Long-Term Effects of Poultry Litter, Alum-Treated Litter and Ammonium Nitrate on Trace Metal Availability in Soils.

Adding aluminum sulfate (alum) to poultry litter has been shown to reduce ammonia emissions as well as phosphorus (P) runoff and leaching; however, little data is available on the long-term effects of alum on trace metal availability in soils.  The objectives of this study were to evaluate the long-term effects of poultry litter, alum-treated litter and ammonium nitrate (NH₄NO₃) on soil chemistry, with an emphasis on trace metal accumulation and leaching.  A small plot (1.5 x 3.0 m) study was initiated in 1995 using 13 treatments (control, four rates of alum-treated litter, four rates of normal litter and four rates of NH₄NO₃), with four replications per treatment in a randomized block design.  The plots were cropped to tall fescue (Festuca arundinacea Schreb.).  Fertilizer applications were made in the spring of each year.  Soil samples were taken from 0-5, 5-10, 10-20, 20-30, 30-40, 40-50 and 50-60 cm after 13 years and analyzed for water soluble, KCl extractable, Mehlich-III extractable and perchloric acid digestable metals.  Additions of poultry litter resulted in the buildup of metals such as Cu, Mo, and Zn in surface soils fertilized with litter, with decreasing concentrations with depth.  Concentration data indicated leaching of metals was occurring.  Phosphorus behaved in a similar manner.  The addition of alum to litter resulted in less leaching of metals and P down the soil profile.