Land-Use Change on Soil C and N Stocks in the Humid Savannah Agro-Ecological Zone of Ghana

Abstract

Land-use conversion and unsustainable farming practices are degrading native forest ecosystems of Ghana’s humid savannah agro-ecological zone. This study assessed the impact of land-use change on soil C and N stocks in different land-use systems and soil types. A total of eighty (80) composite soil samples at two depths (0 - 20 cm and 20 - 50 cm) were sampled from five land use types (Forest, Woodland savannah, Grassland, Fallow and Cropland) for laboratory analyses. Particle size distribution, bulk density, pH, SOC and TN were determined using standard procedures. Results of the study indicated that C and N stocks were significantly lower in croplands (p < 0.05) compared to other land-use systems. There were significant interactions (p < 0.05) within land-use systems, soil types, and soil depth for soil C and N stocks. Acrisol and associated soils had the highest C and N stocks. A strong positive significant correlation (p < 0.05) was observed between C and N stocks with an R 2 value of 0.85 and 0.93 for the 0 - 20 and 20 - 50 cm depth, respectively. Soil C and N stocks in the study area were estimated to be 34.56 kg/m 2 and 4.63 kg/m 2 for soil types and 26.89 kg/m 2 and 3.39 kg/m 2 for land use types, respectively for the 0 to 50 cm soil depth. Our findings indicated that the conversion of native forest to arable land has significantly reduced soil C and N stocks in the top 50 cm (0.50 m) soil layer by 50.77% and 47.77%, respectively. Therefore, we conclude that land-use change, soil type, and soil depth influenced soil C and N stocks of land-use systems in the humid savannah agro-ecological zone of Ghana.