Second-Derivative Spectra for Estimating Crop Residue Cover
Journal - Agronomy Journal
Estimating crop residue is important for soil conservation andtillage management, and such estimates are used in determiningconservation compliance with the U.S. Food Security Act of 1985.This study was conducted to (i) examine the relationship betweenderivative spectra of reflectance and oat (Avena saliva L.)residue covers and (ii) determine if the relation can be usedto estimate oat residue cover from ground-based reflectancemeasurements, using broad-band (MMR) and high-spectral-resolution(SE590) instruments. A simple spectral model was proposed tointerpret the interaction of solar radiation and crop residuewith different soil backgrounds. A spectral derivative techniquewas applied to the field-measured reflectance data to minimizethe soil background noise and extract information about cropresidue. SE590 wavelength at 402 ran and MMR Band I (450–520ran) were the most sensitive. The second-derivative value, definedas the derivative spectral index, strongly correlated (r2 0.85)with oat residue cover using SE590 and MMR data. Four empiricalregression equations were developed from the relationship betweenthe derivative spectral index and the oat residue cover fromfour different data sets. Our results suggest that derivativespectral indices can be useful for estimating fresh oat residuein a disked field. The broad-band data also can be used to calculatethe 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 NationalScience Foundation under Grant no. BSR-9011662.