How does pH influence nutrient availability in soils?

• A. Soils pH has no effect on nutrient availability.
• B. Soil pH affects solubility; certain nutrients become less available in very acidic or alkaline soils, while others may become toxic at extremes.
• C. Only microbial activity matters for nutrient availability.
• D. Nutrients are always available regardless of pH.

Answer: (B)

Soil pH controls how soluble nutrients are, which directly affects how easily plants can take them up. In acidic soils, some nutrients like iron and manganese become very soluble, while others such as phosphorus, calcium, and magnesium may become less available because they get bound or precipitated. In alkaline soils, phosphorus tends to form insoluble compounds with calcium, and micronutrients like iron, zinc, and manganese become less available due to precipitation. At very low or very high pH, certain elements can reach toxic levels (for example, aluminum toxicity in strongly acidic soils) or cause deficiencies in others. That’s why pH has a strong influence on nutrient availability, and extremes can lead to toxicity or deficiency rather than everything remaining available. The other ideas miss this direct link between pH and nutrient solubility, or claim nutrients are always available regardless of pH, which isn’t true.