The seasonal influence of olive mill wastewater applications on an orchard soil under semi‐arid conditions

Abstract

Olive oil production generates large amounts of olive mill wastewater (OMW). OMW has a high nutrient content and could serve as fertilizer, but its fatty and phenolic constituents induce soil water repellency, phytotoxicity, and acidification. An appropriate season of OMW application may mitigate negative consequences while preserving beneficial effects. In order to investigate this, a field study was conducted, in which OMW was applied to an olive orchard in Israel either in winter or summer. Soil-water interactions (water drop penetration time, hydraulic conductivity), soil physicochemical parameters, phenolic compounds, and soil biological activity (bait-lamina test) were determined 12 to 18 months after OMW application. The results showed elevated K + contents in all treatments, but all other soil properties of winter treatments were comparable to the control, which suggested a certain recovery potential of the soil when OMW is applied in winter. By contrast, summer treatments revealed a ten-fold higher soil water repellency, a three-times lower biological activity, and a four-fold higher content of phenolic compounds, independently of whether the soil was kept moist by irrigation or not. Thus, the OMW constituents were neither degraded nor leached by winter rain when applied during the hot season. Further research is needed to distinguish leaching and biodegradation effects, and to understand the development of the composition and degradation kinetics of organic OMW constituents.

Effects of olive mill wastewater disposal on soil: Interaction mechanisms during different seasons

“…The secondary increase in salinity and SPC in SP and SU dry plots during the summer season 2012 suggests an upward directed water flow within the soil profile due to evaporation at the surface layer (Magdich et al, 2013) by which OMW compounds migrated upward by capillary action (Steinmetz et al, 2015). This matches with the clearly upward directed hydraulic gradient down to 50 cm depth in these plots (Fig.…”

“…Other studies showed a rapid decrease in phenolic compounds (Di Serio et al, 2008) and degradation to almost 50% of their initial concentration within the first 2 -3 weeks following OMW application to soil (Saadi et al, 2007a;Sierra et al, 2007;Tsiknia et al, 2014). No such effect was observed when OMW was applied in the winter season (Steinmetz et al, 2015), not even in a depth of 2 m (Chartzoulakis et al, 2010) after one single OMW application during one year study. On the other hand, soluble phenolic compounds were observed in soil at 1.25 m depth during the winter season (Sierra et al, 2001) and phenolic monomers were detected at a depth of 1.2 m one year after OMW spreading on soil (Mekki et al, 2006).…”

“…In a field study comparing different cultivation managements in Israel and West Bank during the summer season, Kurtz et al (2015) found that the OMW effect in SWR and phenolic compounds were lower in irrigated soil compared to non-irrigated soil due to dilution and leaching of toxic compounds as a subsequent impact of irrigation. Steinmetz et al (2015) found in a field study after one year of OMW application under semi-arid conditions, that summer application revealed a higher SWR and higher concentrations of phenolic compounds than the winter application due to low biological activity, whereas Di Bene et al (2013) found no long-term effects neither for OMW application in spring nor in autumn. Thus, understanding of the OMW-soil interactions mechanisms during different seasons or how these mechanisms may be influenced by the season of OMW application are still incomplete.…”

“…It contains 0.5 -24 g L -1 of phenolic compounds (Niaounakis and Halvadakis, 2006), and phytotoxic effects have been observed when it was directly used as an organic fertilizer (Ben Sassi et al, 2006). Many studies showed contradictory results about permanence and toxicity of phenolic compounds in soil which can be attributed to a) the different amounts of toxic organic compounds present in OMW (Piotrowska et al, 2006), b) different soil temperature and moisture during and after OMW application which can affect the biological decomposition process of organic matter constitutes (Steinmetz et al, 2015), or reduce the inhibition effect by dilution and leaching of toxic compound under the influence of irrigation , and c) the general status of soil (Saadi et al, 2007a). However, Buchmann et al (2015) showed in an incubation study of soil treated by OMW under spring conditions, that its phytotoxicity was clearly attributed to phenolic substances.…”

Effects of Olive Mill Wastewater on Soil Microarthropods and Soil Chemistry in Two Different Cultivation Scenarios in Israel and Palestinian Territories

“…It is possible that the irrigation in Gilat suppressed the development of water repellency and increased transport of hydrophobic compounds [60]. Also, Steinmetz et al [61] found a significant effect of irrigation towards water repellency. The stronger persistence of the elevated WDPT in Bait Reema indicates that hydrophobizing compounds like grease, oil and OMW organic matter remained in the upper soil layer [62] and that water repellency has the potential to persist even after one single OMW treatment.…”