3
General Overview
Turfgrass quality is visually evaluated by human assessors
based on a scale of 1 (poorest, the grass is dead) to 9
(ideal, the grass if of outstanding quality) using a common
assessment method. A rating of 6 or greater indicates
adequate turf quality. Because this evaluation practice is
subjective, individual biases are inevitable and lead to
some level of inconsistency, even among the most highly
trained observers. This variability led to the need for a
more objective evaluation technique.
To answer this need, researchers have developed the
Normalized Difference Vegetative Index (NDVI). The
Field Scout TCM 500 “NDVI” Turf Color Meter
measures reflected light from turf grass in the red (660
nm) and near infrared (850 nm -NIR) spectral bands.
Because chlorophyll absorbs the red band (660 nm) of
incoming radiation, the reflectance at that wavelength is
relatively low due to the strong absorption of the light by
the plant pigments. The high reflectance in the NIR (850
nm) band is caused by the cellular structure of the plant
leaves, particularly the spongy mesophyll leaf structure.
