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a Dep. of Soil, Environmental, and Atmospheric Sciences, 302 ABNR Building, Univ. of Missouri, Columbia, MO 65211-7250
b National Institute of Agricultural Science and Technology, Suwon, Korea
* Corresponding author (goynek{at}missouri.edu).
Received for publication March 21, 2007. Two environmental aspects associated with land application of poultry litter that have not been comprehensively evaluated are (i) the competition of dissolved organic matter (DOM) and P for soil sorption sites, and (ii) the sorption of dissolved organic nitrogen (DON) relative to inorganic nitrogen species (e.g., NO3– and NH4+) and dissolved organic carbon (DOC). The competition between DOM and P for sorption sites has often been assumed to increase the amount of P available for plant growth; however, elevating DOM concentrations may also increase P available for transport to water resources. Batch sorption experiments were conducted to (i) evaluate soil properties governing P sorption to benchmark soils of Southwestern Missouri, (ii) elucidate the impact of poultry litter-derived DOM on P sorption, and (iii) 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) using a background electrolyte solution comparable to DOM extracts (I = 10.8 mmol L–1; 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 significant negative impact on P sorption. Dissolved organic nitrogen was preferentially removed from solution relative to (NO3––N + NO2––N), NH4+–N, and DOC. This research indicates that poultry litter-derived DOM is not likely to enhance inorganic P transport which contradicts the assumption that DOM released from organic wastes increases plant-available P when organic amendments and fertilizer P are co-applied. Additionally, this work demonstrates the need to further evaluate the fate and transport of DON in agroecosystem soils receiving poultry litter applications.
Abbreviations: DOM, dissolved organic matter DON, dissolved organic nitrogen DOC dissolved organic carbon OM, organic matter LMWOAs, low molecular weight organic acids SOC, soil organic carbon
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