranged from 63 - 91%. The lighter textured soil in the Coastal region was classified as a loamy sand, whereas the heavier textured soil was classified as a sandy loam to sandy clay loam. In the Breede River region, the lighter textured experimental plot was characterised as a loamy sand to sandy loam. The heavier textured soil was classified as a sandy clay loam. The two plots in the Lower Olifants River region were both sandy. However, one was a deep, sandy soil of aeolian origin, whereas the other had a shallow surface layer of sandy loam soil overlying Dorbank.

TABLE 2. Vineyard characteristics, including scion cultivar, rootstock, plant spacing, planting date and trellis system of the experimental plots in the Coastal, Breede River and Lower Olifants River regions where grapevines were irrigated using the in-field fractional use (augmentation) of winery wastewater with raw water. Plot no. Scion cultivar Rootstock Spacing (m × m) Planting date Trellis system C1 Cabernet Sauvignon US8-7 3.0 × 0.6 2017 Modified Lyre C2 Cabernet Sauvignon US8-7 3.0 × 0.6 2017 Modified Lyre BR1 Shiraz SO4 2.5 × 1.5 2001 5-strand lengthened Perold BR2 Shiraz SO4 2.5 × 1.5 2001 5-strand lengthened Perold LOR1 Shiraz Ramsey 2.0 × 2.0 2012 5-strand lengthened Perold LOR2 Cabernet Sauvignon 99R 1.5 × 2.6 2001 4-strand lengthened Perold TABLE 1. Experimental plots selected for determining the effect of the in-field fractional use (augmentation) of winery wastewater with raw water for vineyard irrigation on soil properties and grapevine responses in different climatic regions according to the Winkler index. Wine region Climatic index Locality Plot Soil texture Cultivar Coastal III Paarl Backsberg farm (C1) Loamy sand Cabernet Sauvignon Backsberg farm (C2) Sandy clay loam Cabernet Sauvignon Breede River V Robertson Madeba farm (BR1) Sandy loam Shiraz Madeba farm (BR2) Sandy clay loam Shiraz Olifants River V Vredendal Lutzville Winery (LOR1) Deep sand Shiraz Spruitdrift Winery (LOR2) Shallow sand Cabernet Sauvignon

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TECHNICAL YEARBOOK 2024