Harvest Index (HI)
Enter economic yield (dry weight of the harvested part) and biological yield (total aboveground dry matter) to compute harvest index HI = economic yield ÷ biological yield (0–1 and %), assessing dry-matter allocation efficiency.
Input Data
Results
At a glance:Harvest index (HI) is defined as crop economic yield divided by biological yield: HI = economic yield ÷ biological yield. Economic yield is the dry weight of the part people actually harvest (e.g. grain of cereals, tuber of potatoes); biological yield is the total aboveground dry matter (harvested part plus stems, leaves and other vegetative organs). HI lies between 0 and 1 and reflects how efficiently the crop 'allocates' photosynthetically accumulated dry matter to the harvestable part. It, together with total biomass, determines economic yield: economic yield = biological yield × HI. In the 20th-century 'Green Revolution', wheat, rice and other yields rose greatly, largely because dwarf breeding raised HI (putting more assimilates into grain rather than stems) rather than merely increasing total biomass. Hence HI is a key indicator for evaluating allocation efficiency in crop breeding and management.
Formula
Harvest index: HI = economic yield ÷ biological yield.
Percentage: HI% = HI × 100.
Reverse: economic yield = biological yield × HI.
$$HI = \frac{Y_{economic}}{Y_{biological}}$$$$Y_{economic} = Y_{biological} \times HI$$How to Use
- Enter economic yield (dry weight of the harvested part).
- Enter biological yield (total aboveground dry matter), same unit as economic yield.
- The tool returns HI (0–1) and percentage; higher HI means better allocation to the harvested part.
Approximate HI ranges for major crops
| Crop | HI range | Note |
|---|---|---|
| Modern rice / wheat | 0.4–0.55 | Dwarf high-yield varieties, high allocation |
| Maize | 0.45–0.55 | High grain proportion |
| Soybean | 0.3–0.45 | Oil seed, high energy cost |
| Potato (tuber) | 0.7–0.85 | Very high below-ground storage proportion |
Ranges are approximate, varying with cultivar, environment and management; HI denominator is usually aboveground biomass (tubers counted separately).
Case Studies
HI of a paddy field
A paddy: economic yield (grain dry weight) = 4 t/ha, aboveground biological yield = 10 t/ha.
HI = 4 ÷ 10 = 0.4, i.e. 40%.
0.4 is reasonable but improvable; better varieties or management can direct more assimilates to grain.
Comparison with a high-allocation variety
An improved variety reaches 5.5 t/ha grain at the same 11 t/ha biological yield.
HI = 5.5 ÷ 11 = 0.5, i.e. 50%, higher than the previous case.
At similar biomass, a higher HI directly gives more harvestable yield — the core contribution of dwarf breeding.
FAQ
Should biological yield include roots?
Most field crops define harvest index with total aboveground dry matter as the denominator, because roots are hard to fully sample and measure, and commercial yield comes mostly from aboveground. A few crops harvested for underground organs (potato, sweet potato) count the tuber as economic yield, while the denominator depends on the study definition. The key is a consistent definition throughout, noting whether roots are included.
Can HI be greater than 1?
No. Economic yield is a part of biological yield, at most equal, so HI lies between 0 and 1. If you get above 1, usually the economic and biological yields have inconsistent definitions or units (e.g. one fresh weight, one dry weight); unify to dry weight and the same unit before recomputing. This calculator clamps an over-range economic yield to 1.
Use fresh or dry weight?
Standard practice uses dry weight. Different organs differ greatly in water content (grain low, stems/leaves high), so fresh weight badly distorts the allocation ratio. Dry each part to constant weight before computing HI. If fresh weight is unavoidable in special cases, state it clearly and do not directly compare with dry-weight HI.
Does high HI always mean high yield?
Not necessarily. Economic yield = biological yield × HI, both matter. With very low total biomass, even a high HI may still give insufficient harvest; conversely large biomass but low HI (assimilates staying in stems/leaves) is also wasted. Ideally raise HI while keeping enough total biomass — both together truly increase yield.
How to raise a crop's harvest index?
In breeding, dwarfing genes shorten stems and reduce vegetative investment, directing more assimilates to grain. In management, timely fertilization (especially nutrients at reproductive growth), reasonable density, and controlling lodging and pests/diseases maintain late-stage leaf function and promote assimilate transport to the harvested part. These raise HI without increasing or even while reducing ineffective biomass.
Related Tools
References
Content review: Calculatorism Science Team. Results are for reference only; please refer to the relevant authorities for the official figures.