Integrating Water and Soil Quality Indices for Assessing and Mapping the Sustainability Status of Agricultural Lands

Soil quality assessment represents the essential step to achieve sustainable agriculture. This study introduces SUITED, a GIS-based approach that overcomes limitations of traditional soil quality indices by using open data, a remote sensing-derived salinity index, and a customized Water Quality Index (WQI) to evaluate soil quality, irrigation water quality, and treated wastewater use. The index was constructed by combining the selected factors across different soil depths and subsequently merging them using a weighted linear combination to produce the result map. Each parameter has been classified using geometrical criteria allowing a site-specific assessment. SUITED was applied to small sub-watersheds of the Volturno and Po rivers plains (southern and northern Italy, respectively). The index maps (0–30 cm depth) show that over 90% of both areas fall into medium to very low sustainability classes. In the Volturno river plain, soil quality is primarily driven by soil type distribution and their inherent heterogeneity, while in the Po river plain, soil texture and shallow saline groundwater mainly control sustainability. Furthermore, the integration of WQI and SUITED maps provided a reliable evaluation of irrigation water impacts, supporting informed decision making for water use and drainage management.