Assessment of Soil Organic Carbon Stocks Under various Land Use/Land Cover Types in the Kintampo North Municipal, Ghana

Abstract

Climate change adaptation and mitigation in soils has gained much attention recently with the introduction of sustainable agriculture and land use management (SALM) practices by the World Bank. SALM enhances the ability of the soil to sink more carbons. This study was to assess soil organic carbons stocks under the major landuse/cover types in Kintampo North Municipal which is located in the Guinea savanna through the transition agro-ecological zone of Ghana. Two LANDSAT images (Landsat 8 & 5) were classified using maximum likelihood to produce LULC maps for 1986 and 2014 in ENVI 4.7 and change detection done in IDRISI 17. Cluster sampling was used for picking ground control points. Random field sampling was done on 34 plots and 24 sample points at depths 0 - 10 cm, 10 - 20 cm and 20 - 30 cm per plot with soil corer. Soil bulk density, pH, particle size distribution and SOC were determined using standard laboratory procedures and computations. Results were subjected to both statistical (ANOVA, Correlation) and Geo-statistical (Kriging) analyses. The soil organic carbon stocks in each land use decreased with depth. The mean SOC for the five (5) land-use systems studied were 11.33 t/ha, 7.95 t/ha and 6.08 t/ha at 0 - 10 cm, 10 - 20 cm and 20 - 30 cm respectively. The vertical variability in SOC distribution across all considered land use/cover types was statistically significant (p < 0.05) but the statistical difference amongst land use/cover types was not significant. The determined mean SOC stocks in descending order at depth 0 - 30 cm were 30.02 (±13.20) > 25.73 (±8.95) > 25.70 (±9.41) > 24.31 (±7.74) > 22.01 (±8.92) t/ha for Savanna woodland/forest > crop land > mango plantation > teak plantation > cashew plantation respectively. The spatial distribution of SOC stocks ranged between 12 t/ha to about 33 t/ha at 30 cm depth by kriging. Available farmers on the sampled farms were interviewed on their land use management practices. Residue use as cover crops was the largest management practice (90%) by farmers especially the plantation farmers. There is no proper management procedure aside crop residue, which call for the introduction of sustainable agriculture and land use management practices to raise SOC stocks thereby increasing yield through better soil fertility and contributing to climate change adaptation. Out of the 120 farmers interviewed on land use decisions, 74.17% had no future plans to change current land use. Only 10.83% will change to mixed cropping which has a capacity of increasing its storage under the SALM project. Both crop and tree plantation was the future plans of 12.5% of the respondents and remaining 2.50% opted for agro forestry and mono cropping in the future. None of the interviewed farmers was aware of climate change and its relation to land use, and the Clean Development Mechanism (carbon credits) since it is not operational in the Municipal. A national carbon inventory will contribute to the monitoring of carbons and proper estimations using any accepted method to determine SOC stocks.