What is soil pH and why is it important for plant nutrition?

• A. A measure of soil color
• B. A measure of soil moisture
• C. A measure of acidity or alkalinity that influences nutrient availability and microbial activity; most plants prefer near-neutral pH
• D. A measure of soil temperature

Answer: (C)

Soil pH is a measure of how acidic or alkaline the soil is, usually on a scale from 0 to 14 with 7 as neutral. It matters for plant nutrition because the chemical form and solubility of minerals in the soil depend on pH. When pH is too acidic or too alkaline, essential nutrients become less available to roots, even if they are present in the soil. Microbes that help break down organic matter and cycle nutrients also work best within certain pH ranges, so pH influences both nutrient availability and microbial activity. Most plants perform best in near-neutral soils, so a pH around 6 to 7.5 is common for good nutrient uptake. That’s why the correct description emphasizes acidity/alkalinity, nutrient availability, and microbial activity, with a note that near-neutral pH is preferred by many plants. Other options describe soil color, moisture, or temperature, which are not what pH measures.