ABSTRACT

This research was conducted in Ikole-Ekiti to evaluate the effects of four land use types (forest plantation, arable land, fallow land and ranchland) and soil depth on soil organic carbon fractions namely; particulate organic carbon (POC), soil microbial biomass carbon (SMBC), total organic carbon (TOC) and water soluble organic carbon (WSOC). Soil samples were taken at 0-5, 5-10, I0-20 and 20-30 cm and 0-30 cm depths at each site using soil auger. The soil samples were analyzed for physical and chemical properties. At O- 5 cm depth, fallow land had the highest TOC, (30.27 g/kg), followed by forest plantation, ranchland and arable land at 29.70, 28.57 and 19.60 g/kg respectively. At 5-10 cm, TOC significant differed across the land use, with fallow land and forest plantation given the highest values while ranchland and arable land had the least values. The SMBC at 20-30 cm depth in the fallow land was significantly different from other land use types. The arable land had the highest concentration of SMBC, POC and WSOC among the agricultural land use types but least TOC content at all depths. The carbon fractions decrease with depth across the land use type. The depth-wise distribution of soil organic carbon forms did not follow a particular trend across the land use types. Generally, soils in Ikole-Ekiti were characterized with medium to high variations in the forms of soil organic carbon except for WSOC with low variations at all depths.

Keywords: Land use, carbon fractions and depths.