What is the effect of sodicity on soil physical properties?

• A. Increases infiltration.
• B. Causes dispersion of clays and reduces infiltration.
• C. Increases aggregate stability.
• D. Has no effect.

Answer: (B)

High sodicity means a large proportion of sodium on the soil’s exchange complex. Sodium ions cause clay minerals to disperse rather than cling together, which breaks down soil aggregates, reduces porosity, and often forms a dense surface crust. This sealing and loss of macropores limit water movement into the soil, so infiltration is markedly reduced. Consequently, aggregate stability declines rather than increases. So the best description is dispersion of clays with a corresponding drop in infiltration. The other statements don’t fit because sodicity does not boost infiltration, does not increase aggregate stability, and it does have a real effect on soil structure and flow of water.