Question

Given below are two statements, one is labelled as Assertion A and the other is labelled as Reason R
Assertion A: Lower oxidation states of Mn, Fe and Cu (reduced state) are more soluble than higher oxidation state at normal range of soil pH.
Reason R: Presence of excess concentration of carbonate and bicarbonate ions in soil due to over liming or sodicity cause Fe deficiency to crops.
In light of the above statements, choose the most appropriate answer from the options given below:

• A. Both A and R are correct and R is the correct explanation of A
• B. Both A and R are correct but R is NOT the correct explanation of A
• C. A is correct but R is not correct
• D. A is not correct but R is correct

Hint:

Micronutrient availability:
- Fe, Mn, Cu, Zn: More available in acidic soils.
- Reduced forms (Fe2+, Mn2+) are more soluble.
- Oxidized forms (Fe3+, Mn4+) are less soluble.
Over-liming can cause micronutrient deficiencies.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
This question tests knowledge of micronutrient solubility in soils.

Step 2: Detailed Explanation:
Assertion A:
Lower oxidation states (reduced forms) of Mn (Mn2+), Fe (Fe2+), and Cu (Cu+) are more soluble.
Higher oxidation states (Fe3+, Mn4+, Cu2+) are less soluble at normal soil pH.
This statement is true.
Reason R:
Excess carbonate and bicarbonate ions cause iron deficiency.
Over-liming (high pH) reduces Fe solubility.
Sodicity (high Na) can also cause Fe deficiency.
This statement is true.
Relationship between A and R:
Both statements are true but they are independent.
A describes the solubility of reduced vs. oxidized forms.
R describes the effect of carbonate/bicarbonate on iron availability.
R does not explain A (the solubility difference between oxidation states).
Thus, R is NOT the correct explanation of A.

Step 3: Final Answer:
Thus, both A and R are correct but R is NOT the correct explanation of A.
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