Influence of treated wastewater irrigation on soil health indicators in cropland: A comprehensive assessment framework

The application of wastewater in agricultural irrigation has attracted considerable global interest, particularly in areas suffering from water scarcity, as it offers a practical solution to mitigate the challenges associated with limited water resources. However, wastewater reuse could potentially adversely affect soil health. This study aimed to evaluate and compare soil health indicators in smallholder farmlands irrigated with treated wastewater (TW) versus those irrigated with groundwater (GW). The soil health index (SHI) was developed by employing both linear (L- SHI) and non-linear (NL- SHI) approaches, using the minimum data set (MDS). A significant difference was observed in most soil indicators between farms irrigated with TW and those irrigated with GW, especially concerning the concentration of heavy metals. Farms irrigated with TW exhibited significantly higher the average concentrations of Zn (30.5–43.6 %), Cu (41.3–54.3 %), Cd (138–242 %), Pb (25.3–47.4 %), and Ni (41.8 t- 67 %) compared to the GW-irrigated farms, implying a substantial enrichment of heavy metal by TW irrigation. The MDS approach identified eight soil health indicators, including Cd, available P, Pb, organic matter, bulk density (BD), electrical conductivity (EC), available Zn, and sodium adsorption ratio (SAR), contributing to the SHIs value by a range of 10–14 %. Compared to the GW-irrigated soils, the mean values of L- SHI and NL- SHI were found to be lower by 5.5–10 % and 6.3–10.4 % in the TW-irrigated soils, respectively, across all farms, suggesting a slight reduction in the SHIs after the adoption of TW irrigation. Corn productivity contributes approximately 30–32 % of the variance recorded in the calculated L- SHI and NL- SHI, which is weak to moderate-supported the influence of SHIs on crop performance. Our research highlights the promising application of SHI assessments, especially NL-SHI, as effective and responsive instruments for quantitatively assessing soil health in agricultural lands affected by TW irrigation. • Impact of treated wastewater irrigation (TW) on soil health index (SHI) was assessed. • Cd, available P, and Pb were major indicators affecting on the SHIs variations. • TW-irrigated soils showed 5.5–10.5 % lower SHIs than the control. • Corn productivity accounts for 30–32 % of the variance in the calculated SHIs. • The non-linear technique proved to be the most sensitive and effective method for assessing SHI.