Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Sulfur in fertiliser

  1. Mar 17, 2010 #1
    Hi,

    I'd just like to know why fertiliser producers refer to "the percentage by mass of sulfur present as sulfate" in their fertilisers?

    Thanks!
     
  2. jcsd
  3. Mar 17, 2010 #2
    Because sulfur in fertilizers is typically present in the form of sulfates ... I'll guess that's because elemental sulfur is not soluble in water, and sulfites are too unstable.
     
  4. Mar 17, 2010 #3

    chemisttree

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    It's possible that it is indeed present as sulfate but if it is time-released, it is usually present as zero valent sulfur or as a sulfur-containing polymer and perhaps both. Rather than speciate all the forms of sulfur present, the assay is given as if all were converted to sulfate.
     
  5. Mar 17, 2010 #4
    Phosphorous is listed as P2O5 though and clearly this is not the active form taken up by plants. I guess it's just a convenient metric, although for the chemist it makes things more complicated.
     
  6. Mar 17, 2010 #5

    chemisttree

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    In the case as phosphorous, all of the P is converted to orthophosphate and the result is multiplied by a factor to express it as P2O5. A little more complicated but not by much.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook