NDVI explained
A plain-English guide for farmers

NDVI turns a picture of your field into a map of crop vigour. Here's what it measures, how to read it, and how farmers actually use it.

What is NDVI?

NDVI stands for Normalised Difference Vegetation Index. Healthy green plants absorb most red light for photosynthesis and reflect a lot of near-infrared light. Stressed or sparse plants reflect less near-infrared. NDVI compares the two to give each part of the field a score, usually shown on a colour scale from red (low vigour) to green (high vigour).

How to read an NDVI map

• Consistent green — even, healthy canopy.
• Patches of yellow or red — something is limiting growth: poor establishment, waterlogging, compaction, pests, disease or nutrient shortage.
• Sharp lines or shapes — often point to a machinery issue, an old field boundary or drainage.

How farmers use NDVI

• Targeting crop walks to the areas that need attention
• Building variable-rate nitrogen or seed prescriptions
• Timing and targeting fungicide or PGR applications
• Checking establishment after drilling and after a wet winter
• Comparing fields and seasons to find persistent problem zones

Drone vs satellite NDVI

Free satellite NDVI is useful for a broad overview, but resolution is coarse and cloud cover often blocks images when you need them. A drone flies under the cloud at a time you choose and maps the field at centimetre-level detail, so individual problem patches and even rows are visible.

When to fly

For most arable crops, two to four flights a season at key growth stages give the most useful picture. We offer 10% off per visit on contracts of three or more flights.

See our NDVI crop health survey service →

Frequently asked questions