This study was performed to evaluate the effect of both cow and chicken manures application on the immobilization
of Ni and Zn in soils. Effect of cow and chicken manures on the bulk density, pH and the distribution of Ni and Zn in
various chemical fractions of an alkaline, sandy loam soil was explored in a PVC columns study. Cow and chicken
manures were mixed at rates of 10, 20 and 30 g/kg of soil. The soil-manure mixture was incubated for two months
at room temperature. Sequential extraction procedure was performed on all samples from each column to determine
Zn and Ni in different fractions (soluble-exchangeable, organic, carbonates and residual). Results obtained showed
a decrease in soil bulk density with an increase of 0.3 units in soil pH as compared to the control. After 60 days
of incubation, Ni concentrations were found to be 28 and 34% of inorganic fraction, while the residual reaction
accounted for 58 and 53% for cow and chicken manure respectively as compared to the corresponding control. In
case of Zn, soil organic matter fraction accounted for 53-57% of the total Zn. The soluble and exchangeable fraction
which, although, slightly increased with time remained very low (2-4%) for the two metals. Therefore, the addition of
the manures resulted in improved soil bulk density and showed a good potential in immobilizing both two metals in
the studied soil.