Soil organic carbon (SOC) plays a key role in regulating soil quality functions and ecosystem services. The objective of our study was to evaluate the impact of deforestation and subsequent land-use change on the SOC and total nitrogen (TN) concentration, quality, and lability under otherwise similar soil and environmental conditions. Geo-referenced composite soils (0 to 30 cm depth at 7.5 cm interval) sampled from agriculture, bioenergy plantations (Miscanthus x giganteus), Conservation Reserve Program (CRP), and wetland were analyzed for SOC, TN, active C (AC), humic- and fulvic acid (HA and FA), non-humic C (NH), E₄: E₆ ratio, humification indices (HI, HR, and DH), and carbon and nitrogen management indices (CPI, NPI, and CMI), compared to soils under protected forest as a control. Results showed that the CRP had the highest depth distribution and profile-wise stocks of SOC, TN, AC, and FA with respect to the lowest in agriculture upon conversion of forest. Moreover, the SOC and TN contents were significantly stratified in the CRP when compared to agriculture. While agriculture had the wider HA: FA ratios with highest HI and HR but lowest DH values, the CRP, in contrast, had the narrow HA: FA ratios with lowest HI but highest DH values, when compared to the forest. Spectral analyses have shown lower E₄: E₆ ratios under the forest when compared to both agriculture and the CRP; however, the later had significantly higher E₄: E₆ ratios than that of agriculture. The CPI, as measures of SOC accumulation or depletion, significantly decreased by 16% under agriculture but increased by 12% under the CRP. While the CMI, as measures of SOC accumulation or depletion and lability, with higher values under the CRP suggested a proportionally more labile SOC accumulation, in contrast, the smaller values under agriculture indicated a greater depletion of labile SOC over time. Moreover, the CRP may have favored a more labile SOC accumulation with higher proportions of aliphatic C compounds, whereas agriculture may have a SOC with high proportions of non-labile aromatic C compounds. Principal components analysis clearly separated and/or discriminated the land-use impacts on soil carbon pools and TN. Likewise, redundancy analysis of the relationship between measured soil parameters and land-use validated that the TOC, TN, FA, humin, and CPI were significantly impacted due to synergism among soil properties as positively influenced by the CRP upon conversion of agriculture.

Land use changes have a profound impact on soil fertility and agricultural production systems in the Forest-Savannah Transition Zone (FSTZ) of Ghana. Soil erosion and shortened fallow periods exacerbate soil fertility loss, further degrading soil quality. This study aimed to: (i) quantify soil quality indices, and (ii) assess soil fertility status across different land use types (Forest, Savannah Woodland, Grassland, Fallow, and Cropland) at two soil depths (0–20 cm and 20–50 cm). The 0–20 cm depth represents the plough layer, while 20–50 cm captures nutrient leaching in the Nkoranza districts. Using principal component analysis (PCA), we reduced the number of indicators from 29 to 9, capturing 94.42 % and 94.81 % of variability in the topsoil and subsoil, respectively. Key indicators included sand, silt, gravel content (Gco), electrical conductivity (EC), available phosphorus (Av. P), exchangeable potassium (Ex. K), microbial biomass carbon (MBC), nitrogen (MBN), and phosphorus (MBP). Results indicated that subsoil had a higher Soil Quality Index (SQI) (0.60) than topsoil (0.57), reflecting surface soil degradation. Forests recorded the highest SQI (0.67), while Croplands had the lowest (0.54). Communality estimates revealed that sand, silt, Gco, EC, Av. K, Av. P, MBC, and MBN were the most influential indicators, with the highest weights (0.11) at both depths. The SQI was positively correlated with maize yield (R² = 0.61, p < 0.05), with available K (0.033) and P (0.010) being critical yield indicators. Croplands (0.54) and Fallow lands (0.53) showed the highest nutrient depletion due to inappropriate land use by smallholders. This research provides the foundation for policymakers at the local, regional, and national levels to develop strategies for improving soil management and increasing maize production in the FSTZ of Ghana.