Assessment of Soil Fertility and Carbon Storage of Different Land Use Types on the Cretacious Sediment of Kogi State, Nigeria

Abstract

This study assessed the impacts of different land use types on soil fertility and carbon storage in Anyigba, Kogi State, Nigeria. The specific objectives were to evaluate the physical and chemical properties of soils under cultivated, forest, and grassland uses, and to assess their impact on soil fertility and carbon storage. Soil samples were collected from depths of 0-15 cm and 15-30 cm across the three land use types. Standard laboratory procedures were used to analyze the soil's physical (particle size) and chemical (pH, Organic Carbon (OC), Total Nitrogen (TN), Available Phosphorus (P), and Effective Cation Exchange Capacity (ECEC)) properties, and the data were subjected to Analysis of Variance (ANOVA). Results showed that all soils had a Loamy Sand texture, but physical conditions varied; forest topsoil had the most favorable structure with the lowest bulk density and porosity (1.16 g/cm³, 56%), while the cultivated land showed high compaction (1.42 g/cm³, 46%). Chemical properties varied significantly. Chemical analysis revealed that the forest topsoil was significantly richer in nutrients and carbon, containing the highest OC (2.36%) and total nitrogen (0.16%), which was significantly higher than the levels in the cultivated land's subsoil (OC 0.64%, TN 0.04%). This trend directly influenced the soil's nutrient-holding capacity, with the forest soil recording a higher ECEC (11.47 Cmol/kg) compared to the cultivated soil (9.06 Cmol/kg). The findings established a clear degradation gradient of Forest > Grassland > Cultivated for key fertility indicators and carbon storage potential. The study concluded that land use is the primary determinant of soil fertility and carbon storage in the area, with continuous cultivation leading to significant soil degradation. Therefore, it is recommended that integrated soil fertility management practices, including the use of organic amendments and conservation agriculture, be adopted on cultivated lands to restore soil health and enhance carbon sequestration.