Concept of Critical Stages of Crop Growth in Relation to Water Supplies

Definition

• A critical stage of crop growth is the growth period when a crop is most sensitive to water stress.
• If irrigation is not provided during this stage, it causes maximum reduction in yield, even if adequate water is supplied later.
• Conversely, supplying water at critical stages ensures minimum yield loss even under limited water availability.

Concept Explanation

• Plants do not need equal water throughout their life cycle. Some stages require more water (e.g., flowering, grain filling). Others are less sensitive (e.g., vegetative growth in some crops).
• Physiological Basis; Critical stages usually coincide with reproductive or yield-forming stages (e.g., flowering, grain filling).
  • Water stress at these stages affects:
    • Cell division & elongation (reducing growth).
    • Photosynthesis & assimilate transport.
    • Fertilization, seed set, and grain filling.
• Relation with Irrigation Scheduling; In areas of limited water supply, irrigation is prioritized at critical stages instead of uniform application. This approach maximizes Water Use Efficiency (WUE) and economic yields.

Critical Stages of Major Crops

Importance of Critical Stage Concept

• Efficient use of limited water → maximum returns from scarce irrigation.
• Prevents yield losses → especially at reproductive stages.
• Guides irrigation scheduling → in regions with low rainfall or canal supply.
• Improves WUE → irrigation targeted where it matters most.

Key Takeaways

• Not all growth stages are equally sensitive to water stress.
• Reproductive stages = most critical in almost all crops.
• For wheat, CRI (21 DAS) is the most important stage.
• For rice, panicle initiation & flowering are most critical.
• Under water scarcity, priority irrigation must be given at critical stages → this ensures better yields with limited resources.