Using the Georgia P-Index to identify high risk management of poultry litter
Gaskin, Julia W.
Cabrera, Miguel L.
Risse, L. Mark
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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.