Methods of treating animal litter and/or bedding material for control of volatile ammonia and soluble phosphorous include applying granular partially hydrated ferric sulfate to the litter. The partially hydrated ferric sulfate ranges from gray to tan in color and is spread onto the litter at a rate effective to reduce ammonia volatilization and reduce soluble phosphorous. Relative to reagent grade ferric sulfate, the partially hydrated ferric sulfate exhibits lower hygroscopicity and higher deliquescence. The ferric sulfate is prepared by a process comprising oxidizing ferrous sulfate with sulfuric acid using a molecular oxygen oxidizing agent at an elevated pressure relative to atmospheric and at a temperature of 60° C. to 140° C. to produce a gray to tan colored granular product.
