MANGANESE-IRON INTERACTIONS IN THE PLANT-SOIL SYSTEM

Dicotyledonous plants had significantly higher Mn and Fe intake rates on a near neutral soil, had a significantly higher Mn intake rate on a slightly calcareous soil, but had lower Mn and Fe intake rates on a calcareous soil, than monocotyledonous plants. This dependency on soil reaction suggests that dicots utilize primarily a chemical reduction mechanism, whereas monocots utilize some less pH-dependent mechanism (possibly Mn(III)-, Fe(III)-organic complexation) to mobilize soil Mn and Fe. Soluble soil Mn and Fe fractions in the rhizosphere were consistently positively correlated with each other, as were Mn and Fe intake rates. These results suggest that for soil-grown plants, Mn and Fe uptake was positively interrelated because both Mn and Fe were mobilized by similar root processes.