Which of the following factors govern the magnitude of the single crop coefficient ($K_c$) across crop growth stages?
Options:
(A) Crop development stage: $K_c$ is lowest during initial stage and reaches maximum during mid-season reproductive stage
(B) Fraction of ground canopy cover and leaf area index ($LAI$)
(C) Frequency of rain or wetting events during initial growth stage
(D) Hydraulic radius of the supplying main canal
Answer Key:
A, B, C
Step-by-Step Solution & Explanation
1. $K_c$ increases from initial ($0.3-0.5$) to mid-season ($1.05-1.25$) with canopy expansion (A is true).
2. Ground shading directly controls the ratio of transpiration to evaporation (B is true).
3. Frequent wetting wet surface drives high soil evaporation during initial stage, elevating initial $K_c$ (C is true).
4. Supply canal cross-section is external conveyance hydraulics and has zero bearing on biological crop transpiration factors (D is false).