PERTANIKA JOURNAL OF TROPICAL AGRICULTURAL SCIENCE

Environmental sustainability of recent adoption of organic farming as a wholesome practice in sub-Saharan Africa needs to be investigated, in order to guide agricultural policy makers. Consequently, an assessment of soil chemical properties was done in an organic farm with different land uses. The experiment was 5 × 3 factorial design (five land uses and three soil depths) replicated temporally (two contrasting seasons) and spatially (four replications). Samples collected systematically at 0 - 20, 20 - 40 and 40 - 60 cm depths were analysed for pH, organic carbon, nutrients and heavy metals. Results indicated that manure application limed the soil. Soil pH ranged from 5.1 to 6.3 in grass-land and 5.8 to 6.4 in amaranth farm during dry and wet seasons, respectively. Generally, nutrients and heavy metals were concentrated at 0-20 cm depth. The effect of season on the parameters was erratic. Amounts of mobile, exchangeable and labile Cu were 0.13 - 0.19, 0.07 - 0.15 and 1.39 - 1.74 mg kg-1, respectively while water soluble and mobile fraction Zn ranged from 0.15 - 0.20 and 0.29 - 0.62 mg kg-1. Comparatively, all the metals labile pool was most abundant, while Pb was the most abundant metal. There was no evidence of heavy metal accumulation in the organic system.