Phosphorus Retention in Coastal Plain Forest Soils: II. Significance to Forest Fertilization1
- R. Ballard and
- W. L. Pritchett2
Phosphorus retention of 42 forest soils collected from the US Southeastern Coastal Plain was found to be significantly correlated with Al and Fe extracted by soils tests for available phosphorus. Aluminum provided better indices of P retention than Fe extracted by these tests and it accounted for more than 81% of the variation in P retention in the case of the NH4OAc (pH 4.8), 0.03N NH4F + 0.025N HCl, or 0.03N NH4F + 0.1N HCl tests.
Concentrations of Fe and Al in the foliage of 4-year old slash pine (Pinus elliottii Engelm. var. ‘elliottii’) growing on these soils were significantly correlated with soil P retention. However, foliar Fe, the most closely correlated, accounted for only 26% of the variation in P retention.
Retention of P from concentrated superphosphate applied at the equivalent 56 or 224 kg P/ha 4 years previously to young slash pine was measured to 20 cm depth at 10 sites, and ranged from −14 to +125%. Retention was almost independent of application rate. Extractable Al values corresponding to 50% retention of the applied P were 40, 330, 400, and 120 ppm for NH4OAc, 0.03N NH4F + 0.025N HCl, 0.03N NH4F + 0.1N HCl, and 0.05N HCl + 0.025N H2SO4 extractions, respectively. It is proposed that in the interest of maintaining long-term growth responses and minimizing possible pollution effects, these values be used for delineating soils of low P retention where less soluble sources of P, such as rock phosphate, should be used if P fertilization is required.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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