Fractionation and Speciation of Copper and Zinc in
Poultry Litter Amended Soil
Authors:
Candice O. Freeman, M.R. Reddy, and W.A.R.N. Fernando
ABSTRACT
North Carolina
is the 5th largest broiler-producing state in the United States.
A common method of disposing the broiler litter is using it as an organic
fertilizer, to improve soil fertility.
Long term disposal of poultry litter can potentially lead to heavy metal
accumulation in the soil which may cause phytotoxicity. The objectives of this study were to
fractionate Cu and Zn, determine the impact of pH on Cu and Zn fractions, and
to determine the speciation of Cu and Zn in the soil. A Toccoa Sandy Loam
(Coarse-loamy, mixed active, nonacid, thermic Typic Udifluvents), was collected
from a field in Wilkes County, North Carolina. The field was amended with poultry litter for
over 20 years. Soil samples were
prepared using standard methods. The pH
of the original soil and the adjusted sub-sample of the soil is 4.7 and 6.3,
respectively. A modified sequential extraction procedure was used to determine
the distribution of copper and zinc among exchangeable, carbonate bound,
organically bound, and the fraction associated with lattice structure of
minerals. The soil with the higher pH
showed the highest amount of copper in the oxidizable
fraction. Zinc was significantly higher
in the exchangeable form as compared to the other forms. These results suggest that copper is strongly
bonded to organic matter as the pH increases and that zinc was readily
exchangeable and available to the plants and potentially mobile through the
soil profile. The speciation of Cu and
Zn using MINTEQA2, Equilibrium Speciation Model computer program will be
presented.