Survey and Geospatial Analysis of Soil Salinity and Organic Carbon Dynamics in Garmian District, Iraq

Soil organic carbon (SOC) is crucial for maintaining soil health, as it supports microorganisms, improves soil structure, and regulates nutrient availability. Typically, SOC and salinity exhibit an inverse relationship, influenced by factors such as vegetation, topography, salt composition, and climate. In this study, we mapped soil salinity (ECe: 0.55–3.14 dS/m) and measured SOC (4.5–10.4 g/kg) at 50 field sites. The study employed statistical and spatial analyses, combined with remote sensing and geographic information systems, to quantify the interaction between them. The study found that SOC generally declines with increasing salinity, with a clear threshold at 1.43 dS/m. Beyond this threshold, further SOC loss slows, likely due to the mitigating effects of salinity-tolerant grasses and calcium-rich parent material on sodium stress. Vegetation cover (short grasses occupying 29.3 % of the area) helped sustain soil organic carbon even under higher salinity. These findings align with our research objectives by quantifying the relationship between SOC and salinity and identifying the primary factors that control it. The results suggest that promoting salinity-tolerant vegetation and applying calcium-based amendments are effective strategies for maintaining SOC levels in semiarid, calcareous soils. The study findings provide actionable spatial guidance for targeted soil management and ecological planning in similar regions.