Comparison of soil phosphorus extraction methods regarding their suitability for organic farming systems

Abstract Background Organic farmers frequently report sufficient yield levels despite low or even very soil phosphorous (P) contents questioning the applicability of widely used laboratory methods for P testing organic farming. Aims The aim this study was to compare validity a broad range different extraction on soils under management from South West Germany and test correlation measured concentration with plant offtake. Methods Twenty‐two samples eight farms were extracted solutions: (1) water, (2) CAL, (3) Olsen, (4) Mehlich 3, (5) Bray P1, (6) P2, (7) NaOH+Na 2 EDTA, (8) total P. results then correlated above ground Results Spearman's rank coefficient ( r s ) correlations between extractable (Water‐P, CAL‐P, Olsen‐P [+active charcoal {+AC}]) determined ICP‐OES strong (0.94, 0.90, 0.93, respectively). Among tested methods, showed CAL‐P as detected by = 0.90) colorimetry 0.91). comparison data provided analyzed during research discrepancies results. Conclusions indicate that CAL method can be in farming (P org ). Furthermore, it is recommended take analyses regularly interpret changes long‐term instead interpreting individual samples.