Tuesday, November 14, 2006

Comparison of Runoff P with P Extracted from Animal Manures.

Tasha Mashburn1, Dorcas Franklin2, Yebin Zhao1, Kang Xia3, Armando S. Tasistro1, and Miguel Cabrera4. (1) Univ of Georgia, 133 Sunny Hills Dr., Athens, GA 30601, (2) USDA-ARS, 1420 Experiment Station Road, Watkinsville, GA 30677, (3) Mississippi State Chemical Lab, PO Box CR, Mississippi State, MS 39762, (4) Univ of Georgia, Crop & Soil Sciences, Plnt Sci Bldg-1201 Mason Mill Rd, Athens, GA 30602

Animal manure is widely available as a source of fertilizer in regions with concentrated poultry and dairy productions.  In those regions, the application of animal manure to grasslands provides plant nutrients, but may contribute water soluble phosphorus to surface waters. Consequently, there is a need for methods to determine the amount of water soluble P that may be released from manures after application. This study evaluated the effect of extracting ratio (1:10, 1:100, 1:200), shaking time (1, 4, 24 h) and extracting pH (original manure pH or buffer at pH 6) on total dissolved P (TDP), dissolved reactive P (DRP), and dissolved unreactive P (DUP = TDP-DRP) extracted from broiler, layer, and dairy manures. The amounts of TDP, DRP, and DUP extracted from the different manures were correlated with the amounts of TDP, DRP, and DUP measured in surface runoff from undisturbed, grassed soil boxes that had  received surface applications of the same manures. Results showed that the best method varied depending on manure type and form of P measured.