Which statement about soil pH and nutrient availability is true?

Which statement about soil pH and nutrient availability is true?

• A. High pH can cause iron and manganese to become unavailable to plants.
• B. High pH increases iron availability.
• C. Soil pH does not affect nutrient uptake.
• D. Only soil organic matter affects nutrient availability.

Answer: (A)

Soil pH controls the chemical form and solubility of nutrients, which in turn determines how available they are to plants. At high pH, iron and manganese become insoluble and precipitate as hydroxides or carbonates, so they can’t be taken up even when the soil contains some of these elements. This is why deficiency symptoms often show up on alkaline soils. In more acidic soils, these micronutrients dissolve more readily, increasing their availability. The idea that high pH increases iron availability isn’t correct, and it’s not true that soil pH doesn’t affect nutrient uptake. Organic matter helps with nutrient retention, but it doesn’t negate the key effect of pH on nutrient solubility.

Soil pH controls the chemical form and solubility of nutrients, which in turn determines how available they are to plants. At high pH, iron and manganese become insoluble and precipitate as hydroxides or carbonates, so they can’t be taken up even when the soil contains some of these elements. This is why deficiency symptoms often show up on alkaline soils. In more acidic soils, these micronutrients dissolve more readily, increasing their availability. The idea that high pH increases iron availability isn’t correct, and it’s not true that soil pH doesn’t affect nutrient uptake. Organic matter helps with nutrient retention, but it doesn’t negate the key effect of pH on nutrient solubility.