Effect of Biochar Amendment on Soil Chemical Properties and Crop Productivity in Strongly Acidic Soils of Enugu State, South East Nigeria

This study investigates the effects of biochar amendment on soil chemical properties and crop productivity in strongly acidic soils of Enugu State, located in Nigeria's South East geopolitical zone. Biochar is a carbon-rich material produced by pyrolysis of organic biomass that has attracted global interest as a soil amendment for acid soils due to its high pH, cation exchange capacity, and recalcitrant carbon content, yet its effectiveness under the specific conditions of South East Nigerian Ultisols has not been systematically investigated. A two-season field experiment was conducted on strongly acidic sandy loam soils (initial pH 4.5) in Igbo-Eze South local government area using a randomised complete block design with five biochar rates (0, 5, 10, 20, and 30 tonnes per hectare) crossed with two nitrogen fertiliser levels. Biochar was produced from rice straw by slow pyrolysis at 450 degrees Celsius. Soil pH, exchangeable aluminium, organic carbon, available phosphorus, cation exchange capacity, and maize grain yield were measured. Findings revealed that biochar at 20 tonnes per hectare raised soil pH from 4.5 to 5.8 and reduced exchangeable aluminium by 74 percent after two seasons. Cation exchange capacity increased by 38 percent at the 20 tonne rate. Maize grain yield increased by 147 percent at the highest biochar rate combined with full nitrogen fertilisation. Organic carbon showed a rate-dependent increase but remained elevated in biochar-amended plots beyond the point attributable to biochar-carbon alone, suggesting priming of native organic matter. Keywords: biochar, soil acidity, aluminium toxicity, maize yield, Enugu State.