Effects of Temporal Variation in Long-Term Cultivation on Organic Carbon Sequestration in Calcareous Soils: Nile Delta, Egypt

Abstract

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.

Long-Term Impact of Wastewater Irrigation on Soil Pollution and Degradation: A Case Study from Egypt

“…Using wastewater application was remunerative for soil fertility, but the associated decline in pH might result in an important loose of nutrients [63,94]. These results are in agreement with those of [33,86,[95][96][97][98][99][100].…”

Detection of Groundwater Quality Changes in Minia Governorate, West Nile River

“…Calcium (Ca) concentration values varied between 20 and 56 mg/L through 2009, where during 2019, the concentrations rose to vary between 27 and 60 mg/L. The loss of soil calcium might be due to the strategy of fertilization and gypsum application, which increases the concentration of calcium in the well's water [64]. The spatial distribution map of Ca classifies the study area into five classes from < 30 and > 45 mg/L, and there is a change in the Ca range in the middle and southern parts of the study area Figure 6a.…”

The Vital Roles of Parent Material in Driving Soil Substrates and Heavy Metals Availability in Arid Alkaline Regions: A Case Study from Egypt

“…They may contain a calcic horizon, a layer of secondary carbonate deposits (typically calcium or magnesium), more carbonate than an underlying layer by at least 5%, and more carbonate than the horizon, so they are identified by the parent material's CaCO 3 content [78]. Acid-forming fertilizers, such as ammonium sulphate and urea fertilizers, sulfur compounds, organic manures, and green manures, are considered effective ways of reducing the pH of soil to a neutral value [20]. Wheat, alfalfa, sunflower, barley, date palm, cotton, and olive were the optimum crops for land use in this unit [79].…”

“…Whatever the climatic circumstances, the prevalence of quartz in the bedrock makes it exceedingly unlikely that the suite of clay minerals present in the soil is the result of weathering [19]. The parent material of CaCO 3 -rich soil in the northwestern coastal region of Egypt is composed of a variety of rocks, e.g., limestone, sandstone, CaCO 3 -rich shale, or marl, formed as a result of weathering, translocation, and deposition processes under the arid climatic conditions [20,21]. The following parameters were used to choose the marine soil profiles: CaCO 3 , soil texture, electrical conductivity (EC), and hydrogen power; macronutrients such as nitrogen, phosphorus, potassium, and organic carbon; micronutrients such as manganese, zinc, iron, and copper; and other sodium and CEC [20].…”

“…The parent material of CaCO 3 -rich soil in the northwestern coastal region of Egypt is composed of a variety of rocks, e.g., limestone, sandstone, CaCO 3 -rich shale, or marl, formed as a result of weathering, translocation, and deposition processes under the arid climatic conditions [20,21]. The following parameters were used to choose the marine soil profiles: CaCO 3 , soil texture, electrical conductivity (EC), and hydrogen power; macronutrients such as nitrogen, phosphorus, potassium, and organic carbon; micronutrients such as manganese, zinc, iron, and copper; and other sodium and CEC [20]. High CaCO 3 content has an impact on soil pH, soil buffering capacity, CEC, base saturation, and nutrient availability, as well as the soil hydraulic conductivity and permeability [22].…”