South Africa Wine Technical Yearbook 2025

the WWW treatments to function effectively. Average activities of urease and β-glucosidase were significantly greater, and phosphatase activity tended to be greater, in the 0-10 than the 10-20 cm depth interval. Assuming that the enzymes were uniformly distributed through the soil columns at the outset, this observation suggests either that the higher enzyme activity in the 0-10 cm horizon was due to enrichment of the 0-10 cm material with metabolisable substrate by the WW, relative to the 10-20 cm interval; that enzyme activity was suppressed in the lower regions of the pots, possibly by poor aeration; or by a combination of both factors. Previously, sample depth had little effect on organic C in any of the soils or water treatments. 15 Neither did the cation exchange capacity differ greatly with depth, implying that depth-wise gradients in organic

colloids had not developed. Better gas exchange in the 0-10 cm interval, therefore, appears to be a likely reason why enzyme activities were greater in the 0-10 cm than the 10-20 cm sample interval. Acknowledgements • This article is an output of WRC Project K5/1881, entitled “The impact of wastewater irrigation by wineries on soils, crop growth and product quality”. This solicited project was initiated, funded and managed by the WRC. The project was co-funded by Winetech and ARC. • Goudini Winery for providing wastewater for the research. • ARC for infrastructure and resources. • Staff of the Soil and Water Science division at ARC Infruitec Nietvoorbij for their assistance, and in particular Mr. F. Baron for his dedicated technical support.

and implies that, compared with municipal water, WWW suppresses phosphatase activity. In the case of the Lutzville sand, differences in phosphatase and β-glucosidase activities due to water quality were not significant, but followed the same trend as the other soils, as was also the case for β-glucosidase in the Rawsonville sand. That both the Rawsonville sand and Lutzville sand were characterised by higher exchangeable Ca levels and higher pHs than the Stellenbosch soils may have contributed to the nonsignificant phosphatase activity responses observed in the Rawsonville sand and Lutzville sand. The tendency for WWW to promote urease and β-glucosidase activities and suppress phosphatase activity was consistent across the four different soils. Conceivably, soil phosphatase may require lower levels of P in the soil solution than are present in

Conclusions Compared with water from uncontaminated dams, rivers and boreholes, irrigation with diluted WWW is likely to promote the activities of urease and β-glucosidase, but suppress the activity of phosphatase, in most soils. This is likely to be especially the case in the superficial soil material. In soils that are sandy, mainly composed of fine to medium sand, and which are characterised by near-neutral or high pHs and reasonably high exchangeable Ca levels, irrigation with WWW had little or no effect on the activities of glycosidase and phosphatase. Such soils may nevertheless promote the activity of urease. 

Reference https://www.wineland.co.za/winery-wastewater-irrigation-part-7/ For more information, contact Reckson Mulidzi at mulidzir@arc.agric.za.

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TECHNICAL YEARBOOK 2025