In this post, Ocean Insight shares spectra of various soil samples as measured with the NIRQuest+ spectrometer (900-2500 nm). NIRQuest+ is distinguished by its high sensitivity and great thermal stability.
In this experiment, Ocean Insight identified the moisture content of organic and topsoil samples using the NIRQuest+2.5 spectrometer (900-2500 nm) as part of a diffuse reflectance system.
Determining moisture content in soil has great significance in agriculture, where crop health is largely dependent on maintaining optimal moisture levels, which vary by factors such as the soil and crop type.
Sample Preparation and Experiment Techniques
Ocean Insight collected four different samples from a local garden center: standard top soil, premium top soil containing compost, compost, and sand.
Samples were removed from each bag, weighed and measured. These samples were labeled as Wet Soil (Figure 1). Note the two strong moisture peaks. Absorption bands for water typically are seen at 970 nm, 1200 nm, 1450 nm and 1950 nm.
Figure 1. Samples comprising topsoil, compost and sand initially were measured with no sample preparation.
Although the data were collected using diffuse reflectance techniques, we plotted the spectra as absorbance (Log (1/Reflectance). This is because observing the trend in intensity/absorbance is more intuitive than observing the plots as %Reflectance.