What is the chemical composition of common agricultural lime?

The correct choice indicates that common agricultural lime is composed of calcium carbonate, represented chemically as CaCO3. This compound serves essential purposes in agriculture, particularly in soil management.

Calcium carbonate acts as a liming agent, which helps to neutralize soil acidity. Acidic soils can lead to nutrient deficiencies and adversely affect crop growth, so amending soil with CaCO3 improves its pH balance. Additionally, it provides a source of calcium, an essential secondary nutrient for plants, promoting healthy root development and improving cell wall structure.

Unlike the other options, which represent different chemical compounds with distinct roles, calcium hydroxide (the first option) is a base that can also be used for soil amendment but is not commonly referred to as agricultural lime. Magnesium carbonate (the third option) is associated with dolomitic lime, which contains magnesium as well as calcium, making it different from agricultural lime. Calcium sulfate (the last option) is gypsum, which is useful for improving soil structure and drainage but does not serve the same lime function to neutralize soil acidity.

Overall, CaCO3 is foundational in agriculture for improving soil health and crop productivity, making it the most relevant choice among the provided options.