Phosphate soil tests and their suitability to assess the phosphate status of soil

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Abstract
Some phosphate soil tests (P‐tests) are evaluated for their suitability to assess the phosphate status (P‐status) of contrasting soils. A P‐test at best only provides a relative estimate of the soil P‐status, which may be thought of as the ability of a soil to release P either to a crop, or more specifically to a given plant root for a given period under optimum conditions with respect to all other growth factors. A P‐test gives no direct information on the crop response to added P.The P‐tests were evaluated on the basis of data from 29 published papers where the anion exchange resin method was among the P‐tests used, and where plant P‐uptake in pot experiments had been used as the evaluation basis.The evaluations ranked the P‐tests in three groups: best group: anion‐exchange resin method, intermediate group: water, and sodium bicarbonate methods, worst group: all ‘acid’ methods: acetate buffer, lactate buffer, citric acid, Bray‐1, Truog and Bondorff methods.