Abstract

MULIDZI, A.R.; CLARKE, C.E.  and  MYBURGH, P.A.. Effect of irrigation with diluted winery wastewater on phosphorus in four differently textured soils. S. Afr. J. Enol. Vitic. [online]. 2016, vol.37, n.1, pp.79-84. ISSN 2224-7904.

The wine industry needs solutions for wastewater treatment, as environmental legislation for its disposal is increasingly being enforced due to non-compliance. The feasibility of re-using diluted winery wastewater was assessed in a pot experiment under a rain shelter over four simulated irrigation seasons. Four soils varying in parent material and clay content, viz. aeolic sand from Lutzville containing 0.4% clay, alluvial sand from Rawsonville containing 3.3% clay, granite-derived soil from Stellenbosch containing 13% clay, and shale-derived soil from Stellenbosch containing 20% clay, were irrigated with wastewater diluted to 3 000 mg/L COD (chemical oxygen demand), whereas the control received municipal water. Irrigation with diluted winery wastewater increased the pH_(KCl) in the shale- and granite-derived soils into the optimum range for P availability. Although pH in the aeolic sand was initially above the optimum range, relatively high Na⁺ levels also caused available P to increase as the pH_(KCl) increased. The pH_(KCl) in the alluvial sand increased beyond the optimum range, thereby causing a reduction in the available P. This indicates that irrigation with diluted winery wastewater may only enhance P absorption if the pH shift is towards the optimum. It must be noted that the results represent a worst-case scenario, i.e. in the absence of rainfall or crops.

Keywords : Chemical oxygen demand; pot experiment; solubility; soil pH; water quality.

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