Assessing Soil Organic Carbon (SOC) With Hyperspectral Imaging

Soil organic matter (SOM) plays a vital part in soil health and fertility, particularly the chemical, physical, and biological functions of the soil, and have a big impact on the sustainability of agricultural production systems. SOM is difficult to measure directly, and the nearest approach is measuring soil organic carbon (SOC), a measurable component of SOM that has a high correlation.

The conventional way to measure SOC is through the Walkley Black (wet combustion) or dry combustion methods. These methods can be laborious, time-consuming, and expensive as they involve collecting soil samples and sending them to the laboratory for oxidization.

Widely used in various plant phenotyping and geological applications due to their ability to offer rapid and non-destructive mapping, characterization, and analysis of their target, hyperspectral imaging (HSI) cameras have also emerged as a promising scientific tool in soil assessment. For instance, MU et al. (2008) use an HSI camera to predict the SOC content to establish optimum soil management, while Sorenson et al. (2018) uses HSI to measure SOC and total nitrogen. In general, reflected light from the soil is collected at different wavelengths (e.g., visible, near-infrared, etc.) by an HSI camera to obtain the spectral reflectance data. The data is then further processed with mathematical models like partial least square regression (PLSR), etc., to estimate SOC.

In-field HSI measurement with Specim IQ. Image courtesy of SPECIM, SPECTRAL IMAGING LTD.

There are many factors to consider when setting up an HSI system. One should consider how the spectral measurement will be carried out in practice as there are various types of HSI cameras (e.g., pushbroom, whiskbroom, etc.), each with its way of acquiring data. Aside from HSI camera selection, factors such as the spectral range, resolution, illumination, light collection efficiency, etc., should also be considered.

Specim has a wide range of HSI solutions covering wavelengths from visible and near-infrared to the long wavelength infrared (LWIR). When it comes to soil research and studies, Specim offers various easy-to-use and reliable HSI systems, from portable HSI camera Specim IQ that is suitable for laboratory and field to airborne HSI systems. Check out this video to learn more about how Specim HSI cameras work.

Interested to learn more about HSI? Need assistance developing and setting up your HSI system? Contact us for a free consultation now.