Question

In field crops Harvest Index is calculated using the growth parameters

• A. Total photosynthesying area and biomass
• B. Total biological mass and economical yield
• C. Total leaf area and grain yield
• D. Plant height and total leaf area

Hint:

The concept of Harvest Index was first introduced by Donald (1962). Modern crop breeding programs continue to select for high HI to maximize yield potential per unit area.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
The Harvest Index ($\text{HI}$) is a metric used in agronomy to evaluate the efficiency of a crop in partitioning its photosynthetic products (assimilates) into harvestable, economically useful parts.
Key Formula or Approach:
The Harvest Index is calculated as: \[ \text{Harvest Index } (\text{HI}) = \frac{\text{Economic Yield}}{\text{Biological Yield}} \times 100 \]

Step 2: Detailed Explanation:
- Economic Yield: The weight of the harvested, marketable part of the crop (such as grain in wheat, tubers in potato, or fibers in cotton).
- Biological Yield: The total dry matter produced by the crop, which includes both the vegetative biomass (straw, leaves, stems, and sometimes roots) and the economic yield.
- A high Harvest Index indicates that the plant allocated a larger proportion of its photosynthetic energy into producing the harvestable economic organs rather than vegetative structures.
- Historically, the increased yields of the "Green Revolution" semi-dwarf wheat and rice varieties were achieved by increasing the Harvest Index (from $\approx 30%$ to $\approx 50%$) rather than increasing total biological biomass production.

Step 3: Final Answer:
The Harvest Index is calculated using the economic yield and total biological mass.