NDVI vs NDRE: Which Vegetation Index Should You Use?
The short answer
NDVI tells you how much canopy there is. NDRE tells you how well-fed that canopy is. They answer different questions, which is why precision growers use them together rather than picking one.
The single most common mistake is treating them as rivals. They are not — NDVI is your growth-stage index, NDRE is your nutrition index. Use NDVI from planting through canopy closure, then switch to (or add) NDRE for the second half of the season when the question shifts from “is it growing?” to “is it well-fed?”
How each one works
Both are normalized ratios — that is, a number between −1 and 1 built from two satellite bands. The difference is which bands:
NDVI = (NIR − Red) / (NIR + Red)
NDRE = (NIR − RedEdge) / (NIR + RedEdge)On Sentinel-2, NDVI uses Band 8 + Band 4, while NDRE uses Band 8 + Band 5 (the red-edge band, ~0.705 µm). That one band change changes everything about what the index “sees.”
| NDVI | NDRE | |
|---|---|---|
| What it measures | Canopy density / green biomass | Leaf chlorophyll / nitrogen status |
| Best band | Red (absorbed by chlorophyll at the surface) | Red-edge (shifts with chlorophyll inside the leaf) |
| Saturation | Saturates over dense canopy (~0.8) | Stays sensitive over dense canopy |
| Strength | Growth stage, biomass, season tracking | Nitrogen status, mid-late season nutrition |
| Weakness | Can’t see nitrogen once canopy closes | Lower absolute values, needs canopy to exist |
| Best season window | Early to mid season | Mid to late season |
When NDVI wins
NDVI is the right default from sowing until the canopy closes. It tracks the bell curve of a seasonal crop — climbing through vegetative growth, peaking at canopy closure, falling at senescence. For growth-stage monitoring, year-over-year comparison, and general canopy health, NDVI is simpler, better calibrated, and universally understood.
NDVI also wins early in the season, when there is little canopy to measure. NDRE needs leaf layers to work; over bare soil or a young seedling it has almost nothing to say.
When NDRE wins
Once the canopy is closed, NDVI saturates — it returns roughly the same 0.8 value whether the crop is well-fed or quietly starving. This is exactly the window where NDRE earns its keep. Because red-edge light penetrates deeper into the leaf stack, NDRE keeps reporting on chlorophyll and nitrogen status after NDVI has gone flat.
NDRE is the index for nitrogen management, variable-rate fertilizer prescription, and detecting hidden stress over a dense crop. A falling NDRE in a still-green canopy is the classic early signal of nitrogen depletion — the window where a side-dress still pays off.
Use them together: the season playbook
| Growth stage | Primary index | What you are asking |
|---|---|---|
| Emergence → canopy closure | NDVI | Is the crop establishing and growing? |
| Canopy closure → grain fill | NDRE | Is the canopy well-fed (nitrogen)? |
| All season | NDVI + NDMI | Is it growing, and is it well-watered? |
| Late season | NDVI + NDRE | Is the decline natural senescence or deficiency? |
A practical rule: if NDVI is high and flat but NDRE is dropping, the crop is nitrogen-stressed. If both are dropping together over a mature crop, it is likely natural ripening, not a problem. Pairing NDRE with NDMI (water status) completes the nutrition picture, because nitrogen uptake depends on available moisture.
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Frequently asked questions
Is NDRE better than NDVI?
Neither is universally better. NDVI is better for early-season growth tracking and general biomass. NDRE is better for nitrogen monitoring once the canopy is dense. For most of the season the right answer is to use both — NDVI to confirm the canopy is there, NDRE to confirm it is well-fed.
Why does NDVI saturate over dense canopy?
NDVI uses the red band, which chlorophyll absorbs almost completely once the canopy is thick. Past that point red reflectance is already near zero, so it cannot drop further — NDVI plateaus around 0.8 even as biomass keeps climbing. Red-edge light (used by NDRE) is only partially absorbed, so it keeps responding to chlorophyll changes inside the leaf.
Can NDRE replace NDVI for nitrogen management?
It complements rather than replaces it. NDRE tells you the nitrogen status, but you still need NDVI to confirm the canopy is dense enough for NDRE to be meaningful. A low NDRE over a thin canopy can just mean there are few leaves to measure, not that the crop is deficient. The two indexes confirm each other.
What is a good NDRE value compared to NDVI?
NDRE runs lower in absolute terms than NDVI by design — a dense canopy might read 0.8 in NDVI but only 0.3 in NDRE. Do not compare the two numbers directly. Instead, track each index against its own seasonal trend, and map spatial variation within your field: patches lower than the field average in NDRE are your nitrogen-deficient zones.