Submitted to: American Society of Agronomy
Publication Type: Abstract Only
Publication Acceptance Date: 10/20/2003
Publication Date: 11/2/2003
Citation: He, Z., Honeycutt, C.W., Griffin, T.S. 2003. Distribution of phosphorus species in dairy manure. American Society of Agronomy.
Technical Abstract: The chemical composition of manure P is a key factor determining its potential bioavailability and susceptibility to runoff. The distribution of P forms in 13 dairy manures was investigated with sequential fractionation coupled with orthophosphate-releasing enzymatic hydrolysis. A large portion of manure P was H2O extractable, varying from 1,400 to 6,810 mg inorganic P (Pi) kg-1 DM and 130 to 1,660 mg organic P (Po) kg-1 DM. In the NaHCO3 fraction, Pi varied between 740 and 4,200 mg P kg-1 DM, and Po varied between 340 and 1,550 mg P kg-1 DM. In the NaOH fraction, Pi fluctuated around 200 mg P kg-1 DM, and Po ranged from 130 to 630 mg P kg-1 DM. Phytate-like P was present as the major hydrolysable Po in all three fractions (26 to 605 mg kg-1 DM). Although the concentrations of P species varied significantly in these manures, correlations among some P forms with total manure P were observed. For example, H2O-extracted Pi was correlated with total manure P (r =0.79), and NaOH-extracted Po was correlated to total manure P (r =0.91). We also demonstrated that P released by a single extraction with sodium acetate (100 mM, pH 5.0) was equal to the summed amount of H2O-, NaHCO3-, and NaOH-extractable P fractionated sequentially. Thus a single extraction by sodium acetate buffer could provide an efficient evaluation of plant available P in animal manure, while the sequential fractionation approach provides more detailed characterization of manure P.