Building irrigation-tailored soil datasets for land suitability assessment in collective irrigation systems

Reliable soil information is critical for irrigation planning, yet data scarcity and spatial variability often constrain its effective use, particularly in Mediterranean collective irrigation systems (CIS). This study presents a transferable, irrigation-tailored soil dataset by integrating legacy soil datasets, point based observations, and pedotransfer functions (PTFs) to estimate and map key soil hydraulic properties. Using the 'Minutos' collective irrigation system (MCIS), in southern Portugal as a case study, soil water contents at field capacity and wilting point were estimated from national class-average and continuous PTFs and compared with SoilGrids 2.0 predictions. Key land suitability factors (soil depth, available water capacity (AWC), slope, drainage), were weighted using the Analytical Hierarchy Process (AHP) and integrated through a GIS-based multicriteria analysis to generate irrigation suitability maps. One-at-a-time and ensemble weight perturbations confirmed that suitability patterns are structurally robust, with only limited changes along the S2–S3 boundary. Results show that 13.8% of the CIS area is highly suitable (S1), 56.1% moderately suitable (S2), 29.6% marginally suitable (S3), and 0.4% not suitable for irrigation, with soil depth and AWC identified as the most influential factors. Class-average PTFs facilitated threshold-based suitability classification, while continuous PTFs captured finer spatial variability, proving valuable for refining management zones and operational scheduling. SoilGrids ensured complete coverage but tended to overestimate AWC, highlighting the need for local validation. Aggregating hydraulic properties by suitability class yields a concise lookup dataset that can be directly coupled to irrigation requirement calculations and district decision-support workflows, improving consistency of demand. • Transferable irrigation-tailored soil dataset supports planning in data-scarce regions • Irrigation suitability maps for collective irrigation using multicriteria analysis • Class-average pedotransfer functions yield stable estimates at suitability cut-offs • SoilGrids overestimates available water capacity requiring local validation