Which statement about nitrate binding is true?

• A. Nitrate binds strongly to soil particles.
• B. Nitrate does not bind strongly because both nitrate and soil particles are negatively charged.
• C. Nitrate binds to sand minerals only.
• D. Nitrate binding increases with higher pH.

Answer: (B)

Nitrate binding in soils is minimal because nitrate is an anion and most soil particle surfaces carry negative charges. The electrostatic repulsion between the negatively charged nitrate and the negatively charged soil surfaces means nitrate does not adsorb strongly to soil minerals or organic matter. This is why nitrate tends to stay in solution and move with water, making it prone to leaching beyond the root zone.

This explains why the other ideas aren’t accurate: adsorption of nitrate isn’t limited to sand minerals; it’s generally weak across most soil types, so the notion of strong binding is not correct. And increasing pH doesn’t increase nitrate binding; higher pH often makes surfaces more negatively charged, further reducing any potential adsorption of nitrate.