Portable Mid Infrared Analyzer for Onsite Measurement of Nitrate and Organic Matter in Soil

Nitrate is an important nutrient for crop production. Soils with excess nitrate amounts and shallow groundwater tables pose a high risk to nitrate leaching into drinking water supplies. A shortage of nitrate decreases agricultural productivity. Measurement of soil nitrate content is a tedious, time consuming, and expensive process. Currently, there are no commercial sensors for in-situ nitrate determination. With measurements in real time and in the field, nitrate application could then be adjusted according to need rather than applied uniformly across a field. The potential benefits of such a system are increased crop yield, a decrease of input costs, and a reduction of the environmental impact. Studies have shown that nitrate content of the soil can be determined by mid infrared analysis. Currently laboratory FTIR's (Fourier Transform Infrared Spectrometers) are very expensive and are not rugged enough for field applications. Initial studies by UC Davis, Jahn and Upadhyaya (2008), with a rugged, portable, filter based mid infrared spectrometer, the Wilks InfraSpec VFA-IR Spectrometer, found the results were good down to 40 ppm nitrate. For the analysis to be of benefit, the system would need to measure down to 10 ppm. This project will support a redesign of the InfraSpec VFA-IR Spectrometer to include a more rugged soil interface, a 5x improvement in sensitivity and a 20% reduction in cost. This system would then be able to interface with existing soil sampling systems to provide on-site nitrate analysis.