Influence of Slope Position on Soil Carbon Stock and Selected Soil Fertility Indices in Lowland Rain-Fed Rice Field

Abstract

Most farmlands in Southeastern Nigeria are associated with low organic matter content and are prone to soil erosion and nutrient loses due to runoffs from undulating soil surfaces. This consequently limits the capacity of these farmlands to produce abundant food. The present study investigated the effect of slope position on soil organic carbon (SOC), carbon stock and selected fertility indices of lowland rice fields in Ebonyi State, Nigeria. This study was conducted in four lowland-rice fields/location in Ishiagu, Ebonyi State, Nigeria. In each location, three slope positions (upper slope, middle slope, and lower slope) were identified. Topsoil samples (0-15 cm) were collected in quadruplicates from each slope position for soil chemical analyses. Results showed significant differences in the soil physicochemical properties across slope positions and locations. The middle slopes had higher (p < 0.05) pH, cation exchange capacity (CEC), and total nitrogen than the upper and lower slopes. Carbon stock varied from 4.22-13.0 t C/ha across slope position but was insignificant across locations. Upper slopes had higher (11.4 g/kg) SOC than lower slopes (9.68 g/kg). The study locations had low SOC, CEC and soil nutrients; an indication of soil erosion impact in that area. The results of study reveal that organic amendment application is needed to build-up the SOC, which is crucial to preventing soil erosion, nutrient losses, as well as enhancing crop productivity and improving the overall soil health.