Phosphorus Fertility of Some Tropical Soils in Sierra Leone1
- E. McKenzie,
- L. T. Kurtz and
- S. W. Melsted2
Chemical fractions and profile distributions of native phosphorus were determined in some soils of Sierra Leone, West Africa. Total P in the horizons of eight profiles ranged from 70 to 420 pp2m. Distributions within profiles were usually rather uniform, with concentrations tending to be somewhat greater in the surface and deepest horizons. Phosphorus fractions extracted by NH4F and NaOH were typically between 18 and 30 pp2m (6 to 12% of the total P), while the acid-soluble fraction was virtually absent. On the average, 15% of the total P was in the reductant-soluble form. Bray P-1 values ranged from 5 to 25 pp2m P in the surface horizons, but were often < 3 pp2m at depths below 40 cm. A very low proportion of the native P in these soils would be expected to be readily utilized by crops.
Estimates were also made of P retention capacities, P equilibrium concentrations in solution, and recovery with the Bray P-1 extractant of added P after different periods of incubation. Behavior of P in Sierra Leone soils in these procedures was not greatly different from that in some Illinois soils where the management of P fertility has become routine. Attaining and maintaining adequate levels of P in Sierra Leone soils by fertilization would not appear to be difficult, assuming phosphate fertilizers can be obtained.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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