The effect of cow manure application on the Distribution Fractions of Fe, Mn and Zn in agricultural soils

Abstract

The speciation of metals in environmental samples is a vital factor in assessing the potential environmental impacts. Fractionation of heavy metals in soils is needed to predict elemental mobility in soil and phytoavailability to plants. A study was conducted to determine the effect of cow manure on Fe, Mn and Zn availability and their redistribution among soil fractions. Chemical properties such as pH, EC, CEC and Lime of concerned soils are also analyzed. A soil was selected from agricultural soil in sistan va baluchestan, southeast Iran and amended with 0, 1 and 5% of Cow Manure (CM) with three triplications and incubated at 60% of field moisture. The amounts of Fe, Mn and Zn were determined from the soil after 4 months of incubation time using sequential extraction procedures. Tessier method was exerted to decompose the metal content into exchangeable (EXC), bond to carbonates (CAR), bound to Fe-Mn oxides (Oxids), bound to organic matter (OM) fractions and Residual (RES) fraction was determined in aqua regia digest. Results of these analysis showed that the concentrations of Fe and Mn decreased mainly in the carbonate-bound and residual fractions but increased in the exchangeable, Fe-Mn oxide and organic matter-bound fractions with cow manure application. It was concluded that cow manure was the most effective in immobilizing Zn. The application of Cow Manure (CM) levels significantly decreases the exchangeable, carbonate-bound and residual fractions (P < 0.05) of Zn and increased in the Fe-Mn oxide and organic matter-bound fractions.