Certified Crop Advisor Practice Exam

Soil pH can influence the availability of which nutrient the most?

1. Potasium

2. Calcium

3. Phosphorus

4. Nitrogen

The correct answer is: Phosphorus

Soil pH plays a crucial role in nutrient availability, particularly for phosphorus. The availability of phosphorus in the soil is highly dependent on pH because it typically becomes less soluble in acidic and alkaline conditions. In acidic soils (low pH), phosphorus can bind with minerals such as iron and aluminum, making it unavailable to plants. Conversely, in highly alkaline soils (high pH), phosphorus can precipitate with calcium, further reducing its availability. Optimal phosphorus availability occurs in a neutral pH range, around 6 to 7, where plants can easily access this essential nutrient for processes such as photosynthesis, energy transfer, and root development. Understanding this relationship helps farmers and agronomists manage soil pH effectively to ensure that phosphorus is available for crop uptake, thereby supporting healthy plant growth and maximizing yields. In contrast, while potassium, calcium, and nitrogen also have their own pH requirements and availability issues, phosphorus is particularly sensitive to changes in pH levels, making it the nutrient most influenced by soil pH.