Development of a soil organic matter measuring device using ultraviolet and visible light spectroscopy

Abstract

A study is focused on the development of an electronic device capable of measuring Soil Organic Matter (SOM) content in a given soil sample using Ultra-Violet and Visible Light (UV/Vis) Spectroscopy. SOM measurement is a high valued procedure in any sustainable agricultural production system. The SOM content measurement was done through image processing and uses the Munsell Colour System as the reference to analyse the soil samples. Fluorescence which causes some substances including organic matters emit light at visible wavelengths when exposed to Ultraviolet and Visible light spectrums was the key phenomenon used in the design and development of the prototype measuring device. By capturing the amount of radiation through a camera, the image will be sent to a computer to quantify the amount of SOM present in a given soil sample. The system was composed of two main parts, the UV/Vis LED array circuit and the computer which runs the developed software to analyze SOM content. The camera used to capture reflected images is integrated to the LED array circuit. A separate testing software was also developed to calibrate the reading consistency of the device. Testing included the effects of moisture content and grain size of the soil samples. Through testing and evaluation of the prototype, the results were compared to the measured SOM using Loss-on-Ignition (LOI) method. Findings show that the measured quantities using the SOM Content Measuring Instrument is comparable with the measured quantities using LOI method.