Residual Available Phosphorus in Near-Neutral and Alkaline Soils: I. Solubility and Capacity Relationships
1982
Fixen, P. E. | Ludwick, A. E.
A continuous cropping greenhouse study of 28 Colorado soils with phosphorus (P) rates of 0 and 30 ppm was conducted. The objective was to investigate the nature and solubility of residual available P in near-neutral and calcareous soils. Solubility and capacity factor comparisons indicate that octacalcium phosphate was not likely an important residue in 27 of the 28 soils. One of the soils which had a history of heavy barnyard manure applications appeared to be buffered in the vicinity of the octacalcium phosphate isotherm. Tricalcium phosphate or a mineral similar in composition and solubility may have accounted for at least a portion of the fertilizer residues. The plant availability of tricalcium phosphate is apparently quite low since seven of the nine calcareous soils initially plotting on or near this isotherm responded to P fertilization.
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