Effect of citrate and tartrate on phosphate adsorption by amorphous ferric hydroxide
Curves for P adsorption by ferric hydroxide in the presence of citrate and tartrate were prepared. From the curves, it appeared as though tartrate at 10−4M has no effect on P adsorption up to 750µmol P g−1 ferric hydroxide adsorbed. However, observation of flocculation patterns show that even when the curves are identical, there is a difference in the way P is adsorbed in the presence of tartrate and citrate in terms of the type of site that is attacked.
Assessment of phosphate - citrate competition using32P and14C showed that citrate is less readily adsorbed by ferric hydroxide than tartrate and that citrate dissolves adsorption sites more readily than tartrate.
The implications of this study are that root exudates containing a greater amount of tartrate would cause more efficient use of added P by plants since tartrate occupies the high affinity sites and therefore reduces phosphate fixation. Plants which produce root exudates high in citrate content would be able to utilize more fixed P than plants which produce exudates lower in citrate content because citrate dissolves sites at which P is held.
Key wordsadsorption citrate organic phosphate tartrate
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