Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/25/1997
Publication Date: N/A
Citation: Interpretive Summary: The objective of this study was to evaluate metal runoff from plots fertilized with alum-treated and normal poultry litter. Alum-treated (10% alum by weight) and normal litter was broadcast applied to small plots in tall fescue. Litter application rates were 0, 1, 2, 3, and 4 tons per acre. Rainfall simulators were used to produce two runoff events; immediately after litter application and 7 d later. Both concentrations and loads of water soluble metals (Al, As, Ca, Cu, Fe, K, Mg, Na and Zn) increased linearly with litter application rates, regardless of the type of litter. Trace metal (As, Cu, Fe, Zn) concentrations in the runoff water from plots fertilized with poultry litter were increased as litter application rates increased and were higher from normal litter compared to alum-treated litter. The metal of greatest concern in poultry litter is Cu, which was found in extremely high concentrations in the runoff of normal litter (1 mg Cu L-1). Since Cu is extremely toxic to algae, it poses the largest threat of the metals studied to aquatic life. Copper concentrations and loads in runoff were significantly reduced by alum-treat of litter. This practice has also been shown to increase fescue yields, reduce P runoff, increase chicken weight gains, and decrease energy use in chicken houses.
Technical Abstract: Research has shown that alum applications to poultry litter can greatly reduce P concentrations in runoff from fields fertilized with poultry litter, as well as decrease NH3 volatilization. However, the effect of aluminum sulfate (alum) on metal runoff is unknown. The objective of this study was to evaluate metal runoff from plots fertilized with varying rates of alum-treated and normal poultry litter. Alum-treated (10% alum by weight) and normal litter was broadcast applied to small plots (3.05 x 1.52m) in tall fescue (Festuca arundinacea Schreb.). Litter application rates were 0, 2.24, 4.48, 6.73, and 8.97 Mg ha-1 (0, 1, 2, 3, and 4 tons acre-1). Rainfall simulators were used to produce two runoff events; immediately after litter application and 7 d later. Both concentrations and loads of water soluble metals (Al, As, Ca, Cu, Fe, K, Mg, Na and Zn) increased with litter application rates. Alum treatment reduced concentrations of As, Cu, Fe, and Zn, relative to normal litter, whereas it increased Ca and Mg. Copper concentrations in runoff water from normal litter were extremely high (up to 1 mg Cu L-1), indicating a potential water quality problem. Soluble Al, K and Na concentrations were not significantly affected by the type of litter. Reductions in trace metal runoff due to alum appeared to be related to the concentration of SOC, as well as the affinity of SOC for trace metals. Elevated levels of Ca and Mg in runoff from alum-treated litter were probably due to carbonate mineral dissolution, since this litter had a lower pH than normal litter (7.59 vs 8.04). Metal runoff from alum-treated litter is less likely to cause environmental problems than normal litter, since threats to the environment by Ca and Mg are far less than those posed by As, Cu and Zn.