Soluble Metal Leaching from a Poultry Litter-Amended Udult under Pasture Vegetation

More than 1 billion broiler chickens (Gallus gallus domesticus) are produced annually in Arkansas, with nearly 900 Gg of waste (i.e., litter) generated. Poultry litter is typically land applied as a means of disposal to nearby pastures as an organic fertilizer. Aside from essential plant nutrients, poultry litter also contains heavy metals, yet little is known about the potential of these metals to leach from soils with a history of litter application. The objective of this study was to continuously monitor the seasonal and annual effect of poultry litter application rate on soil leachate concentrations and leaching losses of metals (As, Cd, Se, Cr, Mn, Fe, Ni, Cu, and Zn) and dissolved organic carbon (DOC) from tall fescue (Festuca arundinacea Shreb.) pasture using automated equilibrium-tension lysimeters over a 2-yr period. Average annual drainage was 447, 235, and 592 mm in Year 1 (May 2003 through April 2004) and 833, 589, and 827 mm in Year 2 (May 2004 through April 2005) for control, low- (5.6 Mg ha-1), and high-litter (11.2 Mg ha-1) treatments, respectively. Drainage was similar among treatments during all time periods except for Winter (November through January) Year 1. Flow-weighted mean concentrations of Mn during Spring Year 1 (February through April 2004) and Ni and Cu for the whole year differed among litter treatments, but there were no consistent trends. In Spring Year 2 (February through April 2005), flow-weighted mean concentrations of Cr and Fe differed among litter treatment, but there were no consistent trends. Metal leaching losses did not differ among litter treatment during Year 1. In Year 2, leaching losses of Zn, Fe, and As differed among litter treatments during Summer, Fall, and Winter, respectively, but there were no consistent trends. Results indicate that poultry litter application rate did not affect metal leaching within two the first 2 yr of altered management; thus simply reducing application rates in areas with a history of litter application may not ensure a short-term reduction of potential further surface and groundwater impairment.