Nutrient value of alum-treated poultry litter for land application.

Alum-treated poultry litter has different chemical composition and biological properties than conventional poultry litter. To develop agronomic application rates for this particular organic fertilizer to cropland, the nutrient value (nutrient plant availability) of alum-treated poultry litter needs to be determined. Typical alum-treated poultry litter was collected from a broiler farm and examined for nutrient content, nutrient release kinetics, and nutrient value by leaching the material for 190 d under simulated weathering conditions. Nutrients recovered in the leachate were characterized and treated as the potentially plant-available portion. The artificial leaching revealed that alum-treated poultry litter released 21.4 g of dissolved organic C, 13.8 g of total dissolved N, 0.6 g of total dissolved P, and 34.6 g of K per kilogram into leachate during the 190-d weathering. The predominant nutrient release occurred in the first 5 wk and fit first-order exponential rise-to-maximum models (for dissolved organic C, total dissolved P, total dissolved N, NH4-N, K+, Na+, Cl-, and SO4(2-)) and logarithmic equations (for Ca2+ and Mg2+). The nutrient value of alum-treated poultry litter is estimated at N, 13.8 g.kg(-1); P, 0.75 g.kg(-1); K, 34.6 g.kg(-1); and S, 24.2 g.kg(-1). The concentration of Al in litter leachate remained below 0.2 mM and thus no Al toxicity should be concerned. Based on these results, it is recommended to apply alum-treated poultry litter at 7.3 t.ha(-1) for achieving an N supply of 100 kg.ha(-1) to common field crops while preventing excessive P runoff losses from high test P soils.