Laboratory characterization of extractable phosphorus in poultry litter and poultry litter ash

One method for handling excess poultry litter (PL) is burning. Implementation of this practice would reduce the volume of PL available for land application while generating electricity. Poultry litter ash (PLA), the by-product of burning PL, contains high concentrations of P, calcium, potassium, and magnesium, which could be used as fertilizers. Sequential extraction of PL has shown that the largest fraction of inorganic P was water (H2O) soluble, which could contribute to eutrophication of surface H2O. However, the forms of P in PLA have not been determined. The objective was to compare the extractable fractions of PLA with those of PL. Poultry litter samples were collected from three poultry farms on the Maryland Eastern Shore, and a portion of each PL sample was ashed at 550 degrees C. An additional sample of PLA was obtained from a pilot study conducted by the Maryland Department of Natural Resources in which PL was used as a fuel source in a wood-burning power plant. P fractions of the PL and PLA were determined with a modified Hedley fractionation technique. The effectiveness of extractants in removing inorganic P from PL was ranked, from highest to lowest, as H2O > HCl > sodium bicarbonate > sodium hydroxide, whereas from PLA, the ranking was HCl > sodium bicarbonate > sodium hydroxide = H2O. The average total inorganic P extracted from PL and PLA by H2O were 55% and 1.45%, respectively, and the averaged total inorganic P extracted by HCl (hydrochloric acid) fractions were 34% and 82% for PL and PLA, respectively. The low H2O-soluble inorganic P observed in the PLA suggests that fertilizers using PLA would be less of a H2O-pollutant problem than PL when used in pastures and range lands. However, further studies are needed to determine the recommended application rate for poultry PLA compared with PL for optimum crop growth without impairing H2O quality.