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Title
Mesures physiques et signatures en télédétection

iring crop residue cover
Line-transect methods
lethods use a system of
: residue is determined
the intercept is read at
on the length of the line
100 feet long and have
itandard technique used
stigated. For example,
pots on the surface for
; a line, it must be used
stereographic pairs of
ographs. An important
or multispectral video
and residue classes on
es between classes (soil
1 time, however video
h experience, Morrison
! minutes per image as
ise primarily when the
l somewhat subjective
residue cover that are
residues with soil using
ice during degradation.
idgment present in the
¡ristics. Unfortunately,
getation (Bauer, 1975)
he near infrared (Aase
ils are often spectrally
tre, iron oxide content,
1980). Furthermore,
particular wavelength
t al. 1993; McMurtrey
It or nearly impossible
>ils is possible using a
dmum first derivative
m. McMurtrey et al.
itered at 440 nm when
be fluorescence in the
in, and NADPH. The
ually contribute more
soils.
i there d am, soybean,
is was a broad band
d low intensity broad
band emissions over the 400-690 nm region for excitations of 300-600 nm. The range of relative fluorescence
intensities (RFI) for the crop residues was much greater than the RFI observed for the soils. Moisture quenched the
fluorescence, but the relative difference between crop residues and soils remained fairly constant regardless of
moisture status. In general, older crop residues had lower minimum and lower maximum RFI values than recentlyharvested
recentlyharvested residues. As the crop residues decompose, their RFI values approach the RFI of the soil. Greater than
90% of the crop residues less than 2 years old could be discriminated from 35 of the 40 dry soils and 39 of the 40
wet soils using fluorescence. They concluded that fluorescence techniques are less ambiguous and better suited for
discriminating crop residues and soils than reflectance methods. Furthermore, if properly implemented, fluorescence
techniques can be used to quantify crop residue cover in the field.
Table 1. Relative fluorescence intensity (RFI) of representative wet and dry soils. (After Daughtry et al., 1993).
SOIL
SERIES
LOCATION
RFIdry
RFI wet
SOIL
SERIES
LOCATION
RFI Puy
RFIwpe
Academy
California
10.5
5.7
Granada
Mississippi
9.5
5.0
Amarillo
Texas
12.0
5.7
Hersh
Nebraska
21.4
8.5
Barnes
Minnesota
10.1
5.4
Palouse
Washington
6.1
3.9
Caribou
Maine
12.4
5.5
Tifton
Georgia
21.5
7.0
Codorus
Maryland
17.7
7.1
Wilhams
North Dakota
8.1
5.3
Gaston
N. Carolina
5.9
4.2
Zahl
Montana
8.3
5.5
Table 2. Relative fluorescence intensity (RFI) of recently-harvested and weathered crop residues. (After Daughtry
et al., 1993).
CROP
AGE
NO.
MIN.
MAX
MEAN
Com
1 week
70
42.9
239.4
97.7
2 months
170
23.6
124.8
58.1
8 months
140
13.6
167.5
52.9
Sorghum
1 year
150
26.5
259.6
101.4
3 years
180
14.0
202.2
64.0
Soybean
1 week
120
15.4
149.5
76.8
1 year
70
17.1
77.2
48.0
Wheat
1 week
70
20.2
56.1
38.9
3 months
70
16.0
52.0
34.2
Wheat
2 months
250
22.6
119.6
63.1
1 year
120
17.3
72.8
40.1
2 years
150
11.2
51.6
25.8
All Residues
1560
11.2
259.6
59.6