Untersuchungen zur Verfügbarkeit Spezifisch Gebundenen Ammoniums für Reispflanzen in Überstauten Böden unter Berücksichtigung von Redoxpotential-Einflüssen im Wurzelraum

In pot experiments with two chinese rice soils we studied the availability of nonexchangeable ammonium for rice plants after flooding and the influence of redox potential (E_h) on fixation and release of NH₄+ in the vincinity of the roots.The results show that the amount of ammonium fixed after submergence was completely released by rice plants in the rhizosphere during the experiments. Mobilization of fixed NH₄+ decreased with growing distance from the roots.The redox potentials of the soils were greatly raised by the influence of the rice roots. In one soil the oxidizing effect reached to more than 5 mm away from the roots.Fixation and release of nonexchangeable NH₄+ appeared to be influenced by the height of the E_h. A close correlation between the content of fixed NH₄+ and E_h in the soils was observed when the redox potential of fallow pots was changed by aeration.