Finally, the bottom section of this chart depicts the light range measured by varying quality instruments. Top-end laboratory NIR instruments can cost upwards of $100,000 and cover roughly 2,100 different light wavelengths. Of the instruments currently being promoted for on farm use, the price range runs from roughly $5,000-$30,000 and the number of wavelengths measured range from 400-1,000. To go back to our eyesight analogy, the difference between these instruments is similar to the difference between trying to recognize a face in broad daylight versus trying to recognize that same face through dense fog at daybreak. The more light we have to work with; the more accurate our perception is of the object we are looking at.
Hopefully, we’ve now established the basic concepts of how moisture, particle size, and instrument quality can change the amount of information available in an NIR analysis. In the next part of this series, we’ll take a look at how this information affects the ability to measure moisture and other nutrients. Then, the third and final part of this series will focus on some practical applications for on-farm NIR.