AdvanSix’s agronomy experts are available to answer your questions about how to get the most out of your ammonium sulfate investment. Mercedes Gearhart has overseen agronomic research at AdvanSix for more than 20 years, and has a wealth of knowledge about fertilizer use efficiency and improving crop yields. Check out the questions asked below or ask your own question.

What are the advantages of ammonium sulfate versus ammonium thiosulfate?


Ammonium sulfate and ammonium thiosulfate, also known as ATS, are both very common nitrogen and sulfur sources in the dry and liquid fertilizer markets. From an agronomic point of view, I can think of a couple of advantages of ammonium sulfate (21-0-0-24S) when compared to ammonium thiosulfate solution (12-0-0-26S):

  • All of the sulfur in ammonium sulfate is in the immediately plant-available sulfate form. In ammonium thiosulfate, by contrast, only half of its sulfur becomes immediately available upon application to the soil, with the other half needing to convert from elemental sulfur to sulfate via bacterial oxidation. In a Missouri field study where both fertilizers were compared in an early spring topdress application on wheat, ammonium sulfate produced yields at rates of 6 to 7 bushels/acre (at rates of 10 and 20 pounds of sulfur/acre) higher than ammonium thiosulfate. The difference narrowed at the 30 pounds of sulfur/acre rate, where the level of sulfate sulfur in ammonium thiosulfate was finally enough to satisfy the crop’s needs.
  • Ammonium sulfate is safer to apply in proximity to the seed. A corn field study by the University of Minnesota tested ammonium sulfate against ammonium thiosulfate as pop-up and starter fertilization. They concluded that ammonium thiosulfate applied in contact with the seed can have a detrimental effect on emergence, which produces lower yields – especially in dry years.

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  1. Mercedes,

    Is there any type of time frame you could guesstimate that it takes the elemental 1/2 of ATS to become available for plant uptake?


    1. Good question, Keith. The oxidation rate of elemental sulfur from a liquid application of ATS would depend on the same factors affecting the oxidation of powder elemental sulfur. Notice I specify “powder” elemental sulfur, since the oxidation of “granular” elemental sulfur would also be influenced by the so-called “locality effect”. Those factors include oxidizing bacterial activity and conditions that affect them, notably temperature and soil pH. To cite one example, in a study by the International Fertilizer Development Center in Muscle Shoals, AL, oxidation of powder elemental sulfur applied to a sandy soil with a pH of 5.3 took about 6 weeks. If we assume the same soil but colder conditions, oxidation would take longer. In summary, when it comes to agronomic effectiveness of sulfur sources, they would follow this order:

      AS ≥ liquid ATS > granular ES or (ES+AS) products

    2. As soon as you have a soil environment favoring sulfur oxidation, it should take place rather fast.