Which of the following best represents the pH range of sodic soils?

Correct option is C

The correct answer is (C) > 8.5

Explanation:
• Sodic soils (also known as alkali soils) are characterized by a high concentration of exchangeable sodium ($Na^+$) and a pH value typically greater than 8.5.
• The high pH is due to the hydrolysis of sodium carbonate ($Na_2CO_3$), which produces strong alkaline conditions.
• These soils have an Exchangeable Sodium Percentage (ESP) greater than 15% and a relatively low Electrical Conductivity (EC < $4 dS/m$).
• Physical properties of sodic soils are very poor; the high sodium causes soil dispersion, leading to a massive or columnar structure that prevents water entry and root growth.

Information Booster:
• Saline soils, by contrast, have a pH less than 8.5 because they contain neutral soluble salts like $NaCl$ and $Na_2SO_4$.
• Sodic soils are often called "Black Alkali" soils because dissolved organic matter accumulates on the surface, giving it a dark color.
• Reclamation involves adding Gypsum to replace the sodium on the soil particles with calcium.

Additional Knowledge:
• Option A (8-10): While sodic soils fall in this range, the defining threshold in soil science is specifically > 8.5.
• Option B (< 8.5): Characteristic of saline soils or neutral/acidic soils.
• Option D (6.0-8.0): The range for most productive agricultural soils.