Integrating soil phosphorus testing into environmentally based agricultural management practices

Soil testing has been an accepted agricultural management practice for deca des. interpretations and fertility recommendations based on soil analyses a nd the information obtained with soil samples on cropping systems, tillage practices, soil types, manure use, and other parameters have contributed to the increased efficiency of agricultural production. Recently, however, an alyses of long-term trends in soil test P values have shown that soil P in many areas of the world is now excessive, relative to crop P requirements. The role of P in the eutrophication of surface waters and emerging concerns about the human health impacts of toxic algal/dinoflagellate blooms have h eightened public awareness of nonpoint source pollution by agricultural P. The greatest concerns are with animal-based agriculture, where farm and wat ershed-scale P surpluses and over-application of P to soils are common. The need For nutrient-management plans based on N and P is now an issue of int ense debate in the U.S. and Canada. This paper addresses three issues: Shou ld the applications of organic wastes and fertilizers be based on soil P an d, if so, what is the most appropriate testing method to assess environment al risk? Now can our knowledge of soil P chemistry be integrated with the e xpertise of hydrologists, agronomists, aquatic ecologists, and others to as sess the risks that P in agricultural soils poses to surface waters? And, f inally, how can we use soil P testing to evaluate new best management pract ices (BMPs) now being developed to reduce P transport from soil to water?