Land-applied swine manure can be an environmental concern when runoff losses of manure constituents occur. The use of chemical amendments to mitigate these losses has been investigated for poultry litter, but materials such as swine manure have received less attention in this context, particularly at the plot scale or larger. The objective of this experiment was to evaluate the impacts of aluminum sulfate (alum; Al 2 (SO 4 ) 3 ), aluminum chloride (AlCl 3 ), and ferric chloride (FeCl 3 )

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... n on runoff of selected constituents of land-applied swine manure. Manure was collected from feeder pigs fed a standard diet. Alum and FeCl 3 were added at a stoichiometric ratio of 1.1:1 [Al:total P (TP)], and AlCl 3 was added at a ratio of 1.3:1 [Al:TP]. The amended manure was incubated for six days prior to land application to fescue (Festuca arundinacea Schreber) plots. Simulated rainfall (100 mm h -1 for 0.5 h of runoff) was applied to the plots on the day of application and followed by two additional simulated rainfall events at 7 d intervals. Runoff samples were collected and analyzed for dissolved reactive phosphorus (DP), TP, ammonia nitrogen (NH 3 -N), nitrate nitrogen (NO 3 -N), total Kjeldahl nitrogen (TKN), total suspended solids (TSS), fecal coliform (FC), and 17β-estradiol. Runoff concentrations of all constituents except NO 3 -N were highest for the first simulated rainfall event, approaching background levels thereafter. Relative to untreated manure, all chemical amendments were effective in reducing first-event DP, TP, and TKN concentrations. Both AlCl 3 and FeCl 3 reduced first-event NH 3 -N concentrations, and FeCl 3 addition led to FC concentrations indistinguishable from the control (no manure) plots. The results indicate that these amendments have potential for promoting both environmental and agronomic benefits, implying that studies involving practicality and long-term considerations should be undertaken.