Environmental impacts of long-term use of pesticides in cocoa ecosystem

Abstract

The study was conducted to evaluate the impacts of long use of pesticides on soil nutrients, water quality and microbial population within cocoa plantations ecosystem. Soil and water samples were obtained from selected cocoa plantations and uncultivated farmlands in major cocoa producing areas of Cross Rivers State, Nigeria. Samples were analyzed according to standard procedures. Soil pH across the various cocoa plantations ranged between 4.5 and 5.5 while uncultivated farmlands adjacent to the cocoa farms had a pH range of 5.12 to 5.8. On average, the level of residual copper in soils obtained from the cocoa farms was 40 folds of the level of copper in the various uncultivated farmlands. The obtained values for pH, TDS, TSS, EC, DO, hardness, turbidity, nitrates, sulphates and phosphates of the surface and underground waters were within the permissible limit set by World Health Organization (WHO) for potable water. The values obtained for BOD in the surface water samples (2.25 and 2.70) were higher than the permissible level (2.0) set by WHO for portable water. Soil bacterial population was reduced by 38.49, 50.53, 50, 40.98, 41.61 and 45.04% under the selected cocoa plantations in Ajassor, Efraya, Yahunde, Okundi, Ochon and Orimekpang respectively compared to the soil bacterial population in uncultivated farmlands adjacent to the various cocoa farms. Long term use of pesticides increased soil acidity, copper residue accumulation while it reduced soil microbial population.