Which amendment is used to increase soil pH?

Lime is a common amendment used to increase soil pH because it contains calcium carbonate, which reacts with acidic soil to raise the pH level, making the soil less acidic. When lime is applied to the soil, it neutralizes excess hydrogen ions, leading to a more balanced pH. This adjustment is essential for improving nutrient availability to plants, enhancing microbial activity, and promoting overall soil health.

In contrast, gypsum is primarily used to improve soil structure and reduce compaction but does not significantly affect soil pH. Compost is an organic matter amendment that can improve soil fertility and structure but generally has a neutral pH that does not raise soil pH levels. Peat moss is also used to improve soil properties and water retention; however, it tends to be acidic and can actually lower soil pH if added in large amounts. Therefore, lime is the most effective choice for increasing soil pH, making it the correct answer.