Technical Yearbook 2024

FIGURE 4. Soil EPP´ measured before the in-field fractional use (augmentation) of winery wastewater with raw water for vineyard irrigation commenced, as well as soil EPP´ of the experimental plots and controls at the end of the trial in September 2021.

winery wastewater which contains salts. 3 In heavier soils, less effective leaching is more likely to result in salt accumulation. In another study, winter rainfall could not leach basic cations, particularly K and Na, from two of six soils in a pot study as the amount of the simulated rainfall was too low. 17 Furthermore, more cations are leached from sandy soil than clayey soils. These trends indicated that the leaching would be a function of soil texture, as could be expected, as well as rainfall. The simulation with low rainfall events showed that the basic cations are more likely to accumulate in soils if climate change results in lower winter rainfall in these regions. It was also previously reported in a study representing the worst-case scenario, i.e. large amounts of wastewater disposed of on a small surface, particularly during harvest and in winter, that land application of winery wastewater resulted in the accumulation of high levels of soil K. 18 In a field study

where the re-use of winery wastewater for irrigation was investigated with micro-sprinkler irrigated Cabernet Sauvignon/99 Richter in the Breede River Valley region of South Africa, soil K also increased. 11,19 Where winery wastewater was used for irrigation for over 30 years, an accumulation of K was reported. 20 Likewise, soil surface K increased where winery wastewater was irrigated on two soils typical of the South Eastern Australia Riverine plains for three years. 21 However, there were no changes in sub-soil K due to the slow mobility of K in the soils, which contained 50 - 60% clay. Soil K levels were also higher in vineyards which were irrigated with winery wastewater compared to control vineyard soils. 9 The addition of wine to simulated wastewater used for vineyard irrigation enhanced K movement to the sub-soil. 20 Although the fate of K in soils and grapevines irrigated with winery wastewater has received limited attention, 3 it is almost certain that high soil

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TECHNICAL YEARBOOK 2024