Spatial distribution and mapping of soil carbon stock in pistachio fields in Şanlıurfa

This study was conducted to determine the spatial distribution of soil organic carbon stock and organic carbon content in agricultural lands of Şanlıurfa province. The study area, characterized by semi-arid climatic conditions, is at risk of soil degradation due to intensive agricultural activities and unsustainable land use practices. The spatial distribution of key soil properties such as soil organic carbon content, total carbon stock, clay, silt, sand ratios, bulk density, and lime content under different land use types was evaluated. The analyses revealed that the soil organic carbon content in the region varies between 8.12 g/kg and 42.69 g/kg, while the total carbon stock ranges from 10.5 tons/ha to 45.3 tons/ha. Analyses based on land use types showed that pasturelands had the highest organic carbon content, with an average of 25.1 g/kg. In contrast, cotton-cultivated lands had an organic carbon content of 15.2 g/kg, while barley-cultivated areas exhibited a value of 15.0 g/kg. In terms of total carbon stock, pasturelands had the highest capacity with 28.4 tons/ha, whereas other land use types had lower values ranging from 18.0 to 22.9 tons/ha. These findings indicate that intensive agricultural activities may lead to soil degradation by reducing soil organic carbon content. To determine the spatial distribution of soil properties, three different kriging methods were applied, and their accuracy performances were compared. The Universal Kriging method emerged as the most successful model with an MSE of 2.4501, RMSE of 1.5652, and an R² value of 0.9407. In contrast, the Disjunctive Kriging method exhibited lower performance with an MSE of 16.3390, RMSE of 4.0421, and an R² value of 0.5860. Similarly, the Ordinary Kriging method demonstrated a comparable accuracy level with an MSE of 16.1616, RMSE of 4.0201, and an R² value of 0.5905. The results indicated that the Universal Kriging method, with its lower error values and higher explanatory power, was the most suitable method for determining the spatial distribution of soil properties. An evaluation of spatial dependence ratios showed that soil organic carbon stock exhibited a moderate level of spatial dependence. The data obtained using the Universal Kriging method provided a better representation of the regional distribution of soil carbon content and offered valuable insights for sustainable soil management. In conclusion, it is suggested that using the Universal Kriging method for accurately modeling the distribution of soil organic carbon can contribute to the development of sustainable land management strategies.