Effects of irrigation with treated agro-industrial wastewater on soil chemical characteristics and fungal populations during processing tomato crop cycle

Abstract

This study was carried out in 2012 at Stornarella (Italy; 41° 15’29 N; 15° 43, 56 E; 154 m a.s.l.). We investigated the effects of reuse of secondary treated agro-industrial wastewater for irrigation, in comparison with conventional groundwater, and we monitored soil chemical characteristics and fungal populations during the crop cycle of processing tomato (Solanum lycopersicum L.). Compared to the groundwater, the wastewater had significantly higher electrical conductivity, total suspended solids, sodium, calcium, magnesium, potassium, sodium adsorption ratio, chemical oxygen demand, biological oxygen demand over five days, ammonium-nitrogen, phenols, bicarbonates, phosphates, sulphates and chlorides. Most of these parameters were significantly greater also in the wastewater-irrigated soil. During the tomato crop cycle, there were significant shifts in the structure of the soil microfungal community. Saprophytic species increased in the wastewater-treated soil, while phytopathogens such as Fusarium oxysporum progressively decreased. More investigations into the mechanisms by which wastewater acts on disease suppression is needed to make the use of such wastewaters more predictable. The irrigation water source did not significantly affect the qualitative traits of the crop yield. For both irrigation treatments, the most important qualitative parameters that characterized the processing tomato fruit (i.e., dry matter content, pH, soluble solid content, colour parameters) were in agreement with reports in the literature.