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Phosphorus Transformations and Availability under Cropping and Fertilization Assessed by Isotopic Exchange
Author(s) -
Morel C.,
Tiessen H.,
Moir J. O.,
Stewart J. W. B.
Publication year - 1994
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1994.03615995005800050023x
Subject(s) - alfisol , mollisol , fertilizer , human fertilization , phosphorus , agronomy , soil water , cropping system , chemistry , field experiment , environmental science , crop , mathematics , soil science , biology , organic chemistry
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 ( C p ) and the time‐dependent isotopically exchangeable P ( E t ). The relationship of C p to E t was further evaluated for short‐term reactions by incubating field samples for 1 d with increasing P rates. Both C p and E t 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 C p values in the more depleted soils. In the Alfisol, field variations in pH and texture affected both E t and C p , obscuring relationships between the field P budgets and availability parameters. In the Mollisol, one single equation described the relationship between E t and C p for both increases of C p due to short‐term additions and decreases due to long‐term crop export, indicating that transformations of available P were fully reversible.