Winery wastewater for irrigation (Part 5): Grapevine and wine responses

by | Dec 1, 2023 | Technical, Viticulture research

Large volumes of poor quality wastewater are produce by wineries.1 On the other hand, scarce irrigation water could be restricted further in future irrigation water allocations.2 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.

 

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.3,4,5,6 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).7 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.

 

Results and discussion

In the 2017/18 season, the macro-element content of the leaf petioles and -blades did not differ between treatments (Tables 1 and 2). According to norms for grapevine nutrient levels in leaf petioles,8 i.e. 0.60% to 0.98% for N, 0.11% to 0.62% for P, 1% to 2.9% for K, 0.6% to 2.2% for Ca, and 0.16% to 0.55% for Mg, analyses of the leaf petioles were well within these norms (Table 1). According to norms for grapevine nutrient levels in leaf blades,8 i.e. 1.6% to 2.7% for N, 0.14% to 0.55% for P, 0.65% to 1.3% for K, 1.2% to 2.2% for Ca, and 0.16% to 0.55% for Mg, analyses of the leaf blades were well within these norms (Table 2). With a few exceptions, similar trends were observed for the petioles and blades in the 2018/19 and 2019/20 seasons.

 

Winery wastewater 1
 

Winery wastewater 2
 

Yield, berry mass at harvest and cane mass did not differ between treatments in the 2017/18 season (Table 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.9 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.9 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.

 

Winery wastewater 3
 

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.

 

Winery wastewater 4

 

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.

 

Acknowledgements
  • The project was funded by Winetech and the Agricultural Research Council (ARC).
  • ARC for infrastructure and resources.
  • Staff of the Soil and Water Science division at ARC Infruitec-Nietvoorbij for technical support.

 

References
  1. Mosse, K.P.M., Patti, A.F., Christen, E.W. & Cavagnaro, T.R., 2011. Review: Winery wastewater quality and treatment options in Australia. Aust. J. Grape Wine Res. 17, 111-122.
  2. Petrie, P.R., Cooley, N.M. & Clingeleffer, P.R., 2004. The effect of post-véraison water deficit on yield components and maturation of irrigated Shiraz (Vitis vinifera ) in the current and following season. Aust. J. Grape Wine Res. 10, 203-215.
  3. Howell, C., Freitag, K. & Sassman, L., 2023. Winery wastewater for irrigation (Part 1): Irrigation application and water quality. Winelands August 2023, 61-63.
  4. Howell, C., Mulidzi, R., Sassman, L. & Freitag, K., 2023. Winery wastewater for irrigation (Part 2): Evaluation of catch crops on open land. Winelands September 2023, 52-54.
  5. Howell, C., Mulidzi, R., Sassman, L. & Freitag, K., 2023. Winery wastewater for irrigation (Part 3): Vineyard catch- and cover crop responses. Winelands October 2023, 63-66.
  6. Howell, C., Mulidzi, R., Sassman, L. & Freitag, K., 2023. Winery wastewater for irrigation (Part 4): Soil responses. Winelands November 2023, 61-64.
  7. Lawless, H.T. & Heymann, H., 2010. Sensory evaluation of food, 2nd edition. Springer, New York.
  8. Conradie, W.J., 1994. Vineyard fertilisation. Proceedings of workshop on vineyard fertilization. Nietvoorbij, 30 September 1994. ARC Infruitec-Nietvoorbij, Private Bag X5026, tellenbosch, 7599 S, South Africa.
  9. Myburgh, P.A. & Howell, C.L., 2014. The impact of wastewater irrigation by wineries on soil, crop growth and product quality. WRC Report No. 1881/1/14. ISBN 978-1-4312-0591-2.

 

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

 

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