EFFECT OF COMPOSTED POULTRY MANURE AND BIOCHAR ON BIOACCUMULATION OF LEAD/ZINC IN OKRA (ABELMOSCHUS ESCULENTUS. L.) IN AMAGU MINING SOILS

Abstract

Remediation of contaminated soils with organic amendments to attenuate the side effect of Heavy metals has been scarcely investigated on okra pods. This study was conducted to evaluate the effect of composted poultry manure and biochar on heavy metals (lead and Zinc) bioaccumulation in Okra plant and the effect of artisanal mineral mining activities on the environment using ecological risk indices in Amagu, Abakaliki, Southeastern Nigeria. Soil samples for this study were collected at farmlands beside mining areas. The treatment consisted of four sources of biochar (control, empty oil palm bunch, maize cob, wood shavings) and two rates of poultry manure (0, 10 t/ha), replicated three times. The study was a 4 × 2 factorial experiment in a completely randomized design. Biochar from three feed stocks were pyrolysed at 320.0 0C, while poultry manure from battery cage system were composted for 90 days before application. Ecological risk assessment using indices were applied on data collected. After harvest, lead and zinc still exceeded the Food and Agricultural Organization (FAO) permissible limit of 100 mg/kg in Agricultural soils. Composted poultry manure (CPM) showed significant (P≤0.05) reduction by 14 % in the amount of Pb in the soil after harvesting of okra. Significant increases were recorded in the level of lead and zinc in the fruit by 50 and 28 % respectively. The ERF values for lead were rated as posing a very high ecological risk within the environment; while zinc was rated as having a low ecological risk.  Also the geo accumulation index (Igeo) of the study showed that the soils are extremely contaminated. In conclusion, the application of EMCB and EOPBB in combination with CPM demonstrated the capacity to reduce bioaccumulation of lead and zinc in okra plant