Spectrophotometry in Agriculture

Spectroscopy is an analytical tool commonly used in various fields such as food, pharmaceutical, environmental, material science, and agriculture. When the light passes through the sample, the radiation of light absorbed by the sample is measured with spectroscopy. When light interacts with the molecules of the sample it provides information about the sample.

Agriculture is the backbone of our country. As agriculture field requires more advanced techniques to increase the production rate. Spectroscopy plays important role in the quantitative and qualitative analysis in agriculture. This article discusses the various application spectroscopy techniques used in the agriculture field.

Depending on the wavelength of the light, several techniques have been developed through which different properties of the sample can be determined. The commonly used spectroscopy techniques in agriculture are,

  • Ultraviolet-Visible or UV/Vis spectroscopy
  • Near-infrared (NIR) spectroscopy
  • Nuclear Magnetic Resonance(NMR) spectroscopy
  • Atomic Absorption (AA) and Atomic Emission (AE) spectroscopy

UV Visible Spectroscopy – Agricultural Food Products and Soil Analysis

UV-Vis spectrophotometer uses wavelengths in the range of 100-750nm and can be used to determine organic molecules that are present in the various agricultural products. It helps to identify the pigments in the apple and the contaminant in eggs.

UV Visible Spectroscopy - Agricultural Food Products and Soil Analysis

UV -Vis measurements in the range of 590 – 700nm are used to monitor the maturity level of yellow apples. The intensity of light that is reflected from the sample at the wavelength of 678 nm is measured to determine pigment content.

Another important application of UV-Vis Spectroscopy in agriculture is to identify the components that are present in fertilizers such as nitrates and phosphates, in soil samples. These components are essential for the growth of crops, it is crucial to monitor the nutrient contents present in the soil to enhance crop growth.

NIR (Near-InfraRed) Spectroscopy in Agriculture

The range of wavelengths in which NIR spectroscopy operates are ranging from 780 nm to 2500nm. The absorbance of radiation of molecular organic functional groups, such as O-H, N-H, C-C, C-O, and N-O is measured with this NIR spectroscopy.

NIR spectroscopy is easy, fast, inexpensive, non-destructive, and quality analysis with limited or no sample preparation. This technique is widely used in agriculture to determine the quality of fruits and vegetables at the industry or semi-industry level.

NIR (Near-InfraRed) Spectroscopy in Agriculture

Near-infrared spectroscopy is used in the quality analysis of wheat, barley, rice, and soybean to monitor crop health and growing conditions. This helps to identify various crop diseases and contaminants to take protective measures and enhance the quality of the crop. This analysis also helps to assess crop quality at harvest for grading and pricing.

Research is going on to enhance the efficiency of product analysis. NIR spectroscopy enables in-line monitoring of products and provides accurate information on the growth stage of the products. This helps in the harvest handling of fruits and vegetables.

One important example is that the VIS-NIR mini-spectrophotometer  (400–1000 nm) is used in the analysis of intact apples and find moldy cores. This enables the successful identification of healthy apples with 100% in cases where the deterioration was above 30%.

Nuclear Magnetic Resonance (NMR) Spectroscopy to Monitor Organic Contaminants

Nuclear Magnetic Resonance (NMR) spectroscopy is an indispensable tool to identify complex chemical compounds. NMR technique applies magnetic field and radiofrequency radiation to the atomic nucleus to characterize the resonant frequency of the atomic nucleus according to its chemical and environmental conditions.

In the molecular identification of agricultural matrices such as plant roots, leaves, soils, etc., using liquid-state in NMR spectroscopy presents some challenges in the preliminary sample preparation. The time-consuming operations such as extraction, purification, and concentration may result in loss or degradation of the sample components.

Advanced NMR techniques are used for the samples like semi-solid and gels. This enables the study of inorganic and organic contaminants in biological tissues and is also used in the study of arsenic-contaminated irrigation water on lettuce. This helps to verify the effect of fresh lettuce leaves on the intake of arsenic. This enables to assess the quality of agri-food products.

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Laser-Induced Breakdown Spectroscopy (LIBS) for Soil Analysis

Laser-Induced breakdown Spectroscopy (LIBS) is an advanced atomic spectroscopy technique that enables the detection of every element present in the sample. It almost does not require any sample preparation and is commonly used in agriculture for the multi-elemental analysis of soils.

A high-power laser pulse is used as an excitation source that excites the electrons of the sample’s atom and generates high-temperature micro-plasma on the sample surface. As the plasma cools down depending on the characteristic elemental components of the sample it emits light with discrete spectral peaks.

LIBS provides important information on the concentration elemental components of soil. This enables to determine the soil nutrients such as Magnesium(Mg), Calcium(Ca), Potassium(K), Nitrogen(N), Phosphorus(P). It is also used to determine the extent of contamination by toxic metals such as lead (Pb), Cadmium (Cd), and Arsenic (As) in soils.

Even though LIBS is a simple, convenient, and versatile technique has limitations. The fluctuations of emission of light intensity are due to the non-homogeneous surface of the samples and there is a need for calibration.

Further research is going on to expand the scope of LIBS in agricultural applications to determine the Cation Exchange Capacity (CEC), which provides the details on the efficiency of soils to hold and transfer nutrients at the soil roots.

This advanced technique requires more field studies with different types of soil and validates the full potential of the technique in agricultural applications. Research is underway to optimize spectroscopy techniques in several aspects for the enhanced applications of agriculture, semi-industrial or industrial level. 


Spectroscopy is the most popular and commonly used technique in various fields. There are different types of spectroscopy available on the market that works on different technique and wavelengths. Agriculture is the backbone of our country. Spectroscopy and its emerging techniques help to analyze the elemental composition of the soil. It also enables to bring enhancements in the agricultural field research.

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