Phosphate and Organic Amendments for Safe Production of Okra from Metal-Contaminated Soils

There is little information available on the impact of superphosphate and compost on the uptake of metals by okra (Abelmoschus esculentus L. Moench). The objective of this study is to evaluate the efficiency of superphosphate and compost in reducing metals uptake by okra to healthy acceptable levels. A field experiment in randomized complete block design (RCBD) was conducted to investigate the effect of superphosphate (SP) and compost (C) on the availability and uptake of heavy metals by okra cultivated on a metals contaminated soil. The application of SP or C significantly (P < 0.05) reduced the availability and uptake of Cu, Pb, and Cd by okra. The C+SP treatment reduced the concentrations of Zn, Pb, and Cd in the edible portion of okra by 14, 35, and 38%. The combined application of C and SP was more effective in reducing the Zn, Pb, and Cd concentrations compared to the sole application of each amendment. The edible portion of okra collected from the unfertilized contaminated soil or that which received only C or SP contained toxic levels of Pb and Cd, while the concentrations of the two metals were below the safe limits when the two amendments were applied together. The result of the current study clearly indicated that it is feasible to apply P fertilizer and compost together to alleviate root - to - shoot transfer of Zn, Cu, Pb, and Cd in okra.