How can sulfur compounds increase soil acidity?

Sulfur compounds increase soil acidity primarily through the process of oxidation. When sulfur or sulfur-containing compounds are present in the soil, specific microorganisms—such as those in the genus Thiobacillus—oxidize these substances, eventually producing sulfuric acid.12

The introduction of this acid releases hydrogen ions into the soil solution, which directly lowers the pH level, making the soil more acidic. This process can occur naturally, such as when salt marshes are drained and exposed to oxygen, or through the intentional application of sulfur to adjust soil conditions for acid-loving plants like blueberries.13

While increasing acidity is a useful tool in gardening and agriculture to manage nutrient availability and plant health, it is important to note that excessive acidity can increase the solubility of metals like aluminum and manganese, which can become toxic to many crops.13