Phosphorus Transformations and Their Relationships with Calcareous Soil Properties of Southern Western Australia
1999
Samadi, Abbas | Gilkes, R. J.
The agronomic effectiveness of phosphate fertilizers is strongly affected by reactions of P with soil constituents. The transformation of P added to soil and the effect of soil properties on these transformations was investigated for 14 alkaline and calcareous soils from southern Western Australia. The decline of NaHCO₃-extractable P (Olsen-P) with time followed a second order kinetic equation. The kinetic rate constant (k) increased with increasing oxalate-extractable Fe (Feₒ), citrate–dithionite–bicarbonate (CDB)-extractable Al and Fe (Ald and Fed), CaCO₃-free clay content, cation-exchange capacity (CEC), and ratio of CDB-extractable Fe (Fed) to active CaCO₃ equivalent (ACCE), and k decreased with increasing ACCE. A combination of these soil properties described 93% of the variation in rate constant, of which 78% of the variation was predicted by the Fed/ACCE ratio alone. A combination of clay related properties (Ald, clay, Feₒ, and CEC) described 62% of the variation in Ca₂–P determined by specific extraction. Carbonate-related properties (ACCE and CCE) together described 71% variation in Ca₈–P. Clay-related and carbonate-related properties jointly described 97% and 81% of the variation in Fe–P and Olsen-P respectively. Surface area (SA) and Ald together accounted for 43% of the variation in Al–P. Scanning electron microscopy analyses showed that added P was uniformly distributed in the soil matrix to the limit of the spatial resolution of the technique (≈2 μm).
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