Conversion equations between Olsen-P and other methods used to assess plant available soil phosphorus in Europe – A review

Autor: Kristin Steinfurth, Juliane Hirte, Christian Morel, Uwe Buczko
In:

Geoderma

Bandangabe: 401
Auflage: 401
ISBN: 0016-7061
Seite: 1 - 17
Jahr: 2021

Einordung:
Institut: Professur Grünland- und Futterbauwissenschaften

Abstract:
Plant available soil phosphorus contents are assessed by various different methods worldwide. The resulting
country-specific methodology prohibits comparison or joint analysis of international data on yield response to
soil P level. A change of the standard method would decrease comparability to older data, require new costly and
time-consuming calibration and familiarization of advisory authorities and farmers. The use of conversion
equations can allow the combination of data derived by different methods, but large differences between
available equations question their reliability. The aim of this review is to provide a comprehensive overview of
conversion options from P extracted by methods commonly used in Europe (acid ammonium acetate, acid
ammonium acetate + EDTA, ammonium lactate, calcium acetate lactate, double lactate, H2O and Mehlich 3) to
the widely used Olsen method. For a given method of soil P extraction, coefficients derived from different
publications often vary by factors above two. Differences in coefficients can, at least to a certain degree, be
attributed to variations in soil type, soil texture and especially pH range and carbonate contents of the soils of the
according databases. In several studies, decreasing pH values increased Olsen-P values in relation to the other
methods. Linear regressions are prone to bias by the right-skewed distribution of P values in most databases and
therefore have to be handled with care on the lower end of the P level range. Even the option most appropriate
for the soil and research purpose at hand can be a considerable source of error, therefore conversions should only
be conducted if absolutely necessary.

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