I just received my second question (via PM) in a month in which the Member was concerned about the use of Gypsum in larger quantities due to the amount of Sulfur in it. The members expressed concerns that the Sulfur could harm germination, the microherd, etc.

The use of Sulfates will NOT harm anything at practical application rates. As a matter of fact, you might notice that almost everything that I recommend for soil nutrients is in the Sulfate form. Zinc Sulfate. Copper Sulfate. Magnesium Sulfate. Calcium Sulfate. Sulfate forms of Iron. Potassium Sulfate.

Plants can only utilize Sulfur in the Sulfate form. This is entirely different than the Elemental Sulfur form ("garden sulfur") which is used for deliberate acidification. Elemental Sulfur reacts with the soil, water and some microherd members and goes through a state in which it becomes sulfuric acid. This conversion/reaction eventually ends when the Sulfur becomes (you guessed it) a Sulfate compound by reacting with a cation (mostly Calcium or Magnesium).

In almost every natural situation, you won't find Sulfur in its elemental form in your lawn or garden you put it there.

Here's a little more reading on the subject: Sulfur and Sulfates

Thanks for the clarification, Andy! Is there a hard and fast rule on the ultimate destination of the sulfate ion once applied? I.e., is it all absorbed by the plant, left in suspension, displaces and locks on to another ion and leeches out, etc? In other words, can you build up sulfur levels in the soil only using sulfates? If so, is there a conversion factor or does it depend on 100 other things like everything else?

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A hundred other things. I dump sulfates in the form of ferrous sulfate and ferrous ammonium sulfate, yet my sulfur levels stay about the same. In my case, most leaches out, some little bit gets used by the plants, and I think I saw worms mining sulfur in one corner to sell to less fortunate worms in other lawns.

They've also built a foundry in another area of the lawn.

Sulfates are highly mobile in the soil, and for the most part behave as if they "leach out".

Several years ago I was on a forum with Dr Ingham for the discussion of compost teas. I asked a question about using aquarium dechlorinator drops to prepare water for compost tea. Dr Ingham posted that the use of sodium thiosulfate at half the recommended dose for chlorine (3 drops per 5 gallons) was going to wipe out any hopes of having living fungi in the compost tea. She went on to say that there were ongoing tests on other forms of sulfate and the preliminary results were not looking good for sulfates and fungi. I have not been on that forum in years and don't know what the current thinking is on that topic. If anyone wants to join that group, it is a yahoo group for compost tea.

Dchall_San_Antonio wrote:If anyone wants to join that group, it is a yahoo group for compost tea.

I quit that group over a year ago for all the bickering. (I've been spoiled by BL. Of course, I haven't been posting here for awhile either, but for other reasons.) There was a lot of good information on the compost tea group - you just had to filter through a lot of nonsense.

While I have some respect for Dr Ingham and I can believe that a chemical like Sodium Thiosulfate could have a negative impact on fungi, I really find it beyond a wild stretch to think that fungi would have a problem with naturally-occurring substances like Calcium Sulfate ("Gypsum"). Nature just doesn't work that way - a whole class of life that didn't evolve to be able to deal with something that is everywhere?

What would she recommend instead of Sulfates? The Nitrates? Harsher. The Carbonates? Even harsher. Let's not even discuss the Chlorides, OK?