Summary
This systematic evaluation compared five established soil phosphorus tests using samples from long-term European field experiments spanning over 100 years. Whilst all tests correlated positively with crop yield, quantity-based tests (ammonium oxalate, ammonium lactate, Olsen P) generally outperformed intensity-based tests (CaCl₂ and DGT) in predicting yield using Mitscherlich models. The study found that combining both quantity and intensity tests performed marginally better than any single test, and that critical P values derived from intensity tests were less soil-type dependent than those from quantity tests.
UK applicability
These findings provide European-wide critical soil phosphorus values applicable to UK soils and farming practices. The systematic evaluation of standardised extraction methods offers guidance for soil testing laboratories and farmers in the UK seeking to interpret phosphorus test results and optimise nutrient management across diverse soil types.
Key measures
Phosphorus content measured by five extraction methods; critical P values; crop yield predictions; goodness of fit in Mitscherlich models
Outcomes reported
The study evaluated five soil phosphorus extraction tests (ammonium oxalate, ammonium lactate, Olsen P, CaCl₂, and DGT) on 218 soil samples from 11 soil types across long-term field experiments in five European countries, and compared their capacity to predict crop yield responses.
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