Carbon and Nitrogen Sequestration Potential of Various Land Use Types in Tai Area, Rivers State

Sequestering Organic Carbon in soil is an important way of mitigating climate change.However, soil Organic Carbon (SOC) sequestration without appropriate check on soil Nitrogen (N) and C: N ratio can offset greenhouse gas (GHG) mitigation balance through N mineralization and Nitrous oxide (N2O) emission.This study assessed the impact of land utilization types (LTUs) on Carbon and Nitrogen sequestration and C:N ratio.The LUTs included secondary forested land, monocropped land (Oil palm Plantation), farmland (under continuous cassava cultivation for over 5 Years) and grassland.Soil samples were collected in seven replicates from each LUTs at depths 0-30 and 30-60 cm and analyzed for soil attributes.Soil organic carbon was analyzed using wet dichromate oxidation method.Fixed depth method was used to determine C and N sequestration.Findings: The LUTs and management practices had significant influence on CS, NS and C:N ratio.At depth 0-30 cm, CS in farmland was highest and varied significantly (P grassland (91.88kg/m 2 )> farm land (75.06 kg/m 2 ) > forest land (41.30kg/m 2 ).NS was highest in farmland (11.92kg/m 2 ) in the top soil.But in the sub soil, monocopped land showed the highest with the trend: monocropped land (13.41kg/m 2 )> grassland (10.93/m 2 )> farmland (10.3 kg/m 2 ) > forest land (6.56 kg/m 2 ).The CN ratio at depth 0-30 cm was lowest (6.79) in farmland and was highest in monocropped soil (8.76).At 30-60 cm depth, monocropped land still showed the highest.CN followed the trend: monocropped land (8.30) > grassland (7.56) > farmland (7.26) > forest land (652).From the result obtained, monocropped and grassland should be considered tor stabilizing and retaining C and N in deeper soils.Farmland LUT showed higher potential to sequester C in top soil but the lower CN ratio in farm land indicates possible net mineralization of N which can cause emission of N2O and thereby offset (GHG) mitigation balance.