FLUORESCENCE AND REFLECTANCE OF CROP RESIDUE AND SOIL

An assessment of fluorescence and reflectance sensing technology for d etecting crop residues from soils was conducted under laboratory condi tions. Residue samples from five crop species (corn, cotton, peanut, s oybean, and wheat) and four soils with different color and albedo were tested. The studies were conducted under wet and dry conditions. Resi dues bad consistently higher fluorescence emission in a band from 415- 550 nm than did soils. Reflectance of the same materials indicated tha t certain residues can be distinguished from certain soils. Many crop residues were significantly higher or lower in reflectance than severa l soils. Other residues and soils could not be readily distinguished f rom each other on the basis of a single reflectance band. Nevertheless , discrimination of many crop residues from soil by reflectance could be possible by calibrating the threshold of discrimination for each so il and crop residue combination. A vegetation index, calculated from i ntegrations of red and near infrared reflectance wavelengths, simulati ng the bands used on the current Landsat remote sensing satellite was also effective in distinguishing differences between many residue/soil combinations. Reflectance data simulating TM3 (630-690 nm) and TM4 (7 60-900 nm) Landsat satellite bands are reported. other bands could be amenable to reflectance detection as well. These initial studies sugge st that fluorescence and reflectance sensing techniques for determinin g crop residue coverage are feasible and should be developed further.