Spectroscopy explained in nine easy steps

Herman Vedder is a senior scientist at AgroCares. Passionate about spectroscopy, he spent 35 years using and developing this technology to analyze feed, soil or leaf samples. Over the years, he specialized in Near-InfraRed (NIR) systems. Today, together with Dr. Mila Luleva and Thomas Terhoeven-Urselmans he is responsible for the evolution of two AgroCares products based on spectroscopy: the Scanner and the Lab-In-A-Box (LIAB). In this blog Herman explains the ins and outs of spectroscopy, NIR, and their link to soil testing and innovation in agriculture.

What is spectroscopy exactly?

Spectroscopy is the branch of science looking at the interaction between matter and electromagnetic radiation. When matter is in contact with certain electromagnetic radiations, it responds with different electromagnetic radiations. Spectroscopy measures and investigates these radiations. Thanks to these analyses, scientists can characterize the matter they want to study.

What do you mean by electromagnetic radiation?

Everybody is familiar with electromagnetic radiations. The most common example of electromagnetic radiation is visible light, but there is a range of radiation beyond what we can see: microwaves, infrared or X-rays. They are classified according to their frequency. If we take visible light as a reference, an example of low frequency radiations is infrared, and an example of high frequency radiations is X-rays. All electromagnetic radiations are gathered in the electromagnetic spectrum (see figure below). At AgroCares, we work with both infrared and X-rays.

Electromagnetic spectrum (Credits: NASA & authors) 

Do you work the same way with infrared and with X-rays?

They are different sources of radiations, and they do not give the same information. With the infrared, we look at the molecular level, while with X-rays we look at the atomic level. Both techniques are different, and we combine them to perform accurate analyses.

Infrared, Near-Infrared (NIR), and Mid-Infrared (MIR)

Infrared techniques allow to study molecules with a spectrometer. The spectrometer has two roles. First, it sends an infrared signal to the sample. Then, it records the infrared signal returning from the sample. The second signal is different than the first because parts of the signal are absorbed by the sample. From the received signal, we can determine what molecules are present in the sample and in which quantity. Not all signals can be detected by all spectrometers. At Agrocares we developed a Scanner that uses the range of infrared called Near-Infrared (NIR), and a tool called Lab-In-A-Box using a larger range of infrared called Mid-Infrared (MIR) (see figure above).

X-rays and X-rays fluorescence (XRF)

With X-rays, we look at atomic level with X-rays fluorescence techniques (XRF). The idea is similar to infrared: we send a signal to the sample and we measure the signal that the sample sends back. However, the reaction of the sample to X-rays is different than to infrared: it is not the molecules but the atoms that react when irradiated. A reorganization of electrons in the inner shell of atoms triggers the emission of photons of light. The collection of released photons is causing a fluorescence radiation. Each element is associated with a specific wavelength and energy of the fluorescence radiation, while its concentration is calculated from the intensity of the fluorescence.

What are the end-results of a soil analysis with spectroscopy?

Both Infrared and XRF methods measure the quantity of total elements present in the sample. At AgroCares, the tools we developed can measure the contents of macro nutrients such as N,P,K, S, Ca, Mg, but also micro nutrients, CEC, pH and organic matter.

Why are spectroscopy technologies relevant for soil testing?

They are relevant because they make soil testing much faster and more affordable than wet chemistry laboratories. Tools such as the Scanner or Lab-In-A-Box (LIAB) can be brought directly in the field or nearby so that all types of farmers can access to soil testing services. Because the technology is faster, several samples can be analyzed from the same field. Take the case of the LIAB: only 2 hours are sufficient to prepare and process a sample, and up to 50 samples can be analyzed per day. It is relevant for farmers because they need a service that is fast, close, affordable and accurate. Conventional laboratories simply cannot offer this.

What makes AgroCares spectroscopy solutions unique?

As far as I know, AgroCares is the only company that connects a research center on spectroscopy directly with end-users. Today, most companies that build spectroscopy tools for soil, feed, or leaf analyses sell exclusively to laboratories. At AgroCares, we develop our products internally, train our customers on how to use it, process the collected data, and give recommendations to end-users via the application. By being active along the whole soil testing value chain, we are able to design the technology directly from the needs of the farmers. The result for the customers is a plug and play solution. Because the system is already calibrated, samples can be analyzed right after the installation of the system. That is pretty unique.

What is your vision for the future of soil testing?

I think soil testing will become more important as agriculture needs to be more productive and efficient. Solutions such as the Lab-In-A-Box can be moved in order to reach farmers, and this key to meet Africa’s increasing demand. For wet chemistry laboratories this is simply not possible: it is too expensive for the area it can reach. In the future, I foresee that spectroscopy will be use at least twice in the lifecycle of an agriproduct like forage: once in the ground before sowing to know the needs of the soil, and once after the harvest to know the quality of the feed. With one tool linked to different applications, farmers will increase the control and efficiency of their production systems.