Monday, November 5, 2007 - 1:15 PM
121-1

Phosphorus Sorption to Soils in Presence of Poultry Litter-Derived DOM and the Relative Sorption of DON.

Keith Goyne1, Hee-Joong Jun2, Stephen H. Anderson1, and Peter Motavalli3. (1) University of Missouri, University of Missouri, 302 ABNR Bldg, Columbia, MO 65211-7250, (2) National Institute of Agricultural Science and Technology, 249 Seodun-Dong, Suwon, South Korea, (3) 302 ABNR Bldg., University of Missouri, University of Missouri, Dept. of Soil Environmental and Atmospheric Sc., Columbia, MO 65211

Two environmental aspects associated with land application of poultry litter that have not been comprehensively evaluated are the competition of dissolved organic matter (DOM) and P for soil sorption sites, and the sorption of dissolved organic nitrogen (DON) relative to inorganic nitrogen species (e.g., NO3- and NH4+) and dissolved organic carbon (DOC). Competition of DOM and P for sorption sites has often been assumed to increase the amount of P available for plant growth; however, competition may increase P amounts available for transport to water resources. Therefore, batch sorption experiments were conducted to (1) evaluate soil properties governing P sorption to soils of Southwestern Missouri, (2) elucidate the impact of poultry litter-derived DOM on P sorption, and (3) investigate DON retention relative to inorganic N species and DOC. Soils were reacted for 24 h with inorganic P (0-60 mg L-1) in the presence and absence of DOM (145 mg C L-1) in a background electrolyte solution comparable to DOM extracts (I = 10.8 mM; pH 7.7). Soil P sorption was positively correlated with metal oxide (r2 = 0.70) and clay content (r2 = 0.79) and negatively correlated with Bray-1 extractable P (r2 = 0.79). Poultry-litter derived DOM had no negative impact on P sorption, and maximum predicted P sorption (b; modified Langmuir equation) was found to significantly increase for half of the soils reacted with DOM. DON was preferentially removed from solution relative to (NO3- + NO2--N), NH4+-N, and DOC. This research indicates that poultry-litter derived DOM is not likely to enhance P transport and it contradicts the assumption that DOM released from organic wastes increases plant available P when organic amendments and fertilizer P are co-applied.