When would you apply lime to a garden soil, and what effect does gypsum have on soil?

• A. Lime raises pH when soil is too acidic; gypsum adds calcium and can improve soil structure and soil sod issues but does not raise pH.
• B. Lime lowers pH; gypsum raises pH and improves soil drainage.
• C. Lime adds calcium and improves soil structure; gypsum lowers pH.
• D. Lime is never used in home gardens; gypsum is used to acidify soil.

Answer: (A)

The main idea here is how lime and gypsum affect soil chemistry and structure. Lime is applied to raise soil pH when the soil is too acidic. By neutralizing excess hydrogen and aluminum ions, lime makes the soil less acidic and moves the pH toward a level where most garden plants grow best. Gypsum, on the other hand, adds calcium (and sulfate) to the soil and can improve soil structure—especially on clay soils—and help with sodic (high sodium) conditions by displacing sodium on cation exchange sites. It does not raise pH, so it won’t make acidic soil less acidic. In home gardens, lime is used to correct acidity, while gypsum is used to improve calcium supply and soil structure, not to lime the soil.