Which soil amendment lowers soil pH, and how does it differ from liming?

• A. Elemental sulfur lowers pH; lime raises pH; choose based on current soil pH and targets.
• B. Lime lowers pH; sulfur raises pH; both are used interchangeably.
• C. Organic compost lowers pH; lime raises pH; compost replaces lime.
• D. Gypsum lowers pH; elemental phosphorus raises pH; they are used together.

Answer: (A)

Adjusting soil pH is about balancing acidity and alkalinity with amendments that react in the soil. Elemental sulfur lowers soil pH because soil bacteria oxidize it to sulfuric acid, which adds hydrogen ions and makes the soil more acidic. Liming, on the other hand, raises pH by neutralizing acidity and adding calcium (and sometimes magnesium in dolomitic lime), which makes the soil more alkaline.

So when you need less acidity, you’d apply sulfur to push pH downward; when you need more alkalinity, you’d apply lime to push pH upward. The choice depends on what the current pH is and what pH range your plants require. Both changes happen gradually, especially in soils with higher buffering capacity, and you should recheck pH after a period to adjust if needed.

Other amendments don’t fit this specific goal: organic compost can influence soil biology and structure but isn’t a reliable acidifier like sulfur; gypsum supplies calcium but doesn’t meaningfully raise pH; lime is used to raise pH, not lower it.