Soil quality assessment is the first step towards precision farming and agricultural management. In the present study, a multivariate analysis and geographical information system (GIS) were used to assess and map a soil quality index (SQI) in El-Fayoum depression in the Western Desert of Egypt. For this purpose, a total of 36 geo-referenced representative soil samples (0–0.6 m) were collected and analyzed according to standardized protocols. Principal component analysis (PCA) was used to reduce the dataset into new variables, to avoid multi-collinearity, and to determine relative weights (Wi) and soil indicators (Si), which were used to obtain the soil quality index (SQI). The zones of soil quality were determined using principal component scores and cluster analysis of soil properties. A soil quality index map was generated using a geostatistical approach based on ordinary kriging (OK) interpolation. The results show that the soil data can be classified into three clusters: Cluster I represents about 13.89% of soil samples, Cluster II represents about 16.6% of samples, and Cluster III represents the rest of the soil data (69.44% of samples). In addition, the simulation results of cluster analysis using the Monte Carlo method show satisfactory results for all clusters. The SQI results reveal that the study area is classified into three zones: very good, good, and fair soil quality. The areas categorized as very good and good quality occupy about 14.48% and 50.77% of the total surface investigated, and fair soil quality (mainly due to salinity and low soil nutrients) constitutes about 34.75%. As a whole, the results indicate that the joint use of PCA and GIS allows for an accurate and effective assessment of the SQI.

There is consensus on the impact of wastewater irrigation on soil properties and heavy metal accumulation. The studies that show the impact of temporal changes as a result of different long-term additions of wastewater on the heavy metal accumulation and degradation of soil are extremely limited. This study was carried out to assess heavy metal contamination in soils irrigated with wastewater for more than 30 years in Egypt. A total number of 12 irrigation water samples and 12 soil profiles were collected during 2020 and were chemically characterized. The results showed that soils irrigated with wastewater over the long term contained significantly higher concentrations of heavy metals compared to fields irrigated with fresh water. Heavy metal levels in water and soil samples were within the permissible limits, with the exception of Cd concentration in water (0.03 mg L⁻¹). Continuous cultivation for a long period of time (30 years) using raw urban wastewater application has led to the adverse effect of increasingly available Pb concentration (5.44 mg kg⁻¹). Similar temporal behavior was seen for Cd and Fe, which increased by 0.98 and 11.2 mg kg⁻¹, respectively, after 30 years. The heavy metals in wastewater-irrigated soils significantly increased in clayey soils, as compared to sandy soils irrigated from the same source. Our findings provide important information for decision makers in Egypt and similar countries for the development of a strategy for the use of wastewater in irrigation for sustainable agricultural management.

Despite studies focusing on soil substrates (carbon and nitrogen) and heavy metal availability, the impact of diversified parent materials in arid alkaline regions has received little attention. To reveal the influence of parent material, we investigated four different parent materials: fluvio-marine, Nile alluvial, lacustrine, and aeolian deposits. We assessed the effect of soil parent materials through selected soil physical and chemical properties, such as clay content, bulk density, pH, and available phosphorus (AP). The Tukey HSD test (SPSS ver. 23) was used to assess the soils derived from these different sediments. Using the R “glmulti” package, we examined this effect in a model of mixed-effects meta-regression. The sum of Akaike weights for models that contained each element was used to estimate the importance of each factor. The average contents of soil organic carbon (SOC) and total N in alluvial deposits were greater (p < 0.001) than those of marine, aeolian, and lacustrine deposits. A multivariate analysis in arid regions revealed that parent material, soil pH, and the availability of P had the greatest effects on SOC concentration, whereas clay content, available P, soil pH, parent material, and bulk density had the greatest effects on soil total nitrogen. The average content of Fe in the aeolian deposits was greater (p < 0.001) than those of marine, alluvial, and lacustrine deposits, without any significant differences between the latter two deposits. We found that the highest average contents of zinc (Zn), manganese (Mn), and copper (Cu) were recorded in alluvial deposits, with significant differences between other deposits. Soil parent material was the major factor impacting soil iron (Fe) content, along with clay content and soil pH. However, soil bulk density was the most important factor controlling soil Zn and Mn contents, while SOC drove Cu content. This study will help in developing a more accurate model of the dynamics of soil substrates and availability of heavy metals by considering readily available variables, such as parent materials, soil pH, soil bulk density, and clay content.

Soil carbon sequestration is a riskier long-term strategy for climate mitigation than direct emissions reduction, but it plays a main role in closing carbon emission gaps. Effects of long-term cultivation on soil carbon sequestration were studied at the western edge of the Nile Delta near Alexandria, Egypt. Seven agricultural fields of different ages (0–50 years in use) were selected and compared with the surrounding desert (virgin soil) and desert shrub-land. Samples were taken at three horizons, 0–30, 30–60, and 60–90 cm, and tested for differences in physical and chemical properties. The results of long-term cultivation reveal that the European Commission (EC) value was 11.77 dS/m in virgin soil, while the EC values decreased to 5.82, 4.23, 3.74, 2.40, and 2.26 dS/m after 5, 10, 20, 30, and 50 years of cultivation, respectively. The calcareous rock fraction smaller than 50 μm in size revealed another phenomenon, where active calcium carbonate content increased with cultivation practices from 1.15% (virgin soil) to 5.42%, 6.47%, 8.38%, and 10.13% after 5, 10, 20, and 30 years of cultivation, respectively, while shrub-land also showed a low amount of active CaCO₃ with 1.38%. In fifty years of cultivation, soil bulk density decreased significantly from 1.67 to 1.11 g/cm³, and it decreased to 1.65, 1.44, 1.40, and 1.25 g/cm³ after 5, 10, 20, and 30 years, respectively. These results reveal that the increase in soil carbon stock in the upper 90 cm amounted to 41.02 t C/ha after five years of cultivation, compared to virgin soil with 13.47 t C/ha. Soil carbon levels increased steeply during the five years of cultivation, with an average rate of 8.20 t C/ha per year in the upper 90 cm. After the first five years of cultivation, the carbon sequestration rate slowed, reaching 4.68, 3.77, 2.58, and 1.93 t C/ha per year after 10, 20, 30, and 50 years, respectively, resulting in sequestration-potential values of 46.78, 75.63, 77.43, and 96.45 t C/ha. These results indicate that potential soil carbon sequestration resembles a logarithmic curve until the equilibrium state between carbon application and decomposition by microorganisms is reached.

The current study was carried on a newly reclaimed area of El-Nubaria where majorof agricultural project for development is underway West of the Nile Delta, Egypt. The objective wasto determine the capability and suitability of soils which are marine- lacustrine silty clay soils withshallow to medium depth in El-Nubaria region. The system of evaluation was on ASLE model(Applied System of Land Evaluation) integrated with the geographic information system (GIS). Threesoil profiles were chosen (representing the pre-specified geomorphological soil unit) which weremorphologically described and samples were analysed. Spatial thematic distribution maps of soilcharacteristics were created for the study unit using GIS software; Arc GIS V. 10.3. Three current landproductivity classes were recognized class 2 "good soil productivity" for profile 3; class 3 "fair soilproductivity" for profile 2 and class 5 "very poor soil productivity" for profile 1. Soil limitations werewater table depth, carbonates, texture, irrigation water salinity, alkalinity (ESP) and organic matter.Wheat, barley, alfalfa, sunflower, cotton, date palm and olive were the optimum crops for land use inthe study unit.