Evaluation of Five Extraction Methods for Available Phosphorus in Intensively Fertilized Greenhouse Soils

Intensively fertilized lime receiving soils encased in greenhouses have complex nature. We collected 11 greenhouse soils and examined the chemical forms of inorganic phosphorus (P) by applying two kinds of sequential extraction methods. The results and the foregoing study on the same soils revealed that the method developed for calcareous soils is better suited for the greenhouse soils. Among the five availability testing methods including Truog method, Mehlich III method, Olsen method, water extraction and CaCl2 extraction, the Truog and the Mehlich III methods gave good estimates for calcium phosphate minerals like dicalcium phosphate and octacalcim phosphate. In view of simplicity of the method, Truog method is considered to be the best method for P-enriched greenhouse soils