Effect of amendments on the extractability, retention and plant uptake of metals on a sewage-irrigated soil

Laboratory and greenhouse experiments were conducted to evaluate the effects of farmyard manure (FYM), CaCO3 and single superphosphate (SSP) on retention and availability of Zn, Cu and Ni in sewage-irrigated soil. We also assessed the suitability of 0.05 M EDTA for predicting the effectiveness of these amendments in reducing the phytoavailability of metals. Results indicated that EDTA could successfully predict the phytoavailability of Zn and Ni in amended soil, whereas it failed in case of Cu. By and large, application of CaCO3, either alone or in combination with FYM had a positive effect on the retention of Zn, Cu and Ni in soil. Application of CaCO3 alone or in combination with FYM was equally effective in reducing the Zn content in lettuce, whereas sole application of CaCO3 significantly reduced Ni content. However, only SSP was found to be effective in reducing the Cu content in lettuce. - Liming reduces the phytoavailability of Zn and Ni in metal contaminated soil, while single superphosphate was effective against Cu