Phosphorus transformation and their relationships with calcareous soil properties of southern Western Australia
1999
Samadi, A. | 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 investigaled for 14 alkaline and calcareous soils from southern Western Australia. The decline of NaHCO(3)-extractable P (Olsen-P) with time followed a second order kinetic equation. The kinetic rate constant (k) increased with increasing oxalate-extractable Fe (Fe(o)), citrate-dithionite-bicarbonate (CDB)-extractable Al and Fe (Al(d) and Fe(d)), CaCO(3)-free clay content, cation-exchange capacity (CEC), and ratio of CDB-extractable Fe (Fe(d)) to active CaCO(3) 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 Fe(d)/ACCE ratio alone. A combination of clay related properties (Al(d), clay, Fe(o), and CEC) described 62% of the variation in Ca(2)-P determined by specific extraction. Carbonate-related properties (ACCE and CCE) together described 71% variation in Ca(8)-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 Al(d) 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 (approximately equal to 2 micrometer).
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