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Research article - Peer-reviewed, 2022

Thresholds of target phosphorus fertility classes in European fertilizer recommendations in relation to critical soil test phosphorus values derived from the analysis of 55 European long-term field experiments

Steinfurth, Kristin; Borjesson, Gunnar; Denoroy, Pascal; Eichler-Lobermann, Bettina; Gans, Wolfgang; Heyn, Johannes; Hirte, Juliane; Huyghebaert, Bruno; Jouany, Claire; Koch, Dierk; Merbach, Ines; Mokry, Markus; Mollier, Alain; Morel, Christian; Panten, Kerstin; Peiter, Edgar; Poulton, Paul R.; Reitz, Thomas; Spiegel, Heide; Buczko, Uwe;
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Phosphorus (P) fertilizer recommendations of individual countries may differ in many aspects, but often the main principle is to reach or maintain a target range of plant-available P in soil. Within this target P fertility class, the soil is expected to supply enough P to the crop, while P fertilization replaces what is exported by the harvested crop. However, the threshold values of the target P fertility classes are based on a multitude of different soil test P (STP) methods and vary by a factor of up to three, even for countries using the same STP method. This study aimed to provide a comparison of the thresholds of target P fertility classes of different European countries and critical soil test P values (P-crit; STP below which the average relative yield falls below 95% due to P insufficiency) derived from the analysis of data from 55 long-term field experiments in eight European countries. To overcome the issue of diverging STP methods, all values were converted to Olsen-P using empirically based conversion equations from the literature. Converted threshold values varied by a factor of up to five. For the experimental data, we fitted multi-level Mitscherlich-type models to determine P(crit )values of unfertilized soils corresponding to 95% of maximum yield. We found an average Olsen-P-crit value of 15 mg P kg(-1) (adj. R-2 = 0.37; RMSE = 14.1% relative yield; n = 2368; 55 experiments), which lies far below several country-specific thresholds of target P fertility classes. Crop-specific analyses resulted in higher Olsen-P(crit )values for sugar beet (22 mg P kg-( 1)), potato (19 mg P kg (-1)) and winter rapeseed (18 mg P kg (-1)). Among the texture classes (loam, sand, silt and clay), sandy soils exhibited the highest average Olsen-P(crit )value (22 mg P kg( -1)). We consider a reevaluation of extraordinarily high country-specific thresholds as well as an inclusion of crop type and soil texture (where not already implemented) to be a reasonable measure towards more cost-effective and environment-friendly P fertilization.


Phosphorus; Olsen-P; Critical soil test P; P fertilization; Fertilizer recommendation

Published in

Agriculture, Ecosystems and Environment
2022, volume: 332, article number: 107926
Publisher: ELSEVIER

Authors' information

Steinfurth, Kristin
Justus Liebig University Giessen
Swedish University of Agricultural Sciences, Department of Soil and Environment
Denoroy, Pascal
Eichler-Lobermann, Bettina
Justus Liebig University Giessen
Gans, Wolfgang
Martin Luther University Halle Wittenberg
Hirte, Juliane
Swiss Federal Research Station Agroscope
Jouany, Claire
Merbach, Ines
Helmholtz Association
Mollier, Alain
Morel, Christian
Panten, Kerstin
Julius Kuhn-Institut
Peiter, Edgar
Martin Luther University Halle Wittenberg
Poulton, Paul R.
Biotechnology and Biological Sciences Research Council (BBSRC)
Reitz, Thomas
Helmholtz Center for Environmental Research (UFZ)
Spiegel, Heide
Austrian Agcy Hlth and Food Safety AGES
Buczko, Uwe
Justus Liebig University Giessen
Rubek, Gitte Holton
Aarhus University
van Laak, Michael
Justus Liebig University Giessen
von Tucher, Sabine
Technical University of Munich
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UKÄ Subject classification

Agricultural Science

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