Evaluation of soil test methods for estimation of available phosphorus in some Portuguese soils: A greenhouse study

The Egner-Riehm method for estimating plant-available soil phosphorus (P) h as been used as the standard soil testing method in Portugal for making fer tilizer recommendations. However, this method does not accurately reflect t he available P status for wheat in some representative soils from the South Region of the country. Therefore, a pot experiment was established with fo ur Luvisols (LVx, LVv, and two different LVh soils) from the South Region o f Portugal in order to evaluate the Egner-Riehm, Bray I, Bray II, Olsen, an d Anion Exchange Resin (AER) methods for their ability to estimate availabl e P in those soils. Wheat (Triticum aestivum L., cv. Panda) was used as tes t the crop. The experiment was arranged into a randomized complete block de sign with three replications and five rates (0, 50, 100, 150, and 200 mg kg (-1)) of P added to each soil. Critical soil P levels for LVx were establis hed in case for Bray I (27.9 mg kg(-1)), Bray II (33.5 mg kg(-1)), Egner-Ri ehm (25.4 mg kg(-1)), and AER (14.7 mg kg(-1)) soil test procedures. Regard ing the other soils, the critical soil P levels could not be estimated. The obtained results confirm that the development of an universal soil test P extraction is of great importance, and that further research should be cond ucted in order to evaluate routine soil fertility tests in different pedocl imatic environments.