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Mineral analysis of forages with near infrared reflectance spectrosopy

Clark, D.H. and Mayland, H.F. and Lamb, R.C. (1987) Mineral analysis of forages with near infrared reflectance spectrosopy. Agronomy Journal. 79(3):485-490.

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Mineral concentration data could easily be generated by near infrared
reflectance spectroscopy (NIRS) while determining quality
parameters in forage samples. However, which minerals can be analyzed
and why they can be determined has not been documented
adequately. Therefore, NIRS spectra were collected on 200 samples
of crested wheatgrass (Agropyron spp.), 203 tall fescue (Festuca
arundinacea Schreb.), and 59 alfalfa (Medicago sativa L.) hays. Concentrations
of Na, K, Ca, P, Mg, Fe, Mn, Cu, and Zn, as determined
by atomic absorption, and calculated values of the Ca/P, K/Mg, and
K/(Ca + Mg) ratios were regressed against reflectance values measured
in 2-nm increments between 1100 and 2500 nm for each sample.
Approximately one half of the samples in each forage set was
used to develop the calibration equations, while the other half was
used to validate the equations. The coefficients of variation [CV =
(standard error of analysis ÷ the mean)X 100] generally ranged from
10 to 20% for K, Mg, Ca, and P concentrations in each forage type.
The Ca/P ratio in alfalfa was determined with a CV of 18%. The
CV values of other minerals and mineral ratios generally exceeded
20%. Chlorophyll and some inorganic salts and organic-acid salts
of Ca, Mg, and K were scanned with NIRS for wavelength comparisons
with those wavelengths used to determine mineral concentrations
in forages. Some of the wavelengths used in the equations
for Ca, K, and Mg were related to peaks and changes in slope observed
in chlorophyll and organic-acid salts of Ca, K, and Mg, suggesting
that NIRS is indirectly measuring these minerals by their
association with organic molecules. Accurate use of NIRS to determine
mineral cation composition in forages appears limited to certain
major minerals (Ca, P, K, and Mg).

Item Type: Article
NWISRL Publication Number: 0602
Subjects: Irrigated crops > Grass forage > Chemistry
Research methodology
Mass Import - autoclassified (may be erroneous)
Depositing User: Dan Stieneke
Date Deposited: 20 Nov 2010 21:52
Last Modified: 13 Jan 2017 18:50
Item ID: 478