Assessing agricultural potential of abandoned land in the Euphrates basin: soil fertility modeling and geostatistical analysis

A soil fertility map is an important tool in agriculture and land management, providing critical information to decision-makers. The aim of this study was to create digital maps of soil properties and fertility for abandoned soils in the Euphrates sedimentary basin (Western Iraq) based on eight soil properties: pH, electrical conductivity, texture, soil organic matter, total nitrogen, available phosphorus, exchangeable potassium, and calcium carbonate concentration. To achieve this purpose, 50 soil samples (0–20 cm) were collected. Then, an SFI model was created to quantify soil fertility in the survey area. Finally, a geostatistical approach based on ordinary kriging was used to generate soil property and fertility maps. The findings revealed that 90% of the sampled locations had low soil fertility, with 10% having moderate or highly fertile soil. Furthermore, geostatistical modeling showed that the Gaussian model was the best fit for EC, CaCO₃, Kava, and clay, with R² values of 0.697, 0.616, 0.789, and 0.597, respectively. On the other hand, the linear model proved to be the best fit for pH, SOM, and P_ava, while the exponential model performed best for silt, sand, and SFI. The spherical model provided the best fit for N_T. The spatial distribution of the Soil Fertility Index (SFI) across the surveyed area, determined using ordinary kriging followed a consistent pattern, with higher values in the northeast, southeast, and west regions and lower values in the center plain. As a result, the developed SFI is a useful tool for assessing soil adequate supply for plant growth and management in other regions with similar properties.