The Georgia P Index was developed as a tool to evaluate the risk of bioavailable P loss in fields under various management practices. We compared the results of the P Index with four years of data from 1.5 m by 4.6 m bermudagrass plots fertilized with poultry litter at 8.9 Mg ha-1 (recommended rate); poultry litter at 17.9 Mg ha-1; composted poultry litter, poultry litter with alum, commercial fertilizer; and a control (no amendments). P Index ratings above 75 indicate high risk where management should be changed. The P Index indicated management changes would be needed for the 17.9 Mg ha-1 treatment during all 4 years, for composted PL during year 4, and for PL with alum during years 3 and 4. The P Index did not indicate management changes were necessary using the recommended rate of 8.9 Mg ha-1 after 4 years of application; however, volume-weighted P concentrations in the 8.9 Mg ha-1 treatment were double the control concentrations during years 3 and 4. The comparison indicates that the P Index does identify high risk management practices under the conditions of this study.Sponsored by:
Georgia Environmental Protection Division
U.S. Geological Survey, Georgia Water Science Center
U.S. Department of Agriculture, Natural Resources Conservation Service
Georgia Institute of Technology, Georgia Water Resources Institute
The University of Georgia, Water Resources Facult