A POSSIBLE MECHANISM FOR MANGANESE RELEAS E FROM ACID SOIL

The objective was to study the principal mechanism responsible for Mn solubility in acid soils in the State of Parana, Brazil. Air-drying, h eating, autoclaving and oxidation with H2O2 in soil samples increased Mn solubility. Soluble Mn after drying or sterilizing soil sample was re-immobilized, respectively, by wetting with water or adding soil sol ution obtained from natural soil. Sterilized soil kept dried or wet wi th sterilized water did not show Mn reimmobilization. The strength of extraction solution was the following: EDTA > CUCl2 > Oxalic acid > Mg Cl2. The Mn solubility was controlled by Mn-organic ligant stability c omplex. Under natural conditions the content of soil organic ligant is maintained by biological activity. Mn-organic complexing reaction was probably the main mechanism responsible for the control of Mn solubil ity in acid soils in the State of Parana.