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UPSC Prelims 2020 · Agriculture · Seeds, Water and Fertiliser
What are the advantages of fertigation in agriculture?
- Controlling the alkalinity of irrigation water is possible.
- Efficient application of Rock Phosphate and all other phosphatic fertilizers is possible.
- Increased availability of nutrients to plants is possible.
- Reduction in the leaching of chemical nutrients is possible.
- (a) 1, 2 and 3 only
- (b) 1, 2 and 4 only
- (c) 1, 3 and 4 only
- (d) 2, 3 and 4 only
Show the answer and explanation
Answer: (c) 1, 3 and 4 only
Alkalinity control, better uptake and less leaching ✓ — rock phosphate can’t dissolve in drip water.
Statement by statement
1. ✓ CORRECT Acid-forming fertilisers added to the water can lower its pH.
2. ✗ WRONG — rock phosphate doesn’t dissolve Fertigation needs water-soluble fertilisers. Rock phosphate is insoluble, so “all phosphatic fertilisers” is wrong.
3. ✓ CORRECT Nutrients reach the root zone in small, frequent doses exactly when the crop needs them.
4. ✓ CORRECT Small doses through drip don’t flood past the roots, so less is washed below them.
The idea
Fertigation = fertiliser + irrigation: soluble fertiliser injected into drip or sprinkler water.
Why the others are wrong
(a) Accepts rock phosphate — it is insoluble, so it can’t flow through drip lines.
(b) Includes the rock-phosphate statement and misses better availability.
(d) Accepts rock phosphate and drops alkalinity control. Fertigation needs soluble fertilisers.
The trap
“Rock Phosphate and ALL other phosphatic fertilisers” — the absolute word and an insoluble rock give it away.
🔒 Fertigation needs water-soluble fertiliser · better uptake · less leaching · can correct alkaline water.
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