EFFECT OF DIFFERENT LAND USE SYSTEMS ON SOIL ORGANIC CARBON AND TOTAL NITROGEN IN UNIVERSITY OF BENIN

ABSTRACT

This study was conducted to evaluate the effects of three land use management (mixed species man made forest, cultivated farm, and single plantation) and soil depth on soil organic carbon and total nitrogen. The study was carried out in university of Benin, Edo State, Nigeria. Soil samples were collected from three different study sites, the single plantation (Teak plantation), mixed man made forest (Arboretum) and cultivated land (Agricultural practical farm) at depth of 0-15, 15-30 and, 30-45cm and using a soil auger. Soil associated with the arboretum had higher organic carbon and total nitrogen apart from soils in depth 30-45cm which had the highest organic carbon and total Nitrogen in Teak plantation 11.21g/kg and 74.77g/kg respectively . Upper layer soil (0-15 cm) total organic carbon (TOC) content was highest under the natural forest (21.85g/kg) and lowest in the cropland (7.61g/kg). From the results it was observed that, natural forest increased the soil carbon content, total Nitrogen and some chemical properties of the soil which include pH (6.16g/kg), organic matter (37.77g/kg),phosphorus (250.900g/kg) and potassium (0.182cmol/kg). Cultivated land use contribution to soil organic carbon and total nitrogen was minimal. This could be attributed to several factors such as erosion, continuous use of soils with no management plan and cutting of vegetation. The contents of total soil organic carbon and nitrogen was significantly influenced by land use management and soil depth. All the different land use types showed highest accumulation of carbon in the surface layer (0-15cm). This high level of organic carbon stock in the surface layer was due to the presence of organic matter.