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

Allelopathy is the biological phenomenon in which one plant releases biochemical compounds, called allelochemicals, that inhibit or sometimes stimulate the germination, growth or development of neighbouring plants. These chemicals are released through root exudates, leaching, volatilisation and decomposition of residues.

Role in major cropping systems of irrigated agriculture

• Natural weed management: allelopathic crops such as sorghum, rice, sunflower and wheat suppress weeds, reducing dependence on chemical herbicides in intensively irrigated systems.
• Crop rotation and sequencing: understanding allelopathic effects helps design rotations that avoid growth suppression and improve yields, for example residue effects in rice-wheat systems.
• Residue management: incorporating or mulching allelopathic residues checks weeds but must be timed to avoid harming the succeeding crop.
• Pest and disease suppression: some allelochemicals deter insects and pathogens, aiding integrated management.
• Cover and intercropping: allelopathic cover crops smother weeds and reduce input costs.

Caution

Allelopathy can also cause autotoxicity and reduce yields if incompatible crops are grown in sequence, so it must be managed knowingly.

Conclusion

Harnessed scientifically, allelopathy is a low-cost, eco-friendly tool for weed and pest control that supports sustainable, chemical-light irrigated agriculture.