Laboratory Procedures for Characterizing Manure Phosphorus

• Published in: Journal of environmental quality 2000-03, Vol.29 (2), p.508-514
• Main Authors: Dou, Z., Toth, J. D., Galligan, D. T., Ramberg, C. F., Ferguson, J. D.
• Format: Article
• Language: English
• Subjects: Agriculture, rearing and food industries wastes; Applied sciences; Exact sciences and technology; Pollution; Wastes
• ISSN: 0047-2425; 1537-2537
• DOI: 10.2134/jeq2000.00472425002900020019x

Phosphorus runoff from agricultural land contributes to accelerated eutrophication of surface waters. In areas with intensive animal farming, P loss from manured fields may be elevated due to high concentrations of soluble P in manure. We characterized P in dairy and poultry manure for the relative dissolution and fraction distribution using deionized water (H2O), 0.5 M NaHCO3, 0.1 M NaOH, 1.0 M HCl, and 5% trichloroacetic acid (TCA). Two extraction procedures were tested: (i) independent, with dried, ground samples being extracted repeatedly and P measured for each extractant; and (ii) sequential, with each sample being repeatedly extracted by H2O, NaHCO3, NaOH, and HCl, in that order. For the independent procedure, H2O extracted 53 to 64%, NaHCO3 64 to 72%, NaOH 33 to 54%, HCl 90 to 97%, and TCA 84 to 96% of the total P in manure. Sequentially, H2O, NaHCO3, NaOH, and HCl extracted 70, 14, 6, and 5% of the total P in the dairy, and 49, 19, 5, and 25% of the total P in the poultry sample, respectively. Manure P release was not greatly affected by shaking time but decreased rapidly with increasing number of repeated extractions. A large portion of P in manure being extractable by H2O or NaHCO3 suggests weak binding energy of P and hence a high susceptibility for loss to waters when conditions favor runoff. A 1‐h shaking of manure with H2O may provide a quick measure of the relative magnitude of P that is most susceptible. Further investigation relating manure P fractions with P in runoff would help identify management alternatives for reduced P losses.