Measurement of Plant Available Phosphorus by Four Extraction Methods in Gypsiferous and Non-gypsiferous Soils of Esfahan Province

Soil test is necessary to identify optimal concentrations of phosphorus required for plant growth. A greenhouse experiment was conducted using 30 soils with widely different properties. Four extraction methods were used in this stduy including Olsen, Soltanpour, Mehlich-3, and saturation extract. The factorial experiment was arranged into a completely randomized design. Thus, rankings of the extractors studied based on their ability to extract phosphorus were as follows: Mehlich-3 >Olsen> Soltanpour> saturation extract. The results showed that saturation extract is not a suitable method for phosphorus extraction. Among the methods studied, Olsen was the most appropriate one because of having the highest correlation coefficient with plant factors such as dry matter yield and phosphorous uptake. On the other hand, Mehlich-3, as a simultaneous extractor of macro- amd micro-elemnts, is a good alternative for Olsen method in gypsiferous soils.