NDVI or Normalized Difference Vegetation Index is not a new concept, and it has been in use since 1973, aiding scientists to assess and monitor plant health in next to no time. Today, NDVI has become the most commonly used vegetation index in remote sensing, especially with the recent advancements in earth observation and drone technologies.
In this blog post, you will get a closer look at what exactly NDVI is and the ample scope for its applications in precision agriculture.
What Is NDVI, and How Is It Evaluated?
Simply put, the Normalized Difference Vegetation Index is an indicator of a plant’s health entirely based on how the cell structures reflect the different light waves in visible and near-infrared bands.
In other words, it aids in detecting and quantifying the presence of live green vegetation based on how objects interact with light. To understand the plant’s health condition, one needs to compare the absorption and reflection values of red and NIR (near-infrared) light. Here is where NDVI comes into the picture.
In mathematical terms, comparing the red and near-infrared light signals can help differentiate between healthy and sick plants or distinguish non-plants from plants.
Take a look at the formula below for the evaluation of NDVI:
NDVI = (NIR-Red)/(NIR+Red)
Now, the values range from -1 to +1. A higher or more positive value indicates greater plant vigor and general health.
But how exactly does this evaluation work? Generally, healthy vegetation, which contains a good measure of chlorophyll and cell structures, tends to absorb a significant amount of visible light while reflecting NIR light. On the other hand, unhealthy vegetation does the opposite; it reflects more visible light while absorbing the NIR light.
Let us now take a look at the various applications of NDVI in agriculture.
5 Top Practical Uses of NDVI in Agriculture
Did you know that NDVI can tell a lot about the crop based on seasonal changes? For example, it helps understand how the plant survived throughout the winter. A value lower than 0.15 indicates that all plants perished in that particular part of the field.
Besides generalized assessment, some of the other practical uses of NDVI in agriculture are as follows:
1. Aids in Tracking Crop Health
Most scientists and agronomists prefer NDVI as an ideal tool for tracking crop health. Primarily, they capture a series of NDVI maps to keep a close check on crop health. It is applicable during the growing season and from year to year.
These NDVI values, when averaged, can help determine the normal growing conditions of crops in a particular area and at a given time of the year.
So, what’s the advantage here? With NDVI, you get a closer look at what the naked eye cannot see. It shows you the problem areas in advance, thereby providing you with the opportunity to fix them faster. Of course, NDVI cannot replace human intervention, but it does make the job remarkably simple.
2. Helps Agronomists Develop Variable Prescription Maps
With NDVI maps, agronomists and other stakeholders can identify nutrient deficiencies, conduct the much-needed ground-truthing, and then upload the data on a farm ERP solution like Cropin, a revolutionary in promoting and making precision farming possible.
Consequently, farmers and farming companies need not spend extra anymore. With data-backed advisories from agronomists, they can spray and seed only as needed to save time, money, and resources significantly.
3. Scouts Fields Faster
The traditional physical process of assessing or tracking a field can be more detrimental to the crops. Plus, it is time-consuming and labor-intensive nonetheless. On the other hand, with NDVI, you can identify the problem areas sooner and take the necessary steps to improve crop health and yield. An absolute win-win situation for both the farmer and the associated brand!
4. Helps Identify Crop Problems Sooner
NDVI also helps agronomists identify stressed crops up to 2 weeks before the naked eye can see. Since crop stress is more apparent in the near-infrared light spectrum than in the visible one, it can aid growers to eliminate pests, diseases, fungus, and arid conditions sooner. In addition, consistently low NDVI values at the same place every crop cycle could indicate problems with drainage, soil pH, or even soil compaction.
Therefore, NDVI is now an indispensable part of precision farming that plays a direct role in maintaining crop health and yield. Cropin, a pioneering agri-tech SaaS-based solution provider, acknowledges this aspect and has developed smart farming solutions that embrace and leverage the benefits of this versatile vegetation index.
5. Indicate drought situations
NASA made a case for using NDVI as an indicator of drought. NASA writes on its website, "more a plant is photosynthesizing, the more it is being productive. Conversely, the less sunlight the plant absorbs, it isn't productive." This gives us NDVI values over a period of time. When averaged, the NDVI values give a region's absorption/reflection capacity. Thus, NDVI indicates the health of the vegetation in that area, compared to the average.
Armed with 20 years of NDVI data over the entire globe, NASA can now compare today's NDVI with the 20-year average to reveal if the productivity of a particular region is more, less or same. A region which is shown reduced plant growth characterized by lower NDVI values compared to average, could be labeled as "in drought." Not always, though. Cloud cover and extreme cold can also cause lower than normal NDVI.
NDVI – Not New, But Never Obsolete!