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Grain · Yield & water · Physiology

Harvest index

0.42

The proportion of total above-ground crop biomass that ends up as harvested grain rather than straw and chaff — a measure of how efficiently the plant converted its growth into saleable product.

Worked example · Grain ÷ total above-ground biomass
0.42 Grain · 42% Straw · 58%
Grain ÷ total above-ground biomass
The benchmark

Modern well-managed wheat crops partition around 0.40–0.50 of their above-ground biomass into grain; a low harvest index signals biomass that never filled to grain.

GRDC Water Use Efficiency ↗
What it signals

A crop can grow plenty of bulk yet return a poor harvest index if a stress at flowering or grain-fill cut the grain short. Watching it separates a biomass problem (early vigour, nutrition) from a grain-fill problem (frost, heat, moisture at the finish).

Data required to calculate
Grain yieldkg/haTotal above-ground biomasskg/ha

Silo pulls each of these from the sources the operation already uses, and keeps the figure current automatically.

How to improve it
01

Protect the grain-fill window from frost and heat through sowing date and variety.

02

Keep the crop green and the flag leaf healthy with timely fungicide and nutrition.

03

Avoid excess early nitrogen that grows straw at the expense of grain.

Questions & answers

What is harvest index?

The proportion of total above-ground crop biomass that ends up as harvested grain rather than straw and chaff — a measure of how efficiently the plant converted its growth into saleable product.

What data do you need to calculate harvest index?

You need: Grain yield (kg/ha), Total above-ground biomass (kg/ha). Silo pulls each of these from the sources the operation already uses and keeps the figure current automatically.

What is a good harvest index benchmark?

Modern well-managed wheat crops partition around 0.40–0.50 of their above-ground biomass into grain; a low harvest index signals biomass that never filled to grain.

How do you improve harvest index?

Protect the grain-fill window from frost and heat through sowing date and variety. Keep the crop green and the flag leaf healthy with timely fungicide and nutrition. Avoid excess early nitrogen that grows straw at the expense of grain.

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