926 
USA). The stems covered 22.2% of the 
area of interest in the video image. 
Codorus, a light-colored silt loam (fine- 
silty, mixed, fluvaquentic Dystrochrept) 
from Beltsville. Maryland and Barnes, a 
dark-colored sandy loam (coarse- 
loamy, mixed, udic Haploboroll) from 
Morris, Minnesota were used as soil 
backgrounds. After acquiring images of 
the residue on the dry soil, the soils were 
sprayed with water until saturated and 
another set of images were acquired. 
3 - RESULTS AND DISCUSSION 
Reflectance factors of the two 
soil and the soybean residue are 
presented in Table 1. Note the 
similarities in reflectance factors for the 
soils and residue. Discrimination of the 
soybean residue from the Barnes soil is 
possible in the visible and near infrared 
wavelength bands regardless of the soil 
moisture conditions. However, the reflectance factors of the soybean residue and the reflectance factors of the 
Codorus soil overlap depending on soil soil moisture and considerable misclassification is likely. Inspection of the 
panchromatic photograph in Figure 2 illustrates the s imil arities in reflectance between the Codorus soil and the 
soybean residue. 
Figure 3 is an image of the fluorescence of the soybean residue on the dry Codorus soil background. In 
the 8-bit video image, the soil is dark with brightness values of 0-7, while the soybean stems are brighter and range 
8-255. The brightest areas in the image correspond to portions of the soybean stems that showed the least evidence 
of microbial colonization. Likewise the darkest areas, i.e., lowest fluorescence intensity, of the soybean stems 
correspond to areas with the most microbial colonization. 
Figure 4 is a histogram of the gray levels for the video image of fluorescence from the soybean residue on 
the dry Codorus soil. Note the pixel count in the 'O' fluorecence intensity bin exceeds 210,000 and is not shown to 
scale. 
Figure 3 Fluorescence image of soybean residue on dry Codorus 
soil background. The soybean residue is brighter than the soil. 
Figure 2 Panchromatic photograph of the soybean residue on the 
dry Codorus soil background. Note the low contrast between the 
residue and the soil in visible light.