What does sodium do to soil structure?

• A. Improves soil structure
• B. Destroys structure and disperses clay
• C. Increases infiltration without affecting structure
• D. Decreases soil salinity

Answer: (B)

Sodium in the soil water and on exchange sites tends to disperse clay particles, breaking apart soil aggregates and reducing structural stability. This happens because sodium ions are monovalent and don't effectively bridge clay platelets like calcium does; their hydration shells also push clay particles further apart, promoting dispersion and swelling. The result is a loose, unstable soil with poorer porosity and clogged pathways for water movement, especially at the surface, leading to crusting and reduced infiltration. That’s why sodium’s impact is to destroy structure and disperse clay.

The other statements don’t fit because sodium generally harms, not improves, soil structure; infiltration is usually hindered rather than increased when structure is dispersed; and sodium contributes to salinity rather than reducing it, so lowering salinity isn’t a direct effect of sodium on soil structure.