Technical Yearbook 2024

FIGURE 3. Soil K measured before the in-field fractional use (augmentation) of winery wastewater with raw water for vineyard irrigation commenced, as well as soil K of the experimental plots and controls at the end of the trial in September 2021.

of salts during the grapevine growing season partly due to irrigation with augmented winery wastewater containing salts. 3 Furthermore, less effective leaching in heavier soils is more likely to result in salt accumulation. Soil K of the C1 experimental plot in September 2021 was higher compared to the baseline levels for all the soil layers (Figure 3). This indicated that under the prevailing conditions, irrigation with the in-field fractional use (augmentation) of winery wastewater with raw water led to an accumulation of soil K even in the loamy sandy soil in the higher rainfall region. Soil K of the C2 experimental plot was substantially higher than baseline levels up to a depth of 90 cm (Figure 3). The accumulation of the K was substantially higher in the sandy loam soil compared to the loamy sand one. In heavier soils, less effective leaching is more likely to result in salt accumulation. In September 2021, soil K in all soil layers of the BR1 and

BR2 experimental plots was higher than the baseline values (Figure 3). Furthermore, K accumulation was substantially higher in the sandy clay loam soil compared to the sandy loam one. Soil K levels of the LOR1 experimental plot in September 2021 were substantially higher than the baseline values up to a depth of 150 cm (Figure 3). The greater accumulation of soil K in the LOR1 experimental plot was a result of higher amounts of K applied via the irrigation water in conjunction with lower winter rainfall. 13 The soil K of the LOR2 experimental plot when the winery wastewater irrigation was terminated was substantially higher compared to the baseline values (Figure 3). At the end of the trial in September 2021, soil K was substantially higher for all of the experimental plots, except for LOR2, compared to their controls (Figure 3). This trend indicated an accumulation of K during the grapevine growing season partly due to irrigation with augmented

59

TECHNICAL YEARBOOK 2024