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