METHOD FOR SOIL CONTENT PREDICTION BASED ON A LIMITED NUMBER OF MID-INFRARED ABSORBANCES

• US 20070073491A1
• Filed: 09/14/2006
• Published: 03/29/2007
• Est. Priority Date: 09/14/2005
• Status: Active Grant

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Jahn, Bernard, Upadhyaya, Shrini, Slaughter, David
• Granted Patent: US 7,671,336 B2
• Time in Patent Office: Days
• US Class Current: 702/23
• CPC Class Codes: G01V 8/02 Prospecting

Abstract

A single absorbance value was found in the mid infrared (mid-IR) region that correlated directly to soil nitrate content while not being influenced by other components in the soil, such as carbonate and organic matter. Using one or two absorbance values, at which interference from other ions is a minimum, to predict a component'"'"'s concentration as opposed to the conventional method of using a continuous spectrum allows for an in-situ real-time soil nitrate content sensor.

Claims

1. A method for determining concentration of a component in a soil sample, comprising:

obtaining mid-infrared attenuated total reflectance spectra of the soil sample;

identifying a single mid-infrared range absorbance value;

wherein the mid-infrared range absorbance value corresponds to a decomposed peak volume of said component; and

determining the concentration of said component in the soil sample by correlating the absorbance value with a predicted component concentration value.

2. A method as recited in claim 1, wherein the component comprises nitrate.

3. A method as recited in claim 1, wherein the component comprises phosphorus.

4. A method as recited in claim 1, wherein the component comprises organic matter.

5. A method as recited in claim 2, wherein the absorbance value comprises a wavenumber corresponding to a decomposed nitrate peak in the soil.

6. A method as recited in claim 5, wherein the decomposed nitrate peak is generated from wavelet analysis of the reflectance spectra.

7. A method as recited in claim 5, wherein correlating the absorbance value comprises inputting the absorbance value into a single calibration equation.

8. A method as recited in claim 7, wherein the calibration equation is generated by:

obtaining mid-infrared attenuated total reflectance spectra data of one or more soil samples;

separating the nitrate peak from a carbonate peak in the soil spectra; and

identifying a first wavenumber corresponding to the location of the nitrate peak.

9. A method as recited in claim 8, wherein generating the calibration equation further comprises:

identifying a second wavenumber to account for and substantially eliminate influence of the carbonate peak.

10. A method as recited in claim 9, wherein the second wavenumber corresponds to a second absorbance value relating primarily to carbonate presence in the soil;

said second absorbance value being substantially free of influence by carbonate or other soil components.

11. A method as recited in claim 9, wherein the first wavenumber comprises approximately 1300 cm⁻

1 to approximately 1350 cm<sup>−

1</sup>.

12. A method as recited in claim 11, wherein the first wavenumber comprises approximately 1350 cm⁻

1.

13. A method as recited in claim 11, wherein the second wavenumber comprises approximately 1500 cm⁻

1.

14. A method as recited in claim 7, wherein said correlation equation is independent of soil type such that it is capable of being applied universally.

15. A method as recited in claim 8, wherein the reflectance spectra data is baseline corrected prior to analysis.

16. A method of correlating FTIR ATR soil spectra to a nitrate concentration, comprising:

obtaining FTIR ATR soil spectra from a plurality of soil samples of different soil types; and

pooling absorbance data from one or more selected wavelengths of each sample into a calibration equation.

17. A method as recited in claim 16, wherein pooling absorbance data comprises:

analyzing the soil spectra to separate a nitrate peak from a carbonate peak; and

identifying a wavenumber at the nitrate peak and calculating a volume of the nitrate peak.

18. A method as recited in claim 17, wherein a wavelet analysis is performed to separate the nitrate peak from the carbonate peak.

19. A method as recited in claim 16, wherein the selected wavelengths comprise a value between approximately 1300 cm⁻

1 and approximately 1550 cm<sup>−

1</sup>.

20. A method as recited in claim 19, wherein a first selected wavelength comprises approximately 1500 cm⁻

1.

21. A method as recited in claim 20, wherein a second selected wavelength comprises approximately 1500 cm⁻

1.

22. A method for determining the concentration of a component in a soil sample, comprising:

obtaining mid-infrared attenuated total reflectance spectra of the soil sample;

correlating a plurality of mid-infrared range absorbance values with a component concentration in soil; and

determining component concentration from said absorbance values;

wherein said absorbance values do not form a continuous spectrum.

23. A method as recited in claim 22, wherein the component comprises nitrate, and wherein one of the mid-infrared range absorbance values corresponds to a decomposed peak volume of nitrate.

24. A method as recited in claim 22, wherein the component comprises phosphorus, and wherein one of the mid-infrared range absorbance values corresponds to a decomposed peak volume of phosphorus.

25. A method as recited in claim 22, wherein the component comprises organic matter, and wherein one of the mid-infrared range absorbance values corresponds to a decomposed peak volume of organic matter.

26. A method as recited in claim 23, wherein said absorbance value comprises a value between approximately 1300 cm⁻

1 and approximately 1550 cm<sup>−

1</sup>.

27. A method as recited in claim 24, wherein said absorbance value comprises a value between approximately 1000 cm⁻

1 and approximately 1550 cm<sup>−

1</sup>.

28. A method as recited in claim 27, wherein said absorbance value comprises a value between approximately 1037 cm⁻

1 and approximately 1508 cm<sup>−

1</sup>.

29. A method as recited in claim 25, wherein said absorbance value comprises a value between approximately 1383 cm⁻

1 and approximately 1452 cm<sup>−

1</sup>.