Nutrients status and soil microbial biomass C and N in charcoal production sites of derived savannah forest of southwestern Nigeria

Abstract

Deforestation and other anthropogenic activities, including charcoal production affect several microbial activities and nutrients availability and status in the savannah forest soil of southwestern Nigeria. However, understandings of the microbial activities and soil nutrients availability in these sites have not been thoroughly studied. Therefore, the study aims to clarify the charcoal production effects on the microbial biomass carbon and nitrogen, nutrients status of charcoal production sites and the surrounding soils. Soil samples were collected to determine the microbial biomass contents in carbon and nitrogen (BC and BN), organic carbon of the soil (SOC), total nitrogen (TN), ammonium and nitrate nitrogen [(NH4+-N) and (NO3N)] in the soil layers between 0–15, 15–30 and 30 – 45 cm, under different locations of charcoal production and non-production sites (CPS and NPS) respectively. We found out that SOC, TN, C/N ratio, Bc and BN and the ratios of Bc/SOC and BN/TN were significantly higher in the NPS than in the CPS. The SOC, TN, BC and BN and the ratios of Bc/SOC and BN/TN declined significantly (P ˂ 0.05) with increase in depth in the two sites under different locations. However, NH4+-N and NO3N contents in the NPS were significantly lower compared to the CPS. The results of the analysis indicate better soil nutrients in term of SOC and TN in the NPS than CPS. It is therefore posited that NPS is healthier and can sustain soil microbial activities than CPS. Although, NPS is lower in inorganic nitrogen contents determined, CPS has the potential to reduce leaching of inorganic nitrogen and increases its availability in the derived savannah agro-ecological region of southwestern Nigeria. Effort must be made to mitigate the large-scale conversions of the native derived savannah forests for traditional charcoal production that contributes to environmental pollution; it is therefore useful to consider biochar strategy in order to mitigate global warming and manage soil health and productivity.