Potentially significant amounts of sulfate‐S found in phosphorus fertilizers

Core Ideas Phosphorus fertilizers contain sulfate‐sulfur (SO4‐S). SO4‐S concentration decreased in the order monoammonium phosphate > diammonium phosphate > triple superphosphate. Liquid ammonium polyphosphate fertilizer contained less SO4‐S than granular P sources. Sulfur applied in granular P fertilizers in some situations can be as much as half of grain S removal. Sulfur applied in P fertilizers should be considered in crop S fertilization needs and cycling in the environment.