BEHAVIOR OF MANGANESE IN SOME ACID SOILS IN WESTERN GERMANY IN RELATION TO PH AND AIR-DRYING

The relationships of pH to Mn concentrations in equilibrium soil solutions of strongly acid soils (pH < 4.5) were studied. The values of Mn concentrations did not conform to the solubility relationships of MnO2, Mn2O3 or Mn(OH)3. On the othr hand, a significant relationship between pMn and exchangeable Mn (r = 0.636**, n =43) was observed. This suggest that the levels of Mn in solution are primarily controlled by exchangeable Mn in response to pH changes. Mineral soil samples when air-dried showed a 1.5 to more than 8-fold increase in amounts of NH4Cl-extractable Mn. This increase was not observed in soil samples rich in organic matter (> 5% organic carbon), thus excluding the possibility of release of Mn from the organic fraction of the soil. The increase is considered a consequence of increased solubility of Mn-oxides. © 1978.