Activities of Soil C and N Enzymes during Charcoal Production in Derived Savannah of Nigeria

Abstract

In recent years, anthropogenic activities, particularly charcoal production and the utilization of large fuelwoods have significantly compromised the deforestation of savannah forest soils in southwest Nigeria. This has had a notable impact on soil enzymes and nutrient cycles. Despite the growing acknowledgment of charcoal’s significant impact on soil properties, there is a notable gap in the literature regarding its specific effects on soil carbon (C) and nitrogen (N) enzymes. To address this, our study therefore aims to examine the effects of charcoal production on the C and N enzymes activities, under different locations and soil depths in the derived savannah of southwestern Nigeria. Soil samples were systematically collected and analyzed at depths 0–15, 15–30, and 30–45 cm under different locations of charcoal production and non-production sites, CPS and NPS respectively. The result showed a significantly higher activity level for amylase (0.54 µg/ml/min) and cellulase (0.90 µg /ml/min) at the NPS compared with CPS. In contrast, the protease and urease activity tended to be higher at CPS (0.54 and 16.66 mg/ml/min respectively) than at NPS, suggesting distinct protein degradation patterns at both sites. In terms of enzyme ratios, amylase/cellulase activity levels is greater at CPS than NPS with no significant difference with values of 1.44 and 0.79 µg/ml/min respectively. Similarly, protease/urease activity ratio levels are identical at both sites (0.04 mg/ml/min). Yet, this ratio decreases with depth due to heightened protease and urease activities, catalyzing the mineralization of organic nitrogen, and resulting in increased nitrogen content and the release of ammonia-N in soils. Overall, our findings suggest that the charcoal production process may influence and alter soil enzyme activities, potentially impacting the breakdown of carbohydrates, cellulose, proteins, and urea in the soil. These variations in enzyme activities could have broader implications for nutrient cycling, microbial processes, and overall soil health in areas with charcoal production areas compared to non-production sites.