Leaching of nutrients and trace elements from stockpiled Turkey litter into soil
Received for publication December 10, 2007. In addition to nutrients, poultry are fed trace elements (e.g., As) for therapeutic purposes. Although a large proportion of the nutrients are assimilated by the birds, nearly all of the As is excreted. Hence, turkey litter constituents can leach into the soil and contaminate shallow ground water when it is stockpiled uncovered on bare soil. This study quantified the leaching of turkey litter constituents from uncovered stockpiles into the underlying soil. Four stockpiles were placed on Orangeburg loamy sand in summer 2004 for 162 d; 14 d after their removal, four stockpiles were created over the same footprints and left over winter for 162 d. Soil samples at depths of 7.6 to 30.5 cm and 30.5 to 61 cm adjacent to and beneath the stockpiles were compared for pH, electrical conductivity, total C, dissolved organic C, N species, P, water-extractable (WE)-P, As, WE-As, Cu, Mn, and Zn. All WE constituents affected the 7.6- to 30.5-cm layer, and some leached deeper; for example, NH4+–N concentrations were 184 and 62 times higher in the shallow and deep layers, respectively. During winter stockpiling, WE-As concentrations beneath the stockpiles tripled and doubled in the 7.6- to 30.5-cm and 30.5- to 61-cm layers, respectively, with WE-As being primarily as As(V). Heavy dissolved organic C and WE-P leaching likely increased solubilization of soil As, although WE-As concentrations were low due to the Al-rich soil and low-As litter. When used as drinking water, shallow ground water should be monitored on farms with a history of litter stockpiling on bare soil; high litter As; and high soil As, Fe, and Mn concentrations.