Pot experiments were conducted to study the effect of incubation periods on
the behaviour of Cd, Pb and Ni in sandy, Nile alluvial and calcareous soils. The
treatments were 0, 2.5; 5,10 and.20 mg Cd kg" soil; 0, 50,100,200 and 400 mg Pb
kg" soil; and 0, 5, .10, 20 and 40 mg Ni kg" soil in the forms of Cd S04, Pb (N03)2
and NiS0₄, respectively. The different soils were exposed to soil removal after 0,7,
14 and 45 days of incubation for extracting the available Cd, Pb and Ni. The results
showed that increasing the levels of Cd, Pb or Ni added to the different studied soils
was associated with a progressive significant increases in their availability. Increasing the time of incubation was accompanied by a gradual· decreases in the available
contents of Cd, Pb and Ni. .Multiple regression analysis showed the important of OM
and pH in influencing the availability of Cd ,Pb and Ni in different soils.