NDRE: The Red-Edge Index for Crops NDVI Can't Read Anymore
By the time a maize canopy closes, NDVI is pinned near its ceiling and blind to the nitrogen differences that still matter. NDRE swaps the red band for the red edge — the steep shoulder of the reflectance curve — to keep resolving canopy chlorophyll deep into the season.
The idea behind it
The red edge (around 705–740 nm) sits between strong red absorption and the NIR plateau, and its position shifts with chlorophyll concentration. Because it does not saturate as quickly as red, NDRE keeps separating fertility and stress gradients in dense, late-season canopy long after NDVI has flat-lined.
The formula
where NIR is near-infrared reflectance, Red Edge is red-edge reflectance.
Reading the values
Higher = more canopy chlorophyll / nitrogen. Discriminates fertility and stress where NDVI has already saturated.
Which bands to use
| Sentinel-2 | NIR B8 · Red Edge B5 |
| Landsat 8/9 | NIR B5 · Red Edge — n/a |
In practice
NDRE drives variable-rate nitrogen application, mid- and late-season crop-stress mapping, and pasture management — cases where the canopy is already closed and NDVI has stopped responding.
Where it struggles
It only exists where a red-edge band does. Sentinel-2 (B5), RapidEye, PlanetScope and many drone multispectral rigs have one; Landsat 8/9 do not, so never design an NDRE workflow around Landsat.
Compute NDRE on your own study area
Skip the code. Draw or upload a boundary and Spatial Research Suite runs NDRE on live Sentinel-2 or Landsat imagery — with cloud masking, exports and citations built in.
Run this analysis in GISforus →Frequently asked
Can I compute NDRE from Landsat 8 or 9?
No — Landsat 8/9 have no red-edge band. NDRE requires a sensor such as Sentinel-2 (band 5), RapidEye or PlanetScope.
Why use NDRE instead of NDVI in crops?
In closed, late-season canopy NDVI saturates; the red edge keeps NDRE sensitive to chlorophyll and nitrogen there.