Effect of Irrigation with Diluted Winery Wastewater on Enzyme Activity in Four Western Cape Soils

Abstract

Irrigating vineyards with winery wastewater is an established practice. However, the effect of this water on soil enzyme activity is unknown. Soils from four vineyard areas were irrigated, in pots, over four simulated seasons with municipal water, and with winery wastewater diluted to a chemical oxygen demand of 3000 ml/L. Urease, ?-glucosidase and phosphatase activities were determined after each season. The experimental soils were: an alluvial vineyard soil from Rawsonville (RS), an aeolian veld soil from Lutzville (LS), and shale (SS)—and granite (SG)—derived soils from Stellenbosch. Compared
with municipal water, irrigating with winery wastewater significantly (p = 0.05) increased urease activity in all four soils, and promoted ?-glucosidase activity in SS and SG. Conversely, winery wastewater suppressed phosphatase activity in the RS, SH and SG soils. Averaged over all soils, winery wastewater promoted the activity of ?-glucosidase and urease, but suppressed that of phosphatase. All-treatment enzyme activities increased in the sequence: LS<RS<SG<SS for urease, LS<RS<SS<SG for phosphatase and LS<RS<SG<SS for ?-glucosidase. Winery wastewater and municipal water therefore affect soil enzyme activity differently. The extent of this activity varies inconsistently between soils. Whether similar results would be obtained under vineyard conditions have yet to be determined.