EFFECT OF ORGANIC WASTE AMENDMENTS ON CADMIUM AND LEAD IN SOIL FRACTIONS OF 2 SOILS

Certain organic soil amendments have been found to ameliorate metal to xicity to plants. A study was undertaken to determine the effects of o rganic amendments on cadmium (Cd) and lead (Pb) distribution among soi l fractions. Two soils (fine-textured and coarse-textured) were amende d with five organic waste materials or commercial humic acid (HA) with and without 5 mg Cd kg(-1) or 300 mg Pb kg(-1), incubated, and fracti onated using a sequential extraction technique. The added Cd and Pb we re found mainly in the organic matter (OM) fraction, although signific ant amounts were in the exchangeable (EXC) fraction for the sandy Norf olk soil. Spent mushroom compost (SMC) and HA lowered Cd in the EXC fr action for both soils and raised Cd in the OM fraction for the sandy N orfolk soil. The SMC and HA lowered Pb in the EXC and OM fractions and raised Pb in the manganese oxide (MnO), amorphous Fe oxide (AFeO) and the crystalline Fe oxide (CFeO) fractions. Poultry-litter amendment c aused higher Cd and Pb in the EXC fraction for the sandy soil. It was concluded from these studies that certain organic amendments like the SMC will lower Cd and Pb availability by redistribution the metals fro m the EXC and/or the OM fraction to less available fractions. Other am endments have little affect on Cd and Pb distribution, or for sandy so ils, poultry litter can cause higher Cd and Pb in the more available f raction presumably due to the formation of soluble organic complexes.