The chemistry of the lowland rice rhizosphere |
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Authors: | Kirk G. J. D. Begg C. B. M. Solivas J. L. |
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Affiliation: | (1) International Rice Research Institute, P.O. Box 933, 1099 Manila, Philippines |
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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 O2 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. |
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Keywords: | cation-anion intake balance iron oxidation lowland rice pH change rhizosphere |
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