Apply elemental sulfur to lower soil pH above 7.5

What to Do

If your soil test shows pH above 7.5, apply elemental sulfur at no more than 5 lbs per 1,000 sq ft on established lawns. Apply in spring when soil microbes are active and can convert sulfur to sulfuric acid.

Why It Works

Sulfur reacts with soil bacteria to produce sulfuric acid, gradually lowering pH. At high pH, iron and other micronutrients become unavailable, causing yellow (chlorotic) grass despite adequate fertilization. Colorado State Extension notes this reaction requires heat and takes 3-6 months.

Tips

• Lowering pH is much harder and slower than raising it. Be patient and adjust over multiple seasons.
• In soils with high natural calcium carbonate (common in arid regions), lowering pH may be impractical and cost-prohibitive.
• Iron sulfate and aluminum sulfate work faster but can burn grass if over-applied.