Decreasing Phosphorus Solubility in Poultry Litter with Aluminum, Calcium, and Iron Amendments

Abstract

AbstractArkansas produces approximately one billion broilers (Gallus gallus domesticus) each year. Phosphorous runoff from fields receiving poultry fitter is believed to be one of the primary factors affecting water quality in northwest Arkansas. Poultry litter contains ≈20 g P kg−1, of which ≈2 g P kg−1 is water soluble. The objective of this study was to determine if soluble P levels could be reduced in poultry litter with Al, Ca, and/or Fe amendments. Poultry litter was amended with alum, sodium aluminate, quick lime, slaked lime, calcitic limestone, dolomitic limestone, gypsum, ferrous chloride, ferric chloride, ferrous sulfate, and ferric sulfate, and incubated in the dark at 25 °C for 1 wk. The Ca treatments were tested with and without CaF2 additions in an attempt to precipitate fluorapatite. At the end of the incubation period, the fitter was extracted with deionized water and water soluble P determined. Water soluble P levels in the poultry litter were reduced from >2,000 mg P kg−1 litter to <1 mg P kg−1 litter with the addition of alum, quick lime, slaked lime, ferrous chloride, ferric chloride, ferrous sulfate, and ferric sulfate under favorable pH conditions. Gypsum and sodium aluminate reduced water soluble P levels by 50 to 60%. Calcitic and dolomitic limestone were less effective. The results of this study suggest that treating litter prior to field application with some of these compounds could significantly reduce the amount of soluble P in runoff from litter‐amended pastures. Therefore, chemical additions to reduce soluble P in litter may be a best management practice in situations where eutrophication of adjacent water bodies due to P runoff has been identified. Preliminary calculations indicate that this practice may be economically feasible. More research is needed, however, to determine any beneficial and/or detrimental aspects of this practice.