The chemistry of the lowland rice rhizosphere uri icon

abstract

  • Models and experimental studies of the rhizosphere of rice plants growing in anaerobic soil show that two major processes lead to considerable acidification (1-2 pH units) of the rhizosphere over a wide range of root and soil conditions. One is generation of H+ in the oxidation of ferrous iron by O-2 released from the roots. The other is release of H+ from roots to balance excess intake of cations over anions, N being taken up chiefly as NH4+. CO2 exchange between the roots and soil has a much smaller effect. The zone of root-influence extends a few mm from the root surface. There are substantial differences along the root length and with time. The acidification and oxidation cause increased sorption of NH4+ ions on soil solids, thereby impeding the movement of N to absorbing root surfaces. But they also cause solubilization and enhanced uptake of soil phosphate.

publication date

  • 1993
  • 1993
  • 1993