Soil organic carbon and total nitrogen stocks as affected by different land use in an Ultisol in Imo Watershed, southern Nigeria

Soil organic carbon (SOC) and soil total nitrogen (STN) concentrations and stocks are essential for improving soil quality and increasing C-reservoir. The study aimed at quantifying the dynamics of soil properties under different land use in Imo watershed where there is no knowledge about the effects of land use on SOC and STN pool. Six land use: arable land (AL), forest land (FL), grassland (GL), shrubland hills (SL), urban built-up green (UL), and freshwater swamp-mangrove wetland (WL) were classified using ArcGIS 10.1 and FAO land use classification system. Soil samples were collected and analyzed from each land use under different soil depths and slope positions with three replications. Topsoil layer (0-30cm) contributed to more than 90% of the total soil nutrients. Land use significantly affected SOC content, STN content, and bulk density. SOC and STN concentrations were in the order of FL>WL>GL>SL>UL>AL which revealed the potentials of FL and WL for SOC and STN sequestration. The study provides land users with the information to improve soil quality, conserve C and N stocks for ecological sustainability and climate change mitigation.