Characterization of Derelict Poultry House Pad Soils.

There are an estimated 2400 derelict poultry houses covering 500 ha on the Delmarva Peninsula.  Studies were conducted from 2007 to 2009 to characterize derelict poultry house pad soils.  Poultry house pad soils become loaded with N and to a lesser extent K over years of production.  There was limited P loading or heavy metal accumulation.   Nitrogen was conserved in pad soils from tight roofed structures.   Nitrogen was found in relatively equal amounts of NO₃-N and NH₄-N in the upper 60 cm of soil at combined levels as high as 7000 mg kg^-1.  Potassium levels were also elevated and present in a ratio of 0.35-0.5 K:N.  Salt levels were extremely high in the upper 30 cm with some samples having electrical conductivity values over 20 mS^.m^-1.  Salt levels were driven largely by NO₃^-, NH₄⁺, K⁺, and Na⁺ ions in that order.  In sites where pad soils were exposed to weathering, N levels were greatly reduced in surface soil and K was moved to deeper depths.  Electrical conductivity was shown to have a significant linear relationship with NO₃-N levels ( R² = 0.97) at derelict poultry house pad sites.  Due to the high salt contents and potentially toxic NH₄ levels, direct remediation of pad soils becomes a challenge requiring tolerant plants or amendments to reduce salt levels.   Because salts are driven by NO₃ and NH₄ ions, high carbon materials could be used to tie up N and reduce salt effects.   If sites are left exposed to weather, significant NO₃ leaching to groundwater can be expected.  However, pad soils also represent a potential resource as a fertilizer material if excavated and spread on crop areas.