Monitoring Plant Greenness

Monitoring Plant Greenness...

Nitrogen is one of the most important nutrients necessary for healthy plant growth.  Although there are laboratory techniques that can quantify plant nitrogen, these can be time-consuming and cost-prohibitive to perform on a regular basis. Because nitrogen is an important component of chlorophyll, it is possible to track plant nitrogen status by measuring the greenness of the leaves.  There are 3 methods for quantifying leaf greenness; the human eye, light reflection/transmission, and digital color analysis.

The human eye is the most subjective of the three methods.  Issues such as light level and color perception impact how a leaf appears. Further, what one evaluator may rate as an acceptably green plant may be rated as nutrient deficient by another.

Because chlorophyll absorbs known wavelengths of red light, devices that measure red and near infrared light can be used to give an objective measurement of leaf greenness. The relative intensities of each wavelength are combined into an index that is used to compare the greenness (and thus the nitrogen level) of different leaves or management zones.  Some common indexes are the Normalized Difference Vegetation Index (NDVI) or the SPAD number.

A relatively new approach to quantifying greenness is the use of digital color photography.  In this case, the Red/Green/Blue (RGB) value of the individual pixels of a digital photograph are used to compute an index that quantifies the level of greenness in the leaf.  This calculation can be carried out on a PC or with a smartphone-based app.

As technology makes it ever easier to take objective measurements of plant greenness, the ability for growers to collect objective data will be an increasingly valuable tool for managing plant nutrition and health.

All the best,

Related Links:
FieldScout GreenIndex+ App
FieldScout GreenIndex+ Turf App
FieldScout CM 1000 Chlorophyll Meter
FieldScout CM 1000 NDVI Meter
SPAD 502 Plus Chlorophyll Meter

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