Design of a pot experiment to study the effect of irrigation with diluted winery wastewater on four differently textured soils

Abstract

Due to the intensification of environmental legislation, the wine industry is expected to find solutions for the treatment or re-use of winery wastewater. The objective of the study was to design and evaluate a pot experiment for determining the effects of irrigation with diluted winery wastewater on different soils. Four pedogenetically different soils were included in the experiment, i.e., (i) alluvial sand containing 3.3% clay from Rawsonville, (ii) aeolic sand containing 0.4% clay from Lutzville, (iii) shale-derived soil containing 20% clay from Stellenbosch, and (iv) granite-derived soil containing 13% clay from Stellenbosch. The pot experiment was carried out under a rain shelter at ARC Infruitec-Nietvoorbij. Soils were packed in 3.54 dm 3 PVC pots to a bulk density of 1 400 kg/m 3 . The four soils were irrigated using winery wastewater that was diluted to 3 000 mg/L COD. Municipal water was used to irrigate the control treatment of each soil. The relatively simple mixing and irrigation infrastructure enabled irrigation of more than one soil with diluted winery wastewater in one experiment. It was possible to irrigate the soils accurately when approx. 85% of the water had evaporated as no visual drainage occurred. Since the pot experiment could be continued under the rain shelter during winter, results were obtained quicker compared to an open field study. However, weighing the pots every second day was time consuming. Therefore, it is recommended that load cells are to be used to record daily mass losses automatically in future pot experiments.

Effect of Irrigation with Diluted Winery Wastewater on Phosphorus in Four Differently Textured Soils

“…RESULTS AND DISCUSSION Some soil physical characteristics, as well as cation and pH (KCl) responses of the four soils to irrigation with diluted winery wastewater, were presented previously (Mulidzi et al, 2015;2016). The irrigation amounts applied to the Rawsonville sand, Lutzville sand and Stellenbosch shale soil were comparable (Table 1), but the Stellenbosch granitic soil received substantially less water due to its coarse texture and high gravel content (Mulidzi et al, 2016).…”

“…Consequently, a total of 24 irrigations were applied over the four simulated seasons. Details of the pot experiment layout and wastewater dilution procedure, as well as the irrigation system and irrigation scheduling, were presented earlier (Mulidzi et al, 2016).…”

“…approximately 0 to 30 cm deep. Soils were packed into 3.54 dm 3 PVC pots to a bulk density of 1 400 kg/m 3 , as described by Mulidzi et al (2016). The pot experiment was carried out under a 20 m x 40 m translucent fibreglass rain shelter at ARC InfruitecNietvoorbij near Stellenbosch.…”

“…Control treatments of all soils were irrigated with water supplied by the Stellenbosch municipality. The winery wastewater treatments were irrigated with wastewater diluted to a chemical oxygen demand (COD) of 3 000 mg/L, as described by Mulidzi et al (2016). The undiluted wastewater was obtained from the wastewater collection pit at a winery near Rawsonville and transported in a tank to Stellenbosch.…”

“…(i) aeolic sand from Lutzville containing 0.4% clay, (ii) alluvial sand from Rawsonville containing 3.3% clay, (iii) granitederived soil from Stellenbosch containing 13% clay, and (iv) shale-derived soil from Stellenbosch containing 20% clay. The properties and characteristics of the soils were presented previously (Mulidzi et al, 2016). Bulked soil samples were collected from the topsoil layers, i.e.…”