Question

Which one of the following stage has the maximum crop coefficient (Kc) value for Watermelon?

• A. Initial stage
• B. Mid season stage
• C. Late season stage
• D. Uniform throughout the growth stages

Hint:

For nearly all field crops and vegetables, the ______mid-season stage______ represents the period of ______maximum leaf area index (LAI)______ and peak reproductive growth, resulting in the highest crop water consumption and maximum $K_c$ value.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
The crop coefficient ($K_c$) varies throughout the growth stages of a crop.
This variation is plotted as a $K_c$ curve, which typically starts low during crop establishment, rises during vegetative growth, plateaus at a maximum value, and declines during senescence.

Step 2: Detailed Explanation:
Let us trace the crop coefficient ($K_c$) stages for watermelon as defined by FAO guidelines:
1. Initial stage (A): During this early phase (from sowing to $10\%$ ground cover), the crop consists of small seedlings. Transpiration is minimal, and water loss is dominated by soil evaporation. The $K_c$ value is low ($0.15\text{--}0.20$).
2. Development stage: The plants grow rapidly, and the canopy expands. The $K_c$ value increases steadily.
3. Mid-season stage (B): This stage corresponds to full canopy cover, flowering, and fruit development.
The crop transpiration is at its maximum absolute capacity due to the dense leaf area.
Therefore, the $K_c$ value reaches its peak ($1.00\text{--}1.15$ for watermelon).
4. Late-season stage (C): During ripening and harvest, the leaves begin to senesce and turn yellow. Transpiration drops, causing the $K_c$ value to decline ($0.80\text{--}0.85$).

Step 3: Final Answer:
The maximum crop coefficient ($K_c$) value occurs during the mid-season stage, which corresponds to option (B).