|Van Kessel, Jo Ann|
Submitted to: Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/24/2008
Publication Date: 8/15/2008
Citation: Dao, T.H., Guber, A.K., Sadeghi, A.M., Karns, J.S., Van Kessel, J.S., Shelton, D.R., Pachepsky, Y.A., Mccarty, G.W. 2008. Loss of Bioactive Phosphorus and Enteric Bacteria in Runoff from Dairy Manure Applied to Sod. Soil Science. 173:511-521. Interpretive Summary: Limited information on manure-borne phosphorus (P) and pathogen indicator microorganism in runoff implies a similarity in their rainfall-induced release from manure and subsequent transport. Phosphorus is released from manure in different chemical forms, including the water-extractable and phytase-hydrolysable phosphorus. The objective of this work was to compare the release of different forms of manure P vs. concentrations of E. coli and Enterococci, the major indicators of fecal contamination. Dairy manure was applied on the turfgrass sod in soil boxes. Runoff from manure was collected under rainfall and analyzed for concentrations of bacteria, phosphorus forms and colloidal material content and distribution. Correlations were found between with all studied forms of phosphorus and concentrations of both indicator bacteria. The strongest correlations were found between phytase-hydrolysable phosphorus, a fraction primarily associated with organic particulate manure, and both E. coli and Enterococci concentrations. This suggests that E. coli and Enterococci are released to runoff in association with manure organic P particulates, and indicates that phytase-hydrolysable phosphorus forms in runoff may serve as surrogate indicator of fecal coliform and Enterococci release from grass-applied dairy manure.
Technical Abstract: Limited information exists on the coupled release and transport of manure-borne fecal microorganisms and phosphorus (P) species in runoff. Under simulated rainfall, a study of the effects of live and dead grass on the release of Escherichia coli (E. coli), Enterococci, and various fractions of manure P was conducted in soil-grass runoff boxes. A general correlation was found between water-extractable P (WEP) and either bacterium released to runoff. However, the relationship between bacteria and WEP may be associated with the presence of colloids and suspended particulates in a clear runoff sample. A continuum of particle size was detected, and suspended particulates, ranging between 0.1 and 100 'm in size were present in runoff water throughout each simulation. In fact, the correlations of bacterium concentration to phytase-hydrolysable P (PHP), a fraction primarily associated with organic particulate manure, or to the more-inclusive total bioactive P or total P were higher than that with WEP. Therefore, E. coli and Enterococci have been released to runoff while associated with manure organic P particulates, and, the PHP forms in runoff may serve as surrogate indicator of fecal coliform and Enterococci release from grass-applied dairy manure.