Heavy Metal Runoff Dynamics From Farmland Around Ikpa River Basin, Nigeria

Discharges of zinc, copper, cadmium and lead from farmland were examined based on field measurements conducted between May 18 and October 14, 2012 on poultry droppings and NPK fertilizers. The study fields are located on 15 % slope gradient area where water body of a river was contaminated with water drained from upstream farmlands. The area of the farmland is 10.7 ha, of which 0.5 ha had been used for cassava cultivation under vetiver hedge management. The mean level of Cu concentration on application of fertilizers was significantly high when compared with the control (C) plot, leading to the conclusion that fertilizer application (organic or inorganic) affects Cu level in a farmland (PD-5.66, NPK-5.82, C- 2.76). Also greater percent of this metal was easily washed off during rainstorm into the stream (PD-5.90, NPK-6.06, C-4.70). Lead concentrations in soil were 0.232, 0.211 and 0.145 mg/kg and in runoff water, 0.12, 0.25, 0.17 mg/kg for Poultry droppings and NPK, amended soils and control respectively. The acidity level in runoff water and soils was the same, whereas organic matter content was 300 % higher in the soil. This implied that the organic matter was not easily removed from the soil during storms that resulted in overland flow.