Which compound is primarily used to provide potassium in fertilizers?

The correct choice is potassium nitrate. This compound is highly valued in fertilizers because it is a rich source of potassium, which is one of the essential macronutrients that plants need for various physiological functions. Potassium plays a vital role in water regulation, enzyme activation, and photosynthesis, significantly contributing to healthy plant growth and development.

While potassium sulfate also provides potassium, potassium nitrate has the added benefit of containing nitrogen, another essential nutrient that promotes growth. This dual nutrient provision makes potassium nitrate particularly effective in supporting plant health. Ammonium nitrate and calcium phosphate, on the other hand, primarily supply nitrogen and phosphorus, respectively, rather than potassium. Therefore, potassium nitrate is often preferred in the formulation of specific fertilizers aimed at enhancing potassium availability to plants.