Paper Title
Effect of Chemical and Natural Chelators on Zinc Fractionation in the Rhizosphere of Maize (Hybrid (KSC.704)) in a Sandy Contaminated Soil

Abstract
Rhizosphere has different physicochemical and biochemical characteristics from bulk soils because of biological activity and the change of the rhizosphere microenvironment. A greenhouse research was performed to compare fractionation of zinc (Zn) between rhizosphere and bulk soils amended with chemical (EDTA and Citric Acid (CA)) and natural chelators (Poultry Manure Extract (PME)). CA and EDTA were added to the soil at concentrations level of 0, 0.5 and 1 mmol kg-1 soil and 0, 0.5 and 1 g kg-1 soil for PME. Fractions of Zn were determined in two subsamples (rhizosphere and bulk soils). The results indicated concentration of Zn-fractions in the rhizosphere soils were significantly (p<0.05) different from concentrations of Zn-fractions in the bulk soils. The order of content of Zn fractions in soils treated by chelators were: OXIDS-Zn fraction> RES-Zn fraction > OM-Zn fraction > CARB-Zn fraction > EXCH-Zn fraction. Keywordsó Rhizosphere, Fractionation, EDTA, Citric Acid, Poultry Manure Extract.