Which statement is true about soil pH and nutrient availability?

Which statement is true about soil pH and nutrient availability?

• A. Extreme pH levels increase the availability of most nutrients
• B. Near-neutral pH reduces uptake of all nutrients
• C. Extreme pH levels reduce the availability of certain nutrients; near-neutral pH generally supports better uptake
• D. pH has no impact on nutrient availability

Answer: (C)

The key idea is that soil pH controls the chemical forms and solubility of nutrients, which in turn affects how easily plant roots can take them up. When pH is very acidic or very alkaline, many nutrients become less available because they either form insoluble compounds or bind to soil particles and stay out of the soil solution that roots access. In the near-neutral range, nutrients tend to remain soluble enough for uptake, so plants can access a broader spectrum of nutrients more efficiently. That’s why extreme pH levels reduce the availability of certain nutrients while near-neutral pH generally supports better uptake. For example, acidic soils can make iron and manganese more available but phosphorus often becomes fixed with aluminum and iron; alkaline soils can render iron, zinc, and copper less available, and phosphorus can also become less accessible due to precipitation with calcium. This contrasts with statements that extreme pH increases nutrient availability, that near-neutral pH reduces uptake of all nutrients, or that pH has no impact.

The key idea is that soil pH controls the chemical forms and solubility of nutrients, which in turn affects how easily plant roots can take them up. When pH is very acidic or very alkaline, many nutrients become less available because they either form insoluble compounds or bind to soil particles and stay out of the soil solution that roots access. In the near-neutral range, nutrients tend to remain soluble enough for uptake, so plants can access a broader spectrum of nutrients more efficiently. That’s why extreme pH levels reduce the availability of certain nutrients while near-neutral pH generally supports better uptake. For example, acidic soils can make iron and manganese more available but phosphorus often becomes fixed with aluminum and iron; alkaline soils can render iron, zinc, and copper less available, and phosphorus can also become less accessible due to precipitation with calcium. This contrasts with statements that extreme pH increases nutrient availability, that near-neutral pH reduces uptake of all nutrients, or that pH has no impact.