Which statement about soil pH is true?

• A. Soil pH affects color and texture but not microbial life.
• B. Soil pH affects only nutrient availability.
• C. Soil pH affects neither nutrient availability nor microbial activity.
• D. Soil pH affects both nutrient availability and microbial activity.

Answer: (D)

Soil pH governs both the chemical availability of nutrients and the activity of soil microbes. The hydrogen ion concentration in the soil solution changes how soluble nutrients are and how they move into or out of plant roots. For example, at low pH certain micronutrients become highly soluble (which can lead to toxicity) while some macronutrients may become less available; at high pH phosphorus tends to precipitate and become less available, and many micronutrients also become less accessible. Microbial life is also shaped by pH because most soil bacteria and fungi prefer near-neutral conditions, and extreme acidity or alkalinity can reduce microbial biomass, alter community composition, and slow essential processes like decomposition and nitrogen cycling. Since pH influences both nutrient availability and microbial activity, the true statement is that soil pH affects both aspects. The other choices misstate the scope by suggesting pH affects only one side, or by implying no effect on biology or on nutrient dynamics at all.