THE MANGANESE CYCLE IN SOILS: II. FORMS OF SOIL MANGANESE IN EQUILIBRIUM WITH SOLUTION MANGANESE

Abstract

Tracer amounts of the radioactive isotope Mn-54 were used to investigate the Mn cycle in an alkaline loam. Mn-54 was added to the solution in equilibrium with the whole soil as well as to the solution in equilibrium with soil from which the chelated Mn fraction had been previously removed. The forms of soil manganese in equilibrium with solution manganese were studied by extracting the soil with ZnSO4 solution followed by hydroquinone. These two extractants removed all the soil manganese equilibrating with solution manganese. Rate studies indicated that there was a rapid exchange reaction operative between solution Mn and the hydroquinone-soluble manganese oxides. There were one or more slower exchange reactions operative between solution Mn and manganese complexed by organic matter.