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Mesures physiques et signatures en télédétection

scence from in
This volume.
irborne measurs.
measurs. Geo Journal,
A Tool for Controlling Soil Erosion
meral oil spills
C.S.T. Daughtry', J.E. McMurtrey III 1 , E.W. Chappelle 2 , and W.J. Hunter 3
'USDA ARS Remote Sensing Research Lab,
ts at sea with
in press.
Building 7 BARC-West, 10300 Baltimore Ave
Belts vii le, MD 20705-2350 USA
using airborne
2 NASA Goddard Space Flight Center
Greenbelt, MD 20771 USA
copic detection
l chlorophyll a
3 USDA ARS Soil-Plant-Nutrient Research Lab
Fort Collins, CO 80522 USA
nd mapping of
Appl. Opt., 22:
ents: evidence
Remote Sens.
Management of crop residues, the portion of a crop left in the field after harvest, is an important conservation
admixtures by
practice for minimizing soil erosion and for improving water quality. Quantification of crop residue cover is required
to evaluate the effectiveness of conservation tillage practices. Current methods for quantifying percent crop residue
cover are tedious and somewhat subjective. There is a need for new methods to quantify residue cover that are rapid,
accurate, and objective. We found the fluorescence of crop residue to be a broad band phenomenon with emission
of subsurface
maxima at 420-495 nm for excitations of 350-420 nm. Soils had low intensity broad band emissions over the 400690
400690 nm region for excitations of 300-600 nm. The range of relative fluorescence intensities for the crop residues
n by dye laser
Engineering in
was much greater than the fluorescence observed for the soils. As the crop residues decompose, their blue
fluorescence values approach the fluorescence of the soil. We conclude 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, not only crop residue cover, but also
photosynthetic efficiency in the field.
lutions: oil in
KEY WORDS: Blue fluorescence, Soil, Litter, Remote Sensing
ensing of the
i, ESA SP-312,
nonitoring sea
n press.
; laser remote
ht and in the
1.1. Soil Erosion.
Agricultural statistics (U.S.D.A., 1991 ) indicate that there is an average of 8.51 Mg/ha of sheet and rill water
erosion on U.S. cropland soils per year. The rate of soil erosion can be significantly decreased by allowing
unharvested dead plant material (crop residue) to remain on the soil surface. As little as 30% coverage of residue
material across the soil surface can reduce soil erosion to 10% of its non-covered state. Over one-third of the tilled
dopment of a
ices in Remote
U.S. cropland or 49.8 million hectares is classified as highly erodible land. Farmers with highly erodible croplands
are required to implement approved control practices that will reduce soil erosion by December 31, 1994. Residue
management is an effective management practice for reducing soil erosion and more than 66 % of the nearly 1.3
million conservation compliance plans include management of crop residue as the primary technique for reducing
T., Braun A.,
time pollution
suits. EARSeL
soil erosion. In order to comply with their plans, farmers must ensure that their highly erodible soils have an
adequate amount of residue cover. An added benefit of conservation practices is that as the movement of eroded
soil into streams and rivers is reduced, the concomitant movement of nutrients and pesticides adsorbed to soil
Particles is also reduced. The overall result is less soil erosion and improved water quality.
1-2 Residue Cover Measurement Techniques.
Quantification of crop residue cover is required to evaluate the effectiveness of conservation tillage practices.
Bonham (1989) reviewed the various methods of measuring terrestrial vegetation cover and grouped them into nine