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Increasing soil organic carbon (SOC) content is crucial for soil fertility, conservation, and combating climate-related issues by sequestering CO 2. While existing studies explore the total content of SOC, few of them investigate the factors that favor its sequestration and the impact of land use type and management. This research aims to study the spatial variation of the total content and the quality or maturity (in terms of aromaticity) of the humic acid (HA) fraction, along with the factors that enhance its formation and conservation for a longer time in the soil. In addition, the study tries to evaluate the performance of the Regression Kriging (RK) method in producing interpolation maps that describe the natural variation of the SOC and its quality with the aim of defining and preventing soil degradation. Finally, the study aims to evaluate the impact of the land use type and the importance of dense vegetation in the sequestration of the organic carbon (OC) in the soil. The analysis of the SOC was performed in northeast Algeria's semi-arid climate, examining content, quality, and chemical composition. Using geostatistical methods (RK), SOC is correlated with most related factors, producing detailed interpolation maps. The results showed that the SOC and its HA fraction (both its total content and its degree of transformation or maturity (measured in terms of aromaticity and structural condensation) are highly correlated to the topography of the area (P < 0.05). Results reveal variations in HAs' composition across land covers. Notably, areas subjected to burning exhibited a 21% increase in HA aromaticity compared to forested regions and a 29% increase relative to cultivated areas. The study highlights that soil cover has a substantial influence on the performance of SOC sequestration, the forested areas have a positive impact on the storage of SOC in the form of HA with a more complex chemical composition that suggests increased aromaticity and resilience. As a whole, the results indicate the potential of geostatistical methods to provide valuable information about the factors that influence the current status and evolution of SOC in the study area. [Display omitted] • Humic acids are used as an indicator of soil organic carbon quality. • The chemical composition of soil organic carbon controls its sequestration. • Soil organic carbon sequestration is considerably affected by land cover. • Soil organic matter rich in aromatic structures is promoted by wildfires and erosion. • The interpolation of soil organic carbon stocks can be improved through regression kriging. [ABSTRACT FROM AUTHOR]

Soil salinity is considered the most serious socio-economic and environmental problem in arid and semi-arid regions. This study was done to estimate the soil salinity and monitor the changes in an irrigated palm grove (42 ha) that produces dates of a high quality. Topsoil samples (45 points), were taken during two different periods (May and November), the electrical conductivity (EC) and Sodium Adsorption Ratio (SAR) were determined to assess the salinity of the soil. The results of the soil analysis were interpolated using two geostatistical methods: inverse distance weighting (IDW) and ordinary Kriging (OK). The efficiency and best model of these two methods was evaluated by calculating the mean error (ME) and root mean square error (RMSE), showing that the ME of both interpolation methods was satisfactory for EC (−0.003, 0.145) and for SAR (−0.03, −0.18), but the RMSE value was lower using the IDW with both data and periods. This can explain the accuracy of the IDW interpolation method. This model showed a dominance of soil salinity distribution in the South and South-East of the study area during the first season, and for the second season, the salts were concentrated in the middle of the area. Several factors could interact in this variation such as the topographic direction of the water flow and the aridity of the climate (evaporation). From this study emerges the need to maintain a better management of agricultural water and soils, avoiding salt accumulation, to ensure a good yield and the sustainability of agriculture in arid environments. [ABSTRACT FROM AUTHOR]