PHOSPHORUS SOIL TESTING - ENVIRONMENTAL USES AND IMPLICATIONS

Phosphorus (P) soil testing has traditionally and successfully focused on rapidly measuring the level of plant-available P in a soil and on interpreting the result in terms of the likelihood of crop response to applied P. Concern about the relationship between soil P and degradation of surface water quality has created a demand for soil testing laboratories to expand beyond their traditional scope and begin offering ''Environmental P Tests'' - soil tests that measure other pools of P or that offer an environmental interpretation of the analytical results. However, with new tests often come new challenges, such as the need for changes in sampling protocols, assimilation of the new test into the laboratory setting, and the development of interpretative guidelines without adequate data from long-term field studies. In this paper we first present a summary of soil tests for P that could be used for environmental purposes, along with current interpretations and applications of these tests in the US. We then discuss some of the constraints to incorporation of these new tests into a traditional soil testing program and offer some alternatives that may improve environmental management of soil P.