Abstract
The impact of agronomic activities on soil carbon sequestration as an adaptation to the impacts of climate change was assessed in Niger state, southern Guinea savanna of Nigeria. Farmers’ observation of climate change parameters was evaluated and the various tillage and fertility methods used by farmers to cultivate maize were verified. The quantification of the vertical distribution of soil organic carbon (SOC) and its fractions as indicators of SOC sequestration under different tillage systems amended with various nutrient sources were also done. Results from the socioeconomic survey showed that 97.5% of the respondents were aware of climate change and variability. The tillage methods used included mechanized tillage practiced by 57%, manual tillage practiced by 37% and other types practiced by 1%. Based on these findings, the field trial was designed to investigate the effect of tillage and nutrient amendments on soil carbon sequestration using maize as a test crop. Treatments consisted of zero tillage, mechanized tillage and manual tillage amended with an equal amount of nitrogen (120 kg ha-1) supplied as poultry droppings (organic source), Nitrogen, Phosphorus and Potassium (NPK) + Urea (inorganic source) and a combination of poultry droppings and NPK + Urea (integrated source). After harvest, soil samples were collected at 0–5 cm, 5-15 cm, 15-25 cm, 25-50 cm and 50-75 cm depths and analysed for SOC and its fractions. Results showed that manual tillage and integrated nutrient source had highest plant height values. All carbon fractions significantly (P<0.05) decreased vertically down soil depths. Water soluble organic carbon fraction (WSOC) and the particulate soil organic carbon fraction (PSOC) were most affected by treatments, highest significant decrease (P<0.05) was recorded at 0-5 cm, 5-15 cm and 15-25 cm depths. Highest significant variation in the non-hydrolysable organic carbon fraction (NHOC) occurred at 25-50 cm depth. Residual soil NPK, plant NPK and plant carbon concentration were not significantly affected by tillage and nutrient sources. Results from the study provided empirical evidences and gave an understanding of the trend at which SOC and its fractions change with land manipulation and land management. The study concluded that manual tillage and organic nutrient source were best land management practices that could be adopted for increased soil carbon sequestration and adaptation to climate change.