Why is NIR used for vegetation?
NIR, or near-infrared, is a region of the infrared portion of the electromagnetic radiation spectrum that is just beyond the visible spectrum. It’s invisible to the naked human eye, but specialised equipment can detect and read it for visual information that we would otherwise be blind to.
By measuring the near-infrared radiation produced by the Sun and how it is absorbed or reflected, scientists have worked out some reliable ways to measure the qualities of vegetation and the soil in which it grows. So, why is NIR used for vegetation? And how exactly is it measured?
How NIR is used in vegetation
Visible wavelengths of length help us to perceive colours and textures of plants. For instance, the green portion of the spectrum is reflected from a leaf so that we perceive it as that colour, whereas other portions of light are absorbed.
NIR radiation, however, is reflected and absorbed in ways that we cannot perceive with the naked eye. Reflected NIR radiation can actually be detected by satellites, allowing scientists to study the health and productivity of plants.
Studying vegetation with NIR can reveal changes in cell structure. Unlike visible light, NIR can penetrate a plant’s top layer of cells and reflect off of lower layers, which can also be useful for measuring soil.
Benefits of using NIR for vegetation?
Why is NIR used for vegetation when we can usually see if a plant is healthy by changes in colour or visible damage?
While this is true for plants that we are up close to, large swathes of vegetation may be harder to discern with accuracy. Healthy plants reflect more NIR light than visible light. By comparing visible and invisible NIR light, subtle differences to plant health can be determined.
For example, normal healthy leaves will absorb red light in the visible spectrum, but as it becomes unhealthy and the cells take on a reddish-brown colour, it will reflect more of this light whilst reflecting less NIR light. A bigger the difference between reflected visible red light and reflected NIR light, the healthier the plant.
This method is referred to as the Normalized Difference Vegetation Index (NDVI). Being able to conduct such a comparison on entire fields of crops means that a bigger overall picture of health can be determined quickly, whilst eliminating the need for high-quality inspection by human eye where a variety of factors could determine the objectivity of results.
NIR technology can be operated simply by anybody. Here at Calibre Control, we supply accessible technology that can utilise NIR and other means to help you analyse your produce and verify quality.
To learn more about NIR or to make any enquiry about our work, please contact us today.