MEASUREMENT OF NITRATE-NITROGEN CONCENTRATION IN SOIL BASED ON ABSORPTION SPECTROSCOPY

• US 20170322148A1
• Filed: 07/25/2017
• Published: 11/09/2017
• Est. Priority Date: 05/07/2009
• Status: Active Grant

• Current Assignee: Winfield Solutions LLC (Land O'Lakes Incorporated)
• Original Assignee: Monsanto Technology LLC (Bayer AG)
• Inventors: PREINER, MICHAEL JOHN, KOSHNICK, NICHOLAS CARLETON, WHITE, JUSTIN STEWART, STRACHAN, JOHN PAUL
• Granted Patent: US 10,488,331 B2
• Time in Patent Office: Days
• CPC Class Codes: G01N 21/00 Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light G01N3/00 - G01N19/00 take precedence
• CPC Class Codes: G01N 21/276 with alternation of sample and standard in optical path
• CPC Class Codes: G01N 21/33 using ultraviolet light G01N21/39 takes precedence
• CPC Class Codes: G01N 21/552 Attenuated total reflection
• CPC Class Codes: G01N 33/24 Earth materials G01N33/42 takes precedence
• CPC Class Codes: G01N 33/245 for agricultural purposes

Abstract

The nitrate-nitrogen concentration in soil is estimated based on the nitrate-nitrogen 200 nm absorption peak. In one embodiment, a device measures the attenuation spectrum of a soil-extractor mixture over a wavelength range that includes wavelengths in the vicinity of the 200 nm absorption peak (the spectral operating range) and then determines the nitrate-nitrogen concentration based on the attenuation spectrum.

Claims

1-36. -36. (canceled)

37. A device for measuring a nitrate-nitrogen concentration in soil based on attenuation over a spectral operating range, the device comprising:

a light source that generates light that spans a spectral operating range;

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;

a processor that is coupled to the detector, and that estimates an attenuation spectrum of the soil-extractant mixture over the spectral operating range based on the soil spectral signal, and that estimates the nitrate-nitrogen concentration based on the attenuation spectrum.

38. The device of claim 37, wherein the processor, when estimating the attenuation spectrum, removes interference in the soil-extractant mixture using one of spectral deconvolution and curve-fitting;

wherein the spectral operating range includes wavelengths proximate a 200 nm nitrate-nitrogen absorption peak;

wherein the 200 nm nitrate-nitrogen absorption peak includes estimated attenuation values for wavelengths greater than 200 nm.

39. The device of claim 37, wherein the sample chamber is optically positioned between the light source and the detector, the light propagating through the soil-extractant mixture in the sample chamber.

40. The device of claim 37, wherein the processor estimates the attenuation spectrum 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;

wherein the dark spectral signal is generated without light from a light source incident on the detector.

41. The device of claim 37, wherein, at different times, the sample chamber contains the soil-extractant mixture or extractant without soil;

wherein the detector generates the soil spectral signal when the sample chamber contains the soil-extractant mixture;

wherein the detector generates a reference spectral signal when the sample chamber contains extractant without soil;

wherein the processor estimates the attenuation spectrum based on the soil spectral signal and the reference spectral signal.

42. The device of claim 37, further comprising a second sample chamber configured to contain extractant without soil;

wherein the processor estimates the attenuation spectrum based on the soil spectral signal and a reference spectral signal;

wherein the reference spectral signal is generated from the second sample chamber containing extractant without soil.

43. The device of claim 37, further comprising a reference optical path from the light source to the detector;

wherein the reference optical path is not attenuated by the soil-extractant mixture;

wherein the processor estimates the attenuation spectrum based on the soil spectral signal and a reference spectral signal;

wherein the reference spectral signal is generated based on the reference optical path.

44. The device of claim 37, wherein the processor curve-fits the attenuation spectrum based on a nitrate-nitrogen 200 nm absorption peak;

wherein the processor receives a soil type and estimates the nitrate-nitrogen concentration further based on the soil type;

wherein the processor receives a soil conductivity and estimates the nitrate-nitrogen concentration further based on the soil conductivity;

wherein the processor applies a partial least squares regression to the attenuation spectrum to estimate the nitrate-nitrogen concentration;

wherein the processor is trained based on a set of absorption spectra and their corresponding nitrate-nitrogen concentrations;

wherein the processor estimates the nitrate-nitrogen concentration based on its training;

wherein the processor estimates the nitrate-nitrogen concentration as a function of a measurement time;

wherein the processor extrapolates the estimates to a final estimated nitrate-nitrogen concentration.

45. The device of claim 37, wherein a UV spectrum of the light source can be controlled separately from a visible spectrum of the light source.

46. The device of claim 37, wherein the light source includes two bulbs, one of which has a relatively stronger UV spectrum than the other, and which can be separately controlled.

47. The device of claim 37, further comprising a filter that filters the soil-extractant mixture and the light propagating through the filtered soil-extractant mixture.

48. The device of claim 37, wherein the light propagates through unfiltered soil-extractant mixture.

49. The device of claim 37, further comprising a centrifuge for separating the soil-extractant mixture, the light propagating through the separated soil-extractant mixture.

50. A method for measuring a nitrate-nitrogen concentration in soil based on attenuation over a spectral operating range, the method comprising:

generating light that spans a spectral operating range;

providing a soil-extractant mixture that attenuates the light;

detecting the attenuated light;

generating a soil spectral signal that indicates the light detected at different wavelengths across the spectral operating range;

estimating an attenuation spectrum of the soil-extractant mixture over the spectral operating range based on the soil spectral signal;

estimating the nitrate-nitrogen concentration based on the attenuation spectrum.

51. The method of claim 50, wherein estimating the attenuation spectrum includes removing interference in the soil-extractant mixture using one of spectral deconvolution and curve-fitting;

wherein the spectral operating range includes wavelengths proximate a 200 nm nitrate-nitrogen absorption peak;

wherein the 200 nm nitrate-nitrogen absorption peak includes estimated attenuation values for wavelengths greater than 200 nm.

52. The method of claim 50, further comprising estimating the attenuation spectrum based on the soil spectral signal, a reference spectral signal and a dark spectral signal;

wherein the reference spectral signal is generated when a sample chamber contains extractant without soil and the dark spectral signal is generated without light from a light source incident on a detector.

53. A device for measuring a nitrate-nitrogen concentration in soil based on attenuation over a spectral operating range, the device comprising:

a light source that generates light that spans a spectral operating range;

a detector having a sensitivity that spans the spectral operating range;

a sample chamber configured to contain a soil-extractant mixture, wherein the light propagates from the light source to the detector and is attenuated by the soil-extractant mixture in the sample chamber, wherein the detector generates a soil spectral signal that represents the light received by the detector at different wavelengths across the spectral operating range;

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 processor estimates the nitrate-nitrogen concentration based on the attenuation spectrum.

54. The device of claim 53, wherein the spectral operating range includes wavelengths at least as short as 230 nm;

wherein the processor estimates an attenuation spectrum of the soil-extractant mixture over the spectral operating rang based on the soil spectral signal, a reference spectral signal and a dark spectral signal.

55. A method for measuring a nitrate-nitrogen concentration in soil based on attenuation over a spectral operating range, the method comprising:

generating light that spans a spectral operating range;

providing in a sample chamber, a soil-extractant mixture that attenuates the light;

detecting the attenuated light with a detector;

generating a soil spectral signal that indicates the light detected at different wavelengths across the spectral operating range;

estimating 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 nitrate-nitrogen concentration is estimated based on the attenuation spectrum.

56. The method of claim 55, wherein the spectral operating range includes wavelengths at least as short as 230 nm;

wherein the nitrate-nitrogen concentration is estimated based on the attenuation spectrum.