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UPSC Prelims 1979 · Agriculture · Soils
It has been found recently that the acidity of the soil increases because of
- (a) Leaching away of bases
- (b) Increased use of ammonia
- (c) Increased use of urea
- (d) Increased use of rock phosphate
Show the answer and explanation
Answer: (a) Leaching away of bases
Rain leaches calcium, magnesium and potassium (bases) out of the soil, leaving it acidic.
Why the others are wrong
(b) Ammonia fertilisers do acidify soil, but leaching is the main natural cause named.
(c) Urea also acidifies soil over time, but it is not the main cause here.
(d) Rock phosphate doesn’t increase acidity.
The trap
Nitrogen fertilisers do acidify soil — but the key picks leaching.
🔒 Acid soils: NE India, Western Ghats, Kerala — leaching. Fix: lime.