NDVI or Normalized Difference Vegetation Index: all plants both absorb and reflect radiation. The chlorophyll in the leaf will reflect Near Infrared. This reflectance is invisible to the human eye, as we cannot see NIR. The more NIR that a plant reflects indicates a robust, healthy plant.
Outside of this, is a plant ‘under stress’ ! An NDVI image can identify those problem areas.
By having this imagery of a crop or field, allows a farmer or agronomist, to go directly to that section that is a problem. Quite often these are not easily seen from the ground and as the NDVI image can detect plant stress that humans just cannot see - preventative treatment can be applied, saving dollars and increasing yield.
Plant stress may be caused from a variety of issues; lack of moisture or nutrition, weeds, bug infestation, heat stress, and many others - but they all will show up as the simply a plant under stress in an NDVI map. Ground proof to establish WHAT the problem is, NDVI mapping will show you WHERE the problem is.
Importantly, the NDVI image will also show exactly where healthy plants are and these do not need expensive crop treatments or chemicals. More savings.