Aluminum sulfate is added to poultry litter in a poultry house to reduce ammonia volatilization,
Over half of the nitrogen excreted by chickens is lost to the atmosphere as ammonia before the litter is removed from the poultry house. Research has shown that adding aluminum sulfate to the litter greatly reduces the ammonia emissions. Lower ammonia levels result in heavier birds, better feed conversion and lower mortality. Alum additions to poultry litter also precipitates the phosphorus into a form that is not water soluble. This greatly reduces phosphorus runoff from fields fertilized with poultry litter. Alum additions also reduce the number of pathogens in the litter.
Alum additions result in less nitrogen being lost due to ammonia volatilization. Ammonia fluxes from alum-treated litter have been shown to be 70% lower than normal litter. This results in higher nitrogen content of the litter which boosts crop yield. Lower ammonia levels in the rearing facilities also improve poultry production and make the environment safer for agricultural workers.
Treating litter with alum is a cost effective best management practice, due to economic returns from improved poultry production and reduced energy costs. Alum is typically applied between each flock of birds.
Source: Treating Poultry Litter With Aluminum Sulfate (Alum) Arthur: Philip Moore, USDA-ARS, Fayetteville, AR