Question

Iron deficiency is common in which soil?

• A. Acid Soil
• B. Red Soil
• C. Calcareous Soil
• D. Black Soil

Hint:

Remember that "Lime-induced chlorosis" is synonymous with iron deficiency in plants growing on calcareous (calcium carbonate-rich) soils.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
The availability of micronutrients to plants is highly dependent on soil pH and chemical composition.
Iron (\(\text{Fe}\)) is abundant in most soils, but its solubility and availability to plants drop drastically as the soil pH increases.

Step 2: Detailed Explanation:
Calcareous soils contain high levels of calcium carbonate (\(\text{CaCO}_3\)), which buffers the soil pH in the alkaline range (typically between \(7.5\) and \(8.5\)).
At alkaline pH, iron rapidly oxidizes from the soluble ferrous form (\(\text{Fe}^{2+}\)) to the highly insoluble ferric form (\(\text{Fe}^{3+}\)), which precipitates as ferric hydroxides and oxides.
This chemical immobilization prevents plants from absorbing iron, resulting in lime-induced chlorosis (characterized by interveinal yellowing of young leaves).
Let us evaluate the other soil types:
1. Acid Soils: Have low pH, which highly increases the solubility of iron, sometimes leading to iron toxicity rather than deficiency.
2. Red Soils: Characterized by high iron oxide content (giving them a red color), and generally do not suffer from iron deficiency unless highly alkaline.
3. Black Soils: Though clayey, they are not primarily defined by high calcium carbonate content unless they are calcareous sub-types.

Step 3: Final Answer:
Therefore, iron deficiency is most commonly observed in Calcareous Soil.