Evaluation of phosphorus in forest soils: Comparison of phosphorus uptake, extraction method and soil properties

Summary

Phosphorus in soils from plantation of red pine (Pinus resinosa Ait.) was determined using six extractants: 0.002N H₂SO₄ (pH 3.0); 0.025N HCl+ +0.03N NH₄F; 0.5N NaHCO₃ (pH 8.5);N NH₄OAc (pH 4.8); anion exchange resin (Dower −2, Cl-form); H₂O. Correlations of extractable P with Al- and Al-+Fe-P indicated that these fractions are the dominant forms of inorganic P in most of the soils.

Uptake of P by corn and Monterey pine seedlings grown in greenhouse culture was correlated with soil P extracted by the different methods. The most successful of the extractants for predicting P uptake was resin extractable P; the simple correlation coefficients were 0.811 and 0.609 for pine and corn respectively. P uptake by pine correlated significantly with 0.002N H₂SO₄ P (r=0.679),N NH₄OAc P (r=0.443), H₂O P (r=0.549) and Al-+Fe-P (r=0.532) while P uptake by corn correlated with 0.002N H₂SO₄ P (r=0.579), H₂O P (r=0.477) and organic P (r=0.460). Per cent P in pine seedling tops correlated significantly with 0.002N H₂SO₄, resin andN NH₄ OAc extractable P. Multiple regressions which included silt+clay and organic P improved correlations of some soil tests with P uptake in corn and pine seedlings respectively.