Patent ID: 8472023

Claim:
A device for measuring the nitrate-nitrogen concentration in soil based on attenuation over a spectral operating range, the device comprising: a light source that generates light that spans the spectral operating range, the spectral operating range including wavelengths at least as short as 230 nm; a detector having a sensitivity that spans the spectral operating range; a sample chamber configured to contain a soil-extractant mixture; the light propagating from the light source to the detector and attenuated by the soil-extractant mixture in the sample chamber, the detector generating a soil spectral signal that indicates the light received by the detector at different wavelengths across the spectral operating range; and a processor coupled to the detector, wherein the processor estimates an attenuation spectrum of the soil-extractant mixture over the spectral operating range based on the soil spectral signal, a reference spectral signal and a dark spectral signal, wherein the reference spectral signal is generated when the sample chamber contains extractant without soil and the dark spectral signal is generated without light from the light source incident on the detector, and wherein the processor estimates the nitrate-nitrogen concentration based on the attenuation spectrum.