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This article in JEQ

  1. Vol. 25 No. 6, p. 1357-1365
    Received: Jan 3, 1996

    * Corresponding author(s): jtsims@strauss.udel.edu
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Phosphorus Transformations in Poultry Litter-Amended Soils of the Atlantic Coastal Plain

  1. M. Mozaffari and
  2. J. Thomas Sims *
  1. Dep. of Plant and Soil Sciences, College of Agric. Sci., Univ. of Delaware, Newark, DE 19717-1303.



Eutrophication is threatening water quality in Delaware's Inland Bays watershed, one of the largest aquatic ecosystems in the eastern USA and also the site of a highly concentrated poultry (Gallus gallus) industry. Since many (>85%) soils in this watershed are now high or excessive in P, a better understanding of P transformations in poultry litter-amended soils is needed. Our objectives were to determine the influence of poultry litter on P release from three soils from this watershed, on the amount and chemical forms of soil P, and on soil P sorption capacity. Phosphorus release from litter-amended soils was determined in a 110-d leached incubation study using three soils and two litter rates (18 and 36 Mg/ha). Phosphorus was separated into nonoccluded (NOC-P), occluded P (OC-P), and calcium bound P (Ca-P) by sequential fractionation. Changes in P sorption capacity were quantified by a P sorption index. Net soluble P (NSP) released from the litter-amended soils ranged from 1.1 to 15.0 mg/kg and was <4% of the total poultry litter P added. Most NSP was in the initial leachate. Soil test P (STP) was increased by an average of 167 and 279 mg/kg at the 18 and 36 Mg/ha rates (6.2 ± 0.2 mg STP/Mg litter). Most of the P in the litter-amended soils (63–90%) was in the NOC-P and OC-P fractions. Phosphorus sorption index values decreased by 3 to 19% and 12 to 24% at the 18 and 36 Mg/ha rates. Future research should focus on the long-term fate and potential leachability of the P in these chemical fractions to determine whether animal waste management in this watershed should be based on P rather than N.

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