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Allelopathy: UPSC Mains 2016 GS3 Q8

Civil Services (Main) Examination, 2016 · GS Paper III · Question 8

What is allelopathy? Discuss its role in major cropping systems of irrigated agriculture.

12.5 marks · 200 wordsEnvironment & Ecology
Key Points & Approach to Answering
1. Allelopathy is the biochemical suppression or

Allelopathy is the biochemical suppression or stimulation of one plant by another through released chemicals.

2. Allelochemicals — phenolics

Allelochemicals — phenolics, terpenoids, alkaloids — are released through root exudates, litter, leaching and volatilization.

3. In irrigated cropping systems

In irrigated cropping systems, decomposing residues of rice and wheat suppress weeds through allelopathic effects.

4. Continuous paddy-wheat rotation in the Indo-Gangetic

Continuous paddy-wheat rotation in the Indo-Gangetic plains shows both weed suppression and residue interference with crop germination.

5. Allelopathic crops like sorghum and sunflower

Allelopathic crops like sorghum and sunflower in mulch or cover crops offer low-cost weed management. They reduce herbicide dependence in irrigated agriculture.

6. Autotoxicity from monoculture accumulates self-inhibitory chemicals

Autotoxicity from monoculture accumulates self-inhibitory chemicals, causing yield decline in rice, sugarcane and alfalfa.

7. Tree-crop interactions matter: eucalyptus and walnut

Tree-crop interactions matter: eucalyptus and walnut release chemicals depressing understory crops.

8. Crop rotation

Crop rotation, residue management and green manuring exploit allelopathy for sustainable agriculture. It strengthens integrated weed management in irrigated systems.

Source: UPSC Civil Services (Main) Examination, 2016 — GS Paper III, official question paper (upsc.gov.in). Full paper: UPSC CSM 2016 — GS Paper III (Full Question Paper).

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