LAUSR

Abstract The sustainable use of P in agriculture, which is a non-renewable and strategic resource, relies on soil P tests. Traditional soil P tests, however, may not accurately assess plant-available P in soils ranging widely in properties. The main objectives of this work were: (i) the study of the accuracy of the widely used Olsen P in assessing available P to plants, and (ii) testing other extraction methods to assess phytoavailable P, in a representative group of soils from Mediterranean areas. To this end, a P depletion experiment was conducted using 18 soils to estimate total available P to plants in soil. In addition to Olsen P, other P extractions were performed to check their accuracy in predicting total available P to plants, including anion exchange resins in Cl− and HCO−3 forms. Poor predictions of total available P with Olsen P (R2 = 0.53, P