Which amendment lowers soil pH?

• A. Lime
• B. Sulfur
• C. Vermiculite
• D. Gypsum

Answer: (B)

Soil pH reflects how acidic or basic the soil is, and amendments change that balance by adding acids or bases. Sulfur lowers soil pH because soil microbes convert elemental sulfur into sulfuric acid. That acid increases the hydrogen ion concentration in the soil solution, making the soil more acidic.

Lime, on the other hand, is a basic amendment (calcium carbonate) that neutralizes acidity and raises pH. Vermiculite is mainly a physical amendment that improves moisture and aeration and cation exchange capacity, but it doesn’t notably acidify or alkalinize the soil. Gypsum adds calcium and sulfate and helps soil structure and nutrient availability, but it does not significantly change soil pH.

So, sulfur is the amendment that lowers soil pH.