Influence of long-term wastewater irrigation on soil quality and its spatial distribution

The main objective of this investigation was to evaluate soil quality and map spatial distribution of heavy metals under long-term irrigation with sewage wastewater. Physical and chemical indicators were designated to assess the soil quality in Elgabal Elasfar farm, Egypt. Thirty-three surface soil samples were collected from the study area (classified as Torriorthents and Quartzipsamments). Heavy metal concentrations in the irrigation wastewater were high compared with Nile fresh water. Copper concentrations were higher than the safe limits for irrigation. applying sewage wastewater in irrigation for long periods adversely affected soil EC, available heavy metals, and clay content while enhanced total N, available P and K, CEC, and TOM. The overall soil quality index (SQI) did not fluctuate much between the studied soils. The "moderate" SQ class were dominant, with the area of 94% of the total study area. But, excluding the available heavy metal concentrations from the SOI function, "high" SQ class in this case occupied 69% of the study area. The huge volumes of sewage wastewater that was applied for long-term increased the salinity and available heavy metals which, adversely affect the soil quality in this area. To preserve or improve soil quality in the study area management plans are needed to avoid the undesirable destructive effects of increasing both salinity and available heavy metals.