Remote measurements of spectral reflectance were made in a laboratory to study sulfur dioxide (SO2) effects on the foliage of soybean (Glycine max (L.) Merr.) and winter wheat (Triticum aestivum) plants. The relationship between spectral reflectance and foliar injury from SO2 was analyzed by separating injury into its components--chlorosis and necrosis--and reflectance into bands within the visible and near-infrared spectra. Results indicate that, for winter wheat, total visible reflectance as well as individual wavelength bands could be used to distinguish the SO2 effects. Three classes of chlorosis and four classes of necrosis, based on severity, could be distinguished by their visible reflectance characteristics. These results indicate that remote sensors that measure visible reflectance may be able to distinguish moderate to severe injury to wheat from low altitudes. Scans of soybeans provided less positive results. There was no statistically significant (alpha = .05) difference among the means of blue, green, red, or near-infrared reflectance or the IR/R ratio when unaffected and chlorotic soybean classes were compared. However, significant (alpha = .05) differences in the means of green, red, and near-infrared reflectance (but not blue and the IR/R ratio) were found when unaffected and moderately to severely necrotic soybean classes were compared. Evidently, unless the SO2 injury to soybeans involves necrosis, reflectance-measuring remote sensors are not likely to detect it from even a low-flying (approx. 500 m above ground level) airborne platform. The necrosis symptom is generally associated with severe levels of foliar injury, whereas chlorosis usually predominates at moderate and light levels.

Project Officer: James Stemmle. Office of Natural Resources, Tennessee Valley Authority "September 1980"--Cover. Includes bibliographical references. "EPA-600/7-80-159." "TVA/ONR-80/11." "Interagency Agreement EPA-IAG-D8-E721-DJ."