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.

Soil and microbial biomass carbon (C), nitrogen (N), and phosphorus (P) play an important role in soil nutrient dynamics in biogeochemical cycles of terrestrial ecosystems. However, increased human activities as a result of agricultural intensification on soil nutrients and microbial C:N:P stoichiometry are poorly understood in this fragile forest-savanna transition agroecosystem. This study aimed to (i) assess soil and microbial C, N, and P stoichiometry in different land use systems, and (ii) examine the effect of soil and microbial C, N, and P stoichiometry on soils susceptible to human-induced land use changes. A total of 82 composite soil samples at a depth of 0–20 cm were sampled from forest, savanna, grassland, fallow and cropland for laboratory analysis. The results revealed that the concentrations of C, N, and P were low in Fallow and Cropland compared to other land use systems. Analysis of variance in microbial C, N, and P stoichiometric ratios revealed a significant decreasing tendency compared to soil C:N, C:P and N:P ratios with no statistical significance (p < 0.05). The C:P and N:P ratios were low compared to the C:N ratio in land uses. A significant positive correlation was observed between MBC and MBN (0.95; p < 0.01), and with C and N (0.69; p < 0.01). There were significant interactive effects of land use on soil and microbial variables. The estimated microbial C:N:P stoichiometric ratios (21:2:1) were well constrained in the study area. The transition from Forest to Cropland resulted in 64%, 52%, and 71% reduction in C, N, and P, respectively. This implies that phosphorus is the main factor limiting productivity. The low availability of phosphorus in these tropical soils may have resulted in low C:P and N:P ratios. Therefore, we conclude that our results highlight the importance of phosphorus limitation on ratios of microbial C:P and N:P in landuse systems. Nutrient inputs such as fertilizers, manure and crop residues should be applied to croplands to improve soil and microbial C, N and P levels. Further, effects of land use on soil nutrient status and stoichiometry at 1-meter depth will be considered in our future work.