Technical Yearbook 2023

DECEMBER

Winery wastewater for irrigation (Part 5): Grapevine and wine responses Large volumes of poor quality wastewater are produced by wineries. On the other hand, scarce irrigation water could be restricted further in future irrigation water allocations. Where wineries are surrounded by vineyards, diluted winery wastewater could be used as an alternative source of water for irrigation rather than water from natural resources.

By Carolyn Howell, Reckson Mulidzi, Karen Freitag, Lester Sassman & Neil Jolly

Introduction 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. The selected fodder producing crops should minimise/prevent leaching and build-up of especially K in these soils and should not have a negative impact on grapevine performance and wine quality. Methods Diluted winery wastewater was applied to a Shiraz vineyard on the Nietvoorbij research farm where combinations of three different fodder producing summer catch crops and two winter cover crop treatments were compared to a control. Catch crops were not cultivated in the control treatment during the summer, but there were two winter

cover crop treatments. The region has a Mediterranean climate. Details of the irrigation application, water quality, catch and cover crop, as well as soil responses, have been given previously. Leaf petiole and blade analyses were determined in November. Cane mass was determined during July. Yield, berry mass, as well as juice pH, total titratable acid and sugar content were determined after harvest. Sensory evaluation of the wines was carried out six months after bottling by experienced tasting panels. The evaluation of the wines was done by a discrimination test (simple difference testing or paired-difference method). Each panellist was presented with two wines at a time, the control and one of each of the other seven treatments. The control wine (Treatment 7) represented the cover crop practice mostly followed in the industry.

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TECHNICAL YEARBOOK 2023