Technical Yearbook 2023

OCTOBER

Winery wastewater for irrigation (Part 3): Vineyard catch and cover crop responses By Carolyn Howell, Reckson Mulidzi, Lester Sassman & Karen Freitag

Grapes are an important crop in the Western and Northern Cape. The wine industry makes a significant contribution to the economy in these regions. In 2022, there were 2 487 primary wine grape growers and 524 cellars which crush grapes. 1 The wine industry also provides a large number of employment opportunities, particularly in rural areas. In 2022, the vineyards planted for wine production in South Africa amounted to 89 384 hectares, of which approximately 90% is four years and older. 1 During wine production, wineries produce large volumes of poor-quality wastewater (between 3 to 5 m 3 per tonne of grapes crushed). 2 This wastewater can be used for irrigation, but this delivers substantial amounts of elements to the soil. 3,4

Introduction In a previous study where diluted winery wastewater was used for irrigation of a Cabernet Sauvignon vineyard, a summer catch crop of Pearl millet and a winter cover crop of oats removed substantial amounts of K from a sandy soil. 5 There are many benefits to cultivating a winter cover crop in a vineyard. 6 These include:

• restricting water runoff and erosion; • maintenance or improvement of the organic matter content of soil; • reducing water consumption of grapevines; • weed control efficacy; and • maximum production of quality grapes.

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TECHNICAL YEARBOOK 2023