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This article in SSSAJ

  1. Vol. 58 No. 5, p. 1439-1445
     
    Received: Aug 23, 1993
    Published: Sept, 1994


    * Corresponding author(s): morel@dijon.inra.fr
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doi:10.2136/sssaj1994.03615995005800050023x

Phosphorus Transformations and Availability under Cropping and Fertilization Assessed by Isotopic Exchange

  1. C. Morel ,
  2. H. Tiessen,
  3. J. O. Moir and
  4. J. W. B. Stewart
  1. Agronomie-INRA, 17 rue Sully, BV 1540, 21034 Dijon Cedex, France
    Soil Science Dep., Univ. of Saskatchewan, Saskatoon, Saskatchewan, S7N 0W0, Canada

Abstract

Abstract

In fertilized agricultural soils, both fertilizer and soil P are partly depleted by crop export, while residual fertilizer P reacts with the soil. As a result, P availability changes in complex ways that cannot be described by an available P pool. Our objective was to characterize the P availability in two long-term field experiments on a Mollisol and an Alfisol (near Lethbridge and Breton, Canada), by using the soil solution P (Cp) and the time-dependent isotopically exchangeable P (Et). The relationship of Cp to Et was further evaluated for short-term reactions by incubating field samples for 1 d with increasing P rates. Both Cp and Et were related to changes in the soil P budget resulting from continuous cropping and wheat (Triticum aestivum L.)-fallow rotations with and without fertilization, with lower Cp values in the more depleted soils. In the Alfisol, field variations in pH and texture affected both Et and Cp, obscuring relationships between the field P budgets and availability parameters. In the Mollisol, one single equation described the relationship between Et and Cp for both increases of Cp due to short-term additions and decreases due to long-term crop export, indicating that transformations of available P were fully reversible.

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