Originally Posted by edwmax

Duh ... Really, more than you can hold.

But in regards to K2SO4, there is not a 1/2 lb of oxygen in a 1/2 lb in the remaining SO4 & impurities. The SO4 combines with water to form a weak sulfuric acid and help to acidify the soil. Sulfur, itself, is beneficial to plants when it further breaks down. The 0-0-50 fertilizer is not pure and has some fillers or impurities as the percentage of potassium varies from different manufactures.

Another source for potassium is Muriate of Potash or Potassium chloride. However, chloride can be detrimental to plants if not flushed (leached) away and builds up in the soil.

Other than that I suggest you do your own chemical molar balance equations for any additional questions you may have as to the chemical make up of K2SO4.