COMPARISON OF SOIL TEST KITS FOR ASSESSING PLANT AVAILABLE PHOSPHORUS IN FLORIDA URBAN SOILS

摘要

The Department of Environmental Protection in Florida has limited fertilizer phosphorus (P) applications to urban lawns in Florida to 12 kg P2O5 ha-1 per application and no more than 25 kg P2O5 ha-1 annually.However,additional applications of P fertilizer are allowed if soils test “low” for available P.A cost effective and a convenient way to test soils for nutrients uses soil test kits.However,soil kits vary in the extractive agent and their rating levels.One problem with this is that one test kit may suggest that the soil is high in P another test may suggest the same soil is low in P.This disparity in soil test kits may lead to unwarranted P fertilizer applications.Therefore,the objective of the this experiment was to compare soil P results of three different commercial soil test kits to Mehlich-1 P which is used by the University of Florida soil testing lab.Poor relationships were observed between the soil test kits and Mehlich-1 P.Furthermore,poor relationships where observed for soil P between each of the soil test kits.Soil test kits indicated low P in 70% of the soils tested while Mehlich-1 only indicated low P in 10% of the same samples.In conclusion,the soil test kits tested in this study were not a reliable way of predicting the need for P fertilization in Florida urban lawns.