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Second-Derivative Spectra for Estimating Crop Residue Cover

Div. of Biology, Manhattan, KS 66506;

Michel D. Ransom

Dep. of Agronomy, Kansas State Univ., Manhattan, KS 66506;

Edward T. Kanemasu

Dep. of Agronomy, Univ. of Georgia, Griffin, GA 30223;

Tanvir H. Demetriades-Shah

Dep. of Plant and Soil Sci., Alabama A&M Univ.,, Normal, AL 35762.

^* Corresponding author.

Estimating crop residue is important for soil conservation and tillage management, and such estimates are used in determining conservation compliance with the U.S. Food Security Act of 1985. This study was conducted to (i) examine the relationship between derivative spectra of reflectance and oat (Avena saliva L.) residue covers and (ii) determine if the relation can be used to estimate oat residue cover from ground-based reflectance measurements, using broad-band (MMR) and high-spectral-resolution (SE590) instruments. A simple spectral model was proposed to interpret the interaction of solar radiation and crop residue with different soil backgrounds. A spectral derivative technique was applied to the field-measured reflectance data to minimize the soil background noise and extract information about crop residue. SE590 wavelength at 402 ran and MMR Band I (450–520 ran) were the most sensitive. The second-derivative value, defined as the derivative spectral index, strongly correlated (r² 0.85) with oat residue cover using SE590 and MMR data. Four empirical regression equations were developed from the relationship between the derivative spectral index and the oat residue cover from four different data sets. Our results suggest that derivative spectral indices can be useful for estimating fresh oat residue in a disked field. The broad-band data also can be used to calculate the derivative spectral index for detecting oat residue.

Support was provided in part by the USDA-SCS under Grant no. 68-6215-8-68, by NASA under Grant no. NAG 5-389, and the National Science Foundation under Grant no. BSR-9011662.

Received for publication October 8, 1992.