Agronomy Degree Practice Exam

If magnesium is needed in the soil, which agricultural amendment should be used?

1. Dolomite

2. Potash

3. Calcite

4. Gypsum

The correct answer is: Dolomite

The use of dolomite as an agricultural amendment is appropriate when magnesium is needed in the soil because dolomite is a naturally occurring mineral that contains both calcium carbonate and magnesium carbonate. This dual composition not only helps to raise soil pH (reduce soil acidity) but also adds magnesium, which is an essential nutrient for plants. Magnesium plays a crucial role in photosynthesis, as it is a central component of chlorophyll, and it also supports various enzyme functions within plant cells. Other amendments listed have different primary functions. For instance, potash primarily provides potassium, calcite serves mainly to supply calcium while affecting soil pH, and gypsum contributes calcium and sulfur without altering pH levels significantly. Therefore, dolomite is the best choice when specifically addressing magnesium deficiencies in the soil.