Technical Yearbook 2023

TABLE 4. The macro-element status of the juice of the Shiraz/110 Richter vines irrigated full surface with micro-sprinklers at Nietvoorbij research farm near Stellenbosch during harvest (February 2018). Treatment no. Catch crop/cover crop combination P (mg/L) K (mg/L) Ca (mg/L) Mg (mg/L) Na (mg/L) 1 Pearl millet/Oats 25 1 215 139 308 9 2 Pearl millet/N-fixing mixture 28 933 144 319 10 3 Dolichos beans/Oats 27 1 132 141 297 7 4 Dolichos beans/N-fixing mixture 29 854 146 334 8 5 Chicory/Oats 33 1 022 146 344 9 6 Chicory/N-fixing mixture 27 1 189 123 302 8 7 None/Oats 29 874 139 293 7 8 None/N-fixing mixture 26 750 122 293 7 LSD (p=0.05) NS NS NS NS NS

3), as well as the 2018/19 and 2019/20 seasons (data not shown). In another study where grapevines were irrigated with diluted winery wastewater, grapevine yield and cane mass was also not affected. Although the nutrient content of the grape juice did not differ significantly with respect to the different combinations of catch and cover crops (table 4), juice K and Na of the treatments irrigated with diluted winery wastewater tended to be higher than those irrigated with raw water. The use of diluted winery wastewater for vineyard irrigation also tended to increase juice K where the level of dilution of the winery wastewater was lower. The tendency towards higher juice K where diluted winery wastewater was used for irrigation is probably due to the higher amounts of K added to the soil via the irrigation water. Sensory analyses of the experimental wines over the three vintages showed no consistent negative attributes that could be linked to potential off-odours that may have been carried over from the winery wastewater (data not shown). Overall, experimental wines made from treatments T2, T3, T6 and T8 were inferior to wines from the control (T7), but these differences were inconsistent with respect to the different catch- and cover crop treatments, as well as the different quality of water used for irrigation. Conclusions Under the prevailing conditions, treatments did not affect vineyard performance negatively in terms of leaf petiole, blade, yield, berry mass, cane mass, as well as juice element composition. Sensory analyses of the wines showed no consistent negative aroma attributes that could be linked to the use of winery wastewater for vineyard irrigation. In regions with lower winter rainfall, situations where the winery wastewater contains more K or where no catch crop is grown, grapevine responses may be more pronounced.

Abstract Wineries produce large volumes of poor quality wastewater. In contrast, scarce irrigation water could be restricted further in the future. Where wineries are surrounded by vineyards, diluted winery wastewater could be used as an alternative source of water for vineyard irrigation. The objective of this study was therefore to determine the growth, yield, juice and wine quality of a vineyard irrigated with diluted winery wastewater where there were different combinations of catch and cover crops. Diluted winery wastewater was applied to a Shiraz vineyard where combinations of three different fodder producing summer catch crops and two winter cover crop treatments were compared to a control. The region where the field trials took place has a Mediterranean climate. The macro-element content of the leaf petioles and blades did not differ between treatments. Yield, berry mass at harvest and cane mass also did not differ between treatments. Irrespective of catch crops, the application of diluted winery wastewater rather than raw water in the vineyard tended to increase juice K. This was expected given that winery wastewater contains high levels of K. Sensory analyses of the wines showed no consistent negative aroma attributes that could be linked to the use of winery wastewater. 

References https://www.wineland.co.za/winery-wastewater-for irrigation-part-5/

For more information, contact Carolyn Howell at howellc@arc.agric.za.

60

TECHNICAL YEARBOOK 2023