How does soil pH influence nutrient availability?

• A. It changes soil color
• B. It affects nutrient solubility and ion exchange, altering nutrient availability to roots.
• C. It determines soil texture
• D. It has no effect on nutrient availability

Answer: (B)

Soil pH controls nutrient availability by changing the chemical form of nutrients and how they interact with soil particles. When pH shifts, the solubility of many nutrients changes: some nutrients dissolve more readily in the soil solution and become available for root uptake, while others become bound to soil particles or form insoluble compounds and are less accessible to roots. pH also influences ion exchange, altering the balance of exchangeable cations in the soil and how readily nutrients can be swapped into the root zone. In practical terms, most nutrients are most available in a moderate pH range; extreme acidity or alkalinity reduces availability for several nutrients and can lead to deficiencies or toxicities. For example, acidic soils can boost iron and manganese solubility (risking toxicity) but reduce phosphorus availability, while alkaline soils can limit iron and manganese uptake and cause phosphorus to precipitate, further limiting uptake.