Remediation of Derelict Poultry House Pad Soils.

Delaware has been a major poultry producer (>70 years) and many obsolete production facilities have become derelict.  Research on derelict poultry house pad soils was conducted to characterize nutrient, metal, and salt loading; evaluate pad soil fertilizer value; and assess soil remediation methods.  Twenty-five derelict poultry house sites were sampled at depths from 5 to 150 cm and analyzed for salts, mineral nutrients, and metals.  Nitrogen (N) was conserved in intact houses as nitrate-N (NO₃-N) and ammonium-N (NH₄-N).  Mean inorganic N was 3342 mg kg^-1 at 0 to 60 cm depth.  Surface soil (30 cm) contained 83% of the N and 92 % of the N was found at 0 to 60 cm depth.  Potassium (K) also accumulated, but in lower amounts.  Salts were high in surface soil; predominantly NO₃^-, NH₄⁺, K⁺, and sodium (Na⁺).  There was a significant linear relationship between electrical conductivity (EC) and NO₃-N in pad soils (R² = 0.96).  Phosphorus accumulation was limited to surface soil. Zinc, copper and arsenic did not accumulate to levels of concern.  When exposed to weathering, large N losses were found at sandy pad sites within a 5-year period. A pad site was excavated and 21 field trials were conducted in crops and turfgrass where nitrogen from fertilizer was replaced with pad soil up to 120 kg ha^-1 N equivalent.  There were no differences in yield or quality measurements in any trials when fertilizer was replaced by pad soil.  In salt tolerance tests, none of the 15 common crop and 41 salt tolerant species tested grew in non-amended pad soil; however, when amended with sawdust as a carbon source (C), germination was enhanced >80%.  In three pad site remediation field studies, soil EC was reduced four-fold with C addition, annual species performance (growth and N uptake) was superior to perennial crops; and Sorghum species and small grains had the highest dry weights and N removal.  This research suggests dual remediation strategies for pad soils: 1) excavation of surface soil to spread as fertilizer and 2) adding high C:N materials followed by planting successive annual crops with high N removal potential.