The availability of P from phosphate-goethite bridging complexes. Desorption and uptake by ryegrass
Pot trials using phosphated-goethite (bridging complex) as the source of P for ryegrass were established. No P was readily available to ryegrass until the surface was >40% covered with phosphate ions. Availability increased as the P level in solution increased up to 2 μM. Maximum availability was attained when the initial concentration of P in solution was 2 μM which occurred at about 75% coverage on geothite. Mycorrhiza increased the availability of phosphate at a level of about 0.5–2 μM P (60–70% coverage of the goethite surface).
Laboratory experiments showed that citrate ions were particularly effective in displacing P from goethite and the Olsen reagent was a good predictor of P availability to ryegrass.
Key WordsAluminium hydrous oxides Goethite Iron hydrous oxides Mycorrhiza Phosphate Root exudates Ryegrass
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